Nutritional Factors
Publications under ‘Nutritional Factors’ examine the association of diet and various dietary components with fertility and reproductive outcomes.
Among Danish women planning pregnancy, over one third were not taking any dietary supplement (such as folic acid or a multivitamin).
Among Danish women planning pregnancy, caffeine intake and coffee intake were not associated with fecundability. Soda consumption was associated with slightly reduced fecundability. Tea drinking was associated with slightly increased fecundability.
Among Danish pregnancy planners, women who took a folic acid supplement were less likely to have a short menstrual cycle (<27 days). Other menstrual cycle characteristics (cycle regularity, duration and intensity of menstrual bleeding) were not associated with folic acid supplementation.
Folic acid supplementation (alone or as part of a multivitamin) was associated with increased fecundability in Danish pregnancy planners. This association appeared to be stronger among women with irregular menstrual cycles and among women with either short (<27 days) or long (≥30 days) menstrual cycles.
Low- or high-fat dairy intake was not consistently associated with fecundability in North American or Danish women. Our findings do not support the hypotheses that higher consumption of high-fat dairy improves fertility or that higher consumption of lactose or low-fat dairy harms fertility.
We studied the relationships between several types of dietary fat and fecundability in North American and Danish women. Intakes of total fat and saturated, monounsaturated, polyunsaturated, and omega-6 fatty acids were not associated with fecundability. High intake of trans fatty acids and low intake of omega-3 fatty acids were associated with reduced fecundability in North American women.
Higher intake of sugar-sweetened beverages, particularly sodas and energy drinks, was associated with lower fecundability in men and women. Intake of diet soda and fruit juice was not associated with fecundability.
Overall, dietary intake of iron was not consistently associated with fecundability in North American and Danish pregnancy planners. However, dietary iron intake was associated with higher fecundability among women with risk factors for iron deficiency (heavy menstrual bleeding and short menstrual cycles). Taking an iron supplement (alone or through a multivitamin) was associated with slightly higher fecundability among North American, but not Danish, pregnancy planners.
Among women, intake of fruits and vegetables with high pesticide scores was not associated with fecundability.
Phytoestrogens are hormonally-active compounds found in foods such as soy, cruciferous vegetables, nuts, and seeds. Phytoestrogen intake was not strongly associated with fecundability among women planning pregnancy in Denmark and North America.
Glycemic load measures the impact of eating a food on blood sugar. Among women attempting to conceive in Denmark and North America, diets high in glycemic load, carbohydrate-to-fiber ratio, and added sugar were associated with slightly lower fecundability.
Among North American and Danish women planning pregnancy, seafood intake was not associated with fecundability. However, greater intake of fried shellfish was associated with lower fecundability among North American women.
Glycemic load measures the impact of eating a food on blood sugar. Among women attempting to conceive in Denmark and North America, diets high in glycemic load, carbohydrates and added sugars (e.g., white bread, white rice, and noodles) were not consistently associated with risk of miscarriage.
Among Danish pregnancy planners, we found evidence that adherence to Danish dietary guidelines—which recommends greater intake of fish, root vegetables and rye bread—was associated with a lower rate of early miscarriage (pregnancy losses <8 weeks of gestation).
We studied the association between preconception intake of protein-rich foods (e.g., red meat, poultry, processed meat, seafood, eggs, plant-based proteins, and dairy) and risk of spontaneous abortion in PRESTO and Snart Foraeldre (Danish sister study). We did not find any consistent associations across cohorts.