Diet and fertility: a review

The literature on the relationship between diet and human fertility has greatly expanded
over the last decade, resulting in the identification of a few clear patterns. Intake of
supplemental folic acid, particularly at doses higher than those recommended for the
prevention of neural tube defects, has been consistently related to lower frequency of
infertility, lower risk of pregnancy loss, and greater success in infertility treatment. On the
other hand and despite promising evidence from animal models, vitamin D does not
appear to exert an important role in human fertility in the absence of deficiency. Antioxidant
supplementation does not appear to offer any benefits to women undergoing
infertility treatment, but it appears to be beneficial when it is the male partner who is
supplemented. However, the available evidence does not allow discerning which specific
antioxidants, or at which doses, are responsible for this benefit. Long-chain omega-3
fatty acids appear to improve female fertility, although it remains unclear to what extent
contamination of shared food sources, such as fish with high levels of environmental
toxicants, can dampen this benefit. Lastly, adherence to healthy diets favoring seafood,
poultry, whole grains, fruits, and vegetables are related to better fertility in women and
better semen quality in men. The cumulative evidence has also piled against popular
hypotheses. Dairy and soy, once proposed as reproductive toxicants, have not been
consistently related to poor fertility. In fact, soy and soy supplements appear to exert a
beneficial effect among women undergoing infertility treatment. Similarly, because data
from large, high-quality studies continue to accumulate, the evidence of a potentially
deleterious effect of moderate alcohol and caffeine intake on the ability to become
pregnant seems less solid than it once did. While a complete picture of the role of
nutrition on fertility is far from complete, much progress has been made. The most salient
gaps in the current evidence include jointly considering female and male diets and testing
the most consistent findings in randomized trials.