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a Bradfield Hall, Dep. of Crop and Soil Sci., Cornell Univ., Ithaca, NY 14853
b Div. of Nutritional Sci., Cornell Univ., Ithaca, NY 14853
* Corresponding author (cjp20{at}cornell.edu).
Received for publication January 11, 2003.
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ABSTRACT |
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 TOPNOTES ABSTRACT INTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Abbreviations: ERS, economic research service • RDA, recommended daily allowance
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INTRODUCTION |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Today, the interrelationship of diet, health, and agriculture is a matter of both national and international concern. At the national level, the growing body of research on the relationship between diet and incidence of chronic disease has initiated interest in how agriculture would need to change to support more healthful diets. Internationally, the incidence of micronutrient malnutrition, or hidden hunger, has sparked thinking about the purpose of agriculture for meeting a broad range of nutritional needs rather than simply supplying adequate food energy. Both perspectives represent a shift in thinking of agriculture as a producer of food commodities to agriculture as a provider of nutritious diets. Concomitant with this shift in thinking is a renewed need to examine how agricultural resources are allocated.
The body of research addressing this issue is still in a nascent stage. Agriculture relies on a host of resources (skilled farmers, land, labor, capital, energy, research, crops, livestock, etc.); all of which may need to be redirected to provide more nutritious diets. One key question for agronomists is how can the allocation of cropland be modified such that improvements in the nutritional quality of agricultural production can be integrated with improvements in agroecological sustainability. No universally agreed method exists for estimating how land should be allocated to meet nutritional needs. However, the work conducted to date suggests that food guides, like the USDA Food Pyramid, cannot only serve as a tool for nutrition education, but can also provide a basis for assessing the nutritional adequacy of the food supply. Our goal is to review these issues; we will not address the aspects of agricultural policy that follow from these considerations.
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RELATIONSHIP AMONG DIET, HEALTH, AND AGRICULTURE |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Toward this end, the USDA and the U.S. Department of Health and Human Services jointly published Dietary Guidelines for Americans (Table 1) in 1980 to help Americans plan more healthful diets (Cronin et al., 1987). These guidelines have been updated every 5 yr, and in 1992, the USDA Food Guide Pyramid (hereafter referred to as the Pyramid) was released to provide Americans with an easy-to-follow reference for putting the Dietary Guidelines into practice (Davis and Saltos, 1999). Unfortunately, recent research by Tippett and Cleveland (1999) and by McNamara et al. (1999) shows that diets of Americans fall short of meeting the Pyramid recommendations for the basic food groups (grains, vegetables, fruits, dairy products, and protein sources) and exceed suggested limits for fat and added sugars. Consistent with these findings, the U.S. food supply data shows insufficient availability of whole grains, green leafy vegetables, fruits, and dairy products for all Americans to be able to meet the Pyramid recommendations (Kantor, 1998; Putnam et al., 2000). Conversely, fats and sugars are available in excess (Kantor, 1998; Putnam et al., 2000).
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Nutritional Issues at the International Level
Obesity and chronic diseases related to overnutrition are problems worldwide, particularly in other developed nations but also among the more affluent populations of the developing world. However, in spite of the prevalence of diseases of excess, many countries continue to struggle with diseases of nutritional deficiency. More than 800 million people worldwide do not get adequate calories (Foster and Leathers, 1999), and approximately two billion are deficient in one or more micronutrients (Graham and Welch, 2000).
Chronic undernutrition increases risk of other threats to health. Inadequate intake of food energy, over time, can depress the ability of the immune system to resist disease and is responsible for increased morbidity and mortality among the underfed, particularly young children (Foster and Leathers, 1999). Prolonged deficiency of calories also reduces a person's ability to learn and perform work, and as a result, it can effectively trap a person in poverty (Dasgupta, 1998; Foster and Leathers, 1999). Micronutrient malnutrition can be similarly debilitating. Deficiencies of four nutrients (Fe, I, vitamin A, and Zn) are believed to be the most widespread and can hamper early brain development, weaken the immune system, increase both mortality and morbidity, and reduce one's capacity to work (Combs et al., 1996; Welch and Graham, 1999; Graham and Welch, 2000). As with chronic undernutrition, such deficiencies generally promote a cycle of poverty (Welch and Graham, 1999; Graham and Welch, 2000).
