Dietary Intakes of Nutrients Thought to Modify Cardiovascular Risk from Three Groups of American Indians: The Strong Heart Dietary Study, Phase II

RESEARCH Current Research

Continuing Education Questionnaire, page 1905 Meets Learning Need Codes 3000, 3020, 4000, and 5160

Dietary Intakes of Nutrients Thought to Modify Cardiovascular Risk from Three Groups of American Indians: The Strong Heart Dietary Study, Phase II JAMIE STANG, PhD, MPH, RD; ELLIE M. ZEPHIER, MPH, RD; MARY STORY, PhD, RD; JOHN H. HIMES, PhD, MPH; J. L. YEH, PhD; THOMAS WELTY, MD, MPH; BARBARA V. HOWARD, PhD

ABSTRACT Background Cardiovascular disease (CVD) is the leading cause of mortality among American Indians. Rates of CVD appear to be increasing among American Indians while they are decreasing among other racial and ethnic groups in the United States. Rates of comorbid conditions associated with CVD, such as obesity, impaired glucose tolerance, and hypertension, are also higher among American Indians than among other racial and ethnic groups in the United States. Dietary factors play a role in the development of CVD and associated comorbid conditions, yet surprisingly few data exist to describe the di-

J. Strang is a project director and continuing education specialist, Leadership Education and Training Program in Maternal and Child Health Nutrition, M. Story is a professor, Division of Epidemiology and Community Health, and an associate dean for academic and student affairs, and J. H. Himes is a professor, Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis. E. M. Zephier is chief, Nutrition and Dietetics Branch, Indian Health Service, Aberdeen Area Office, Aberdeen, SD. J. L. Yeh is an assistant professor, Center for Epidemiological Research, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City. T. Welty is a physician in private practice in Flagstaff, AZ. B. V. Howard is president, MedStar Research Institute, Hyattsville, MD. Address correspondence to: Jamie Stang, PhD, MPH, RD, Division of Epidemiology, University of Minnesota, 1300 S Second St, Suite 300, Minneapolis, MN 554541015. E-mail: [email protected] Copyright © 2005 by the American Dietetic Association. 0002-8223/05/10512-0004$30.00/0 doi: 10.1016/j.jada.2005.09.003

© 2005 by the American Dietetic Association

etary intakes and nutritional adequacy of American Indian adults at risk for CVD. Objective To describe intakes of nutrients that may affect CVD risk consumed by members of 13 nations of American Indian adults, aged 45 to 70 years, who reside in tribal communities in Arizona, North Dakota, South Dakota, and Oklahoma. A secondary objective was to compare dietary intake estimates to nationally representative data from adults of similar age to determine potential dietary differences that may account for the disparities seen in rates of CVD and related conditions. Finally, dietary intake estimates were compared with national dietary guidance to determine areas for improvement. Methods Data from a 24-hour dietary recall provided by 3,482 adults who participated in the Strong Heart Dietary Study, Phase II, were analyzed to describe dietary intakes of nutrients that may alter CVD risk. Nonparametric analyses of variance were used to compare data by center, age, and sex. Dietary intake data for each sex/ center group were compared with data from the Third National Health and Nutrition Examination Survey (NHANES III), Phase I, dietary estimates, and to national dietary guidelines. Results Nutrient intakes varied little between centers. Sex differences were noted in energy and nutrient intakes across all centers. Age-related decreases in energy and total and saturated fat intakes were noted among all sex/center groups. Median intakes of vitamins A and C and folate were low among all sex/center groups. Remarkably few differences in dietary intake were noted between NHANES III and Strong Heart Dietary Study, Phase II, participants. Carbohydrate and sodium intakes were higher among participants compared with NHANES III estimates, whereas intakes of several vitamins were lower. Conclusions Dietary intakes of American Indians vary by age, sex, and geographic location, but do not differ substantially from national estimates of dietary intake. The

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dietary differences noted between NHANES III and Strong Heart Dietary Study, Phase II, participants are not consistent with the remarkably different rates of CVD and associated comorbidities that currently exist. J Am Diet Assoc. 2005;105:1895-1903.

