Fertility Diet May Improve Fertility Outcomes in Women
News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd
November 12, 2007 — Higher intake of monounsaturated fats; vegetable protein; and high-fiber, low-glycemic carbohydrates improved fertility outcomes in women with ovulatory disorder infertility, according to the results of a cohort study reported in the November issue of Obstetrics & Gynecology.
“Although treatment options for infertility are available, their large cost and frequency of adverse events have motivated the identification of potentially modifiable risk factors,” write Jorge E. Chavarro, MD, ScD, from the Harvard School of Public Health in Boston, Massachusetts, and colleagues. “We have previously found that body weight, physical activity, and dietary factors, such as intakes of specific fatty acids, protein, dairy foods, iron, and multivitamins, are related to infertility due to ovulation disorders. These findings suggest that an overall dietary and lifestyle pattern aimed at increasing the intake of certain micronutrients and improving insulin sensitivity through the modification of diet composition, weight control, and increased physical activity may help prevent ovulatory disorder infertility.”
As part of the Nurses’ Health Study II (NHS II), the investigators observed a cohort of 17,544 women with no history of infertility as these women tried to become pregnant or became pregnant during an 8-year period. Based on factors previously related to lower incidence of ovulatory disorder infertility, a dietary score was calculated, with a higher score reflecting greater consumption of monounsaturated rather than trans fats, vegetable rather than animal protein sources, low glycemic carbohydrates, high-fat dairy products, multivitamins, and iron from plants and supplements. The dietary score and other lifestyle factors were prospectively related to the incidence of infertility.
Women who followed the “fertility diet” pattern more closely had a lower risk for ovulatory disorder infertility. For women in the highest quintile of the “fertility diet” pattern score vs women in the lowest quintile, the multivariable-adjusted relative risk for ovulatory disorder infertility was 0.34 (95% confidence interval [CI], 0.23 – 0.48; P for trend < .001).
Subgroups based on women’s age, parity, and body weight exhibited a similar inverse relationship. Women who had a combination of 5 or more low-risk lifestyle factors, including diet, weight control, and physical activity, had a 69% lower risk for ovulatory disorder infertility and an estimated population-attributable risk for 66% (95% CI, 29% – 86%).
“Following a ‘fertility diet’ pattern may favorably influence fertility in otherwise healthy women,” the study authors write. “Further, the majority of infertility cases due to ovulation disorders may be preventable through modifications of diet and lifestyle.”
Limitations of the study include the cohort not known to be planning to become pregnant; inability to determine the effects of individual components of the “fertility diet” score; imperfect measurement of diet, physical activity, and other lifestyle factors; observational study with possible confounding factors; and use of multiple statistical comparisons that could overestimate the statistical significance of some results.
“Our results suggest that a ‘fertility diet’ pattern may have favorable effects on the fertility of otherwise healthy women and that combining this dietary strategy with body weight control and increased physical activity may help prevent the majority of infertility cases due to problems with ovulation,” the study authors conclude. “Because data on the potential role of specific dietary patterns on fertility are scarce, it is important that these findings are reproduced, preferably in large randomized trials. In the meantime, women trying to become pregnant could consider following these lifestyle practices because they are consistent with an overall healthy lifestyle and may also help them become pregnant.”
The NHS II grant, the Yerby Postdoctoral Fellowship Program, and the National Institutes of Health supported this study. The study authors have disclosed no relevant financial relationships.
Obstet Gynecol. 2007;110:1050-1058.
Infertility is a common problem affecting 1 in 6 couples during their reproductive lifetime, and problems with ovulation can be identified in approximately 18% to 30% of cases. Although treatment options are available, some lifestyle risk factors such as body weight, physical activity, and dietary factors have been shown to be related to ovulation disorders. Increasing the intake of certain micronutrients and physical activity may help prevent ovulatory infertility. A high “fertility diet” score is characterized by lower intake of trans fats, higher intake of monounsaturated fats, lower intake of animal protein with higher intake of vegetable protein and fiber, low glycemic carbohydrates, greater preference for high-fat dairy products, higher intake of nonheme iron, and higher frequency of multivitamin use.
This is a prospective observational analysis of diet, physical activity, and body weight in relationship to incident infertility from ovulation disorders among healthy women enrolled in the NHS II.
- Included were 17,544 women from within the NHS II cohort who were aged 25 to 42 years at baseline and who completed a dietary intake questionnaire biennially.
- Inclusion criteria were married women with no history of infertility who provided a complete dietary history and information on physical activity, height, and weight.
- Every 2 years, women were asked if they had tried to become pregnant for more than 1 year without success and to indicate the possible cause such as tubal blockage, ovulatory disorder, or endometriosis.
- A validation study of a subset of women found that self-report was confirmed by medical record review in 95% of cases.
- Women were asked if they tried to become pregnant in the preceding 2 years.
- Women were followed up until they reported infertility from any cause, reached menopause, or underwent sterilization by any method.
- Reports of infertility were considered cases, and all other events such as pregnancy and miscarriages were considered noncases.
- Body mass index (BMI) was calculated, and physical activity was classified as average time spent in 8 activities for moderate and vigorous activities.
- A validated food frequency questionnaire was used to report how often, on average, participants consumed certain foods, beverages, and supplements, with 9 options for frequency, from “never or less than once per month” to “6 or more times a day.”
- A summary “fertility diet” score was calculated for each woman based on variables found to predict ovulatory disorder infertility, the highest score in the category indicating the lowest risk.
- The “fertility diet” score ranged from 8 to 40, and the median score was 24 points.
- Women were divided into 5 groups according to quintiles.
- Mean age of the women was 32 years, alcohol intake was 2 g/day, 22% drank 2 or more cups of coffee daily, 7% were current smokers, and 23% were nulliparous.
- During 8 years of follow-up, 25,217 pregnancies and pregnancy attempts were accrued among the 17,544 women.
- Women with a high “fertility diet” score were more likely to consume coffee and alcohol and be physically active and were less likely to smoke, have long menstrual cycles, and be recent users of hormonal contraception.
- Increasing adherence to the “fertility diet” was associated with lower risk for ovulatory disorder infertility (P for trend < .001).
- Compared with women in the lowest quintile of the “fertility diet,” women in the highest quintile had a 66% lower risk for ovulatory disorder infertility and a 27% lower risk for infertility from other causes.
- There was a J-shaped relationship between BMI and ovulatory disorder infertility.
- Compared with women with a BMI between 20 and 24.9 kg/m2, women with a BMI of less than 20 kg/m2 and more than 30 kg/m2 had a higher risk for ovulatory infertility.
- Time spent in vigorous physical activity was unrelated to infertility overall.
- Women with vigorous physical activity for 30 minutes or more each day had a slightly lower risk for ovulatory infertility.
- Age, parity, and BMI did not alter the relationship between “fertility diet” score and risk for ovulatory infertility.
- The risk for ovulatory infertility was lower for each additional low-risk lifestyle habit followed, up to 69% lower risk for women adhering to 5 or more habits.
- Diet composition had a greater impact on fertility than either BMI or vigorous physical activity alone.
Pearls for Practice
- BMI, adherence to a “fertility diet,” and time spent in vigorous physical activity for 30 minutes or more daily are associated with ovulatory fertility in women.
- Women following 5 or more lifestyle habits, including diet and weight control, have a 69% lower risk for ovulatory infertility.