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Nutrition and agriculture
How nutrition priorities can be integrated into
crop improvement programmes
Improvement of the nutritional quality of sorghum and Pearl Millet
Progress in nutritional improvement of maize and triticale
The need for food utilization and processing studies to supplement nutritional evaluation
Interpretation of data on human food availability and nutrient consumption
How nutrition priorities can be integrated into crop improvement programmes
J.H. Hulse and O.E. Pearson
International Development Research Centre (IDRC), Ottawa, Ontario, Canada
Nutritional survey statistics are a constant reminder that the world food situation is serious, even precarious. By recent estimates,1 500 million people live on the edge of starvation and over twice that number would benefit from a more varied diet. The greatest majority of these people live in Asia, Southeast Asia, and sub-Saharan Africa. Clinical surveys and hospital records indicate that malnutrition wherever it exists is most severe among infants, pre-school children, and pregnant and lactating women; that it is most prevalent in depressed rural areas and the slums of large cities; and that the problem is lack of calories as much as lack of protein.
According to a recent report of the International Food Policy Research Institute (IFPRI),1 to provide the undernourished in the developing countries with 100 per cent of the caloric levels recommended by the 1971 Joint FAO/WHO Expert Ad Hoc Committee on Energy and Protein Requirements,2 would have required, in 1975, additional imports of 45 - 70 million tons of cereal equivalent, over and above the 31 million tons of cereal actually imported. Asia would have required some 60 per cent of these additional imports, sub-Saharan Africa 25 per cent, with lesser amounts (5 - 10 million tons) going to each of North Africa/Middle East, and Latin American regions. In order to balance indigenous production with projected demand by 1985, food production in the developing countries will have to increase by 4.2 per cent annually, or again by 5.5 per cent per annum if internal production is to bridge the caloric gap.3
The Problems of Protein and Dietary Energy
Estimates of the caloric gap based on global production and population statistics must be carefully interpreted, in that production figures are not always a true measure of food supplies available to meet human nutritional requirements. In the first place, available data assume total consumption of whole grain. However, most cereals and legumes are processed by dehulling, soaking, boiling, milling, and cooking, all of which result in significant nutrient losses. Second, it is known that many of the seeds of edible subsistence plants, including cereals and legumes, contain substances that seriously interfere with the nutritional quality of protein and other nutrients. Sorghum, for instance, which covers a world acreage larger than that planted with maize and is the primary subsistence crop of millions of the poorest people of the semi-arid tropics, contains tannins that reduce the digestibility of the cereal protein. Third, national averages are also misleading in that they take little account of the problem of maldistribution of food supplies among countries within regions, among families within a community, and even among members within a family. Finally, recommended daily nutrient standards used in the calculation of the calorie gap may not be suitable for assessing the adequacy of diets and national food supplies in developing countries.
The subject of nutrient requirements has fascinated physicians and nutritionists for over 100 years and continues to be the subject of much debate. The first comprehensive set of recommended allowances for 12 nutrients, including energy and protein, was produced by the Technical Commission on Nutrition of the League of Nations in 1938. The difficulties encountered in defining recommended dietary levels that describe an "optimum diet" cannot be overlooked. In setting nutritional requirements, it is necessary to decide on an average per capita requirement for a nutrient based on available information and then to set recommended daily allowances at levels intended to cover at least 95 per cent of the population. Adequate intake standards for energy and protein vary among different regions of the world, reflecting body size, climate, physical activity, differences in dietary protein quality, and other factors.
Since the mid-1950s, successive expert committees on energy and protein requirements from the Food and Agriculture Organization and the World Health Organization of the United Nations have convened to re-evaluate estimates of adequate energy and protein intakes for humans. In April 1971 the Joint FAD/WHO Expert Committee2 lowered the levels of dietary protein intake for protein malnutrition. Nutritionists working with the planning commissions of several developing countries suddenly found themselves preparing a vigorous attack on a problem that no longer existed as a priority issue.
Many nutritionists, economists, and planners concluded, from comparison with per capita dietary intakes, that emphasis on protein could now be dropped or at least greatly reduced in the formulation of agricultural, educational, health, and economic policies, and in overall nutrition planning. The lowering of the protein requirement led to the conclusion that, except in areas where roots and tubers are major dietary components, protein levels are adequate if caloric needs are met. According to Scrimshaw,4 however, there is increasing evidence that these revised recommended levels for protein may be too low.
