- Email: [email protected]
Results of a Population-Based Survey of Adults' Attitudes and Beliefs About Herbal Products
RESEARCH
Results of a Population-Based Survey of Adults’ Attitudes and Beliefs About Herbal Products Lisa J. Harnack, Kim L. DeRosier, and Sarah A. Rydell
Objective: To assess attitudes and beliefs about herbal products held by adults in a large metropolitan area. Design: Descriptive study. Participants: Adults in the Minneapolis-St. Paul, Minn., metropolitan area were randomly selected from data tapes supplied by the Minnesota Department of Public Safety Driver and Vehicle Service Division. Intervention: Cross-sectional mailed survey. Main
Outcome Measures: Attitudes and beliefs were assessed via scaled responses to a series of statements about herbal products. Results: Most participants indicated an awareness of safety concerns with herbs, although a majority felt there was no harm in trying herbal products. Most agreed that it was a good idea to visit a physician before taking an herbal product and that one should inform his or her physician of any herbs being used. The majority of participants agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated.”
Conclusion: Although many participants acknowledged that use of herbal products poses risks, the perception persists that there is no harm in trying these products. Hence, education may be warranted to alert patients to clear safety concerns regarding herbal products. Our findings suggest that most adults know they should talk with their physician about their herb use, although other research suggests that many do not. Thus, obstacles to patients’ disclosure of herbal product use need to be identified and addressed to facilitate communication of this important information by patients to their health care providers.
Keywords: Dietary supplements, herbal products, attitudes, beliefs. J Am Pharm Assoc. 2003;43:596–601.
Sales of herbal products in the United States have increased dramatically in recent years. From the early 1990s through 1998, sales increased by approximately 25% annually.1 In 1999 sales of herbs exceeded $3.3 billion.2 Since 1998 sales have plateaued, although market analysts projected an average annual growth rate of 9.7% through 2004 for the herbal product market segment.2 In agreement with sales data, survey data indicate that herbal product use among Americans is sizable3-5 and growing.6 For example, in a 1997 survey of alternative medicine practices by adults in the United States, 12% of respondents reported using an
Received April 29, 2002, and in revised form May 13, 2003. Accepted for publication May 29, 2003. Lisa J. Harnack, DrPH, RD, is assistant professor; Kim L. DeRosier is research assistant; Sarah A. Rydell is research assistant, Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis. Correspondence: Lisa J. Harnack, DrPH, RD, Division of Epidemiology, School of Public Health, University of Minnesota, 1300 South 2nd Street, Suite 300, Minneapolis, MN 55454. Fax: 612-624-9328. E-mail: [email protected]. See related article on page 602.
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herbal product in the past 12 months, an increase of 380% over the prevalence of use of herbal remedies found in a 1992 survey that used the same sampling and interviewing methods.6 Because the safety and efficacy of many herbs used in the United States remain essentially unknown, the increasing use of these products is of concern. Some herbs (e.g., germander, comfrey, pennyroyal) have well-documented toxic effects.7 Because of the lack of standardization, herbal product content and efficacy varies among manufacturers. Contamination during manufacturing and misidentification of plant species are also concerns.8–10 Herb-drug interactions are possible, but the extent to which they occur remains unknown due to the limited amount of research.7–11 With the rising use of herbal products, pharmacists and other health care providers are increasingly confronted with the need to educate patients about the risks and benefits of their use. Unfortunately, much basic information that is critical to developing educational strategies is unavailable. More specifically, little is known about the general public’s attitudes and beliefs regarding herbal medicines. A small number of studies have examined attitudes and beliefs relating to herbal products,12–17 but the findings have been limited because of the use of selective populations and small sample sizes.
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Objective Our objective was to assess the attitudes and beliefs about herbal products held by adults in a large metropolitan area. Survey questions were designed to assess perceptions of the safety and efficacy of herbal products, beliefs about appropriate use, and the extent to which participants believe physicians should be informed of their patients’ use of herbal products.
Methods We mailed the survey to adults in the Minneapolis-St. Paul, Minn., metropolitan area between June 1999 and August 1999. To obtain a representative sample, we randomly selected 752 persons aged 18 years and older with ZIP codes in the Minneapolis-St. Paul metropolitan area from data tapes supplied by the Minnesota Department of Public Safety’s Driver and Vehicle Service Division. The survey mailing was conducted based on the Dillman method18: a first survey mailing, a reminder postcard, a second survey mailing, and a third survey mailing. As an incentive, we offered $10 to participants who returned the survey. The survey included a section designed to assess attitudes and beliefs about herbal products. In this section, participants were asked to indicate on a 4-point Likert scale how strongly they disagreed or agreed with a series of statements. Several statements assessed perceived safety and efficacy. In addition, statements were included to assess beliefs about appropriate use of herbal products, including the need to consult a physician before taking herbal products and the need to inform physicians of any herbal products being used. In the absence of an existing validated questionnaire to assess attitudes and beliefs about herbal products, the survey questions were developed by the research team. We pilottested the survey instrument for comprehension and readability with a convenience sample of 10 adults. We asked participants whether they had used any herbal product during the past 12 months. Herbal products were defined in the survey instrument as extracted preparations of parts of fruits, vegetables, trees, shrubs, grasses, fungals, and herbs. We told participants that we were only interested in their use and perceptions of herbal products that are taken orally (i.e., tablets, capsules, extracts, tinctures, teas). Frequency distributions and means were calculated using SAS version 6 (SAS Institute, Cary, N.C.).19 c2 tests were used to test for differences in attitudes and beliefs by age, sex, education, and herbal product use. Statistical significance for all tests was set at P £ .05.
Results Participants Of the initial sample of 752 individuals, 172 (23%) were ineligible because of change of address (n = 156) or death (n = 16). Of
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the 580 eligible individuals, 376 returned a completed survey, for a response rate of 65%. Table 1 shows survey participants’ demographic characteristics and population distribution data for the Minneapolis-St. Paul metropolitan area from the 1990 U.S. Census.20 The characteristics of the survey sample are similar to the population distribution data from the U.S. Census Bureau, although some differences are evident. Most notably, a higher proportion of survey participants were women, and a lower proportion had less than a high school education, compared with the overall Minneapolis-St. Paul area population.
