Fertility and diet: To Soy or not to Soy

With the rising infertility rates amongst couples in today’s society, there has been much confusion on what foods to avoid and what foods to eat in order to help couples conceive. One of these foods is soy – do we eat it or not? Although there have been studies for either side, the gist of it is that a glass of soy milk a day probably won’t hurt your fertility. Like everything else with diets, moderation is best. This will leave room for you to get variety in your diet, as well as avoid any potential harm to your fertility due to over-consumption.

There have been a few studies that suggest high levels of soy protein may decrease fertility. According to the American Journal of Clinical Nutrition, it has been shown that a woman ingesting 60g of soy a day gains an average of two and a half days on her cycle. If you are wondering, that is about three 12-ounce glasses of soymilk a day for a month – an amount that most people don’t consume in western culture. In other words, it’s quite excessive!

Conversely, there have been just as many papers published on how soy does not affect fertility or a woman’s cycle. If you compare countries like Japan and China who consume soy products regularly due to their diets, their fertility rates are not lower than that of Canada or the USA. The reason being that Japanese and Chinese diets utilize up to 10g of soy a day as a condiment, whereas western diets use soy as a filler in a majority of processed foods. Furthermore, excess soy is produced and marketed as a health food and an alternative to meat – this leads to an overload in soy consumption.

Physiologically, soy lowers the levels of Follicle Stimulating Hormone (FSH – responsible for stimulating the ovaries in producing eggs) as well as Luteinizing Hormone (LH – responsible for triggering the release of the egg) – so how does this affect a woman’s body?

For normal bodily function, the ovaries are stimulated by FSH and the ovaries produce estrogen (Estrogen is the primary hormone in regulating menstrual cycles). For the typical woman, it takes little FSH to stimulate the ovaries in producing estrogen. Now because soy foods contain phytoestrogens (literally meaning plant derived estrogens, a much weaker version as compared to estrogen within the body), the body thinks that it is producing too much of it’s own estrogen and compensates by lowering FSH levels. Lowering FSH levels results in lower estrogen levels and leads to longer cycles.

For the average woman, consuming soy will not likely upset the hormonal balance between FSH, LH and estrogen to impact their ability to conceive. On the other hand, women who have been struggling to get pregnant should consider cutting soy foods from their diet.

Is there any actual benefit for fertility with the ingestion of soy? Like many IUI (intra-uterine insemination) or IVF (in-vitro fertilization) protocols which require women to take estrogen pre-ovulatory, soy is a natural way to boost the body’s estrogen without going on a high dose of artificial hormones and the side effects that can coincide.  Because soy is a plant-derived estrogen, it has also been shown to aid in menopausal symptoms when the woman’s body stops producing estrogen on its own. Another bonus would be because soy’s form of estrogen is far less potent than what the body produces, women won’t get as much exposure to ovarian hormones which decreases risk in breast cancer. Aside from hormone levels, it also decreases LDL cholesterol (Low Density Lipoproteins, the ‘bad’ kind that accumulates within your arteries), and increases HDL cholesterol (High Density Lipoproteins, the ‘good’ kind that sucks the LDL out of your system).

With all this talk of women being affected by soy and estrogen, what about men? Are they get impacted by soy products as well? According to the Lancet, a medical journal from the UK, eating phytoestrogens like soy can possibly lower sperm counts. Soy contains phytates, which are substances known to interfere with Zinc absorption. Since male fertility is strongly tied to Zinc, a mineral necessary for sperm creation as well as testosterone metabolism, sperm counts decrease. To top it off, the estrogens in soy can interfere with the thyroid’s ability to absorb iodine – iodine is required by the thyroid to produce hormones. And with low thyroid levels, it equates to low libido.

So should you eat soy or shouldn’t you? If you’re experiencing fertility problems, it would be a good idea to limit the amount of soy in your diet to eliminate the possibility of it’s effect on your fertility. Of note, it is only the protein portion of soy that contains the phytoestrogens, so flavorings such as soy sauce are fine. Tofu, textured vegetable protein (TVP), soy nuts and soy milk are then ones you should be trying to avoid or have in moderation.

Soy can also be hidden in many foods: Flour, oils, milk and lecithin as examples can all contain soy, so be sure to read the ingredient labels when you buy your food.  TVP is also commonly found in many fast foods and imitation meat products. As with any food, it is best not to over-consume. Eating soy in moderation allows you broaden your scope of diet to help you get all the important nutrients your body needs, and allows you to avoid any potential harm to your fertility due to over-consumption.

For more information on soy and its effects on your fertility consult our acupuncturists or naturopathic doctors here at ALIVE Holistic Health Clinic.