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Tuesday, April 22, 2008

Lactose Not Associated with Fertility

A study of the role that dairy plays in causing infertility has been getting a lot of press attention.

"A prospective study of dairy foods intake and anovulatory infertility."
J.E. Chavarro, J.W. Rich-Edwards, B. Rosner, and W.C. Willett.
Advance Access published online on February 28, 2007
Human Reproduction, doi:10.1093/humrep/dem019

According to

Drinking whole fat milk and eating ice cream appears to be better for women trying to become pregnant than a diet consisting of low-fat dairy products such as skimmed milk and yoghurt, according to new research published in Europe's leading reproductive medicine journal, Human Reproduction.

Researchers in the United States have found a link between a low-fat dairy diet and increased risk of infertility due to lack of ovulation (anovulatory infertility). Their study showed that if women ate two or more servings of low-fat dairy foods a day, they increased their risk of ovulation-related infertility by more than four fifths (85%) compared to women who ate less than one serving of low-fat dairy food a week. On the other hand, if women ate at least one serving of high-fat dairy food a day, they reduced their risk of anovulatory infertility by more than a quarter (27%) compared to women who consumed one or fewer high-fat dairy serving a week.

Interesting, but not something I would normally bring to your attention.

However, the last sentence in the article took me by complete surprise:
Previous studies had suggested that lactose (a sugar found in milk) might be associated with anovulatory infertility, but Dr Chavarro's study found neither a positive nor negative association for this, and nor was there any association between intake of calcium, phosphorus or vitamin D and anovulatory infertility.

I wasn't familiar with any such studies. Even after a search I'm not finding any studies claiming this.

The closest association between lactose and infertility I found was a weak possibility that since low-fat milk products affected fertility more than high-fat milk products, lactose was the cause, since low-fat milk products tend to be slightly higher in lactose.

But if you take a look at my Lactose Percentages page on my website, you'll see that the difference is extremely small and probably completely meaningless. Why they didn't blame the fat instead baffles me.

If this weren't a study from a respected medical journal, I'd think that the use of "lactose" was a typo for "galactose." Galactose is another sugar. It's produced when lactose is digested. And galactose is known to affect fertility.

See Adult Hypolactasia, Milk Consumption, and Age-specific Fertility by Daniel W. Cramer, Huijuan Xu and Timo Sahi. American Journal of Epidemiology Vol. 139, No. 3: 282-289

Their conclusions about lactose is that lactose tolerance, the ability to digest lactose, leads people to drink more milk and more milk leads to greater infertility. That's the opposite of lactose causing infertility.

Whatever the previous thinking, this new study is an indication that consumption of lactose is irrelevant to those trying to get pregnant.

Don't go out and eat buckets of high-fat ice cream, though. That's as bad an idea for your health as it is tasty to your tongue.

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