C.G. Neumann
School of Public Health and Medicine, University of California at Los Angeles, USA
The paper argues that consumption of livestock products may contribute to improved human health through alleviation of micronutrient deficiencies particularly in women and children. Examples of livestock programmes with human nutrition linkages are illustrated.
Globally, particularly in developing countries, both deficient diet quantity and quality are major nutritional challenges. Diet quantity is concerned with the availability and consumption of total food energy (kcal) and diet quality with the ability to supply protein of high biologic value (presence of all essential amino acids) and adequate supplies of micronutrients such as minerals, trace metals and vitamins. For human nutrition, the micronutrients of major concern are iron, iodine, zinc, calcium and vitamins A and B12 (Allen 1993). Animal source foods both meat, milk and eggs are compact and efficient source of micronutrients yet the majority of people in developing countries eat little or no animal source foods because of poverty and poor availability and accessibility to animals for inclusion in the household diet (Calloway 1995). Utilisation is limited also because of lack of knowledge about the necessity for and modes of preparation and preservation of animal source foods. Also, food insecurity is a widespread and daunting problem, particularly for resource poor smallholder subsistence farmers or the landless.
From late 1980s there has been an increasing awareness of 'hidden' malnutrition or multiple micronutrient deficiencies and that diet quality is as important as diet quantity. The role of micronutrients in adversely affecting the growth and cognitive development of young children and women of reproductive age and pregnancy has been receiving increasing attention in the human nutrition community (Scrimshaw 1994; Pollitt 1997).
Micronutrient deficiencies are widespread, affecting large numbers of the population globally, particularly in developing countries. Estimates are that 42% of women and up to 70% of older infants and pre-schoolers suffer from iron deficiency. About 10% of global iron deficiency occurs in Africa. Of late, deficiencies of zinc, vitamin B12 and folic acid are being increasingly recognised as causing profound health problems. Iodine deficiency and vitamin A deficiency continue to affect millions of the world's population (Scrimshaw 1994).
The central role of animal source foods in providing high quality and readily digested protein, micronutrients and high energy density because of the fat content provides the key rationale for linking livestock and mini-livestock production to human nutrition improvement. Animal source foods offer a practical means for diet quality improvement for the most vulnerable groups—women of reproductive age and children. The main micronutrients offered in abundant and bioavailable form by animal products are calcium, iron, zinc, vitamins A and B12. Iodine is furnished only by seafood and oceanfish and not livestock (Neumann et al 1996).
Stunting affects over 50% of children in Africa and even a higher percent in Asia. In addition to inadequate energy intake, deficiencies of zinc, calcium and iodine have been implicated. Low birth weight due to fetal malnutrition has been associated with deficient maternal intakes of iron, zinc, iodine and vitamin B12 (UN ACC/SCN 1992). These infants are at heightened risk for fatal infections, neurologic and cognitive impairment and poor catch-up growth (Neumann and Harrison 1994).
Impaired cognitive function and learning ability are caused by micronutrient deficiencies involving iron, iodine, B12 and probably zinc. Decreased physical activity and decreased exploratory behaviour, a major pathway in learning, are seen in iron and probably zinc deficient children. Blindness and profound mental retardation are the legacy of vitamin A and iodine deficiency, respectively (Lozoff et al 1991; Pollitt 1997).
Nutritional anemias are caused by multiple micronutrient deficiencies, most notably iron, B12, folate, vitamin A and pyridoxine deficiencies. Anemia in general, but particularly iron deficiency, causes decreased work capacity and thus decreased economic productivity. Iron is a component of myoglobin, a major muscle protein. Malaria, hookworm and schistosomiasis in poor populations also contribute heavily to anemia (Lozoff et al 1991; Pollitt 1997)
Impaired resistance to infection, through the impairment of the cell-mediated immune (CMI) system and the decreased bacteriocidal function of white blood cells, occurs most commonly with zinc, iron and vitamin A deficiencies. The CMI is the body's first line of defense against viral, fungal and certain bacterial infections, notably tuberculosis and defense against malignancy. Microbial ingestion and killing functions of granulacytic white blood cells are particularly impaired by iron deficiency (Neumann et al 1992).