Perceived Safety To assess perceived safety, participants were asked to indicate on a 4-point Likert scale how strongly they disagreed or agreed with a series of statements (see Table 2). When asked whether they agreed or disagreed that “some herbal products may have side effects or may interact with medications,” most (94%) strongly agreed or agreed. Similarly, most (94%) strongly agreed or agreed that “some herbal products can be dangerous, especially if taken in high doses,” and most (93%) strongly disagreed or disagreed with the statement “when using herbal products you don’t need to be concerned about overdosing or taking too much.” In contrast, a modest majority (61%) strongly agreed or agreed that “there’s no harm in trying herbal products.” When asked whether herbal products tend to be safer than over-the-counter (OTC) medications or medications prescribed by a physician, 42% disagreed and 44% agreed. Aside from the scaled response questions, participants were asked to indicate whether they thought that most, some, or few Table 1. Demographic Characteristics of Survey Participants (n = 376) Compared With the Minneapolis-St. Paul Metropolitan Area Population Aged 18 Years or Oldera
Characteristic
Survey Participants No. (%)
Metropolitan Area Population %
Age, years 18-24 25-44 45-64 ³ 65
47 164 121 44
(12.5) (43.7) (32.0) (11.7)
13.8 49.6 23.2 13.4
Sex Men Women
167 (44.4) 209 (55.6)
48.9 51.1
Education level Less than high school 15 (4.0) High school and some college 216 (57.4) College graduate or higher 140 (37.2)
12.8 b 60.0 b 27.1 b
Race/ethnicity White African American Other
92.1 3.6 4.2
a
339 (90.2) 12 (3.2) 19 (5.1)
Percentages may not total 100 because of rounding.
b Education information for persons aged 25 years and older.
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Table 2. Frequency of Attitudes and Beliefs About Herbal Products
Attitude/Belief
Strongly Disagree 1 No. (%)
Disagree 2 No. (%)
Agree 3 No. (%)
Strongly Agree 4 No. (%)
18 (4.9)
237 (63.9)
112 (30.2)
18 (4.9)
179 (48.6)
167 (45.4)
176 (47.4)
16 (4.3)
10 (2.7)
136 (36.9) 154 (41.6)
195 (52.8) 27 (44.3)
29 (7.9) 27 (7.2)
18 (5.0)
156 (43.5)
168 (46.8)
17 (4.7)
3 (0.8)
63 (17.1)
254 (69.0)
48 (13.0)
4 (1.1)
83 (22.4)
208 (56.2)
75 (20.3)
1 (0.3)
42 (11.4)
212 (57.3)
115 (31.3)
62 (17.0)
235 (64.4)
57 (15.6)
11 (3.0)
38 (10.4)
181 (49.7)
97 (26.6)
48 (13.2)
2 (0.6) 8 (2.2)
48 (13.2) 116 (32.6)
256 (70.5) 189 (53.1)
57 (15.7) 43 (12.1)
21 (5.8)
165 (45.8)
143 (39.7)
31 (8.6)
Perceived safety Some herbal products may have side effects or may interact 4 (1.1) with medications Some herbal products can be dangerous, especially if taken 4 (1.1) in high doses W hen using herbal products, you don’t need to be 169 (45.6) concerned about overdosing or taking too much There’s no harm in trying herbal products 9 (2.4) Herbal products tend to be safer than medications 25 (6.8) prescribed by a doctor or available over-the-counter Perceived efficacy There is a lot of scientific evidence to support the effectiveness of herbal products The use of herbs for health promotion and healing since ancient times provides support for the use of these products today Beliefs about appropriate use It’s a good idea to visit a physician before taking herbal products You should inform your physician of any herbal products you are taking Herbal products are only appropriate for treating minor conditions such as a cold or stomachache Herbal products should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure Other There is a lot of misinformation about herbs circulating Health claims on the labels of many herbal products are exaggerated or unsubstantiated Herbal products tend to be less expensive than prescription and over-the-counter medications
herbal products were safe. In response, 46% thought that most were safe, 52% felt that some were safe, and just 2% thought that few were safe.
Perceived Efficacy To assess perceived efficacy, participants were asked to indicate how strongly they agreed or disagreed that “there is a lot of scientific evidence to support the effectiveness of herbal products” and that “the use of herbs for health promotion and healing since ancient times provides support for the use of these products today” (Table 2). Responses to the former statement were closely divided, with 44% disagreeing and 47% agreeing. Most (82%) strongly agreed or agreed with the latter statement. Nine percent of respondents thought that most herbal products were effective, 82% felt that some were effective, and 7% thought that few were effective. Beliefs About Appropriate U se The survey included questions assessing attitudes and beliefs about the need to discuss herbal product use with a physician and
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the appropriateness of using herbs for treating minor and serious health conditions (Table 2). A majority of participants (77%) agreed or strongly agreed that it is “a good idea to visit a physician before taking herbal products,” and most (89%) agreed or strongly agreed that “you should inform your physician of any herbal products you are taking.” Most (81%) disagreed or strongly disagreed with the statement, “Herbal products are only appropriate for treating minor conditions such as a cold or stomachache.” A modest majority (60%) disagreed or strongly disagreed with the statement, “Herbal products should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure.”
O ther Attitudes and Beliefs In response to questions intended to assess participants’ perceptions regarding the quality of the information available on herbal products, most (86%) agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” (Table 2). Likewise, a modest majority (65%) agreed or strongly agreed that “health claims on the labels of many herbal products are exaggerated or
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Table 3. Comparison of Attitudes and Beliefs of Herbal Product Users and Nonusers Users
Perceived safety Herbal products tend to be safer than medications prescribed by a doctor or available over-the-counter Some herbal products can be dangerous, especially if taken in high doses There’s no harm in trying herbal products Some herbal products may have side effects or may interact with medications W hen using herbal products, you don’t need to be concerned about overdosing or taking too much Perceived efficacy There is a lot of scientific evidence to support the effectiveness of herbal products The use of herbs for health promotion and healing since ancient times provides support for the use of these products today Beliefs about appropriate use It’s a good idea to visit a physician before taking herbal products You should inform your physician of any herbal products you are taking Herbal medicines should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure Use of herbs is only appropriate for treating minor conditions such as a cold or stomachache Other attitudes and beliefs There is a lot of misinformation about herbs circulating Health claims on the labels of many herbal products are exaggerated or unsubstantiated Herbal products tend to be less expensive than prescription and over-the-counter medications a P value for c 2
Strongly Disagree/ Disagree No. (%)
Strongly Agree/ Agree No. (%)
Strongly Disagree/ Disagree No. (%)
Pa
134 (58.5)
95 (41.5)
57 (40.4)
84 (59.6)
< .01
214 (93.9)
14 (6.1)
132 (94.3)
8 (5.7)
.88
148 (65.2) 213 (93.4)
79 (34.8) 15 (6.6)
76 (53.5) 136 (95.1)
66 (46.5) 7 (4.9)
.03 .50
15 (6.6)
213 (93.4)
11 (7.7)
132 (92.3)
.68
121 (54.5)
101 (45.5)
64 (46.7)
73 (53.3)
.15
201 (87.8)
28 (12.2)
101 (72.7)
38 (27.3)
< .01
155 (68.3)
72 (31.7)
128 (89.5)
15 (10.5)
< .01
198 (87.2)
29 (12.8)
129 (90.2)
14 (9.8)
72 (32.1)
152 (67.9)
73 (52.1)
67 (47.9)
< .01
30 (13.3)
196 (86.7)
38 (27.3)
101 (72.7)
< .01
198 (88.4)
26 (11.6)
115 (82.7)
24 (17.3)
.13
136 (62.4)
82 (37.6)
96 (69.6)
42 (30.4)
.17
107 (47.8)
117 (52.2)
67 (49.3)
60 (50.7)
.78
.38
tests conducted to compare responses of herbal product users and nonusers.