C

ardiovascular disease (CVD) is the leading cause of death among adults (1). Whereas CVD-related mortality rates have declined among the US adult population as a whole, they appear to be increasing among American Indians (2,3). Rates of CVD vary among groups of American Indians. Tribes residing in the Northern Plains experience higher rates of CVD than do tribes living in the Southwest, although rates of CVD among the latter group appear to be rising (4-6). Recent studies have demonstrated an increase in the prevalence of CVD risk factors within many American Indian communities (711), including impaired glucose tolerance (IGT), type 2 diabetes, dyslipidemia, and hypertension. The Strong Heart Study is a longitudinal study of CVD risk factors among three groups of American Indians aged 45 years and older from Arizona, North/South Dakota, and Oklahoma. Data collected during Phase II of the Strong Heart Study from 1993 to 1995 demonstrated that 20% of male and 22% of female participants had triglyceride levels that exceeded 2.26 mmol/L* and 8% of men and 13% of women had total cholesterol levels that exceeded 6.24 mmol/L† (11). Strong Heart Study, Phase II, data show that 45% of male participants had highdensity lipoprotein (HDL) cholesterol levels below 0.91 mmol/L and 35% had low-density lipoprotein (LDL) cholesterol levels that exceeded 3.38 mmol/L (11). The prevalence of suboptimal HDL levels was estimated at 41% and that of elevated LDL levels was estimated at 20% among National Health and Nutrition Examination Survey (NHANES) participants (12). Among female Strong Heart Study, Phase II, participants, the prevalence of dyslipidemia was about twice that of women in the general population; 27% of women in Strong Heart Study, Phase II, had low HDL cholesterol levels whereas 34% had high LDL cholesterol levels, compared with 15% and 17% of women in NHANES, respectively (11,12). Hypertension was present in 36% of Strong Heart Study, Phase II, participants compared with 28% of adults included in the NHANES III survey (11,13). The mean body mass index among male Strong Heart Study, Phase II, participants was calculated at 29.8 and the mean body mass index was 31.7 among female participants (11). Twenty-nine percent of women and 37% of men in Strong Heart Study, Phase II, were determined to be overweight, whereas 56% of women and 44% of men were found to be obese (11). The prevalence of obesity was

*To convert mmol/L triglyceride to mg/dL, multiply mmol/L by 88.6. To convert mg/dL triglyceride to mmol/L, multiply mg/dL by 0.0113. Triglyceride of 1.80 mmol/L⫽159 mg/dL. † To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.7. To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.026. Cholesterol of 5.00 mmol/L⫽193 mg/dL.

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estimated to be 27% among a representative sample of the US population during NHANES III, which occurred during the same time period as the Strong Heart Study, Phase II (14), suggesting that American Indian adults experience obesity at twice the prevalence of the US population. Almost half of the Strong Heart Study, Phase II, participants (48% of men and 61% of women) were found to have diabetes (11). These prevalence data are four to five times higher than national estimates of 12% for the general adult population at the time of the study (15). Rates of diabetes among Strong Heart Study, Phase II, sex/ center groups ranged from a low of 39% of men from North/South Dakota to a high of 78% of women from Arizona. An additional 14% of men and 16% of women in the Strong Heart Study, Phase II, were found to have IGT (11). Numerous dietary factors have been implicated in modifying risk factors of CVD. Excessive intakes of total and saturated fatty acids have been shown to elevate total and LDL cholesterol levels, and high intakes of refined carbohydrates and fats are known to increase triglyceride levels (16,17). Suboptimal dietary intakes of folate and vitamin B-6 have been shown to be inversely related to risk of CVD (18,19), and poor intakes of B vitamins along with B-12 can increase serum homocysteine levels, which in turn increases risk of CVD (20,21). Ample intakes of antioxidants such as beta carotene and vitamins A, C, and E can lessen the risk of CVD by reducing oxidative damage (22,23). Excessive intake of energy affects the development of obesity, which in turn increases the risks of IGT and type 2 diabetes, both risk factors for CVD. Obesity is also implicated in increasing risks of both hyperlipidemia and hypertension. Dietary intakes of American Indian populations have not been well documented. A review of dietary intake studies of populations of American Indians from the Midwest and Southwest found 15 published studies in the past decade, with a great deal of variation in sample size, age group, and nutrients studied (24-27). The few studies that focused specifically on nutrients related to CVD risk factors reported dietary intakes of cholesterol, sodium, and percent of energy from total and saturated fat above recommended levels and intakes of fiber below recommended levels (28,29). Few studies examined vitamin or mineral intakes of American Indian populations, so limited data are available on dietary intake of micronutrients that may moderate CVD risk factors among American Indians. The purpose of this study was to analyze nutrient intake data from a cohort of adult American Indian men and women participating in Phase II of the Strong Heart Dietary Study to describe the intake of nutrients thought to affect the risk of CVD and related comorbid conditions. In addition, a comparison of nutrient intake estimates to nationally representative data gathered at the same time as the Strong Heart Study, Phase II, was done to determine if differences in nutrient intake were consistent with differences in CVD risk factors. Finally, comparison of dietary intake among Strong Heart Study, Phase II, participants with national dietary guidance related to CVD risk was done to determine areas of dietary intake