Thus, if ignored, micronutrient deficiencies cause from mild to serious impairment of the individual as well as widespread societal consequences which directly hamper social and economic development ( Scrimshaw 1994).
The predominant East African diet consists of a few basic staples of cereals or tubers, plus varying amounts of legumes, greens, vegetables and fruits grown on small farm holdings. Animal source foods such as meat, fish, fowl, or eggs are infrequently eaten, particularly by women and young children. Animal milks are consumed mainly in tea or in fermented form. The few animals owned are only infrequently eaten (Calloway 1992; Neumann et al 1992; Calloway et al 1993).
Diets devoid of or low in animal products are generally low in energy density because of low fat content. Moreover, these diets are often intrinsically deficient in micronutrients such as iron, zinc, vitamin B12, calcium, pre-formed vitamin A, or if present, not readily absorbed as is the case for iron and zinc from legumes and maize, millet, sorghum or teff. For example, beans contain substantial iron but only 5% is available and only 10% of zinc is actually available for absorption by humans from cereals (Murphy et al 1992).
Not only do animal source foods supply the above micronutrients in bioavailable form, but the heme iron of meat, fish or fowl promotes the absorption of iron and zinc when mixed with non-animal foods which contain non-heme iron, thereby increasing their bioavailability. Diets which are predominantly cereal-based are high in phytate and fibre content which form insoluble complexes with iron, zinc, and other metals, thereby reducing their bioavailability (Layrisse et al 1990).
To assess iron or zinc availability of a given diet, molar zinc or iron phytate ratios are calculated, as well as the fibre in the diet to assess bioavailability. Also enhancers of iron and zinc absorption in the diet such as citrus fruits are also factored in. Coffee and tea taken at mealtimes can reduce iron and zinc availability because of the tannic acid. Milk likewise can reduce the bioavailability because the casein and calcium in milk can also form insoluble complexes with iron and zinc if taken at mealtimes (Murphy et al 1991).
To meet the daily requirements for energy, iron or zinc, it would take far more maize and beans (over 1.7–2.0 kg) that a child is likely to tolerate, while 60 grams of meat per day or about 2 ounces would completely satisfy the average requirements of a child. Thus meat consumption could play an important role in iron and zinc nutrition (Murphy et al 1991).
Animal products are almost the exclusive sources of dietary vitamin B12 and a good source of pre-formed vitamin A, in addition to carotenoids supplied by plants. Both meat and milk supply substantial amounts of riboflavin. Milk products are an important source of calcium; it is difficult for a child to even approach the average calcium requirements (estimated as 345 mg/d) on a cereal-based diet. Calcium from plant sources may have low bioavailability because of the high oxalate content. Unless seafood or oceanfish or sea products are eaten, iodine must be supplied through fortification or supplied as a supplement in areas of endemic deficiency. It is important to point out that milk, although a rich source of protein, calcium and vitamins A and B12 is a poor source of iron and zinc (Murphy et al 1991).
The findings presented below are based on the NCRSP and will serve to illustrate the role of animal source food in physical growth and cognitive development in toddler and school children. The NCRSP was a non-intervention longitudinal observational study conducted in rural areas in Kenya and Mexico and in a semi-rural area in Egypt in the mid-1980s (Calloway et al 1988).
In Kenya, the diet was deficient in energy intake for all age groups studied. The predominance of maize in the Mexican and Kenyan diets and very low intake of animal products and fat posed difficulties, particularly for young children, where 60–70% of energy intakes come from maize and beans and in Kenya, only 7% from milk (57 gm/day) and less than 1% from meat (5 mg/day). Schoolers proportionately ate even less animal products, with over 75% of their energy intake from maize and beans, 1% from milk (28 gm/day) and less than 1% from meat (11 gm/day). Low energy density of the bulky diet was a problem as well (Calloway et al 1992).
Early growth faltering, as early as the third month of life, was seen particularly in the Kenyan and Mexican infants. Both length and weight were affected, but length to a greater extent, particularly in Kenya. Poor catch-up growth occurred, but by 18 to 30 months, children began to grow at a normal rate, albeit at a lower level at the 3 to 5 percentiles (Neumann et al 1992).