Infants and preschool children and pregnant and lactating women are the primary target groups of nutrition intervention programmes. I n response to the statement that protein-calorie malnutrition can be prevented by increasing the quantity of the traditional diet consumed by children, Scrimshaw replies that it is useless to suggest that a child can obtain sufficient protein and calories from a cereal diet if he merely eats more of it, when he is unable to do so. The traditional diets in developing countries are frequently bulky, and young children do not have the capacity to ingest the large quantities that would be necessary to satisfy their full nutrient requirements. Furthermore, according to the PAG,5 dietary protein needs of the very young in developing countries are increased not only by the poorer absorption of dietary protein caused by intestinal parasites and chronic damage to the gastrointestinal tract from repeated infections but also by the extra protein lost from the body during the acute infections so commonly experienced by these children. This loss is induced by the stress response, which causes amino acids to be mobilized from the protein in the lean body tissues for use by the liver in making glucose. The need for dietary calories may also be increased by impaired intestinal absorption and by fever, but the stress response is specific for protein. Moreover, whereas a deficit in calories may be compensated in part by reduced activity, the body has no comparable mechanism for protein deficiency. Scrimshaw concludes: "There is no doubt that good nutrition requires a balanced complement of protein and calories, and neither can be neglected in the diets of the underprivileged and vulnerable. To the extent that the pendulum swung too far in emphasizing protein in the 1960s, and too far in emphasizing calories in the 1970s it must come to a more appropriate intermediate position for the 1980s and beyond."6
Significance of Cereal Grains and Legumes in Nutrition
Among the food crops of the world, cereal grains contribute more than any other single group of food staples to both calories and protein in the human diet. In its major document on world agricultural development plans,7 the FAO stated that cereals-particularly wheat, rice, maize, sorghum, millet, and barley-provided more than 50 per cent of calories and protein for the people of the Sahelian region, more than 60 per cent of calories and protein for the people of Asia, and more than 65 per cent of calories and protein for the Near East. In Central America, maize provided 57 per cent of the daily intake of calories and 45 per cent of the daily protein for the adult population.
Dietary surveys indicate that the diet of the majority of the population in developing countries is based on a cereal grain and food legume combination. In Southeast Asia soybeans and mung beans supplement the rice staple; in Africa cowpeas and pigeon peas supplement sorghum and millets; and in Latin America maize and beans are a familiar dietary combination.
Nutritionally, cereals and legumes are complementary. Whereas most common varieties of cereal grains are deficient in certain essential amino acids (primarily lysine) and are relatively good sources of sulfur-containing amino acids, legume grains contain twice as much protein as do the cereal grains and are a rich source of lysine, although relatively low in total sulfur-containing amino acids. The optimum nutritional combination is provided by a diet composed of roughly 65 per cent cereal and 35 per cent legume. However, only in Latin America does the ratio of cereals to legume production approach the desirable 2:1 ratio. In South and Southeast Asia, because of the significant decline in per capita legume production over the past 25 years, the ratio of cereals to legumes produced is of the order of 9:1. The production of legumes throughout most of the developing world has been steadily declining over the past two decades in relation both to cereal production and to population increase. During the past two decades in Asia, population increased by about 51 per cent, total food production by 65 per cent, but legume production by little more than 20 per cent. Consequently, unless some significant changes occur, we may, over the next 20 years, witness seriously inadequate food production in developing countries, both in terms of quantity and nutritional balance.
Priorities of Crop Improvement Programmes
Keeping in mind the world food situation, agricultural scientists have focused most of their attention on increasing the total production and productivity of cereal grains and food legumes. To achieve increased productivity, scientists are attempting to maximize the efficiency of the plant to utilize energy, carbon dioxide, water, and soil nutrients; attention is also being given to increasing the availability and efficiency of limiting soil nutrients and to biological processes dealing with a more efficient control of plant diseases and pests.
However, in any major international breeding programme, attention must not only be given to the quantitative aspects of production. Overall, the more efficient use of available land is defined by three factors: s a. Yield (kg/ha). New varieties must be bred so as to give higher yields on the lands they now occupy. They must also be adapted for other areas that can be economically opened up for cropping. b. Nutritive value. Nutritional considerations such as protein content, protein yield/hectare, and amino acid balance also contribute to improving the efficiency of utilization of foods. c. Technological value. Technological value refers to the attributes related to consumer acceptance, including milling and cooking characteristics.
Need for Food and Agricultural Research
Further agricultural research is needed to gain a better understanding of the processes responsible for the attributes of mixed cropping so that proper screening of new high-yielding genotypes can be effected. Agriculturalists, nutritionists, and economists should be working together in assessing the social, economic, and nutritional impact of better cropping systems. Nutritionally, intercropping is destined to have a major impact on the nutritional status of the malnourished in the less developed countries. For example, in regions where cassava is a staple, the diet is generally low in essential vitamins, minerals, and protein. Increasing the legume content in the diet would overcome the vitamin and mineral deficiency and supply an increased amount of protein. To increase the availability of legumes, their production must be expanded. This could be achieved through an intercropping system in which production of the major staple is maintained.