unsubstantiated.” When asked to indicate how strongly they disagreed or agreed with the statement, “Herbal products tend to be less expensive than over-the-counter medications,” 46% disagreed and 40% agreed.
Differences in Attitudes and B eliefs Results of c2 tests conducted to determine whether attitudes and beliefs about herbal products differed among herbal product users and herbal product nonusers are presented in Table 3. Those who reported using herbal products in the past 12 months (users) were significantly more likely than nonusers to strongly agree or agree that herbal products tend to be safer than medications prescribed by a physician or available OTC and that there is no harm in trying herbal products. In addition, users were significantly more likely to strongly agree or agree that “the use of herbs since ancient times provides support for use of these products today.” Users were sig-
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Nonusers
Strongly Agree/ Agree No. (%)
September/October 2003
nificantly less likely than nonusers to strongly agree or agree that it is a “good idea to visit a physician before taking herbal products.” Users were also significantly less likely to strongly agree or agree that herbs should not be used to treat serious health conditions. c2 tests were used to examine possible differences in attitudes and beliefs by age, sex, and education level (data not shown). Just one significant difference by age was found. Older individuals were more likely to agree that herbal products should not be used to treat serious health conditions (P = .01). With respect to sex, several significant differences were evident. Women were more likely than men to believe that herbal products may be dangerous, especially if taken in high doses (P = .02). Men were more likely to strongly agree or agree that the use of herbs since ancient times provides support for their use today (P = .04), that health claims on the labels of many herbal products are exaggerated or unsubstantiated (P = .03), and that herbal products tend to be less expensive than prescription and OTC medications (P = .01).
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Some differences in attitudes and beliefs in accord with education level were found. Participants with a higher education level (college of postgraduate degree) were more likely to strongly agree or agree that some herbal products may be dangerous, especially if taken in high doses (P < .01). Furthermore, this same group was more likely to believe that “there is a lot of misinformation about herbs circulating” (P = .02) and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated” (P = .01).
Discussion A variety of safety concerns surround the use of herbal products, including potential toxic effects, herb-drug interactions, and contamination during manufacturing. Most participants in our survey indicated an awareness of safety concerns; for example, a majority agreed or strongly agreed that some herbal products may have side effects or may interact with medications, and most strongly agreed or agreed that some herbal products can be dangerous, especially if taken in high doses. Yet, despite an awareness of safety concerns, a modest majority of participants felt that there was no harm in trying herbal products. When asked whether herbal products tend to be safer than OTC medications or medications prescribed by a physician, overall responses were dichotomous, with about 42% disagreeing and 44% agreeing. A different picture emerged, however, when analyses were stratified by herbal product use. Among users, a modest majority strongly agreed or agreed with this statement, whereas a minority of nonusers strongly agreed or agreed. In congruence with this finding, participants in a study of St. John’s wort reported believing that herbal medications were purer and safer than prescription medications.13 While scientific evidence exists to support the use of some herbs for some indications, sufficient evidence regarding efficacy is lacking for many herbs available in the marketplace.21 Our findings suggest that most adults recognize that not all herbs are effective. When asked to indicate whether they thought that most, some, or few herbal products were effective, the majority of participants indicated they thought that some were effective. A clear majority agreed or strongly agreed that use of herbs for health purposes since ancient times provides support for their use today, suggesting that scientific evidence may not be the only criterion applied by the public when considering the potential efficacy of an herb. Given the potential safety concerns with use of herbal products, including possible herb-drug interactions, medical guidance in the use of herbs has been recommended.13,15,16,22–24 We found that most survey respondents strongly agreed or agreed that a physician should be consulted before or while one is taking herbal products, although herbal product users were somewhat less likely to agree that such notification was necessary. The literature, however, indicates that many patients do not inform their health care providers of their herbal product use. For example, Bennett and Brown,12 in a
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survey of members of a health maintenance organization, found that the majority of users in their sample did not discuss their herb use with their physician (85.7%) or pharmacist (95.8%). Similarly, Wagner et al.13 found that only 30% of the St. John’s wort users in their sample discussed their use of this herb with their physician. Research is needed to better understand why many patients, including a significant proportion of those with serious health conditions such as HIV,25 do not discuss their use of herbs with their health care providers. Special consideration should be given to the role pharmacists can play in eliciting herb use through a medication history. Thought should be given to the implications of herb use information gathered from such an assessment; for example, do pharmacists have a role or duty to inform physicians if they learn that patients are taking an herbal product to treat a health condition? Among both users and nonusers in our sample, a majority agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated.” These perceptions may reflect the U.S. marketplace, where herbal products, regulated under the 1994 Dietary Supplement and Health Education Act (DSHEA),26 may be marketed with no proof of efficacy. Although DSHEA requires that manufacturers not promise a specific cure on the supplement label, they may claim effect. Pharmacists can serve as sources of reliable information about the risks and benefits of using herbal products, although this necessitates that pharmacists stay up-to-date with information on the herbal products available in pharmacies.