In Kenya, the rate of growth of infants for both weight and length were related to maternal diet quality or the amount of animal products in her diet during pregnancy and lactation. Maternal intake of vitamin B12, iodine, and available zinc and breast milk levels of B12 predicted infant growth controlling for gestational age and socio-economic status. Thus growth failure in infants was related to maternal malnutrition during pregnancy and lactation. Low breast milk vitamin B12 content appears to be a contributing factor (Neumann and Harrison 1994).
In Kenyan toddlers and schoolers, intake of animal products and available iron, zinc and iodized salt were significant predictors of growth, both height and weight. This was true even after controlling for total energy intake, illness burden, socio-economic status (SES) of the family and parental size. For the Kenyan children where total food intake was very low, energy intake positively predicted growth (Neumann et al 1992). In Mexico, diet quality, as in Kenya, was an important predictor for growth (Murphy et al 1992).
Food patterns constructed by using principal component analyses of the diet, identified groups of foods in the diet that were associated with positive and negative growth. In Kenya toddlers, the principal component including milk, fat and sugar (concentrated energy sources) was a positive predictor of growth. The families with such a diet enjoyed higher SES, and more animal protein and fat. The food pattern associated with poor growth and lower SES included diets with more maize, sorghum, beans, and higher intakes of phytates and fibre in the diet. A similar picture was seen in Mexico (Murphy et al 1991; Murphy et al 1995).
Toddlers: Toddlers who ate little or no animal protein and those who were stunted performed less well on cognitive tests in all three countries. Even when controlling for parental and SES factors and energy intake, stunting and poor diet quality predicted poor cognitive performance (Sigman et al 1989; Neumann et al 1992).
An impressive finding in the Kenyan children was that intake of animal source products between 18–30 months was significantly and positively associated with cognitive performance when the children reached five years of age on a follow-up testing. The best set of predictors of cognitive function at age five years was previous intake of animal protein, even when controlling for household and SES factors and duration of schooling (Sigman et al 1991).
In regard to play and physical activity in the Kenyan toddlers, those who were fed more animal protein verbalised and used more symbolic play. Symbolic play is felt to be predictive of future cognitive performance (Sigman et al 1989). Strikingly, Mexican children on poor quality diets displayed apathy and passivity and were often sedentary (Allen 1993). Complete reversibility of these deficits are unlikely, although nutrition intervention and mental stimulation can help to ameliorate the deficits, at least in part.
School-age children: As in the toddlers, the taller and heavier children performed the best on cognitive tests, particularly the verbal and performance tests. In Kenya, where both diet quantity and quality were deficient, all dietary variables and anthropometric indicators were positively associated with cognitive test scores and school performance to some degree (Sigman et al 1991).
Among the Kenyan schoolchildren, after controlling for confounders, intake of meat was positively associated with attentiveness to classroom work and to the teacher and to scores of school performance. Also schoolers with greater intake of total energy, animal foods and fat in their diet were more active and showed more leadership behaviour in a free-play setting such as the school recess (Espinosa et al 1992).
Among the Mexican children, it was noted that boys on poor quality diets were apathetic in the classroom. As for the Egyptian children, animal source products, and particularly specific nutrients such as iron, zinc, vitamin A and B12, all derived from meat and/or milk, positively predicted developmental outcomes, behaviour, verbal ability and involvement in classroom activities. These remained significant even when controlling for SES (Calloway et al 1988).
Thus, the NCRSP studies in three diverse areas of the world have documented that animal source foods with their high energy density and constituent micronutrients of heme iron, zinc, B12 and high quality protein, all in bioavailable form, contribute positively to physical growth, physical activity, and cognitive function essential to learning in school (Calloway et al 1992). Animal source foods such as meat, fish, poultry incorporated into the daily diet, even in modest amounts, can supply critically needed micronutrients in bioavailable form. There no doubt will be formidable economic and cultural barriers to overcome in some communities which participatory nutrition education and social marketing and income generation may be able to overcome. Such food-based interventions are much more sustainable than dietary supplements and capsules. Although this presentation has emphasised micronutrient deficiencies, energy deficits and poor food security are also major and pervasive problems.
