Dietary factors have been implicated in the pathogenesis of multiple health problems and the idea that dietary changes may enhance fertility seems promising. The impact of diet and dietary supplements is of interest among couples seeking pregnancy. Therefore, this text is going to be articulated around 3 questions.
Is my weight a problem?
Body mass index (BMI) affects fertility by both excess and defect.
Obesity (BMI ≧ 30 kg/m2) is related to a 3-fold increased risk of infertility in women, as well as a reduced chance of success in in vitro fertilization (IVF) treatment. Ovulatory dysfunction is considered to be the main cause of infertility in obese women, although alterations in follicular recruitment, problems in oocyte quality, embryo development and implantation have also been described. In fact, in women who ovulate normally, each one-unit increase in BMI above 29 is associated with a 5% reduction in the probability of spontaneous conception.
The mechanisms by which obesity interferes with male fertility are less well defined. It has been suggested that decreased fertility may be due to hormonal alterations (lower testosterone concentration and higher estrogen and leptin concentration), increased oxidative stress and erectile dysfunction (due to peripheral atherosclerosis).
What should I eat?
The definition of a reproductively healthy diet varies among the different published studies, but there are points on which most agree: it should be rich in whole grains, fruits, vegetables, fish and olive oil. This kind of diet is associated with better ART results and higher probabilities of pregnancy, although it is not related to the risk of miscarriage.
- Carbohydrates
In general, ART has worse outcome rates in patients who regularly consume foods high in refined sugars. It has not been established whether carbohydrate intake has an effect on ovulatory and reproductive function in healthy women, but reducing carbohydrate intake in women with polycystic ovary syndrome improves ovulatory function.
- Proteins
The importance of consuming a sufficient amount of protein is a fact, but the role in reproduction of its different sources is not clear. Available studies point to a relationship between red meat consumption and the risk of infertility and inadequate embryonic development.
As for fish consumption, although it is considered an adequate source of protein, the degree of environmental contamination may modify its relationship with fertility. Couples seeking pregnancy should avoid consuming fish with high mercury content and from waters with high levels of contamination.
Dairy products have been suggested to have a toxic effect on fertility due to their high galactose content (in mice it decreases ovulation) and potential estrogen content (marketed milk comes from pregnant cows). To date, no association has been found between dairy consumption and the risk of ovulatory infertility and its relationship with seminal quality is quite controversial.
Concerns have been raised regarding the potential impact on reproduction by phytoestrogens contained in soybeans and soy derivatives. In initial mammalian studies, phytoestrogens were found to be deleterious to reproductive function, although so far human studies have shown that they may improve ART outcomes and do not worsen seminal quality or testosterone levels in the male.
- Fatty acids
We can consider the consumption of high amounts of polyunsaturated fatty acids, especially omega-3 fatty acids, and low amounts of unsaturated fatty acids to be beneficial.
Should I take any supplements?
- Folic acid: folic acid supplementation has been associated with better embryo quality, higher chances of gestation, lower risk of miscarriage and reduced risk of infertility due to ovulatory factor.
- Vitamin D: no significant associations with conception or miscarriage have been found in healthy human populations, so its supplementation in patients who are not deficient in vitamin D is controversial.
- Antioxidants: the Cochrane review on the use of oral antioxidants in subfertile males with altered seminogram found that it could be associated with an improvement in pregnancy and live birth rate. Due to the heterogeneity of the studies and the broad definition of “antioxidant” it was not possible to specify which compounds and doses were recommended.