Limitations Several limitations of our study should be noted. Our sample may not be representative of the total Minneapolis-St. Paul area population. Because the sample was selected from the Minnesota Department of Public Safety’s Driver and Vehicle Service Division data tapes, persons without a Minnesota driver’s license or Minnesota identification card were excluded. Also, the final sample did not include those whose address change had not been reported to the Driver’s License Bureau. With respect to the representativeness of the responses of the 65% of the sample that completed the survey, the demographic characteristics of the survey sample are similar to those of the area population found by the U.S. Census Bureau in 1990. However, compared with the proportions in the overall population, a higher proportion of the survey participants were women and a lower proportion had less than a high school education. Because some significant differences in attitudes and beliefs in accord with sex and education were found, the overrepresentation of women and higher-educated individuals in our sample may have affected the estimates of the overall frequency of various attitudes and beliefs. Because participants were adults residing in a metropolitan area in the Midwest with a predominately white population, strictly interpreted, our findings should be generalized only to similar populations.
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Although we pilot-tested the survey for comprehension and readability, the questions have not been validated, and thus may provide poor measures of the targeted attitudes, beliefs, and behaviors. Of special concern, the definition of “herbal products” provided to participants may have resulted in the reporting of herbs used for nonmedicinal purposes. For example, some participants could have understood “herbal tea” to be an herbal product under the definition provided. Consequently, the expansiveness of the definition provided could have led to overreporting of herb use. Also, participants were asked whether they had used an herb in the past 12 months, but information about frequency and duration of use was not assessed. Thus, survey respondents classified as users would include infrequent and irregular users. Finally, this survey was conducted almost 4 years before the results were published. Hence, current attitudes and beliefs about herbal products may differ from those described in this article.
Conclusion Our findings provide information that may be useful to pharmacists and other health care providers who are increasingly confronted with the need to educate patients about herbal products. Although many acknowledge that herb use may pose risks, the perception persists among patients that there is no harm in trying herbs. Hence, education may be warranted to alert patients to the clear safety concerns associated with some herbal products. Our findings suggest that most patients know they should talk with their physician about their herb use; however, other researchers’ findings suggest that many patients do not. Thus, obstacles to patients’ disclosure of their use of herbal products need to be identified and addressed to facilitate communication of this important information by patients to their health care providers. The authors declare no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, gifts, stock holdings, or honoraria. This research was supported by a grant from the Minnesota Medical Foundation.
References 1. Grauds C. Botanicals: strong medicine for health and profit. The Source.1997;3:1. 2. Popovich B. What is the cure for leveling botanical sales? Chem Market Rep. 2000;258:3–7.
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3. Roe B, Derby B, Levy A. Commission on Dietary Supplement Labeling. Demographic, Lifestyle and Information Use Characteristics of Dietary Supplement User Segments. Washington, DC: Division of Market Studies, Center for Food Safety and Applied Nutrition, Food and Drug Administration; 1997. 4. Frate D, Croom E, Juergens J. Self-treatment with herbal and other plant-derived remedies—rural Mississippi, 1993. MMWR Morb Mortal Wkly Rep. 1995;44:204–7. 5. Harnack L, Rydell S, Stang J. Prevalence of use of herbal products by adults in the Minneapolis/St Paul, Minn., metropolitan area. Mayo Clin Proc. 2001;76: 688–94. 6. Eisenberg D, Davis R, Ettner S, et al. Trends in alternative medicine use in the United States, 1990–1997. JAMA. 1998;280:1569–75. 7. Ernst E. Harmless herbs? A review of the recent literature. Am J Med. 1998;104:170–8. 8. Slifman N, Obermeyer W, Aloi B, et al. Contamination of botanical dietary supplements by Digitalis lanata. N Engl J Med. 1998;339:806–11. 9. Ko R. Adulterants in Asian patent medicine. N Engl J Med. 1998; 339:847. 10. Nortier J, Muniz Martinez M, Schmeiser H, et al. Urothelial carcinoma associated with the use of a Chinese herb. N Engl J Med. 2000; 342:1686–92. 11. D’Arcy P. Adverse reactions and interactions with herbal medicines. Part 1. Adverse reactions. Adv Drug React Toxicol Rev. 1991; 10:189–208. 12. Bennett J, Brown C. Use of herbal remedies by patients in a health maintenance organization. J Am Pharm Assoc. 2000;40:353–8. 13. Wagner P, Jester D, LeClair B, et al. Taking the edge off. Why patients choose St. John’s wort. J Fam Pract. 1999;48:615–9. 14. Brown J, Marcy S. The use of botanicals for health purposes by members of a prepaid health plan. Res Nurs Health. 1991;14:339–50. 15. Dole E, Rhyne R, Zeilmann C, et al. The influence of ethnicity on use of herbal remedies in elderly Hispanics and non-Hispanic whites. J Am Pharm Assoc. 2000;40:359–65. 16. Kassler W, Blanc P, Greenblatt R. The use of medicinal herbs by human immunodeficiency virus-infected patients. Arch Intern Med. 1991;151:2281–8. 17. Anderson D, Shane McWhorter L, Crouch B, Anderson S. Prevalence and patterns of alternative medication use in a university hospital outpatient clinic serving rheumatology and geriatric patients. Pharmacotherapy. 2000;20:958–66. 18. Dillman D. Mail and Telephone Surveys. New York, NY: John Wiley; 1978. 19. SAS Language and Procedures: Usage Version 6. Cary, NC: SAS Institute; 1999. 20. US Census Bureau. General Population Characteristics: Minnesota [publication online]. Available at: www.census.gov/prod/cen1990/ cp1/cp-1-25.pdf. Accessed June 12, 2003. 21. Foster S, Tyler V. Tyler’s Honest Herbal. New York, NY: Haworth Herbal Press; 1999. 22. Johns Cupp M. Herbal remedies: adverse effects and drug interactions. Am Fam Physician. 1999;59:1239. 23. Cirigliano M, Sun A. Advising patients about herbal therapies. JAMA. 1998;280:1565–6. 24. Corbin Winslow L, Kroll D. Herbs as medicine. Arch Intern Med. 1998;158:2192–9. 25. Fairfield K, Eisenberg D, Davis R, et al. Patterns of use, expenditures, and perceived efficacy of complementary and alternative therapies in HIV-infected patients. Arch Int Med. 1998;158:2257–64. 26. Dietary Supplements. U.S. Food and Drug Administration Center for Food Safety and Nutrition Web site. Available at: ww.cfsan.fda.gov/~dms/supplmnt.html. Accessed June 12, 2003.