Both forms of malnutrition are confounding problems, and their causes are complex. They involve many (if not all) of the factors implicated in the dietary problems of the USA (i.e., food price, nutritional knowledge, and agricultural policy), but the balance of these factors is different. As Kiess et al. (2001) explain, all food security problems are the products of three determinants—food availability, food access (affordability), and food choices—but the importance of each factor varies over time and location. Whereas food choice is a critical factor in the USA, where food is generally abundant and affordable, food access and availability are more important in areas where food is relatively expensive or in short supply. In this context, it is easy to understand the widespread agreement that poverty is a primary cause of chronic undernutrition and micronutrient malnutrition (Hulse, 1995; Foster and Leathers, 1999). Indeed, the relationship between hunger and poverty is so strong that, as Haddad et al. (1997) point out, some consider agriculture as irrelevant to the solution of the hunger problem. However, agriculture has a critical role to play in alleviating both types of nutritional deficiency.
First of all, though global per capita food availability improved over the latter half of the 20th century, the food supplies of many countries still lack sufficient calories to adequately feed all their people (Haddad et al., 1997). In addition, many believe that food-based approaches that improve the diversity of the food supply are essential to the long-term reduction and prevention of micronutrient malnutrition as supplement and fortification programs cannot be sustained indefinitely (Combs et al., 1996; Ali and Tsou, 1997; Welch and Graham, 1999; Amoaful, 2001). Finally, such food-based solutions stand to improve household incomes and help alleviate poverty (Kiess et al., 2001), thus doubly linking agriculture to health, both as a supplier of food and provider of livelihood.
Implications for Agriculture
Adequate food supplies (both in terms of calories and micronutrients) are a necessary precondition for proper nutrition and good health. Whether in the USA or abroad, the key for agriculture is to improve the nutritional quality of the food available without hampering food access or food choice. How then is agriculture to respond to these discrepancies between food supply and health?
While Abbott (1999) contends that gaps in the U.S. food supply for fruit, vegetable, and dairy products will increasingly be met with imported production, research from the USDA–ERS suggests the need for changes in cropland allocation. The ERS economists Young and Kantor (1999) estimate that if all members of the current U.S. population were to eat according to the Pyramid recommendations, total planted cropland area would increase slightly [by 2.3 million hectares (5.6 million acres)], but major adjustments in the allocation of land would need to take place for certain crops. To provide foods in proportion to Pyramid recommendations, the amount of land devoted to fruits, green leafy vegetables, and dry legumes would need to increase sharply while the amount of land devoted to oil and sugar crops would decline markedly (Young and Kantor, 1999). Because of the concentration of production, they predict that such adjustments could have significant regional impacts. Indeed, Duxbury and Welch (1999) suggest that meeting the dietary guidelines will require some geographic shifts in production, proposing that states in the eastern USA could play a greater role in providing an increased number of vegetables and fruits. Rethinking land use appears to be a key strategy for realizing agriculture's role in improving the diets of Americans.
A similar line of reasoning can be found in the research surrounding micronutrient malnutrition. Welch and Graham (1999) claim that a new paradigm is needed for agriculture. They argue that while the production paradigm helped world agriculture to provide adequate calories and while the sustainability paradigm has addressed many of agriculture's environmental problems, there is a need to view agriculture as a producer of balanced nutrition. In part, this role of agriculture can be addressed by increasing the nutrient content of individual foods (through breeding more nutrient-rich plants and micronutrient fertilization of crops) (Combs et al., 1996; Welch and Graham, 1999; Graham and Welch, 2000). However, it is widely believed that alleviation of micronutrient deficiencies will require increased production of fruits, vegetables, and animal products to provide adequate diversity in the diet (Combs et al., 1996; Ali and Tsou, 1997; Welch and Graham, 1999). McIntyre et al. (2001) offer strong evidence in favor of this approach in their recent article on a cropping systems model in Uganda. Their work shows that it is possible to improve the nutritional output of cropping systems in two regions of Uganda simply by modifying the amount of land allotted to each crop. A strategy capable of improving nutrition in the absence of increased yields or increased land clearly warrants consideration as an avenue for improving health.
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METHODS FOR ASSESSING THE ADEQUACY OF FOOD PRODUCTION |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Calories as a Yardstick for Nutritional Adequacy
Although energy is but one of many nutritional requirements provided by food, it is common for calories to serve as the sole parameter for measuring the adequacy of food supplies in discussions of agricultural production. Indeed, Foster and Leathers (1999) claim that measuring the availability of calories using food balance sheets is likely the most common method for measuring malnutrition. As Alexandratos (1999)(p. 5908) states, "Progress is measured in terms of the per person availability of food products for direct human consumption as a national average in each country, expressed in kcal/day" [emphasis added].