that should be targeted by current and future CVD risk reduction programs for American Indian adults.

Table 1. Demographic characteristics of Strong Heart Dietary Study, Phase II, participants Characteristic

n

%

1,754 1,164 564

50 34 16

2,173 1,309

62 38

1,188 1,082 1,212

34 35 31

METHODOLOGY Subjects The Strong Heart Dietary Study, Phase II, was developed as part of the Strong Heart Study, Phase II, to examine intakes of dietary nutrients that contribute to CVD risk. During Phase I of the Strong Heart Study (1989-1991), 4,549 men and women aged 45 to 74 years who were members of 13 tribes of American Indians from Arizona (Akimel O’odham/PeePosh/Tohon O’odham of the Gila River, Salt River, and Ak-Chin Indian communities), North Dakota (Spirit Lake Sioux), Oklahoma (Apache, Caddo, Comanche, Delaware, Fort Sill Apache, Kiowa, and Wichita), and South Dakota (Oglala and Cheyenne River Sioux) and who resided in the tribal community participated in a study examining the prevalence of CVD risk factors. These risk factors included smoking status, weight status (ie, weight, body mass index, waist circumference, waist-to-hip ratio, and percent body fat), blood pressure, serum lipid levels (ie, total, LDL, and HDL cholesterol and triglycerides) and glucose tolerance and proteinuria (ie, IGT, diabetes, proteinuria, microalbuminuria, and macroalbuminuria). A randomly selected subsample of participants was invited to participate in the Strong Heart Dietary Study, which involved the collection of dietary data via a single 24-hour recall (28). Detailed descriptions of the selection criteria and methodology for both the Strong Heart Study and Strong Heart Dietary Study, Phase I, have been previously published (28,30). Phase II of the Strong Heart Study began 4 years later and included 3,638 (88%) of the surviving cohort members from Phase I (415 men and women from Phase I died before Phase II). All participants were invited to participate in the Strong Heart Dietary Study, Phase II. A participation rate of 96% resulted in 3,482 participants in the Strong Heart Dietary Study, Phase II.

hour recall interviews conducted by all staff with volunteers. When the supervisory dietitian had concerns about the data collection methods used by individual interviewers, follow-up practice interviews were conducted until dietary assessment techniques were consistent and satisfactory for all interviewers at all centers. Data from each 24-hour recall were recorded on standardized dietary assessment forms at each interview center. Data coding and entry were performed by a contract Indian Health Service data entry clerk who was trained in the use of the Nutrition Data System (Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN). When dietary intake data appeared incomplete or if questions about the 24-hour recall arose, data entry staff contacted the interviewer responsible for the specific recall for clarification. Indian Health Service dietitians performed random checks of data entry to ensure accuracy. This study was approved by Institutional Review Boards of the National Institutes of Health and the tribal councils of the American Indian nations that participated in this study.

Dietary Assessment Nutrient intakes of study participants were estimated from single interviewer-administered 24-hour recalls that were collected at Strong Heart clinics. Interviews were conducted by local field staff, who were trained and supervised by Indian Health Service dietitians. The week-long training included didactic information, practice interviews, and observation and critiquing of fellow interviewers. Each interviewer was supplied with dietary assessment aids to use during the study, including two- and three-dimensional models of foods commonly consumed by American Indian populations; marked bowls, cups, glasses, and spoons; and rulers, cardboard circles, and styrofoam shapes. A quality assessment checklist, utilized by supervising dietitians when monitoring interviewers, included the following items: explanation of the project, confidentiality and obtaining informed consent, completeness of probing during dietary assessment, portion size estimation, food preparation methods, and accuracy of recording data. To ensure consistency in interview techniques across all centers, the supervisory dietitian listened to recorded 24-

