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Agricultural potentials
PREVENTIVE
MEDICINE
8,
596-599
(1%‘)
Agricultural D. Human Nutrition
MARK
Potentials’ HEGSTED
Center, U.S. Department of Agriculture,
Washington, D.C. 20250
In discussing the relationship between agriculture and food production and dietary recommendations and objectives, it is important that we recognize that at least three criteria must be used in developing the dietary recommendations. Appropriate dietary recommendations must provide the essential nutrientsprotein, vitamins, and minerals-that people require; they must also deal with the limitation in intake of fat, cholesterol, or other materials that is desirable; and, third, they must be reasonable recommendations-reasonable in terms of what Americans now eat and what one might expect them to eat. Precise definitions are not available for any of these criteria and probably never will be. The pressures -both scientific and public-pull in opposite directions and compromises must be reached. Definitions of the nutrient needs of the populations that have been widely accepted in this country are the Recommended Dietary Allowances (RDA’s) of the Food and Nutrition Board. In defining recommended intakes of nutrients, the primary concern is that we do not unnecessarily limit the intake of anyone in the population to less than the amount needed for optimal health. The assumption must be made that individuals within the population vary in their nutrient needs. Some individuals require more of a given nutrient than others even though they appear to be grossly similar in terms of age, sex, activity, etc., in the same way that individuals consuming the same diet have different serum cholesterol levels. Thus, recommended nutrient intakes will inevitably tend to be on the high side and greater than the defined average nutrient need. The average need of most nutrients is not well defined and, indeed, not really well defined for any nutrientand the range of requirements is even less well evident. The philosophical position that, given the current state of knowledge, it is better to be on the high side in making such recommendations appears to be unassailable, but this leads us into two obvious difficulties. It leads, more or less, to a “more-is-better” attitude which we all deny but we see no way to be safe and not be on the side of generosity rather than restriction. A more difficult practical problem is now becoming evident, however. Recent data on the food consumption of Americans from the Health and Nutrition Examination Survey (HANES) demonstrate the rather low energy intakes of most Americans. I have plotted on Fig. 1 the recommended calorie intakes from the Food and Nutrition Board as well as the average calorie consumption levels of the various age and sex groups taken from the HANES data. These estimates of energy intakes are obtained from 24-hr recalls of rather large numbers of individuals in each ’ Presented at the American Health Foundation Conference on the Health Effects of Blood Lipids: Optimal Distributions for Populations, New York, N.Y., April 12, 1979. 596 0091-7435/79/050596-04$02.00/O Copyright All rights
@ 1979 by Academic Press, Inc. of reproduction in any form reserved.
CONFERENCE:
1,000
HEALTH
EFFECTS OF BLOOD
LIPIDS
597
t 0
m
40
60
80
@hrn
FIG. 1. A comparison of the RDAs for energy (calories) and the median energy intake recorded for various age and sex groups in the Health and Nutrition Examination Survey.
group. It is understood that a 24-hr recall is of no value in defining the dietary pattern of an individual, but the average value for any group is presumably as well defined by this technique as any other available. What is obvious is that even though everyone recognizes obesity as a significant health problem in nearly all age and sex groups of Americans, the estimated average energy intake is substantially below recommended levels. Although we know that there are poor people in the country who have limited financial capacity to buy food, relatively few people are starving or seriously undernourished as far as energy intake is concerned. That is to say, the low mean value is not due to large groups who are starving, which counterbalances groups that are adequately fed or overfed. Indeed, there is essentially no evidence that those who are obese consume more food than those who are not obese. The average American is simply a rather sedentary individual who consumes relatively small amounts of food while at the same time struggling to keep his weight down. This is the population we must be concerned about. We cannot recommend that the average American consume more food. I place considerable emphasis upon this because our most recent calculations (and unfortunately they are not sufficiently complete for me to present the actual values) tell us that at the actual food consumption levels defined by HANES data, the national food supply will not provide the RDAs of a number of the essential nutrients. This is particularly true of women and elderly persons whose total food intake falls so far below what many people believed to be usual levels of intake. Restriction of fat and sugar consumption will improve the nutrient composition of the ordinary American diet; but for a number of nutrients, the intake by women and the elderly will still fall below the RDAs. This is a point of substantial concern to groups like the USDA and others who have a legal and moral obligation, for example, to provide nutritious diets in feeding programs of various kinds-in institutional feeding and dietary instructions to the general population. It is one thing, of course, to conclude that a proportion of the U.S. population-either large or small-is consuming a diet inadequate in essential nutrients. It is quite another thing to conclude that practically the entire female and elderly population is not receiving the essential nutrients in adequate amounts and that which is or has been generally perceived as a well-balanced diet is inadequate in essential nutrients.