Several papers on the growth of world food supplies from a recent colloquium of the National Academy of Sciences exemplify this common trend. Alexandratos (1999), for example, discusses the medium and long-term future of food and agriculture in terms of the per capita availability of calories. Similarly, Dyson (1999) and Johnson (1999) confine their respective discussions of world food trends and world food demand to the major cereal crops. Furthermore, Cassman (1999) focuses on the need for ecologically sound intensification of cereal production systems.
Some analyses employ a broader definition of food. For example, the Pinstrup-Andersen et al. (2000) treatment of world food prospects expands the definition of food to include meat products, but their discussion of agriculture revolves around food and feed grains. Similarly, Guilland (2002) defines food need in terms of calories and animal protein in his assessment of the ability of food production to keep pace with population over the next 50 yr. The inclusion of meat products in the discussion of world food supplies is most relevant in light of the projected surge in demand for animal products in the developing world and the added pressure such demand places on agriculture. However, it does not expand the concept of nutritional adequacy in the food supply. Rather, animal products are chiefly viewed as a more coveted source of energy than grains.
The priority given to calories and cereal crops has some validity. Adequate energy intake is arguably the most important nutritional requirement after adequate water, and cereal crops provide the majority of calories in the human diet. Furthermore, the data needed to perform such analyses is readily available via the United Nations Food and Agriculture Organization (FAO) or the agricultural ministries of individual countries. However, the concomitance of chronic diseases among the world's affluent populations and micronutrient deficiency among the world's poorer populations testifies to the need to consider overall nutrition in discussing the future of national and global food supplies.
Moreover, it appears that overemphasis of the importance of calories comes at the expense of overall diet quality. Combs et al. (1996) claim that the Green Revolution spurred micronutrient deficiencies as the thrust to improve cereal production resulted in the decline of dietary diversity. Welch and Graham (1999) confirm this trend, noting that iron deficiency anemia in south Asia is positively associated with increases in caloric output. The fact that per capita availability of pulses (often rich in Fe) has decreased in the region since the 1960s (Young et al., 1998) and that growth in production of cereals in south Asia has been four times that of legumes (Graham and Welch, 2000) only strengthens the argument. A more holistic approach to gauging adequacy of food supplies would, hopefully, permit agriculture to more effectively contribute to alleviating the problems of nutrition.
Judging Nutritional Adequacy of Production with a Complete Diet Approach
At present, no generally accepted method exists for assessing the adequacy of food supplies and food production using this broader definition of nutrition. One approach is to increase the number of parameters included in the analysis such that major nutrient deficiency problems are accounted for. McIntyre et al. (2001), for example, examined the nutritional adequacy of the diet in two regions of Uganda based on the ability of the local cropping systems to provide energy, protein, vitamin A, Ca, Fe, and Zn in amounts that are consistent with human nutrient requirements. While this approach is expedient, it does not account for all nutrients nor does it account for the dietary issues associated with chronic disease. However, the USDA–ERS assessment of the U.S. food supply and U.S. agriculture in light of the Food Pyramid recommendations provides a method that addresses this larger picture.
Kantor (1998) calculated the number of servings of each food group that are available per capita in the U.S. food supply. In general, a disadvantage of using food supply data to assess nutritional adequacy is that it tends to overstate the actual amount of food available because it includes the weights of inedible portions (e.g., peels, cores, and tough stems) and of food that will spoil or otherwise be lost in the distribution system (Putnam and Allshouse, 1999). However, Kantor (1998) accounted for inedible portions and for distribution and consumer losses to estimate the amount that could be consumed from the food supply. This loss-adjusted measure was calculated for all 250 commodities tracked in the ERS data set and was converted to Food Pyramid servings using standard serving weights. Kantor's (1998) work thus provides a valuable method for estimating the nutritional adequacy of the food supply in terms of the Pyramid recommendations.
