Humans are primates, designed to breast feed for years not months

EDITOR—With respect to the article by Leeson et al on duration of breast feeding and arterial distensibility in early adult life, of course the duration of breast feeding matters—the longer the better.1

Humans are animals, mammals, and primates. Research on correlates of weaning age in non-human primates, such as adult body size, length of gestation, timing of permanent tooth eruption, timing of sexual maturity, and growth rates during childhood, predict that modern humans should be breast fed for between two and a half and seven years.23 Humans have slightly longer durations of all stages of the life span than our nearest relatives, chimpanzees. We have slightly longer gestation, later dental eruption, later sexual maturity, and therefore would expect slightly later ages of weaning. Chimpanzees breast feed for four to five years. Around the world, many children are breast fed for two and a half to seven years, including some in the United States, Canada, and Great Britain.

Maybe a healthy start in life of several to many years of breast feeding should be followed by a lifelong diet low in animal protein and fat and high in physical exercise, to maximise heart health in adulthood. But we will not know this until researchers study the effects on blood vessel flexibility of normal durations of breast feeding (2.5-7.0 years), and of the combination of normal durations of breast feeding with different post-weaning diets and amounts of exercise. I find it appalling that researchers would suggest that more than four months of breast feeding could be harmful to children, when research shows that 2.5-7.0 years is clearly the normal and natural duration for our species. On a final note, it is always good advice to question the credibility of research and researchers funded by infant formula companies.