In view of the very important developments in agricultural research programmes, there is little doubt that through the continued support of the international agricultural research centres and the expansion and strengthening of national agricultural programmer, significant improvements can be made both in quantity and quality of the food crops of the less developed countries. However, improving productivity and agronomic properties is only a first step in the integration of nutritional priorities within agricultural research programmes.
In addition to yield and nutritional considerations, equal attention must be accorded to the selection of genotypes that meet consumer criteria in terms of grain size, colour, texture, milling, and cooking characteristics. Clearly, consumer acceptance of new varieties that cannot be milled using available tools, or that require longer cooking, may be delayed. Also, there is little purpose in increasing grain production in order to enhance the caloric intake of rodents, insects, and micro organisms. For these reasons, post-harvest systems research that comprehends the total food system from the time of, and including, harvest until the grain is delivered as food to the table must become part and parcel of research programmes dedicated to the improvement of crop characteristics and cropping methods. As such, interdisciplinary approaches to agricultural research involving plant breeders, agronomists, food technologists, nutritionists, and economists will bring us that much closer, that much sooner, to alleviating the world food problem.
One might anticipate the reasonable question: How long will it take for these genetic and agronomic improvements to find their way into farmers' gelds and the results into consumers' stomachs? Though it is a difficult question to answer, there is no doubt that the lead time can be gradually and effectively reduced by involving farmers in the early stages of the research process. I n the research that it supports, IDRC encourages scientists to carry out at least part of their research in farmers' fields, where they can gain a better understanding of the farmers' primary constraints and their attitudes to risk and change. Also, only in on-farm trials can research results be adjusted to farmers' actual levels of resource availability and management capabilities. Inasmuch as scientists strive to understand local social and economic circumstances, they must comprehend why farmers do what they do so that their biological and technical research will be more likely to fit the farmers' needs.
The world's recent history of support for international agricultural development represents an important first step. There is yet a long distance to travel, however, before we can view with satisfaction the state of nutritional well being among our poorest neighbours. If the distance between nutritional need and food supply is to be bridged during our lifetime, we must immediately move more swiftly, more imaginatively, and more unselfishly in our support and encouragement for international food and agricultural research and development.
1. International Food Policy Research Institute, Recent and Prospective Developments in Food Consumption: Some Policy Issues, July 1977
2. Joint FAD/WHO Ad Hoc Expert Committee, Energy and Protein Requirements, Wrld. Hlth. Org. Techn. Rep. Ser., No. 522 (1973).
3. J.D. Gavan and D.E. Hathaway, "Recent and Prospective Developments in Food Consumption: Some Policy Issues ", PAG Bulletin, Vol. VII, No. 1 - 2 March-June 1977
4. N.S. Scrimshaw, "Shattuck Lecture-Strengths and Weaknesses of the Committee Approach: An Analysis of Past and Present Recommended Dietary Allowances for Protein in Health and Disease," New Engl. J. Med., 294: 136, 203 (15, 22 January 1976).
5. Protein Advisory Group Statement No. 20, "The Protein Problem," PAG Bulletin, Vol. III, No. 1 (1973)
6. N.S. Scrimshaw, "W.O. Atwater Memorial Lecture-Through a Glass Darkly: Discerning the Practical Implications of Human Dietary Protein-Energy Interrelationships," Nutr. Rev., 35 (12): 321 (1977).
7. Food and Agriculture Organization, Provisional Indicative World Plan for Agricultural Development, C69/4 (FAO, Rome, Italy, 1969).
8. R. Bressani and L.G. Elias, "Tentative Nutritional Objectives in the Major Food Crops for Plant Breeders," in J.H. Hulse, K.O. Rachie, and L.W. Billingsley, ads., Nutritional Standards and Methods of Evaluation for Food Legume Breeders (Ottawa: International Development Research Centre, 1977).
Martonvásár Workshop Proceedings Published
The proceedings of the Workshop on Agricultural Potentiality Directed by Nutritional Needs, held in Martonvásár, Hungary, in June 1978, edited by Sándor Rajki, have been published by Akadémiai Kiadó, the publishing house of the Hungarian Academy of Sciences, and are being distributed by Kultura, P.O.B. 149, H-1389 Budapest, Hungary.
A summary of the proceedings of the workshop, which was sponsored by the UN University and organized by the Hungarian Academy of Sciences and the Swedish Academy of Sciences, was published in Food and Nutrition Bulletin, Volume 1, Number 1, in October 1978. The summary was based on notes prepared by Dr. Mogens Jul. Professor of Food Preservation, Royal Veterinary and Agriculture University, Copenhagen, Denmark.
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