Young and Kantor (1999) connect Kantor's (1998) findings to agriculture by predicting the maximum adjustments in domestic crop acreage that would be necessary if all Americans were to eat according to the Food Pyramid. They perform this calculation by estimating the changes needed in the food supply and then determining the requisite changes in land use based on the current planted acreage and probable changes in imports and exports. Though their analysis is not intended to be exhaustive, it illuminates the need for large changes in certain agricultural sectors (such as fruit production) if all Americans are to be able to follow the nation's dietary recommendations. Furthermore, this work supports thinking of agriculture in terms of the Pyramid, and it provides some baseline estimates of what one should expect to find in calculating the amount of land needed to produce a diet consistent with these nutritional guidelines. This of course raises the question, "How well does the Food Pyramid represent a healthful diet?"
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THE FOOD PYRAMID AS A STANDARD OF NUTRITIONAL ADEQUACY |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Validity of Using the Food Pyramid to Link Nutrition and Agriculture
The Food Pyramid was released in 1992 to provide a quantitative interpretation of the Dietary Guidelines for Americans (Shaw et al., 1996). It established consumption targets for five major food groups—grains, vegetables, fruits, dairy, and protein-rich foods (meat, poultry, fish, eggs, dry legumes, and nuts)—and suggested consumption limits for fats and sugars (Fig. 1)
. These consumption targets and limits are intended both to guide people to eat diets that reduce their risk of developing chronic diseases and to satisfy requirements for essential nutrients. The efficacy of these recommendations for reducing chronic disease are up for debate, but sample diets show that compliance with the Pyramid servings recommendations usually results in satisfying (or exceeding) the recommended daily allowances (RDAs) for vitamins, minerals, and macronutrients (Cronin et al., 1987).
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The food-based approach employed by the Food Pyramid is quite versatile. Indeed, the recommendations are generic enough that they can be readily adapted to suit cultural preferences or individual values. Haddad et al. (1999), for example, discuss a conceptual framework for a vegetarian version of the Pyramid that would assist the various groups of vegetarians (ovo-lacto, lacto, and vegan) in eating according to Pyramid principles. Similarly, Willett et al. (1995) show that ethnic diets can be consistent with the recommendations by outlining a Mediterranean food pyramid. Furthermore, Wilkins and Bokaer-Smith (1996) offer a Northeast Regional Food Guide for people who wish to eat a diet based on locally grown foods. Finally, Russell et al. (1999) offer some modifications to reflect the smaller appetites and nutritional needs of older individuals on a food pyramid for the healthy and elderly (70 yr and older). Though in all cases, these researchers suggested modifications of certain food groups, they maintain the framework of the Pyramid and speak to the versatility of this concept as a dietary guidance tool.
Critiques of the Food Pyramid
Though the Food Pyramid has many strengths, there are at least two major points of contention of using it to guide food choices. One is the argument that politics has corrupted the nutritional messages. The other is that the Pyramid recommendations are not suitable for reducing chronic disease risk because they allow for excessive consumption of animal products and refined carbohydrates while demonizing all fat. If the Pyramid is used to determine how agriculture should change to provide better nutrition, it is essential to know where such weaknesses lie.
The issue of political influence has implications for the value of the Food Pyramid as a nutrition education tool and for the likelihood of establishing accurate dietary advice through a government agency. However, this topic cannot be discussed in adequate detail here. Nestle (2002) and Sims (1998) provide detailed accounts of the politics involved in the release of the Food Pyramid and the writing of the Dietary Guidelines. Based on their analyses, the political influence of USDA's constituents in the food and agriculture industry has weakened and confused the language used in the Dietary Guidelines and generally undermined the effectiveness of the Pyramid as a nutrition education tool. The clarity of nutritional messages is important for linking nutrition to agriculture in that it affects the rate at which consumers demand healthier foods. However, for the purpose of understanding what agriculture needs to produce to provide good nutrition, the accuracy of the Pyramid's message is of greater relevance.
With regard to the amount of animal products allowed in a Pyramid diet, one point of contention is the recommendation for the dairy food group. The primary reason for having a separate dairy group is that dairy products are rich in Ca and thus are supposed to promote the development of strong bones and prevent bone fractures. Unfortunately, approximately 25% of Americans lose their ability to produce lactase after weaning and experience negative digestive symptoms (gas, bloating, and other complaints) when they consume milk (Bertron et al., 1999). Since dairy products are not the only foods rich in Ca, Bertron et al. (1999) contend that a discrete recommendation for dairy products is not consistent with good health for those who cannot digest lactose.