598
D.
MARK
HEGSTED
I have emphasized the role RDAs play, and have played, in the development of nutrition policy because we believe there is now abundant evidence that sensible instruction to the American public in general, and primarily in relation to chronic disease, is well advised to restrict the consumption of fat and cholesterol, of sugar and salt, to modify the composition of the dietary fat, and to increase the consumption of fruits, vegetables, and grain products. The development of plans to accomplish these general aims must be made with due consideration of the provision of essential nutrients as well as desirable or optimal levels of fat, sugar, etc., but judgment must also be utilized in distinguishing between optimal and achievable if these do not agree. By achievable I do not mean diets that a nutritionist can concoct-I mean diets that a rather sizable proportion of the American public is likely to accept. Many groups have produced ad hoc judgments on what kind of diet this will actually be. Most have assumed that these kinds of diets can only be achieved by a substantial reduction in consumption of meat and products in the United States. That is simply not true. Indeed, our preliminary calculations indicate to us that with a shift toward lean cuts of meat and low-fat dairy products, a relatively low-fat diet providing no more than 30% of calories as fat and no more than 300 mg of cholesterol per day can be achieved without a reduction in consumption of either of these two major items in the diet. Indeed, if we attempt to achieve the RDAs for calcium, for iron, for vitamin B-6 and zinc, and perhaps for some other nutrients, it may be necessary to recommend increased consumption of lean meat and low-fat dairy products. This, of course, raises additional nutritional considerations. The protein consumption of Americans is now very high-much above recommended levels. Some data or opinion suggest that this very high protein consumption may not be advantageous. High levels of fat consumption have no known nutritional merit. Fat is expensive to produce in terms of energy inputs. It dilutes the diet, lowering its nutrient content. It has its disadvantages in terms of cardiovascular disease, obesity, and probably other diseases. The primary issue then becomes what is a reasonable level of fat to shoot for in the American diet. Many off-the-cuff judgments have been made. It has been claimed that a diet with less than 35% of the calories as fat is unpalatable and unacceptable. I know actual studies which demonstrate this to be true. Indeed, it is probable that the average fat consumption of Americans is now less than that often stated-40 to 45% of the calories eaten. These levels are those available in the food supply but we know that a substantial amount of the fat purchased is not actually consumed. When adequate data are available (and the results of the National Food Consumption Survey which are now being compiled should provide probably the best data) we will have a better estimate of what Americans actually eat. Although the extent of change that has occurred in the national diet is not known with any accuracy, we do know that many Americans have modified both the amount and kind of fat in their diet in recent years. There is one aspect of education that is rarely emphasized. It is relatively easy to recommend dietary change but it should be entirely clear that the acceptance of such recommendations depends largely upon the acceptability of the alternatives available. If the consumption of a product or material is to be limited, something must replace it in the diet. The willingness of the American public to choose
CONFERENCE:
HEALTH
EFFECTS
OF
BLOOD
LIPIDS
599
satisfactory alternatives is self-evident in the acceptance of modified margarines, low-fat milk products, and the like. The commercial opportunities are obvious. Marked shifts have already occurred toward production of leaner pork and beef by breeding and productive methods. Given the increased pressure on the world food supply, the energy costs of production, and the health advantages of low-fat products, we can confidently expect further improvements in the development of lower-fat, yet acceptable, meat products. If Americans are to consume more fruits, vegetables, and other plant products, there would appear to be an obvious need to consider the availability of such products. Of the vegetables and fruits available in the world, the U.S. population is acquainted with, and has available, relatively few. Increased emphasis is needed to expand the varieties, to educate consumers on methods of preparation, and to get the fruits into the marketplace at more reasonable cost, etc. Vegetables to most people mean corn, peas, green beans, spinach, cabbage, lettuce, and tomatoes. Other than citrus and bananas almost none of the wide variety of tropical fruits find their way into American markets. There must be substantial commercial opportunities in expanding the range of produce available. Many Americans find the level of bread and cereal consumption that occurs in many other countries to be unusually high but-obviously-rather high consumption levels are reasonable and acceptable to many people. High levels of bread consumption, as a replacement for high-fat, more expensive products, will not be achieved, however, unless good bread is available. By good I am not talking about nutritious. The ordinary white bread available to Americans is as nutritious or more nutritious than that available in most countries but it is not as “good” as that available in many other places. I find it difficult to believe that there are not substantial opportunities to improve both the image and market, consonant with improved nutrition practice. “‘A loaf of bread, a flask of wine, and thou beside me. . . . .’ as long as the flask is small and we add some cheese or meat, low fat dairy products, and plentiful amounts of fruits and vegetables” is not a bad dietary prescription.
