High-Fat Dairy Intake Reduces Risk for Anovulatory Infertility

March 5, 2007 — Intake of high-fat dairy products is linked with a lower risk for anovulatory infertility, whereas low-fat dairy foods increased the risk for this condition, according to the results of a prospective study of healthy women reported in the February 28 Advance Access issue of Human Reproduction.

"Dairy foods and lactose may impair fertility by affecting ovulatory function," write J. E. Chavarro, MD, of the Harvard School of Public Health in Boston, Massachusetts, and colleagues. "Yet, few studies have been conducted in humans and their results are inconsistent. We evaluated whether intake of dairy foods was associated with anovulatory infertility and whether this association differed according to fat content."

During an 8-year period, the investigators prospectively followed up 18,555 married, premenopausal women without a history of infertility who attempted a pregnancy or became pregnant, and they evaluated their diet twice using food frequency questionnaires (FFQ).

Infertility caused by an ovulatory disorder was reported by 438 women during follow-up. After multivariate adjustment, the relative risk (RR) for anovulatory infertility for women consuming 2 or more servings of low-fat dairy foods per day vs women consuming 1 or fewer servings per week was 1.85 (95% confidence interval [CI], 1.24 - 2.77; P for trend = .002), and for high-fat dairy foods, the RR was 0.73 (95% CI, 0.52 - 1.01; P = .01).

Although dairy fat intake was inversely associated with anovulatory infertility (P for trend = .05), intakes of lactose, calcium, phosphorus, and vitamin D were unrelated to anovulatory infertility.

"High intake of low-fat dairy foods may increase the risk of anovulatory infertility whereas intake of high fat dairy foods may decrease this risk," the authors conclude. "Further, lactose (the main carbohydrate in milk and dairy products) may not affect fertility within the usual range of intake levels in humans."

Study limitations include failure to study a cohort of women known to be planning a pregnancy, lack of information on exposures of the participants' partners that might influence female fertility, and possibly spurious association of eating low-fat dairy foods with an increased risk for anovulatory infertility.

"We observed a positive association between intake of low-fat dairy foods (especially yogurt and sherbet/frozen yogurt) and anovulatory infertility and an inverse association between intake of high-fat dairy foods (especially whole milk and ice cream) and this disease," the authors conclude. "The intake of dairy fat, or a fat-soluble substance present in dairy foods, may partly explain the association between high-fat dairy and anovulatory infertility.... Clarifying the role of dairy foods intake on fertility is particularly important since the current Dietary Guidelines for Americans recommend that adults consume three or more daily servings low-fat milk or equivalent dairy products (United States Department of Health and Human Services and United States Department of Agriculture, 2005); a strategy that may be deleterious for women planning to become pregnant."

The main Nurses' Health Study II (NHS II) grant (National Institutes of Health) and the training grant T32 DK-007703 supported this study.

Hum Reprod. Published online February 28, 2007.

Source: http://www.medscape.com/viewarticle/553094?src=mp