In addition, while positive Ca balance is necessary during the ages when bone is growing (Kushi et al., 1995a), the role of Ca in preventing osteoporitic fractures remains dubious. Rates of bone fractures in populations with Ca intakes well below the U.S. recommendation of 800 mg/d are often far lower than fracture rates in populations that consume a western diet (Kushi et al., 1995a; Bertron et al., 1999; Anderson and Sjoberg, 2001; Hegsted, 2001). This apparent paradox is not completely understood, but it is clear that Ca intake is not the only important variable in bone health. If providing Ca is the primary rationale for the existence of the dairy group, then the necessity of a separate food group appears questionable.
Another point of contention is the degree to which meat is emphasized as a protein source. The food group for protein-rich foods is commonly referred to as the "meat, poultry, fish, dry beans, eggs, and nuts" group (Kantor, 1998; Young and Kantor, 1999) or simply as the "meat" group (Tippett and Cleveland, 1999; McNamara et al., 1999). Though this nomenclature reflects the cultural preference of Americans for animal sources of protein, there are substantial reasons to take issue with the consideration of meats as the predominant source of protein-rich food.
To begin, regular meat consumption is generally associated with a higher risk of coronary heart disease (Kushi et al., 1995b). This association is mostly attributed to the cholesterol and saturated fatty acids found in red meat though research suggests that the high concentrations of heme iron may also play a role (Kushi et al., 1995b). To its credit, the Pyramid stresses that Americans should opt for leaner cuts of meat to reduce their risk of heart disease. However, Kushi et al. (1995a)(p. 1412S) note that the leftover fat from low-fat dairy products "is largely transferred in the form of surplus cheese or butter to the diets of schoolchildren or the poor, or to populations in other countries." Thus, high-fat meat products will likely find their way to another market and simply shift the dietary problem to another group of people.
The National Research Council (1989) suggests that average protein intake be limited to no more than two times the RDA on the basis that high intakes of protein can increase urinary Ca excretion and may contribute to osteoporosis. Sample diets used to test the nutritional adequacy of the food guide show that compliance with the serving recommendations results in protein intakes ranging from 138 to 254% of the RDA (Cronin et al., 1987). Though recent research suggests that high protein intake will not increase the rate of bone loss in the presence of ample Ca (Dawson-Hughes and Harris, 2002), the required levels of Ca intake are difficult (if not impossible) to achieve without supplements. Such evidence suggests that the Pyramid recommendations for protein can lead to overconsumption of animal products and may not be consistent with good nutrition.
A final point of contention with the Pyramid recommendations is the limit placed on fat consumption. Willett and Stampfer (2003) find fault with this recommendation, claiming that not all fats have the same effect on the risk of cardiovascular disease. Indeed, while saturated fats have the effect of raising LDL cholesterol (associated with increased risk), mono- and polyunsaturated fats actually reduce LDL cholesterol (associated with reduced risk) (Kushi et al., 1995b; Willett and Stampfer, 2003). Moreover, the advice to substitute fats with carbohydrates that is promoted by the Pyramid may actually lead to poorer health outcomes since high intake of refined carbohydrates is associated with increased risk of both cardiovascular disease and Type 2 diabetes (Willett and Stampfer, 2003). In this light, the placement of unsaturated fats (oils) at the top (use sparingly) of the Pyramid appears inappropriate, and oils may be given a more prominent position in future dietary advice.
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KEEPING SIGHT OF AGRICULTURAL SUSTAINABILITY |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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Diet and Agricultural Sustainability
No other dietary habit has raised more ire than has the tendency for the world's affluent to increase their consumption of meat and other animal products as incomes allow. The rapidly increasing consumption of animal products is a valid concern, yet animals are also an essential part of sustainable agricultural systems. As such, the place of animal products in a nutritious diet serves as an excellent example of the interplay between food consumption and sustainability.
Animals are essential to a sustainable agriculture. Among the most compelling reasons is that sustainable cropping systems require protective crops, such as perennial forages, that are only of food value if used as feed for milk- and meat-producing animals. Worldwide the area of pasture, grassland, and rangeland far exceeds the amount of land that is arable. Even in arable lands, forage crops are an integral part of cropping systems, credited with reducing soil erosion, disrupting pest cycles, improving soil quality, and (in the case of legumes) increasing soil fertility when they are present in crop rotations (Entz et al., 1995, 2002; Fick and Clark, 1998). Thus, production of milk and meat from forages clearly increases the total amount of food available to humans. Furthermore, Oltjen and Beckett (1996) display that even when some humanly edible grain is fed to ruminants, they can still provide more humanly edible protein or energy than they consume so long as their rations are based primarily from forage and byproduct feeds. However, the predominant trend has been to feed livestock (both ruminant and non-ruminant) rations that are more grain based in an effort to boost production and reduce costs.
