Speaking on Friday during the 2005 AAAS annual meeting in Washington, Lindsay H. Allen, director of the US Agricultural Research Service, said that studies have shown that increasing intake of meat and milk among children has a significant benefit on their growth and cognition.
Dr Allen pointed to a two-year study in rural Kenya, completed in 2003, in which scientists supplemented the usual corn- and bean-based lunches of several hundred school children with meat, milk or an equivalent amount of energy from vegetable oils.
Children in all three groups, whether they received meat, milk or oil, gained about 400 grams more weight and increased their upper-arm muscle mass compared to classmates who received no supplements.
But the children who received the 68-gram meat supplement (2 ounces) also performed significantly better than all the groups on a test of problem-solving ability and fluid intelligence.
The research in Kenya also found that either meat or milk supplements greatly improved the vitamin B12 status of the children, reducing the prevalence of the deficiency to about 10 per cent in the treated groups compared to 50 per cent in the general school population.
The 68 grams of meat provided 106 per cent of a child's B12 requirement, 68 per cent of the zinc requirement, and 26 per cent of the iron, Allen said.
The results were consistent with earlier observational studies in Kenya, Egypt and Mexico, which suggested that children might benefit from some changes in their diets.
The findings have implications for the developed world too, especially in families that do not eat meat. Allen told the conference that putting children on vegan diets is 'unethical' and could harm their development.
"There have been sufficient studies clearly showing that when women avoid all animal foods, their babies are born small, they grow very slowly and they are developmentally retarded, possibly permanently," she said.
She added that adding animal source food to the diet would be a better way of tackling malnutrition than using supplements.
"With pills it's very hard to be certain that the quantity of nutrition is right for everybody and it's hard to sustain."
In Kenya, scientists found that animal source foods, especially meat products, are consumed by less than 14 per cent of children and usually in small amounts (less than 17 grams a day).