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Results of a Population-Based Survey of Adults’ Attitudes and Beliefs About Herbal Products Lisa J. Harnack, Kim L. DeRosier, and Sarah A. Rydell
Objective: To assess attitudes and beliefs about herbal products held by adults in a large metropolitan area. Design: Descriptive study. Participants: Adults in the Minneapolis-St. Paul, Minn., metropolitan area were randomly selected from data tapes supplied by the Minnesota Department of Public Safety Driver and Vehicle Service Division. Intervention: Cross-sectional mailed survey. Main
Outcome Measures: Attitudes and beliefs were assessed via scaled responses to a series of statements about herbal products. Results: Most participants indicated an awareness of safety concerns with herbs, although a majority felt there was no harm in trying herbal products. Most agreed that it was a good idea to visit a physician before taking an herbal product and that one should inform his or her physician of any herbs being used. The majority of participants agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated.”
Conclusion: Although many participants acknowledged that use of herbal products poses risks, the perception persists that there is no harm in trying these products. Hence, education may be warranted to alert patients to clear safety concerns regarding herbal products. Our findings suggest that most adults know they should talk with their physician about their herb use, although other research suggests that many do not. Thus, obstacles to patients’ disclosure of herbal product use need to be identified and addressed to facilitate communication of this important information by patients to their health care providers.
Keywords: Dietary supplements, herbal products, attitudes, beliefs. J Am Pharm Assoc. 2003;43:596–601.
Sales of herbal products in the United States have increased dramatically in recent years. From the early 1990s through 1998, sales increased by approximately 25% annually.1 In 1999 sales of herbs exceeded $3.3 billion.2 Since 1998 sales have plateaued, although market analysts projected an average annual growth rate of 9.7% through 2004 for the herbal product market segment.2 In agreement with sales data, survey data indicate that herbal product use among Americans is sizable3-5 and growing.6 For example, in a 1997 survey of alternative medicine practices by adults in the United States, 12% of respondents reported using an
Received April 29, 2002, and in revised form May 13, 2003. Accepted for publication May 29, 2003. Lisa J. Harnack, DrPH, RD, is assistant professor; Kim L. DeRosier is research assistant; Sarah A. Rydell is research assistant, Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis. Correspondence: Lisa J. Harnack, DrPH, RD, Division of Epidemiology, School of Public Health, University of Minnesota, 1300 South 2nd Street, Suite 300, Minneapolis, MN 55454. Fax: 612-624-9328. E-mail: [email protected]. See related article on page 602.
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herbal product in the past 12 months, an increase of 380% over the prevalence of use of herbal remedies found in a 1992 survey that used the same sampling and interviewing methods.6 Because the safety and efficacy of many herbs used in the United States remain essentially unknown, the increasing use of these products is of concern. Some herbs (e.g., germander, comfrey, pennyroyal) have well-documented toxic effects.7 Because of the lack of standardization, herbal product content and efficacy varies among manufacturers. Contamination during manufacturing and misidentification of plant species are also concerns.8–10 Herb-drug interactions are possible, but the extent to which they occur remains unknown due to the limited amount of research.7–11 With the rising use of herbal products, pharmacists and other health care providers are increasingly confronted with the need to educate patients about the risks and benefits of their use. Unfortunately, much basic information that is critical to developing educational strategies is unavailable. More specifically, little is known about the general public’s attitudes and beliefs regarding herbal medicines. A small number of studies have examined attitudes and beliefs relating to herbal products,12–17 but the findings have been limited because of the use of selective populations and small sample sizes.
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Objective Our objective was to assess the attitudes and beliefs about herbal products held by adults in a large metropolitan area. Survey questions were designed to assess perceptions of the safety and efficacy of herbal products, beliefs about appropriate use, and the extent to which participants believe physicians should be informed of their patients’ use of herbal products.
Methods We mailed the survey to adults in the Minneapolis-St. Paul, Minn., metropolitan area between June 1999 and August 1999. To obtain a representative sample, we randomly selected 752 persons aged 18 years and older with ZIP codes in the Minneapolis-St. Paul metropolitan area from data tapes supplied by the Minnesota Department of Public Safety’s Driver and Vehicle Service Division. The survey mailing was conducted based on the Dillman method18: a first survey mailing, a reminder postcard, a second survey mailing, and a third survey mailing. As an incentive, we offered $10 to participants who returned the survey. The survey included a section designed to assess attitudes and beliefs about herbal products. In this section, participants were asked to indicate on a 4-point Likert scale how strongly they disagreed or agreed with a series of statements. Several statements assessed perceived safety and efficacy. In addition, statements were included to assess beliefs about appropriate use of herbal products, including the need to consult a physician before taking herbal products and the need to inform physicians of any herbal products being used. In the absence of an existing validated questionnaire to assess attitudes and beliefs about herbal products, the survey questions were developed by the research team. We pilottested the survey instrument for comprehension and readability with a convenience sample of 10 adults. We asked participants whether they had used any herbal product during the past 12 months. Herbal products were defined in the survey instrument as extracted preparations of parts of fruits, vegetables, trees, shrubs, grasses, fungals, and herbs. We told participants that we were only interested in their use and perceptions of herbal products that are taken orally (i.e., tablets, capsules, extracts, tinctures, teas). Frequency distributions and means were calculated using SAS version 6 (SAS Institute, Cary, N.C.).19 c2 tests were used to test for differences in attitudes and beliefs by age, sex, education, and herbal product use. Statistical significance for all tests was set at P £ .05.
Results Participants Of the initial sample of 752 individuals, 172 (23%) were ineligible because of change of address (n = 156) or death (n = 16). Of
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the 580 eligible individuals, 376 returned a completed survey, for a response rate of 65%. Table 1 shows survey participants’ demographic characteristics and population distribution data for the Minneapolis-St. Paul metropolitan area from the 1990 U.S. Census.20 The characteristics of the survey sample are similar to the population distribution data from the U.S. Census Bureau, although some differences are evident. Most notably, a higher proportion of survey participants were women, and a lower proportion had less than a high school education, compared with the overall Minneapolis-St. Paul area population.