Small livestock have an extremely important role to play in the sustainable and affordable improvement of diet quality of families in less technically developed and poor countries heavily dependent on subsistence agriculture. Improved physical growth, mental development and overall health is a critical and cost-effective investment in the future economic development of a country and improvement in the quality of life as stated in the World Development Report of 1993.
Small livestock and mixed farming systems have important potential to alleviate micronutrient malnutrition. Opportunities for non-intensive smallholder livestock production, e.g. goats, free range chickens, rabbits, small rodents (cavies) and fish are critical to sustainable food-based multiple micronutrient delivery. Micronutrient rich plants in combination with animal foods play a critical role. Small livestock provide a number of advantages. Livestock in addition to dietary improvement can provide transport, draft, manure, and income generating commodities.
The challenge is to increase availability and accessibility of poor household to small livestock through credit and accompanied by education and extension services: increased utilisation through processing and preservation through appropriate technology and participatory nutrition and health education; and income generation and control of the income by the women themselves. The NGOs and agricultural extension are extremely well-suited as partners in such efforts.
There are relatively few livestock development programmes linked to human nutrition improvement component. The majority of such linkages have been found as part of the research efforts to measure the impact of livestock or other agricultural efforts, but few have had active nutrition components as part of the interventions or linked to the programme. The few examples of incorporation of human nutrition improvement have focused on increased milk production and hopefully consumption by the vulnerable family members and income generation. Increasing the intake of meat to improve diet quality has not been addressed.
Some impressive attempts to integrate human nutrition improvement with livestock production have been occurring in Ethiopia. Two NGOs, FARM–Africa and Heifer Project International, have had projects attempting to link livestock production to human nutrition improvement. However, increasing milk production and consumption, and not increased meat consumption, was the focus. It was hoped through increased income generation through the sale of milk that perhaps earnings might go toward the purchase of animal source foods for the family other than milk. Nutrition education was not intensive and did not promote inclusion of meat in the diet.
FARM–Africa in Ethiopia, through the Dairy Goat Development Project, aimed at increasing the welfare and incomes of the poorest families in the highland areas by improving goat production by women. 1500 goats were granted to women's groups on credit as well as training in the care of goats. The major objective of the project was to increase the milk consumption of children and their micronutrient intake in order to improve their growth and development. Increasing meat consumption was not included. Improved household food security was accomplished through increased potential of families in times of hardship. In conjunction with Alemaya Agricultural University and the International Centre for Research on Women (ICRW), FARM–Africa introduced educational activities focusing on milk consumption and the cultivation and integration of dark green leafy vegetables, sweet potatoes and other carotene-containing foods. The post-intervention evaluation was completed in late 1997 and was not yet available (Peacock 1996).
Heifer Project International, in some projects in the Coast Province in Kenya, worked with several women's group in Kilifi, Kenya in 1989. Women's groups came together to increase milk production. The objective for milk production were to treat and prevent Kwashiorkor in their own children and have milk for income generation. The women incorporated zero-grazing and forage production as their activities. This was a small but highly successful project until an East Coast fever outbreak reduced the herds by 30% (Personal Communication 1998).
It is premature to speak of the accomplishments or findings of the research project 'Role of Animal Source Foods in Improving Diet Quality and Growth and Development in Young Kenyan Children.' A research team from the University of Nairobi and University of California now have an opportunity to test the importance of increased meat and milk in the diet and their impact on growth and cognitive development of school children using a controlled feeding intervention of 6–8 year old children. Following this phase, we are planning appropriate community-based interventions to increase the availability of a variety of small livestock to increase meat and other animal source foods in the household diet and to increase their utilisation by children to improve their growth and development through participatory health and nutrition education (Neumann and Bwibo 1998).
Also through dialogue with the other GLCRSP projects and NGOs, the linkage of human health and nutrition improvement has been stimulated and these livestock projects are beginning to incorporate nutrition activities and impact measures into their projects. Hopefully this trend will be furthered as a result of this IDRC–ILRI sponsored workshop.
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