The impact of vegetarian diet on sperm quality, sex hormone levels and fertility: a systematic review and meta‐analysis

Abstract

BackgroundAn increasing number of people have adhered to vegetarian diet since several years ago. Nowadays, the favorable effect of this dietary pattern on metabolic diseases is well established, but its impact on fertility and reproductive health as a serious health concern is not clear yet.Hence, we aim to summarize existing evidence, regarding the possible association between a vegetarian diet, and fertility as measured by key indicators such as sperm quality, and sex hormone levels.MethodsWe systematically searched online databases, including PubMed, ISI, Scopus, and Google Scholar, up to December 1st, 2022 using relevant keywords. We included observational studies that compared semen quality, sex hormone levels, and infertility in people who adhered to a vegetarian diet versus. Heterogeneity between studies was assessed using I2 and Chi‐square tests. Standardized mean differences (SMD) using a random/fixed model were calculated to assess outcomes between vegetarians and omnivores in included articles.ResultsFinally, out of 972 documents that were retrieved, 20 articles met our inclusion criteria, and 16 were eligible for quantitative synthesis. Results of meta‐analyses showed that there were no significant differences between vegetarians and omnivores in terms of semen quality parameters, including total sperm count, total and progressive sperm motility, sperm morphology, and sperm concentration. Seven studies on female sex hormones profiles were eligible for meta‐analysis. The only significant difference was the lower level of plasma estrone in vegetarians (Pooled SMD: ‐0.56; 95% CI: ‐1.08, ‐0.05; P‐value = 0.03) compared to the omnivores. Furthermore, our meta‐analysis revealed significantly higher sex‐hormone‐binding globulin (SHBG) levels in vegetarians men than in omnivores (Pooled SMD: 0.52; 95% CI: 0.18, 0.86; P‐value = 0.002).ConclusionDespite the numerous health benefits of a vegetarian diet, our review suggested that there were no conclusive positive or negative associations between vegetarian diet and semen quality, sex hormone levels, and infertility. Further studies are recommended to better understand vegetarian dietary pattern effect on infertility and reproductive health.This article is protected by copyright. All rights reserved.

Dietary Patterns and Fertility

“…Conversely, a vegan diet eliminates all animal products. The consequences of a vegetarian or vegan diet on fertility are still debated [122]. From one point of view, the possible lack of some nutrients, such as iron or essential fatty acids, could increase the risk of infertility.…”

Do Popular Diets Impact Fertility?

“…Lim et al [ 45 ] observed in a cohort of 805 Asian women, who reported their dietary data on FFQs, that those with a higher adherence to a healthy plant-based diet (higher vegetable and fruit intake) took less time to get pregnant than the women who followed an unhealthy plant-based diet (high intake of fast food and sugary drinks). Finally, a recent meta-analysis examined sex hormone levels and concluded that it was not possible to associate the vegetarian diet with a positive or negative effect on fertility and reported only a reduction in estrone levels in the vegetarian population [ 46 ].…”

“…Some studies have observed better sperm quality in vegan men compared to nonvegan men [ 49 ], and others have indicated lower quality [ 50 ]. Moreover, a recent meta-analysis reported no conclusive effect of a vegetarian diet on semen characteristics [ 46 ].…”