The infant formula market has evolved in recent years towards products that replicate, as closely as possible, the nutrient content of human breast milk. Although the clear message is that breast is best, the aim is to ensure that babies who, for whatever reason, are not breast-fed do not miss out on the nutrients needed for growth and development.
But from the age of six months, it is advised infants tend to be weaned onto semisolids rather then relying just on milk - in particular because breast milk does not meet their iron and zinc needs at this stage of development.
According to Nancy Krebs, MD, professor of paediatrics at the University of Colorado Health Sciences Center and former chair of the American Academy of Paediatriacs Committee on Nutrition, the iron and zinc needs of the older breast-fed infant may be best provided by meat and liver.
The same nutrients, she said, are not provided in a plant based diet or one without food fortification or nutrient supplements. In a review article in the February issue of The Journal of Nutrition, Dr Krebs weighs up the potential for boosting zinc intake with cereals like maize, wheat, rice and roots - however these are accompanied by factors that make the minerals less bioavailable.
"In contrast to current practices in both developed and developing countries, meats should be considered as an early complementary food for breast-fed infants to provide essential micronutrients," concluded Dr Krebs.
The same issue of the Journal of Nutrition also contains a review of recent findings on iron deficiency and development of the central nervous system.
"Infants are at risk for iron deficiency as breast milk or formula is replaced by semisolid foods during weaning," wrote John Beard of the Department of Nutritional Sciences, Pennsylvania State University.
"Depending on the stage of development at the time of iron deficiency, there may be an opportunity to reverse adverse effects, but the success of repletion efforts may be time dependent."
Dr Beard reviewed preclinical and clinical studies to identify the regions of the brain and behaviors affected, and perhaps irreversibly altered, by early-life iron deficiency in humans, monkeys, and rodents.
"These cross-species studies indicate a vulnerable period in early development that may result in long-lasting damage," he wrote.
Source: The Journal of Nutrition J. Nutr. 2007 137: 511S-517S "Recent Evidence from Human and Animal Studies Regarding Iron Status and Infant Development" Author: Nancy F Krebs
Source: The Journal of Nutrition J. Nutr. 2007 137: 524S-530S "Recent Evidence from Human and Animal Studies Regarding Iron Status and Infant Development" Author: John Beard