A new study published in Frontiers in Nutrition has identified a surprising connection between diet and female infertility, revealing that both low and excessively high scores on a gut-related dietary index may increase the risk of infertility.
Researchers used the Dietary Index for Gut Microbiota (DI-GM)—a novel tool designed to reflect how diet impacts gut health—to examine the diets and fertility outcomes of 3,053 American women aged 18 to 45. The findings suggest that while a better gut-friendly diet generally lowers infertility risk, pushing the score too high may have the opposite effect.
The study showed a non-linear relationship between DI-GM scores and infertility. Women with lower scores were more likely to experience infertility. However, once a DI-GM score surpassed 8, the risk began to rise again—a surprising inflection point that researchers say highlights the importance of dietary balance over extremes.
“This pattern suggests that dietary interventions targeting the gut microbiota could help address infertility,” the authors noted, adding that the key may lie in maintaining an optimal range rather than maximizing gut-friendly food intake.
Infertility, defined as the inability to conceive after 12 months of unprotected intercourse, affects roughly 12.5% of couples of reproductive age worldwide. It is increasingly seen as a major public health issue—second only to cardiovascular diseases and cancers, according to some health agencies.
Common causes include ovulatory dysfunction, polycystic ovary syndrome (PCOS), endometriosis, fallopian tube issues, and immune-related disorders. In recent years, researchers have begun to explore how modifiable lifestyle factors, such as diet, could play a role in reproductive health—especially as gut health is increasingly linked to various female reproductive conditions.
The researchers pulled data from the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2018. Participants completed two 24-hour dietary recall questionnaires, which were used to compute individual DI-GM scores ranging from 0 to 13. The index includes 10 favorable food components—such as fiber, fermented dairy, green tea, soy, and whole grains—and four unfavorable ones, including red meat, processed meat, refined grains, and high-fat foods.
Infertility status was determined through responses to two questions in the Reproductive Health Questionnaire, while additional demographic and health-related data were factored into the analysis.
Out of the initial 29,400 NHANES participants, the study focused on 3,053 eligible women. Among them, 370 (12.12%) reported infertility. These women were more likely to be older, have a higher body mass index (BMI), be married, smoke, and have pelvic or metabolic health issues.
Statistical analyses initially showed a straightforward trend: lower DI-GM scores correlated with a higher risk of infertility. But further analysis using restricted cubic spline (RCS) models revealed a more complex picture. While increasing DI-GM scores up to 8 reduced infertility risk, scores beyond this point appeared to reverse the benefit—suggesting that excessive consumption of certain “gut-friendly” foods might not be as beneficial as previously assumed.
The researchers also found that participants with lower DI-GM scores had higher levels of triglycerides and fasting plasma glucose, and lower levels of HDL cholesterol. Additionally, infertility rates were highest among those in the lowest DI-GM quartiles (Q1 and Q2), and significantly lower in the higher quartiles (Q3 and Q4).
Subgroup analysis showed that the non-linear relationship between DI-GM scores and infertility held true across different demographic and health categories, reinforcing the robustness of the findings.
The study concludes that while diet does play a significant role in female fertility through its influence on gut microbiota, the relationship is far from simple. Pushing for extremely high DI-GM scores may backfire, and dietary interventions should prioritize balance over excess.
“Achieving an optimal DI-GM score—not merely the highest score—may be key to reducing infertility risk,” the researchers emphasized.
As infertility continues to rise globally, these findings offer promising insights into non-pharmaceutical strategies for prevention, highlighting the gut-fertility connection as a new frontier in reproductive health.
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