Animal products can be part of a healthful diet. Though the excessive consumption of animal products is often implicated (and correctly so) in the incidence of chronic disease, increased consumption of animal products could improve health in populations suffering from micronutrient malnutrition. However, the research of Luyten et al. (1997) and Penning de Vries et al. (1997) demonstrates that not all countries have enough productive capacity to support an affluent diet. Their calculation of global food supply capacity demonstrates that certain regions (namely East Asia and South Asia) would not be able to provide their populations with more than a vegetarian diet without risking food security. The issue, therefore, is how much land (or other natural resources) can be allocated to animal agriculture without competing against the production of other foods needed in a balanced diet.
Such thinking applies equally to plant foods as well. Consider soybean [Glycine max (L.) Merr.], which currently occupies nearly 30 million hectares and accounts for 22% of the total area planted to principal crops in the USA (USDA Natl. Agric. Stat. Serv., 2002). The vast majority of this crop is pressed for oil, begging the question "Does oilseed soy outcompete more nutritious crops for land and agricultural resources?" In investigating the possible sustainability constraints posed by diet, perhaps oil crops must be scrutinized as carefully as animal feed.
The Importance of Scale
As has been argued throughout, linking nutrition and health to agriculture is an international imperative. Assessing land allocation will be important at all scales from the worldwide to the individual farm. Work done thus far highlights the importance of looking from different vantages because they illuminate different concerns.
In the United States, Young and Kantor's (1999) research shows that major shifts in U.S. agriculture would occur if Americans ate according to Food Pyramid recommendations, but the regional implications of these shifts are beyond its scope. Duxbury and Welch (1999) begin to address some of the regional issues, suggesting that the nation's major vegetable-producing states (California and Florida) may not have the water and land resources to support such vigorous growth in fruits and vegetables. They conclude that the Northeast and Midwest could play a much larger role in producing these foods, implying a need to reassess current land use in the eastern part of the country.
Internationally, a major concern related to the sustainability of food production is crop yields. It is widely believed that the rate of yield increases is slowing (Rosegrant and Ringler, 1997; Alexandratos, 1999; Ruttan, 1999). Reduced availability of water for agriculture, limits to the availability of N fertilizers (Rosegrant and Ringler, 1997; Alexandratos, 1999), and the difficulty of making further improvements in crop yield potential have all been implicated in slowing the growth of crop yields worldwide. Nonetheless, McIntyre et al. (2001) show that it would be possible to improve nutritional output at the household level in Uganda by modifying the cropping system, even in the absence of increased land or yields. Indeed, they concluded that the main constraints to change in the study region would be cultural acceptability and limited labor availability.
As the preceding examples demonstrate, one's perspective clearly affects what is seen as a constraint. In order for improvements in nutrition and agricultural sustainability to go hand in glove, it will be necessary to integrate the wisdom of many disciplines gathered from many vantage points.
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CONCLUSIONS |
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TOPNOTESABSTRACTINTRODUCTIONRELATIONSHIP AMONG DIET, HEALTH,...METHODS FOR ASSESSING THE...THE FOOD PYRAMID AS...KEEPING SIGHT OF AGRICULTURAL...CONCLUSIONSREFERENCES |
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The critiques of the Food Pyramid merit attention. Though the Pyramid generally represents an improvement from the current U.S. diet, it is still a work in progress, and its weaknesses must be acknowledged. The Pyramid can serve as a template for assessing the changes needed to improve the nutritional quality of the U.S. food supply, but we should keep in mind how recommendations are likely to change as the knowledge base linking diet and chronic disease grows. This approach can be adapted to other countries so long as the resource limits to agricultural production are incorporated. A nutritious diet that requires more land than is available will not assist nations in improving food security. Indeed, our concept of a good diet must incorporate both nutrition and agricultural sustainability.
Reassessing our production goals and our allocation of agricultural resources will be an important part of the strategy for helping agriculture to better provide for human nutritional needs. It is hard to envision it otherwise. Though the information is available to begin, agricultural research has yet to place much emphasis on this issue. The evidence summarized here suggests it is time that it should.
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