Dietary Interventions Improve Fertility Outcomes Among Women With PCOS

A systematic review of articles on randomized controlled trials (RCTs) from the Cochrane Central Register of Controlled Trials, PubMed, Embase, Web of Science, and 3 Chinese databases (China National Knowledge Infrastructure, VIP information database, Wanfang Data) shows that diet has a statistically significant effect on improved fertility outcomes among women with polycystic ovary syndrome (PCOS).

A search of the above 7 databases through January 31, 2021, produced 20 RCTs and 1113 participants for final analysis from China, Iran, the United States, Australia, the United Kingdom, Canada, Denmark, Egypt, and Mexico.

The fertility outcomes investigated were increasing clinical pregnancy, ovulation, and menstrual regularity rates; reducing the miscarriage rate; increasing sex hormone-binding globulin (SHBG) levels; and decreasing anti-mullerian hormone (AMH), free androgen index (FAI), total testosterone, and clinical hyperandrogenism (hirsutism assessed by Ferriman-Gallwey score). Hyperandrogenism, in particular, the authors note, is a core etiologic characteristic of PCOS, with a principal symptom being infrequent or absent menstruation.

These findings were published in Frontiers in Endocrinology

“Diet has been reported as the first-line management of PCOS. However, this relationship is still controversial,” the authors wrote. “We aimed to evaluate whether diet could promote reproductive health in women with PCOS, while providing evidence-based nutrition advice for clinical practice.”

Among their results, 9 of the RCTs investigated outcomes related to a low-carbohydrate diet; 6, a low glycemic index/load diet; 4, the DASH diet; and 1, the Mediterranean diet. Diets lasted from 1 month to 1 year, with a median length of 3 to 6 months. For the fertility outcomes, the following results were seen with dietary interventions:

• Clinical pregnancy rate increased, especially with the Mediterranean and low-carb diets, and was shown to improve even more the longer the treatment.
• Miscarriage rates dropped.
• Ovulation improved vs minimal dietary treatment.
• Menstrual cycles increased and became more regulated, with the low-carb and Mediterranean diets and longer dietary interventions producing superior results.
• AMH concentration decreased more.
• FAI had more obvious improvement, with the low-carb diet and long treatment duration having more significant effects.
• Ferriman-Gallwey score for improvement of hyperandrogenism symptoms was superior vs control groups.
• SHBG level improvement was superior compared with minimal dietary intervention.
• Total testosterone levels decreased more, with continued drops seen with longer interventions and better improvements seen with the DASH or calorie-restricted diets.

Overall, the authors noted, their findings indicated that positive dietary changes both improved the participants’ fertility outcomes and mitigated hyperandrogenism, with longer dietary intervention having more significant effects on outcomes. In particular, a potential link was found between low-carb diets and higher pregnancy rates.

“From the results of subgroup analyses, we found that low-carbohydrate diets tended to be better on improving pregnancy rate, reducing the risk of miscarriage, and optimizing ovulation function,” they wrote.

To continue to increase knowledge on diet’s effect on pregnancy- and fertility-related outcomes,
the authors recommend additional studies, especially because of the heterogeneity and various phenotypes of PCOS, and for physicians to pay more attention to how sociodemographic disparities (eg, economic status, education level) can adversely affect diet.

“Since not all women with PCOS are overweight or obese, the impact of diet independent of weight loss is of great clinical interest,” they concluded. “This review only compared diet with minimal intervention. Future studies should expand the research scope and make comparisons with other commonly used pharmacological and surgical treatments or explore the possibility of combining interventions.”

Reference

Shang Y, Zhou H, He R, Lu W. Dietary modification for reproductive health in women with polycystic ovary syndrome: a systematic review and meta-analysis. Front Endocrinol. Published online November 1, 2021. doi:10.3389/fendo.2021.735954