Data Analyses Only nutrients thought to play a significant role in altering risk of CVD, and for which adequate and reliable data on food composition were available, were entered into analyses, including energy (kilocalories); total and saturated fats; percentage of energy from total and saturated fats; carbohydrate; protein; sodium; dietary cholesterol; folate; and vitamins A, B-6, B-12, C, and E. Estimates of dietary intakes of beta carotene and n-3 and trans-fatty acids were not included in analyses due to the lack of complete, reliable data on nutrient composition of many of the foods consumed by Strong Heart Dietary Study, Phase II, participants at the time of this study. Data were analyzed using SAS (version 8.1, 2002, SAS Institute Inc, Cary, NC). Frequency data were used to describe characteristics of the study populations. Nonparametric analyses of variance were used to compare data by center, age category, and sex. Dietary intake estimates were compared with data collected from a cohort of similarly aged adults who participated in NHANES III, Phase I, which occurred about the same time as the Strong Heart Di-

Age (y) 45-54 55-64 ⱖ65 Sex Female Male Center Arizona North/South Dakota Oklahoma

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Table 2. Mean and median nutrient intakes of men from the Strong Heart Dietary Study, Phase II, (by center) and the Third National Health and Nutrition Examination Survey (NHANES III), Phase I Arizona (nⴝ391) b

Energy (kcal) Protein (g) Carbohydrate (g) Total fat (g) Saturated fat (g) Energy from total fat (%) Energy from saturated fat (%) Vitamin A (mg REd) Vitamin B-6 (mg) Vitamin B-12 (␮g) Vitamin C (mg) Vitamin E (mg) Folate (␮g) Cholesterol (mg) Sodium (mg)

Dakotas (nⴝ434)

Oklahoma (nⴝ484)

NHANES IIIa

MeanⴞSD

Median

MeanⴞSD

Median

MeanⴞSD

Median

Mean

Median

1,907⫾913 75⫾38 237⫾128 73⫾42 25⫾16 34⫾10 12⫾3 1,078⫾1,891 1.8⫾1.3 5.5⫾11.4 112⫾146 8.2⫾8.6 406⫾314 398⫾286 3,143⫾1,611

1,765 67 215 65 22 34 12 516 1.5 3.3 64 5.5 311 418 2,863

1,942⫾1,012 75⫾42 229⫾129 79⫾49 27⫾18 36⫾10 12⫾4 859⫾1,551 1.7⫾1.3 5.9⫾11.1 85⫾118 8.3⫾10.5 285⫾279 383⫾342 3,608⫾2,188

1,777 68 206 71 24 36 12 462 1.4 3.6 46 5.5 191 308 3,292

2,067⫾938 81⫾40 244⫾120 85⫾48 29⫾18 36⫾9 13⫾4 990⫾1,383 1.8⫾1.2 5.9⫾7.3 96⫾112 8.9⫾7.9 330⫾258 356⫾267 3,544⫾1,705

1,947 75 223 76 26 37 12 486 1.6 4.2 58 6.5 243 294 3,333

2,341 93 266 NAc NA 36 NA 1,085 2.1 5.8 114 11.3 318 322 3,640

2,221 88 246 NA NA NA NA 738 1.8 4.4 84 8.6 270 270 3,278

a

Data are from 50- to 59-year-old participants in NHANES III, Phase I, 1988-1991. SD⫽standard deviation. c NA⫽not available. d RE⫽retinol equivalent. b

etary Study, Phase II (31). Nutrient intake estimates were also compared with American Heart Association (AHA) dietary guidelines (32) and to the Dietary Reference Intakes (33-37) to determine compliance with national dietary guidance to reduce CVD risk factors. RESULTS Table 1 illustrates the demographic characteristics of Strong Heart Dietary Study, Phase II, participants. Half of the participants who provided dietary recall data in Strong Heart Dietary Study, Phase II, were younger than age 55 years and 16% were age 65 years or older. Sixtytwo percent of participants were women. Each of the study centers (Arizona, North/South Dakota, and Oklahoma) contributed approximately one third of the participants included in this study. Nutrient Intakes by Center and Age Group Mean and median intakes of nutrients among centers for each sex are shown in Tables 2 and 3. Nutrient intakes varied little between centers. Male participants from Oklahoma had somewhat higher intakes of energy, protein, and vitamins B-12 and E (P⬍.05) compared with men at other centers, while men from Arizona had higher intakes of cholesterol, folate, and vitamin C (P⬍.05). Women from Oklahoma reported higher intakes of vitamins A and E than those at other centers (P⬍.05). Sex differences were noted in nutrient intakes at all centers, with men consuming greater amounts of energy, total and saturated fats, carbohydrate, protein, folate, vitamin B-12, cholesterol, and sodium compared with women (P⬍.05 for all variables). Significant differences in nutrient intakes among par-