Perceived Safety To assess perceived safety, participants were asked to indicate on a 4-point Likert scale how strongly they disagreed or agreed with a series of statements (see Table 2). When asked whether they agreed or disagreed that “some herbal products may have side effects or may interact with medications,” most (94%) strongly agreed or agreed. Similarly, most (94%) strongly agreed or agreed that “some herbal products can be dangerous, especially if taken in high doses,” and most (93%) strongly disagreed or disagreed with the statement “when using herbal products you don’t need to be concerned about overdosing or taking too much.” In contrast, a modest majority (61%) strongly agreed or agreed that “there’s no harm in trying herbal products.” When asked whether herbal products tend to be safer than over-the-counter (OTC) medications or medications prescribed by a physician, 42% disagreed and 44% agreed. Aside from the scaled response questions, participants were asked to indicate whether they thought that most, some, or few Table 1. Demographic Characteristics of Survey Participants (n = 376) Compared With the Minneapolis-St. Paul Metropolitan Area Population Aged 18 Years or Oldera
Characteristic
Survey Participants No. (%)
Metropolitan Area Population %
Age, years 18-24 25-44 45-64 ³ 65
47 164 121 44
(12.5) (43.7) (32.0) (11.7)
13.8 49.6 23.2 13.4
Sex Men Women
167 (44.4) 209 (55.6)
48.9 51.1
Education level Less than high school 15 (4.0) High school and some college 216 (57.4) College graduate or higher 140 (37.2)
12.8 b 60.0 b 27.1 b
Race/ethnicity White African American Other
92.1 3.6 4.2
a
339 (90.2) 12 (3.2) 19 (5.1)
Percentages may not total 100 because of rounding.
b Education information for persons aged 25 years and older.
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Table 2. Frequency of Attitudes and Beliefs About Herbal Products
Attitude/Belief
Strongly Disagree 1 No. (%)
Disagree 2 No. (%)
Agree 3 No. (%)
Strongly Agree 4 No. (%)
18 (4.9)
237 (63.9)
112 (30.2)
18 (4.9)
179 (48.6)
167 (45.4)
176 (47.4)
16 (4.3)
10 (2.7)
136 (36.9) 154 (41.6)
195 (52.8) 27 (44.3)
29 (7.9) 27 (7.2)
18 (5.0)
156 (43.5)
168 (46.8)
17 (4.7)
3 (0.8)
63 (17.1)
254 (69.0)
48 (13.0)
4 (1.1)
83 (22.4)
208 (56.2)
75 (20.3)
1 (0.3)
42 (11.4)
212 (57.3)
115 (31.3)
62 (17.0)
235 (64.4)
57 (15.6)
11 (3.0)
38 (10.4)
181 (49.7)
97 (26.6)
48 (13.2)
2 (0.6) 8 (2.2)
48 (13.2) 116 (32.6)
256 (70.5) 189 (53.1)
57 (15.7) 43 (12.1)
21 (5.8)
165 (45.8)
143 (39.7)
31 (8.6)
Perceived safety Some herbal products may have side effects or may interact 4 (1.1) with medications Some herbal products can be dangerous, especially if taken 4 (1.1) in high doses W hen using herbal products, you don’t need to be 169 (45.6) concerned about overdosing or taking too much There’s no harm in trying herbal products 9 (2.4) Herbal products tend to be safer than medications 25 (6.8) prescribed by a doctor or available over-the-counter Perceived efficacy There is a lot of scientific evidence to support the effectiveness of herbal products The use of herbs for health promotion and healing since ancient times provides support for the use of these products today Beliefs about appropriate use It’s a good idea to visit a physician before taking herbal products You should inform your physician of any herbal products you are taking Herbal products are only appropriate for treating minor conditions such as a cold or stomachache Herbal products should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure Other There is a lot of misinformation about herbs circulating Health claims on the labels of many herbal products are exaggerated or unsubstantiated Herbal products tend to be less expensive than prescription and over-the-counter medications
herbal products were safe. In response, 46% thought that most were safe, 52% felt that some were safe, and just 2% thought that few were safe.
Perceived Efficacy To assess perceived efficacy, participants were asked to indicate how strongly they agreed or disagreed that “there is a lot of scientific evidence to support the effectiveness of herbal products” and that “the use of herbs for health promotion and healing since ancient times provides support for the use of these products today” (Table 2). Responses to the former statement were closely divided, with 44% disagreeing and 47% agreeing. Most (82%) strongly agreed or agreed with the latter statement. Nine percent of respondents thought that most herbal products were effective, 82% felt that some were effective, and 7% thought that few were effective. Beliefs About Appropriate U se The survey included questions assessing attitudes and beliefs about the need to discuss herbal product use with a physician and
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the appropriateness of using herbs for treating minor and serious health conditions (Table 2). A majority of participants (77%) agreed or strongly agreed that it is “a good idea to visit a physician before taking herbal products,” and most (89%) agreed or strongly agreed that “you should inform your physician of any herbal products you are taking.” Most (81%) disagreed or strongly disagreed with the statement, “Herbal products are only appropriate for treating minor conditions such as a cold or stomachache.” A modest majority (60%) disagreed or strongly disagreed with the statement, “Herbal products should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure.”
O ther Attitudes and Beliefs In response to questions intended to assess participants’ perceptions regarding the quality of the information available on herbal products, most (86%) agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” (Table 2). Likewise, a modest majority (65%) agreed or strongly agreed that “health claims on the labels of many herbal products are exaggerated or
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Table 3. Comparison of Attitudes and Beliefs of Herbal Product Users and Nonusers Users
Perceived safety Herbal products tend to be safer than medications prescribed by a doctor or available over-the-counter Some herbal products can be dangerous, especially if taken in high doses There’s no harm in trying herbal products Some herbal products may have side effects or may interact with medications W hen using herbal products, you don’t need to be concerned about overdosing or taking too much Perceived efficacy There is a lot of scientific evidence to support the effectiveness of herbal products The use of herbs for health promotion and healing since ancient times provides support for the use of these products today Beliefs about appropriate use It’s a good idea to visit a physician before taking herbal products You should inform your physician of any herbal products you are taking Herbal medicines should not be used to treat serious health conditions such as heart disease, Alzheimer’s disease, or high blood pressure Use of herbs is only appropriate for treating minor conditions such as a cold or stomachache Other attitudes and beliefs There is a lot of misinformation about herbs circulating Health claims on the labels of many herbal products are exaggerated or unsubstantiated Herbal products tend to be less expensive than prescription and over-the-counter medications a P value for c 2
Strongly Disagree/ Disagree No. (%)
Strongly Agree/ Agree No. (%)
Strongly Disagree/ Disagree No. (%)
Pa
134 (58.5)
95 (41.5)
57 (40.4)
84 (59.6)
< .01
214 (93.9)
14 (6.1)
132 (94.3)
8 (5.7)
.88
148 (65.2) 213 (93.4)
79 (34.8) 15 (6.6)
76 (53.5) 136 (95.1)
66 (46.5) 7 (4.9)
.03 .50
15 (6.6)
213 (93.4)
11 (7.7)
132 (92.3)
.68
121 (54.5)
101 (45.5)
64 (46.7)
73 (53.3)
.15
201 (87.8)
28 (12.2)
101 (72.7)
38 (27.3)
< .01
155 (68.3)
72 (31.7)
128 (89.5)
15 (10.5)
< .01
198 (87.2)
29 (12.8)
129 (90.2)
14 (9.8)
72 (32.1)
152 (67.9)
73 (52.1)
67 (47.9)
< .01
30 (13.3)
196 (86.7)
38 (27.3)
101 (72.7)
< .01
198 (88.4)
26 (11.6)
115 (82.7)
24 (17.3)
.13
136 (62.4)
82 (37.6)
96 (69.6)
42 (30.4)
.17
107 (47.8)
117 (52.2)
67 (49.3)
60 (50.7)
.78
.38
tests conducted to compare responses of herbal product users and nonusers.
