Wednesday, April 26, 2006

Dairy milk and birth weight

On 25 April 2006 a Canadian study reported that low intake of milk was associated with decreased birth rate. This study concluded that 'restricting fortified milk or vitamin D intake during pregnancy lowered infant birth weight in otherwise healthy, non-smoking, well-educated mothers. Our study is limited because only 24% of women who reported restricting milk consumption agreed to participate. Thus, our study demonstrates that in pregnant women living where sun conditions for year-round vitamin D synthesis are less than ideal, poor vitamin D intake from food sources (including fortified milk) and failure to select appropriate vitamin and mineral supplementation can result in lower infant birth weight..' (Source: Cynthia A Mannion, et al, Association of low intake of milk and vitamin D during pregnancy with decreased birth weight, CMAJ o April 25, 2006; 174 (9). doi:10.1503/cmaj.1041388).

The study looked at a total of 72 women (an extremely small sample for any kind of study of this sort). The study found that restricting vitamin D during pregnancy resulted in decreased birth weight. The study specifically said that protein from milk made no difference to birth weight: the study 'indicated no independent contribution of protein to birth weight, infant length or head circumference in our otherwise healthy mothers. Neither did calcium or riboflavin predict birth weight, infant length or head circumference.'

Furthermore the study concluded that 'Milk and vitamin D intakes during pregnancy are each associated with infant birth weight, independently of other risk factors.' In other words, vitamin D affects birth weight. But milk, with or without vitamin D, also affects birth weight. Naturally, anybody who consumes significant dairy milk will put on weight, whether or not pregnant. But it does not follow that increased birth weight as a result of consuming milk is beneficial, and there are no studies that show this. On the contrary, some research is showing that increased birth weight (above the norm) makes the baby more prone to cancer later in life (source: Susan E. McCann, et al, Birth Weight and Breastfeeding in Infancy May Affect Premenopausal Breast Cancer Risk, April 2006, The University at Buffalo School of Public health and Health Professions, NY State, USA).

The cited Canadian study does not say or imply that milk consumption is good or that it benefits babies in any way - and this, in spite of the fact that the study is sponsored by Dairy Farmers of Canada. The only conclusion drawn by the study is that it is important for pregnant women to get enough vitamin D as this ensures a healthy birth weight. Milk is mentioned in the study but it is a red herring because Canadian milk has a high amount of added vitamin D3. Thus milk per se is of no benefit, it is the vitamin D in the milk that benefited the mothers in the Canadian study. It is much healthier to get vitamin D from sunlight or supplements than from dairy milk.

Press headlines like 'Avoiding milk in pregnancy could lead to a smaller baby' (Daily Mail, UK)are totally misleading because milk in other parts of the world has little or no added vitamin D. Avoiding milk in pregnancy will benefit both mother and baby. The mother benefits because by avoiding dairy milk she will avoid antibiotics, cow hormones, and other harmful substances in milk that get passed into the unborn child.

Just as important, a mother should not consume dairy milk after birth because hormones in dairy milk inhibit the production of human milk. This happens because the hormones in dairy milk are similar to the hormones produced by a breastfeeding woman. This upsets the woman's body chemistry, making the body reduce or shut down the production of human milk.

Also, if the mother consumes dairy milk after birth, the cow hormones will interfere with the human hormones oxytocin, leptin and prolactin. These hormones act to help the body shed surplus body fat, and suppress food cravings and over-eating. By consuming milk, the mother will have a much harder time regaining her former slim and healthy figure.

Russell Eaton
Author of The Milk Imperative