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ticipants were noted by age group (data not shown; all P⬍.05). Among women in Strong Heart Dietary Study, Phase II, intakes of total and saturated fat decreased with age at all centers (range 75 to 53 g and 25 to 19 g, respectively). Dietary intakes of carbohydrate (range 221 to 171 g), protein (range 73 to 54 g), cholesterol (range 309 to 225 mg), and sodium (range 3,052 to 2,449 mg) decreased with age among female participants from Arizona, whereas percentage of energy from fat decreased with age among women from North/South Dakota and Oklahoma (range 36% to 31%). Among male Strong Heart Dietary Study, Phase II, participants, total and saturated fat intakes decreased at all centers as age increased (range 95 to 52 g and 34 to 19 g, respectively). Protein and carbohydrate intakes decreased with age among men from North and South Dakota (86 to 63 g for protein; 278 to 172 g for carbohydrate), whereas sodium and carbohydrate intake decreased with age among Arizona men (3,348 to 2,671 mg for sodium; 277 to 205 g for carbohydrate). Nutrient Intakes of Strong Heart Dietary Study, Phase II, Participants Compared with NHANES III Participants Tables 2 and 3 compare nutrient intakes of Strong Heart Dietary Study, Phase II, participants to nutrient intake estimates of the general US population aged 50 to 59 years as obtained in NHANES III, Phase I. Mean and median energy and protein intakes among Strong Heart Dietary Study, Phase II, male participants were lower and median dietary cholesterol intakes higher than those reported in NHANES III, particularly among men from the Arizona and North/South Dakota centers (P⬍.05). Median intakes of all vitamins except folate were lower among men in Strong Heart Dietary Study, Phase II,

Table 3. Mean and median nutrient intakes of women from the Strong Heart Dietary Study, Phase II, (by center) and the Third National Health and Nutrition Examination Survey (NHANES III), Phase I Arizona (nⴝ797) b

Dakotas (nⴝ571)

Oklahoma (nⴝ728)

NHANES IIIa

Nutrient

MeanⴞSD

Median

MeanⴞSD

Median

MeanⴞSD

Median

Mean

Median

Energy (kcal) Protein (g) Carbohydrate (g) Total fat (g) Saturated fat (g) Energy from total fat (%) Energy from saturated fat (%) Vitamin A (mg REd) Vitamin B-6 (mg) Vitamin B-12 (␮g) Vitamin C (mg) Vitamin E (mg) Folate (␮g) Cholesterol (mg) Sodium (mg)

1,623⫾678 65⫾31 202⫾95 63⫾35 21⫾13 34⫾10 12⫾4 949⫾1,427 1.7⫾1.3 5.2⫾9.3 111⫾128 9.4⫾10.6 377⫾317 304⫾236 2,717⫾1,306

1,553 61 188 57 19 34 12 413 1.3 3.2 67 5.5 261 231 2,524

1,624⫾726 62⫾30 205⫾101 63⫾35 22⫾13 34⫾9 12⫾4 914⫾2,127 1.5⫾1.1 5.5⫾11.3 86⫾98 7.9⫾11.2 248⫾195 275⫾234 2,858⫾1,449

1,565 57 194 58 19 34 12 429 1.3 3.1 53 5.2 186 209 2,669

1,708⫾674 66⫾29 217⫾98 66⫾33 23⫾13 35⫾10 12⫾4 1,102⫾1,614 1.8⫾1.3 5.6⫾9.4 96⫾102 9.7⫾10.6 326⫾252 265⫾189 2,879⫾1,274