unsubstantiated.” When asked to indicate how strongly they disagreed or agreed with the statement, “Herbal products tend to be less expensive than over-the-counter medications,” 46% disagreed and 40% agreed.
Differences in Attitudes and B eliefs Results of c2 tests conducted to determine whether attitudes and beliefs about herbal products differed among herbal product users and herbal product nonusers are presented in Table 3. Those who reported using herbal products in the past 12 months (users) were significantly more likely than nonusers to strongly agree or agree that herbal products tend to be safer than medications prescribed by a physician or available OTC and that there is no harm in trying herbal products. In addition, users were significantly more likely to strongly agree or agree that “the use of herbs since ancient times provides support for use of these products today.” Users were sig-
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Nonusers
Strongly Agree/ Agree No. (%)
September/October 2003
nificantly less likely than nonusers to strongly agree or agree that it is a “good idea to visit a physician before taking herbal products.” Users were also significantly less likely to strongly agree or agree that herbs should not be used to treat serious health conditions. c2 tests were used to examine possible differences in attitudes and beliefs by age, sex, and education level (data not shown). Just one significant difference by age was found. Older individuals were more likely to agree that herbal products should not be used to treat serious health conditions (P = .01). With respect to sex, several significant differences were evident. Women were more likely than men to believe that herbal products may be dangerous, especially if taken in high doses (P = .02). Men were more likely to strongly agree or agree that the use of herbs since ancient times provides support for their use today (P = .04), that health claims on the labels of many herbal products are exaggerated or unsubstantiated (P = .03), and that herbal products tend to be less expensive than prescription and OTC medications (P = .01).
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Some differences in attitudes and beliefs in accord with education level were found. Participants with a higher education level (college of postgraduate degree) were more likely to strongly agree or agree that some herbal products may be dangerous, especially if taken in high doses (P < .01). Furthermore, this same group was more likely to believe that “there is a lot of misinformation about herbs circulating” (P = .02) and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated” (P = .01).
Discussion A variety of safety concerns surround the use of herbal products, including potential toxic effects, herb-drug interactions, and contamination during manufacturing. Most participants in our survey indicated an awareness of safety concerns; for example, a majority agreed or strongly agreed that some herbal products may have side effects or may interact with medications, and most strongly agreed or agreed that some herbal products can be dangerous, especially if taken in high doses. Yet, despite an awareness of safety concerns, a modest majority of participants felt that there was no harm in trying herbal products. When asked whether herbal products tend to be safer than OTC medications or medications prescribed by a physician, overall responses were dichotomous, with about 42% disagreeing and 44% agreeing. A different picture emerged, however, when analyses were stratified by herbal product use. Among users, a modest majority strongly agreed or agreed with this statement, whereas a minority of nonusers strongly agreed or agreed. In congruence with this finding, participants in a study of St. John’s wort reported believing that herbal medications were purer and safer than prescription medications.13 While scientific evidence exists to support the use of some herbs for some indications, sufficient evidence regarding efficacy is lacking for many herbs available in the marketplace.21 Our findings suggest that most adults recognize that not all herbs are effective. When asked to indicate whether they thought that most, some, or few herbal products were effective, the majority of participants indicated they thought that some were effective. A clear majority agreed or strongly agreed that use of herbs for health purposes since ancient times provides support for their use today, suggesting that scientific evidence may not be the only criterion applied by the public when considering the potential efficacy of an herb. Given the potential safety concerns with use of herbal products, including possible herb-drug interactions, medical guidance in the use of herbs has been recommended.13,15,16,22–24 We found that most survey respondents strongly agreed or agreed that a physician should be consulted before or while one is taking herbal products, although herbal product users were somewhat less likely to agree that such notification was necessary. The literature, however, indicates that many patients do not inform their health care providers of their herbal product use. For example, Bennett and Brown,12 in a
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survey of members of a health maintenance organization, found that the majority of users in their sample did not discuss their herb use with their physician (85.7%) or pharmacist (95.8%). Similarly, Wagner et al.13 found that only 30% of the St. John’s wort users in their sample discussed their use of this herb with their physician. Research is needed to better understand why many patients, including a significant proportion of those with serious health conditions such as HIV,25 do not discuss their use of herbs with their health care providers. Special consideration should be given to the role pharmacists can play in eliciting herb use through a medication history. Thought should be given to the implications of herb use information gathered from such an assessment; for example, do pharmacists have a role or duty to inform physicians if they learn that patients are taking an herbal product to treat a health condition? Among both users and nonusers in our sample, a majority agreed or strongly agreed that “there is a lot of misinformation about herbs circulating” and that “health claims on the labels of many herbal products are exaggerated or unsubstantiated.” These perceptions may reflect the U.S. marketplace, where herbal products, regulated under the 1994 Dietary Supplement and Health Education Act (DSHEA),26 may be marketed with no proof of efficacy. Although DSHEA requires that manufacturers not promise a specific cure on the supplement label, they may claim effect. Pharmacists can serve as sources of reliable information about the risks and benefits of using herbal products, although this necessitates that pharmacists stay up-to-date with information on the herbal products available in pharmacies.
