The recommendation to choose full fat dairy over reduced fat or fat free dairy may come as a surprise. Low fat diary is touted as the calcium source of choice by most nutrition and medical experts. It even has its own section on the My Plate guide (I know that little cup just says dairy but when you read the recommendations it states to choose low fat or fat free varieties.) The findings from A Prospective Study of Dairy Foods Intake and Anovulatory Infertility turned common knowledge and advice on its ear.
Researchers studied a group of women over a period of years, collecting information about their diet, pregnancy, and infertility. The women were then divided based on how much full fat and low fat dairy was in their diet.
The women who ate more full fat dairy were less likely to have anovulatory infertility while the women who ate more low fat dairy were at an increased risk for anovulatory fertility.
The exact reason is unclear but the researchers offered a few educated guesses:
- Skim milk contains androgen precursors which might affect women's hormonal balance
- When fat is removed from milk, whey protein is added which in animal studies has been shown to have masculinizing effects
- Milk can increase insulin-like growth factor I levels, which may play a role in the development of PCOS.
The researchers recommended more research be done in this area to find out for sure if different levels of dairy fat affect fertility and if so, how. Based on what we have seen so far it does seem like choosing whole fat dairy is the best choice for women actively trying to conceive or planning to do so in the future. This however is not a license to go hog on a pint of ice cream. Moderation should still be practiced.