1,631 62 205 60 20 35 12 625 1.5 3.7 68 6.3 248 222 2,733

1,629 64 199 NAc NA 34 NA 938 1.5 4.3 93 7.5 239 222 2,575

1,545 59 187 NA NA NA NA 610 1.3 2.9 72 5.9 207 176 2,382

a

Data are from 50- to 59-year-old participants in NHANES III, Phase I, 1988-1991. SD⫽standard deviation. c NA⫽not available. d RE⫽retinol equivalent. b

than intakes reported by male subjects from NHANES III. Estimated median intake of folate among North/ South Dakota men was significantly lower than NHANES estimated intakes (P⬍.05) and was the lowest of the three Strong Heart Dietary Study, Phase II, centers. Few differences were noted when comparing nutrient intake estimates of women surveyed in Strong Heart Dietary Study, Phase II, with women surveyed in NHANES III. Mean vitamin A intakes among women from Arizona and North/South Dakota centers were lower than those reported among women in NHANES III. Intakes of vitamin B-12 and sodium were estimated to be higher among Strong Heart Dietary Study, Phase II, female participants than women interviewed in NHANES III. Folate intakes were higher among women from Arizona and Oklahoma but were lower among women from North/South Dakota compared with NHANES III estimates. Comparison of Strong Heart Study, Phase II, Results to National Dietary Guidance Mean nutrient intake estimates from the Strong Heart Study, Phase II, were compared with AHA dietary guidelines and the Dietary Reference Intakes to determine compliance with national dietary guidance aimed at reducing CVD and other chronic disease risk among the US population (Tables 4 and 5). Median dietary intake estimates among Strong Heart Study, Phase II, male participants demonstrated intakes of cholesterol, protein, percent of energy from total fat, and sodium in excess of national recommendations, whereas intakes of folate and vitamin C were below recommended intakes. Female Strong Heart Study, Phase II, participants reported intakes of cholesterol, protein, and sodium in excess of

national recommendations and intakes of vitamins A, C, and folate below recommended intakes. DISCUSSION The Strong Heart Dietary Study, Phase II, was undertaken to determine estimated nutrient intakes from a representative sample of American Indian adults aged 45 to 74 years to describe the nutrient intakes of this group of adults and to determine which dietary factors may be related to the increased risk of CVD seen in this population. There appeared to be remarkably little variation in nutrient intakes among the American Indian nations, despite great variations in traditional food habits, geographic location, and climate. The higher intakes of vitamin C and folate seen among Arizona participants may reflect the increased availability of citrus fruits that are commonly grown in that US region. Interestingly, American Indian tribes residing in the US Southwest have been shown to experience lower rates of CVD compared with those tribes living in the northern United States (4,5), supporting the idea that vitamins, particularly vitamin C and some B vitamins, may reduce the risk of CVD. Sex differences were noted in energy and nutrient intakes across all Strong Heart Dietary Study, Phase II, centers, reflecting the increased need for energy and nutrients among men. Age-related decreases in energy and total and saturated fat intakes were noted among all sex and center groups. This is similar to findings from the overall US population found in other surveys, like NHANES III. Comparison of dietary intake estimates from Strong Heart Dietary Study, Phase II, and NHANES III, Phase I, suggest that diets consumed by American Indian adults

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Table 4. Mean and median intakes of male participants in the Strong Heart Dietary Study, Phase II, compared with selected Dietary Reference Intakes (DRIs) (33-37) and American Heart Association (AHA) dietary guidelines (32) Arizona

Dakotas

Oklahoma

Nutrient

MeanⴞSDa

Median

MeanⴞSD

Median

MeanⴞSD

Median

AHA dietary guidelines

DRIs

Energy Energy from fat (%) Carbohydrate (g) Protein (g) Vitamin A (mg REc) Vitamin B-6 (mg) Vitamin B-12 (␮g) Vitamin C (mg) Vitamin E (mg) Folate (␮g) Dietary cholesterol (mg) Sodium (mg)

1,907⫾913 34⫾10 237⫾128 75⫾38 1,078⫾1,891 1.8⫾1.3 5.5⫾11.4 112⫾146 8.2⫾8.6 406⫾314 398⫾286 3,143⫾1,611

1,765 34 215 67 516 1.5 3.3 64 5.5 311 418 2,863

1,942⫾1,012 36⫾10 229⫾129 75⫾42 859⫾1,551 1.7⫾1.3 5.9⫾11.1 85⫾118 8.3⫾10.5 285⫾279 383⫾342 3,608⫾2,188

