Estimates indicate that between 8% and 12% of couples of reproductive age face challenges related to infertility, which is defined as the inability to conceive after 12 months of unprotected intercourse. This issue is significant and affects public health globally, with many cases attributable to female-specific factors impacting millions of individuals.
Research has identified a connection between oxidative stress—caused by an imbalance between reactive oxygen species (ROS) and the body’s antioxidant defenses—and female infertility. Oxidative stress negatively influences critical reproductive processes, including follicle development, endometrial receptivity, and oocyte quality, underscoring the vital role of antioxidants in supporting reproductive health.
Key antioxidants contribute to reproductive well-being in various ways. For instance, vitamin A is essential for gene expression related to development, while vitamin C acts to neutralize harmful radicals through its antioxidant properties. Vitamin E plays a protective role for cell membranes, and essential minerals like zinc and selenium are crucial components of antioxidant enzymes that help shield cells from oxidative damage.
Antioxidant intake can be quantified using the Composite Dietary Antioxidant Index (CDAI), which measures the consumption of various dietary antioxidants, including carotene, selenium, zinc, and vitamins A, C, and E. The CDAI adjusts antioxidant consumption against total energy intake, allowing for comparisons across diverse dietary patterns and caloric needs.
Researchers hypothesized that a diet rich in antioxidants, reflected by a higher CDAI score, could mitigate oxidative stress and protect reproductive tissues, thereby reducing infertility rates. They utilized data from the National Health and Nutrition Examination Survey (NHANES), collected between 2013 and 2018 in the United States, to investigate this relationship.
After excluding males, individuals below or above reproductive age, and those with incomplete data, the study sample consisted of 2,162 women. Participants’ CDAI was assessed through two dietary recall interviews, in which they reported their food intake over the past 24 hours.
Infertility was evaluated using two specific questions in the survey. The researchers employed statistical models to analyze the relationship between CDAI and infertility, adjusting for various lifestyle factors such as alcohol consumption, smoking, physical activity, health conditions (including hypertension and diabetes), income, education, marital status, ethnicity, and age. The analysis revealed that 13.5% of participants reported experiencing female infertility.
Women reporting infertility differed significantly in terms of their CDAI levels, health conditions, income, marital status, and age. Notably, women who experienced infertility had higher CDAI levels, particularly in carotenoids, selenium, and vitamin C, but were also more likely to have health issues such as diabetes and hypertension.
In an initial unadjusted model, no association between antioxidant intake and infertility was found. However, after adjusting for various factors, the results indicated a significant relationship: a higher CDAI was associated with a reduced risk of infertility, suggesting a linear negative correlation. Specifically, selenium and vitamin C emerged as protective against infertility.
The negative associations between CDAI and infertility remained consistent across various subgroups, including lifestyle factors, health conditions, education, ethnicity, and age. The link appeared particularly pronounced in groups with earlier menarche (ages 11 to 13), heavy drinkers, and those not engaged in recreational activities, although these findings were not statistically significant.
This study presents a diverse and representative sample of the American population, enhancing the relevance of its findings. By utilizing CDAI to measure antioxidant intake, the research captures the combined effects and interactions of multiple antioxidants on reproductive health.
Despite its contributions, the study’s cross-sectional design limits the ability to establish causality, and the reliance on self-reported dietary data may introduce inaccuracies or biases. Additionally, it did not account for genetic factors influencing infertility, nor did it differentiate between various causes, such as polycystic ovary syndrome. Other dietary factors beyond antioxidants were also not assessed.
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