Limitations Several limitations of our study should be noted. Our sample may not be representative of the total Minneapolis-St. Paul area population. Because the sample was selected from the Minnesota Department of Public Safety’s Driver and Vehicle Service Division data tapes, persons without a Minnesota driver’s license or Minnesota identification card were excluded. Also, the final sample did not include those whose address change had not been reported to the Driver’s License Bureau. With respect to the representativeness of the responses of the 65% of the sample that completed the survey, the demographic characteristics of the survey sample are similar to those of the area population found by the U.S. Census Bureau in 1990. However, compared with the proportions in the overall population, a higher proportion of the survey participants were women and a lower proportion had less than a high school education. Because some significant differences in attitudes and beliefs in accord with sex and education were found, the overrepresentation of women and higher-educated individuals in our sample may have affected the estimates of the overall frequency of various attitudes and beliefs. Because participants were adults residing in a metropolitan area in the Midwest with a predominately white population, strictly interpreted, our findings should be generalized only to similar populations.
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Although we pilot-tested the survey for comprehension and readability, the questions have not been validated, and thus may provide poor measures of the targeted attitudes, beliefs, and behaviors. Of special concern, the definition of “herbal products” provided to participants may have resulted in the reporting of herbs used for nonmedicinal purposes. For example, some participants could have understood “herbal tea” to be an herbal product under the definition provided. Consequently, the expansiveness of the definition provided could have led to overreporting of herb use. Also, participants were asked whether they had used an herb in the past 12 months, but information about frequency and duration of use was not assessed. Thus, survey respondents classified as users would include infrequent and irregular users. Finally, this survey was conducted almost 4 years before the results were published. Hence, current attitudes and beliefs about herbal products may differ from those described in this article.
Conclusion Our findings provide information that may be useful to pharmacists and other health care providers who are increasingly confronted with the need to educate patients about herbal products. Although many acknowledge that herb use may pose risks, the perception persists among patients that there is no harm in trying herbs. Hence, education may be warranted to alert patients to the clear safety concerns associated with some herbal products. Our findings suggest that most patients know they should talk with their physician about their herb use; however, other researchers’ findings suggest that many patients do not. Thus, obstacles to patients’ disclosure of their use of herbal products need to be identified and addressed to facilitate communication of this important information by patients to their health care providers. The authors declare no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, gifts, stock holdings, or honoraria. This research was supported by a grant from the Minnesota Medical Foundation.
References 1. Grauds C. Botanicals: strong medicine for health and profit. The Source.1997;3:1. 2. Popovich B. What is the cure for leveling botanical sales? Chem Market Rep. 2000;258:3–7.
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3. Roe B, Derby B, Levy A. Commission on Dietary Supplement Labeling. Demographic, Lifestyle and Information Use Characteristics of Dietary Supplement User Segments. Washington, DC: Division of Market Studies, Center for Food Safety and Applied Nutrition, Food and Drug Administration; 1997. 4. Frate D, Croom E, Juergens J. Self-treatment with herbal and other plant-derived remedies—rural Mississippi, 1993. MMWR Morb Mortal Wkly Rep. 1995;44:204–7. 5. Harnack L, Rydell S, Stang J. Prevalence of use of herbal products by adults in the Minneapolis/St Paul, Minn., metropolitan area. Mayo Clin Proc. 2001;76: 688–94. 6. Eisenberg D, Davis R, Ettner S, et al. Trends in alternative medicine use in the United States, 1990–1997. JAMA. 1998;280:1569–75. 7. Ernst E. Harmless herbs? A review of the recent literature. Am J Med. 1998;104:170–8. 8. Slifman N, Obermeyer W, Aloi B, et al. Contamination of botanical dietary supplements by Digitalis lanata. N Engl J Med. 1998;339:806–11. 9. Ko R. Adulterants in Asian patent medicine. N Engl J Med. 1998; 339:847. 10. Nortier J, Muniz Martinez M, Schmeiser H, et al. Urothelial carcinoma associated with the use of a Chinese herb. N Engl J Med. 2000; 342:1686–92. 11. D’Arcy P. Adverse reactions and interactions with herbal medicines. Part 1. Adverse reactions. Adv Drug React Toxicol Rev. 1991; 10:189–208. 12. Bennett J, Brown C. Use of herbal remedies by patients in a health maintenance organization. J Am Pharm Assoc. 2000;40:353–8. 13. Wagner P, Jester D, LeClair B, et al. Taking the edge off. Why patients choose St. John’s wort. J Fam Pract. 1999;48:615–9. 14. Brown J, Marcy S. The use of botanicals for health purposes by members of a prepaid health plan. Res Nurs Health. 1991;14:339–50. 15. Dole E, Rhyne R, Zeilmann C, et al. The influence of ethnicity on use of herbal remedies in elderly Hispanics and non-Hispanic whites. J Am Pharm Assoc. 2000;40:359–65. 16. Kassler W, Blanc P, Greenblatt R. The use of medicinal herbs by human immunodeficiency virus-infected patients. Arch Intern Med. 1991;151:2281–8. 17. Anderson D, Shane McWhorter L, Crouch B, Anderson S. Prevalence and patterns of alternative medication use in a university hospital outpatient clinic serving rheumatology and geriatric patients. Pharmacotherapy. 2000;20:958–66. 18. Dillman D. Mail and Telephone Surveys. New York, NY: John Wiley; 1978. 19. SAS Language and Procedures: Usage Version 6. Cary, NC: SAS Institute; 1999. 20. US Census Bureau. General Population Characteristics: Minnesota [publication online]. Available at: www.census.gov/prod/cen1990/ cp1/cp-1-25.pdf. Accessed June 12, 2003. 21. Foster S, Tyler V. Tyler’s Honest Herbal. New York, NY: Haworth Herbal Press; 1999. 22. Johns Cupp M. Herbal remedies: adverse effects and drug interactions. Am Fam Physician. 1999;59:1239. 23. Cirigliano M, Sun A. Advising patients about herbal therapies. JAMA. 1998;280:1565–6. 24. Corbin Winslow L, Kroll D. Herbs as medicine. Arch Intern Med. 1998;158:2192–9. 25. Fairfield K, Eisenberg D, Davis R, et al. Patterns of use, expenditures, and perceived efficacy of complementary and alternative therapies in HIV-infected patients. Arch Int Med. 1998;158:2257–64. 26. Dietary Supplements. U.S. Food and Drug Administration Center for Food Safety and Nutrition Web site. Available at: ww.cfsan.fda.gov/~dms/supplmnt.html. Accessed June 12, 2003.
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