Dietary factors and reproductive outcomes
Embargo Date
2022-05-14
OA Version
Citation
Abstract
Approximately 10–15% of couples experience infertility, the inability to conceive within 12 months of unprotected intercourse. Infertility often results in substantial psychologic and economic burden and has been associated with long-term adverse health outcomes including cardiovascular disease and gynecologic cancers. As reproductive failures may occur at any point in the cascade of processes necessary for pregnancy to occur, identifying mechanisms of and risk factors for infertility is an important public health goal.
Diet, a complex and multi-faceted lifestyle factor, has changed dramatically in both developed and developing nations over the last few decades and currently accounts for nearly a tenth of the global burden of disease. While many studies have examined the role of the intake of specific dietary nutrients or food groups in relation to reproduction, few studies have examined the effect of dietary patterns on reproduction, especially in women without conditions known to impact menstrual function or fertility. Compared with examining individual nutrients, dietary patterns better reflect how individuals eat, thus investigations of the health effects of dietary patterns provide more translatable evidence for designing health interventions and improving population health. The objective of this dissertation is to examine the impact of dietary patterns and food allergens, which may have increased due in part to shifting dietary patterns, on fertility in women. Examining the association between dietary patterns and reproductive hormones may help elucidate the potential mechanism of how diet relates to fertility.
In study one, we used data from BioCycle, a prospective cohort of regularly-menstruating premenopausal women living in New York state, to examine the association between three dietary patterns (the Healthy Eating Index (HEI)-2010, the alternative Mediterranean diet (aMed), and the Dietary Inflammatory Index (DII)) and reproductive hormone serum concentrations and anovulation. We observed that greater adherence to each of these dietary patterns was associated with slight hormonal changes and that these changes may be associated with ovulatory function. We found that women with the greatest adherence to the HEI-2010, the aMed, or the most anti-inflammatory diet had greater risk of anovulation than those with the lowest level of adherence or the least anti-inflammatory diet (Risk Ratio (RR): 2.65, 95% Confidence Interval (CI): 2.02; 3.47; RR: 2.05, 95% CI: 1.62, 2.60; RR:1.62, 95% CI: 1.23–2.14, respectively).
In study two, we used data from Snart Foraeldre (SF) and Pregnancy Study Online (PRESTO), two preconception cohorts of pregnancy planners in Denmark and North America, respectively, to evaluate the association between the same three dietary patterns assessed in study one (HEI-2010, aMed, and the DII), with the addition of the Danish Dietary Guidelines Index (DDGI), and fecundability, the per-cycle probability of conception. In both cohorts, we observed that consuming a dietary pattern lower in anti-inflammatory properties was associated with reduced fecundability. In the PRESTO cohort, we observed greater fecundability with greater adherence to the HEI-2010 or the aMed. We did not observe an appreciable association between greater adherence to the DDGI or the aMed and fecundability in SF.
In study three, we used data from PRESTO to evaluate the association between food allergens and fecundability. We found no appreciable association between history of diagnosed food allergy and fecundability. Within subsets of the cohort, including among those with a BMI ≥25 kg/m2 or women born ≥1990, we observed a slight association between food allergens and reduced fecundability.
In conclusion, we observed that those with greater adherence to each of the dietary patterns or to more anti-inflammatory diets had an increased risk of anovulation. Conversely, we observed that those with greater adherence to specific dietary patterns or a more anti-inflammatory diet had improved fecundability. We observed a slight association between dietary patterns and reproductive hormone levels, a potential mechanism underling the association between dietary patterns and anovulation and fecundability. We observed no appreciable association between food allergies and fecundability. These findings indicate that dietary factors likely play a role in the etiology of infertility but there may be different mechanisms, likely multifactorial and not yet understood, underlying each of these associations.