Like with fats and carbs, the type of protein you eat is probably just as important as the amount. Many people advise following a plant-based diet for fertility but does the research really support this?
Well, studies looking at different diet types as a whole, we tend to find that diets with less red or processed red meat are associated with better fertility.
In a prospective cohort study of women undergoing assisted reproduction, women who more closely followed a ‘Profertility Diet’ (with higher intake of seafood, dairy, and soy foods) had a significantly higher probability of implantation, clinical pregnancy, and live birth.
But these studies didn’t specifically look at the effect of different food groups so it’s hard to tell how much of a role the type of protein actually played.
What about when you look at protein types specifically?
The Nurses Study found that adding one serving of meat (red meat or poultry) per day, while maintaining the amount of calories was associated with a 32% greater risk of ovulatory infertility. Interestingly, this was due mostly to intake of poultry – chicken and turkey. Intakes of fish and eggs were unrelated to infertility. Overall, they found that consuming 5% of energy (about 25 grams) as vegetable protein as opposed to as animal protein was associated with a more than 50% lower risk of ovulatory infertility.
On the other hand, a study in the Netherlands looking at the Meddeterian diet found that poultry intake was the only food group (out of 30) that directly improved fertility! It’s possible that the differences seen between the two studies could be related to the differing use of hormones and antibiotics used in poultry across the world.
A Brazilian study on IVF patients found that consumption of red meat had a negative influence on the likelihood of blastocyst formation and rates of clinical pregnancy.
But another recent study in assisted reproduction found that total meat intake (as well as intake of eggs and vegetable protein) was not associated with outcomes. In fact, their study suggested there may be some benefits of meat intake of IVF outcomes. Only processed meat intake was associated with a lower fertilisation rate, but this did not translate into significant differences in the number of usable embryos.
While The Nurses Study carries a lot of weight, it’s clear that the evidence for plant-based proteins vs animal and fertility is mixed! This is an area we definitely need to see more studies on before making strong recommendations.
Meat is a great source of protein and other essential nutrients including zinc, iron, and B12 which are vital when trying to conceive. But evidence shows it can also increase exposure to hormones, antibiotics and environmental pollutants.
It has also been suggested that the negative effect of the consumption of red meat on fertility may be due to the increase in advanced glycation end-products (AGEs). AGEs are compounds formed when fat or proteins combine with sugar and change structure. Meat is especially prone to AGE formation during the cooking process. Studies have found that AGE accumulation is associated with a lower likelihood of ongoing pregnancy.
One thing that seems clearer is that excess preconception red meat intake is linked with an increased risk of gestational diabetes Mellitus (GDM) in pregnancy.
One study showed a higher intake of any animal protein, in particular red meat, was significantly associated with a greater risk of GDM. Another supported this, finding that higher pre-pregnancy consumption of total meat, especially red and processed meat, were significantly associated with an increased GDM risk.
At this stage, there is not enough evidence to say that you should cut out meat and follow an entirely plant-based diet for fertility.
But having more plant-based proteins doesn’t seem to be harmful to fertility and may indeed have benefits. It’s certainly been shown to have many other health benefits, including reducing the risk of gestational diabetes.
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I help people trying to conceive to ovulate, so they can get pregnant faster.
Tweaking your diet *before* you get pregnant not only improves your cycles and fertility, it also ensures that you have the healthiest pregnancy possible.