The association of protein intake (amount and type) with ovarian antral follicle counts among infertile women: results from the EARTH prospective study cohort

Abstract

Objective: To evaluate the association between protein intake (amount and type) and antral follicle count (AFC).

Design: Prospective cohort.

Setting: Academic fertility centre.

Population: Two hundred and sixty-five women undergoing fertility treatments at an academic fertility centre and participating in an ongoing study on environment and reproductive health.

Methods: We measured AFC in ultrasonographic evaluation among women undergoing infertility treatments. Women completed a previously validated semi-quantitative food frequency questionnaire. We used Poisson regression to evaluate the relation between protein intake and AFC while adjusting for age, body mass index, race, smoking status, and total energy intake.

Main outcome measures: Antral follicle count.

Results: Among 265 women (mean age: 35.0 ± 3.9 years, 85% Caucasian), total protein intake (% energy) was unrelated to AFC. When protein from different food sources was considered separately, we found a negative association between dairy protein intake and AFC. The mean AFC was 14.4% (3.9-23.7%) lower for women in the highest quintile of dairy protein intake than for women in the bottom quintile after adjusting for potential confounders (P-trend = 0.04). This association was stronger among women who had never smoked (P-trend = 0.002) but was not observed among previous smokers (P-trend = 0.36). There were no associations between protein intake from either non-dairy animal or vegetable sources and AFC.

Conclusion: Higher dairy protein intake (≥5.24% of energy) was associated with lower antral follicle counts among women presenting for infertility treatment. These findings should be further investigated in prospective studies also designed to clarify the biology underlying the observed associations.

Tweetable abstract: Higher dairy protein intake was associated with lower antral follicle counts in an infertile population.

Keywords: Antral follicle count; dairy intake; female infertility; ovarian reserve; ovary; protein intake.

Conflict of interest statement

DISCLOSURE OF INTERESTS

Author: MCA is employed by Nestle Research Center. Authors: IS, YHC, MB, PLW, RH and JEC report no conflicts of interest. The ICMJE disclosure forms are available as online supporting information.

© 2017 Royal College of Obstetricians and Gynaecologists.

Figures

Figure 1

Antral follicle count (AFC) according to quintiles of dairy protein intake among never (Fig. 1A) and ever smokers (Fig. 1B). Values are adjusted antral follicle counts with 95% confidence intervals. Results are adjusted for total energy intake, age, BMI, smoking status (ever vs. never), race (white vs non-white), vegetable protein intake and non-dairy protein intake, with each of these covariates at their mean levels. Tests for trend were conducted across quintiles using the median intake in each quintile as a continuous variable.