1,777 36 206 68 462 1.4 3.6 46 5.5 191 308 3,292

2,067⫾938 36⫾9 244⫾120 81⫾40 990⫾1,383 1.8⫾1.2 5.9⫾7.3 96⫾112 8.9⫾7.9 330⫾258 356⫾267 3,544⫾1,705

1,947 37 223 75 486 1.6 4.2 58 6.5 243 294 3,333

NAb 25-35 NA 50-100 NA NA NA NA NA NA ⬍300 ⬍2,400

3,067 NA 130 56 900 1.7 2.4 90 15 400 NA 1,200-1,500

a

SD⫽standard deviation. NA⫽not available. c RE⫽retinol equivalent. b

Table 5. Mean and median intakes of female participants in the Strong Heart Dietary Study, Phase II, compared with selected Dietary Reference Intakes (DRIs) (33-37) and American Heart Association (AHA) dietary guidelines (32) Arizona

Dakotas

Oklahoma

Nutrient

MeanⴞSDa

Median

MeanⴞSD

Median

MeanⴞSD

Median

AHA dietary guidelines

DRIs

Energy Energy from fat (%) Carbohydrate (g) Protein (g) Vitamin A (mg REc) Vitamin B-6 (mg) Vitamin B-12 (␮g) Vitamin C (mg) Vitamin E (mg) Folate (␮g) Dietary cholesterol (mg) Sodium (mg)

1,623⫾678 34⫾10 202⫾95 65⫾31 949⫾1,427 1.7⫾1.3 5.2⫾9.3 111⫾128 9.4⫾10.6 377⫾317 304⫾236 2,717⫾1,306

1,553 34 188 61 413 1.3 3.2 67 5.5 261 231 2,524

1,624⫾726 34⫾9 205⫾101 62⫾30 914⫾2,127 1.5⫾1.1 5.5⫾11.3 86⫾98 7.9⫾11.2 248⫾195 275⫾234 2,858⫾1,449

1,565 34 194 57 429 1.3 3.1 53 5.2 186 209 2,669

1,708⫾674 35⫾10 217⫾98 66⫾29 1,102⫾1,614 1.8⫾1.3 5.6⫾9.4 96⫾102 9.7⫾10.6 326⫾252 265⫾189 2,879⫾1,274

1,631 35 205 62 625 1.5 3.7 68 6.3 248 222 2,733

NAb 25-35 NA 50-100 NA NA NA NA NA NA ⬍300 ⬍2,400

2,403 NA 130 46 700 1.3-1.5 2.4 75 15 400 NA 1,200-1,500

a

SD⫽standard deviation. NA⫽not applicable. c RE⫽retinol equivalent. b

living on tribal reservations do not differ greatly from those consumed by the general population, despite documented disparities in CVD risk factors and associated comorbidities (2-14). Estimates collected from Strong Heart Dietary Study, Phase II, men show that mean and median intakes of several vitamins (vitamins A, B-6, and E) were lower than those collected during NHANES III. Because optimal intake of these nutrients is thought to reduce CVD risk, these findings are consistent with the increased incidence of CVD noted among American Indian adults. However, energy intake among male Strong Heart Dietary Study, Phase II, participants was lower than that reported by a similar age cohort in NHANES III, Phase I, yet rates of obesity were significantly higher among Strong Heart Dietary Study, Phase II, partici-

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pants (11,14). These findings are not consistent with the increased incidence of CVD and related comorbid conditions found among American Indian adult men. Female Strong Heart Dietary Study, Phase II, participants reported similar mean but lower median intakes of vitamins A and C and folate compared with women of similar age surveyed in NHANES III, Phase I, which may help to partly explain the higher rates of CVD experienced by American Indian women. Energy intakes were similar among women surveyed in both surveys, yet rates of obesity among women in Strong Heart Dietary Study, Phase II, were more than twice as high (11,14). These findings are not consistent with the increased incidence of CVD and related comorbid conditions found among American Indian adult women.

