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Original articles: Richard M Martin, Sarah H Goodall, David Gunnell, and George Davey Smith Breast feeding in infancy and social mobility: 60-year follow-up of the Boyd Orr cohort Arch Dis Child 2007; 92: 317-321 [Abstract] [Full text] [PDF]

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This could be due to increased DHEA

James M. Howard   (16 February 2007)

Plausible, but probably smaller and of doubtful contemporary relevance

Geoff Der   (20 February 2007)

This could be due to increased DHEA 16 February 2007
James M. Howard, Biologist independent Send letter to journal: Re: This could be due to increased DHEA jmhoward{at}anthropogeny.com James M. Howard	Dear Editor, Milk contains maternal prolactin, which has been linked to positive growth and development of the neonate (J Mammary Gland Biol Neoplasia 1996; 1: 259-69). Prolactin has been determined to specifically stimulate dehydroepiandrosterone (DHEA) production in young baboons (Endocrinology 1985; 117: 1968-73). Breast feeding augments a neonates natural prolactin levels. It is my hypothesis that all tissues rely on sufficient DHEA levels for optimal growth and development and, subsequently, maintenance of all tissues. DHEA has been linked by many research article with positive effects on neurons and the brain. I suggest the findings of Martin, et al., may be explained by stimulatory effects of prolactin in breast milk on DHEA levels in breast-fed children.
Plausible, but probably smaller and of doubtful contemporary relevance 20 February 2007
Geoff Der, Statistician Medical Research Council Send letter to journal: Re: Plausible, but probably smaller and of doubtful contemporary relevance Geoff{at}msoc.mrc.gla.ac.uk Geoff Der	Dear Editor, The effect reported by Martin and colleagues is plausible, but likely to be smaller than suggested and of doubtful contemporary relevance. The effect of breastfeeding is relative to the alternatives available which clearly are very different now from the 1920’s and 30’s when the Boyd Orr cohort were born. Although its use was declining, some of the artificially fed might have been given condensed milk which is associated with poorer development1. Much of it was skimmed and so provided too little fat2. It was also difficult to keep an opened tin free from contamination. Fresh cow’s milk was more expensive and the quality was variable. Most of London’s supply would have been pasteurised at that time, but this was not true of all areas3. Keeping the feeding equipment sterile would also have been more challenging. In short, artificial feeding was a considerable health risk. Most women wanted to breast feed because it was cheaper, safer and offered some contraception. The main reasons for not doing so were poor health on the part of the mother and returning to employment. The effect of breastfeeding on social mobility in the Boyd Orr data is not apparent at durations below 6 months. Mothers who were able to breastfeed for this long are likely to have been healthier and less likely to have been employed outside the home. Their birth spacing might also have been greater. The child would be less likely to have been illegitimate, a factor associated both with artificial feeding and lower social mobility4. The siblings analysis conducted by Martin and colleagues gives an effect estimate less than half that of their main analysis. Factors such as those mentioned might explain some of the rest. References: 1. Hoefer C, Hardy M. Later development of breast fed and artificially fed infants. Journal of the American Medical Association 1929;92:615-20. 2. Fildes V. Infant feeding practices and infant mortality in England, 1900-1919. Continuity and Change 1998;13 (2):251-280. 3. Atkins P. Mother's milk and infant death in Britain, circa 1900-1940. Anthropology of Food 2003;2. 4. Modin B, Koupil I, Vågerö D. The impact of early twentieth century illegitimacy across three generations. Intra-generational longevity and inter-generational health correlates. Lund/Mölle, Sweden, 2006.