MEDICINE
8,
596-599
(1%‘)
Agricultural D. Human Nutrition
MARK
Potentials’ HEGSTED
Center, U.S. Department of Agriculture,
Washington, D.C. 20250
In discussing the relationship between agriculture and food production and dietary recommendations and objectives, it is important that we recognize that at least three criteria must be used in developing the dietary recommendations. Appropriate dietary recommendations must provide the essential nutrientsprotein, vitamins, and minerals-that people require; they must also deal with the limitation in intake of fat, cholesterol, or other materials that is desirable; and, third, they must be reasonable recommendations-reasonable in terms of what Americans now eat and what one might expect them to eat. Precise definitions are not available for any of these criteria and probably never will be. The pressures -both scientific and public-pull in opposite directions and compromises must be reached. Definitions of the nutrient needs of the populations that have been widely accepted in this country are the Recommended Dietary Allowances (RDA’s) of the Food and Nutrition Board. In defining recommended intakes of nutrients, the primary concern is that we do not unnecessarily limit the intake of anyone in the population to less than the amount needed for optimal health. The assumption must be made that individuals within the population vary in their nutrient needs. Some individuals require more of a given nutrient than others even though they appear to be grossly similar in terms of age, sex, activity, etc., in the same way that individuals consuming the same diet have different serum cholesterol levels. Thus, recommended nutrient intakes will inevitably tend to be on the high side and greater than the defined average nutrient need. The average need of most nutrients is not well defined and, indeed, not really well defined for any nutrientand the range of requirements is even less well evident. The philosophical position that, given the current state of knowledge, it is better to be on the high side in making such recommendations appears to be unassailable, but this leads us into two obvious difficulties. It leads, more or less, to a “more-is-better” attitude which we all deny but we see no way to be safe and not be on the side of generosity rather than restriction. A more difficult practical problem is now becoming evident, however. Recent data on the food consumption of Americans from the Health and Nutrition Examination Survey (HANES) demonstrate the rather low energy intakes of most Americans. I have plotted on Fig. 1 the recommended calorie intakes from the Food and Nutrition Board as well as the average calorie consumption levels of the various age and sex groups taken from the HANES data. These estimates of energy intakes are obtained from 24-hr recalls of rather large numbers of individuals in each ’ Presented at the American Health Foundation Conference on the Health Effects of Blood Lipids: Optimal Distributions for Populations, New York, N.Y., April 12, 1979. 596 0091-7435/79/050596-04$02.00/O Copyright All rights
@ 1979 by Academic Press, Inc. of reproduction in any form reserved.
CONFERENCE:
1,000
HEALTH
EFFECTS OF BLOOD
LIPIDS
597
t 0
m
40
60
80
@hrn
FIG. 1. A comparison of the RDAs for energy (calories) and the median energy intake recorded for various age and sex groups in the Health and Nutrition Examination Survey.
group. It is understood that a 24-hr recall is of no value in defining the dietary pattern of an individual, but the average value for any group is presumably as well defined by this technique as any other available. What is obvious is that even though everyone recognizes obesity as a significant health problem in nearly all age and sex groups of Americans, the estimated average energy intake is substantially below recommended levels. Although we know that there are poor people in the country who have limited financial capacity to buy food, relatively few people are starving or seriously undernourished as far as energy intake is concerned. That is to say, the low mean value is not due to large groups who are starving, which counterbalances groups that are adequately fed or overfed. Indeed, there is essentially no evidence that those who are obese consume more food than those who are not obese. The average American is simply a rather sedentary individual who consumes relatively small amounts of food while at the same time struggling to keep his weight down. This is the population we must be concerned about. We cannot recommend that the average American consume more food. I place considerable emphasis upon this because our most recent calculations (and unfortunately they are not sufficiently complete for me to present the actual values) tell us that at the actual food consumption levels defined by HANES data, the national food supply will not provide the RDAs of a number of the essential nutrients. This is particularly true of women and elderly persons whose total food intake falls so far below what many people believed to be usual levels of intake. Restriction of fat and sugar consumption will improve the nutrient composition of the ordinary American diet; but for a number of nutrients, the intake by women and the elderly will still fall below the RDAs. This is a point of substantial concern to groups like the USDA and others who have a legal and moral obligation, for example, to provide nutritious diets in feeding programs of various kinds-in institutional feeding and dietary instructions to the general population. It is one thing, of course, to conclude that a proportion of the U.S. population-either large or small-is consuming a diet inadequate in essential nutrients. It is quite another thing to conclude that practically the entire female and elderly population is not receiving the essential nutrients in adequate amounts and that which is or has been generally perceived as a well-balanced diet is inadequate in essential nutrients.
