Can Drinking Milk Cause Acne?

Professor Bodo Melnik of the Department of Dermatology, University of Osnabrueck, Germany, has published a thought-provoking perspective on a causal relation between cow’s milk consumption and Acne in Western societies (1).
Since the vast majority of adolescents in North America suffer to some degree from acne, an environmental factor may be the cause. One of the pillars of the Western diet is the consumption of cow’s milk. This paper points out that a study of over 10,000 teenagers has shown a strong correlation between milk consumption (particularly reduced fat milk) and acne in teenagers. In contrast, a study of inhabitants of Papua, New Guinea and of hunters and gatherers in Paraguay that do not drink or eat dairy products, shows that not a single case of acne is found. Such results suggest that milk consumption contributes to acne in Western society.
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The milk hypothesis says that the level of growth hormone (GH, somatotropin) and Insulin-like-Growth-Factor -1 (IGF-1), which already are increased at the onset of puberty, are further increased as a result of milk consumption. These hormones are powerful mitogens and play a central role in growth and homeostasis of the skin and various other tissues. It turns out that the levels of these hormones also correlate strongly with the occurrence of acne.
IGF-1 (as well as insulin) stimulates sebocogenesis (2) and the production of oil by the sebaceous glands (3). It is this stimulation of the sebaceous glands that results in acne, when this coincides with infection.
Scientifically speaking, let us point out that a problem in comparing different populations is that it is an over-simplification to assume that two groups only differ in one aspect. So, one always has to keep this in mind when comparing population groups. Keeping that in mind, this data suggests a potential role of milk consumption in the development of acne.

References
(1) Melnik B. Milk consumption: aggravating factor of acne and promoter of chronic diseases of Western societies. J Dtsch Dermatol Ges. 2009 Feb 19.
(http://www.ncbi.nlm.nih.gov/pubmed/19243483)
(2) Deplewski D, Rosenfield RL. Role of hormones in pilosebaceous unit development. Endocr Rev 2000; 21: 363-392
(http://www.ncbi.nlm.nih.gov/pubmed/10950157) (3) Smith TM, Cong Z, Gilliland KL, Clawson GA, Thiboutot DM. Insulin- like growth factor-1 induces lipid production in human SEB-1 sebocytes via sterol response element-binding protein-1. J Invest Dermatol 2006; 126: 1226–1232. (http://www.ncbi.nlm.nih.gov/pubmed/16575389)