A lower dietary index of gut microbiota, reflecting a reduced microbial diversity, is associated with a higher risk of female infertility. Although the relation is non-linear, a large study, published on Frontiers in Nutrition, highlights the possibility of targeting gut microbiota diversity through dietary interventions to improve fertility in women.

Infertility affects one in eight couples worldwide, representing a significant clinical concern. Multiple factors, including genetic, environmental, and lifestyle, contribute to female infertility. Despite its high prevalence, effective preventive measures are still limited. 

Emerging evidences support the role of the gut microbiota also in fertility. At the same time, diet influences the diversity and abundance of the gut microbiota. The Mediterranean diet, for example, has been linked to a positive impact on reproductive health, with a higher ratio of pregnancies and live births. In contrast, the Western diet is associated with worse fertility. 

Given the relationship between gut microbiota composition and dietary patterns, it is important to use standardised indices to assess their impact. Among these, the recently developed dietary index for gut microbiota (DI-GM) addresses inconsistency in previous indices. To do that, DI-GM evaluates the influence of diet on the gut microbiota through 14 components identified as beneficial or unfavourable to gut health, effectively capturing the relationship between dietary quality and gut microbiota diversity. A lower DI-GM score has already been associated with a higher risk of certain conditions, such as diabetes, stroke, etc. However, its correlation with infertility remains unclear. 

This study involved over 3.000 women (18-45 years) over two years, collecting information about diet, nutritional status, health, and lifestyle.  These data were then correlated with the DI-GM score (ranging from 0 to 13) and fertility status, with infertility defined as the absence of ability to conceive after at least one year of unprotected intercourse.

Participant characteristics

Out of the 3.053 participants, 370 were infertile. About the infertile group:

  • Women in this group were generally older, with higher body mass index (BMI), higher income, and with common features, such as being married, smoking, cardiovascular and metabolic conditions (hypertension, dyslipidemia, diabetes, etc.)
  • The average DI-GM value was significantly lower in this group
  • Participants with lower DI-GM also showed higher triglyceride levels and fasting plasma glucose (FPG), but lower high-density lipoprotein cholesterol (HDL-C)

Correlation between DI-GM and infertility

DI-GM scores demonstrated a strong negative, though non-linear, association with infertility risk. Indeed, a lower score was linked to a higher risk. 

  • Below the threshold (score of ≤8), identified as the inflexion point, each unit increase in DI-GM was associated with a 14% reduction in the risk of infertility, supporting the hypothesis that gut-friendly dietary patterns support reproductive health.
  • Above that value (>8), higher scores correlated with an increment of 197% relative increase of infertility risk, suggesting harmful consequences of extreme diets
  • The association between DI-GM scores and the risk of female infertility is confirmed when considering demographic, socioeconomic status, lifestyle and health factors. 

“As a new dietary quality index that reflects gut microbiota diversity, further research and interventions using DI-GM could help develop strategies to prevent and reduce the risk of female infertility.”