598
D.
MARK
HEGSTED
I have emphasized the role RDAs play, and have played, in the development of nutrition policy because we believe there is now abundant evidence that sensible instruction to the American public in general, and primarily in relation to chronic disease, is well advised to restrict the consumption of fat and cholesterol, of sugar and salt, to modify the composition of the dietary fat, and to increase the consumption of fruits, vegetables, and grain products. The development of plans to accomplish these general aims must be made with due consideration of the provision of essential nutrients as well as desirable or optimal levels of fat, sugar, etc., but judgment must also be utilized in distinguishing between optimal and achievable if these do not agree. By achievable I do not mean diets that a nutritionist can concoct-I mean diets that a rather sizable proportion of the American public is likely to accept. Many groups have produced ad hoc judgments on what kind of diet this will actually be. Most have assumed that these kinds of diets can only be achieved by a substantial reduction in consumption of meat and products in the United States. That is simply not true. Indeed, our preliminary calculations indicate to us that with a shift toward lean cuts of meat and low-fat dairy products, a relatively low-fat diet providing no more than 30% of calories as fat and no more than 300 mg of cholesterol per day can be achieved without a reduction in consumption of either of these two major items in the diet. Indeed, if we attempt to achieve the RDAs for calcium, for iron, for vitamin B-6 and zinc, and perhaps for some other nutrients, it may be necessary to recommend increased consumption of lean meat and low-fat dairy products. This, of course, raises additional nutritional considerations. The protein consumption of Americans is now very high-much above recommended levels. Some data or opinion suggest that this very high protein consumption may not be advantageous. High levels of fat consumption have no known nutritional merit. Fat is expensive to produce in terms of energy inputs. It dilutes the diet, lowering its nutrient content. It has its disadvantages in terms of cardiovascular disease, obesity, and probably other diseases. The primary issue then becomes what is a reasonable level of fat to shoot for in the American diet. Many off-the-cuff judgments have been made. It has been claimed that a diet with less than 35% of the calories as fat is unpalatable and unacceptable. I know actual studies which demonstrate this to be true. Indeed, it is probable that the average fat consumption of Americans is now less than that often stated-40 to 45% of the calories eaten. These levels are those available in the food supply but we know that a substantial amount of the fat purchased is not actually consumed. When adequate data are available (and the results of the National Food Consumption Survey which are now being compiled should provide probably the best data) we will have a better estimate of what Americans actually eat. Although the extent of change that has occurred in the national diet is not known with any accuracy, we do know that many Americans have modified both the amount and kind of fat in their diet in recent years. There is one aspect of education that is rarely emphasized. It is relatively easy to recommend dietary change but it should be entirely clear that the acceptance of such recommendations depends largely upon the acceptability of the alternatives available. If the consumption of a product or material is to be limited, something must replace it in the diet. The willingness of the American public to choose
CONFERENCE:
HEALTH
EFFECTS
OF
BLOOD
LIPIDS
599
satisfactory alternatives is self-evident in the acceptance of modified margarines, low-fat milk products, and the like. The commercial opportunities are obvious. Marked shifts have already occurred toward production of leaner pork and beef by breeding and productive methods. Given the increased pressure on the world food supply, the energy costs of production, and the health advantages of low-fat products, we can confidently expect further improvements in the development of lower-fat, yet acceptable, meat products. If Americans are to consume more fruits, vegetables, and other plant products, there would appear to be an obvious need to consider the availability of such products. Of the vegetables and fruits available in the world, the U.S. population is acquainted with, and has available, relatively few. Increased emphasis is needed to expand the varieties, to educate consumers on methods of preparation, and to get the fruits into the marketplace at more reasonable cost, etc. Vegetables to most people mean corn, peas, green beans, spinach, cabbage, lettuce, and tomatoes. Other than citrus and bananas almost none of the wide variety of tropical fruits find their way into American markets. There must be substantial commercial opportunities in expanding the range of produce available. Many Americans find the level of bread and cereal consumption that occurs in many other countries to be unusually high but-obviously-rather high consumption levels are reasonable and acceptable to many people. High levels of bread consumption, as a replacement for high-fat, more expensive products, will not be achieved, however, unless good bread is available. By good I am not talking about nutritious. The ordinary white bread available to Americans is as nutritious or more nutritious than that available in most countries but it is not as “good” as that available in many other places. I find it difficult to believe that there are not substantial opportunities to improve both the image and market, consonant with improved nutrition practice. “‘A loaf of bread, a flask of wine, and thou beside me. . . . .’ as long as the flask is small and we add some cheese or meat, low fat dairy products, and plentiful amounts of fruits and vegetables” is not a bad dietary prescription.