When mean and median intakes of nutrients were compared to Dietary Reference Intake and AHA dietary guidelines to determine if dietary intake estimates among Strong Heart Dietary Study, Phase II, participants were consistent with national dietary guidance to reduce CVD risk factors, it was noted that mean dietary intakes of participants at all centers exceeded recommended intakes for carbohydrate, sodium, and protein. Mean estimates of percent of energy from fat exceeded AHA recommendations among male participants from two of the Strong Heart Dietary Study, Phase II, centers, and were at the top of the recommended range of intake for all other sex/center groups. Median and mean dietary cholesterol intakes of Strong Heart Dietary Study, Phase II, men, but not women, were higher than recommended among almost all centers. Median and mean intakes of vitamins A and C and folate were lower than national recommendations among all centers, suggesting a low intake of fruits, vegetables, and fortified whole grains. Similar findings were reported among previous studies of American Indian nations. Harnack and colleagues (38) reported poor quality of fruits and vegetables available on Lakota Indian reservations, seasonal variations in fresh produce, and expense as reasons that make consumption of more fruits and vegetables difficult.

American Indians experience higher rates of CVD and related risk factors than the US population as a whole. One limitation of our study is the fact that nutrient intake estimates were derived from a single 24-hour recall. Multiple 24-hour recalls would have provided better estimates of intake, but would have also increased participant burden, which in turn may have decreased participation in this study. Another limitation of this study is that data on intake of some dietary constituents known to modify CVD risk, such as trans fats and n-3 fatty acids, were not complete for many of the foods consumed by Strong Heart Dietary Study, Phase II, participants, thus reliable estimates for these components were not available for inclusion in analyses. It should also be noted that data in our study were collected before increased fortification of grain products with folic acid; thus, current dietary intakes of folate may be somewhat higher than are estimated here. The strengths of our study include the large number of American Indian participants (n⫽3,482) who represented 13 tribes from varied geographic locations across the United States. Dietary intake data were collected by interviewers who were carefully trained by the principal investigator to collect 24-hour recall data using two- and three-dimensional dietary assessment aids. In addition, field staff members were familiar with local food customs and were able to prompt participants when needed to collect reliable food intake estimates.

CONCLUSIONS American Indians experience higher rates of CVD and related risk factors than the US population as a whole. Dietary habits play a significant role in modifying CVD risk. Data from our study suggest that dietary intake of nutrients related to CVD risk does not differ greatly between American Indians and the overall US population of adults as determined in NHANES III, Phase I, and do not account for the disparities in rates of CVD and related comorbid conditions currently seen. However, dietary intake estimates of several vitamins known to modify CVD risk were below national recommendations and intake estimates of several macronutrients and dietary cholesterol were higher than recommended among many Strong Heart Dietary Study, Phase II, participants, suggesting that further education related to diet and CVD risk is needed. Several recommendations for nutrition education and counseling are implied by the findings of this study. These include: ●

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The prevalence of CVD and related comorbidities among Strong Heart Dietary Study, Phase II, participants suggests a need for increased awareness of CVD risk factors among adult American Indians. Social marketing campaigns or other public education programs, focusing on diet and physical activity as a means to reduce CVD risk factors, should be developed and distributed to tribal communities. Nutrition education and counseling related to increasing dietary intake of B vitamins and antioxidants among adult American Indians should be incorporated into routine health care visits. Counseling should focus on increasing intakes of fruit, vegetables, and whole grains to improve dietary compliance with national nutrition guidelines. The incorporation of traditional food sources of these nutrients should be emphasized.

The authors thank the tribes that participated and the Indian Health Service facilities that serve those tribes for their assistance and cooperation. The authors also thank the study participants, the directors of Strong Heart Study clinics (Betty Jarvis, Martha Stoddart, Beverly Price, Marcia O’Leary, and Tauqeer Ali, PhD) and their staff members, and the Strong Heart Investigators for their input into the design and implementation of the study and for review of the manuscript. The opinions expressed in this article are those of the authors and not necessarily those of the Indian Health Service. This study was supported by cooperative agreements U01-HL41642, U01-HL41652, and U01-HL41654 from the National Heart, Lung, and Blood Institute. Support was also provided by the Maternal and Child Health Bureau, Health Resources and Services Administration, US Department of Health and Human Services, and US Public Health Service (grant No. 6T79M000007-16-1). References 1. Minino AM, Arias E, Kochanek KD, Murphy SL, Smith BL. Deaths: Final data for 2000. Natl Vital Stat Rep. 2002;50:1-119. 2. Sytkowski PA, Kannel WB, D’Agostino RB. Changes

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