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Can Soy Affect Fertility?

Soy foods are becoming increasingly popular all over the world due to mounting scientific evidence that they are a healthy, vegetarian form of protein. Studies have also shown that soybeans contribute towards lower levels of cholesterol, less risk of heart disease, breast cancer, and osteoporosis and fewer menopausal symptoms.

Soy contains phytoestrogen, a plant-derived estrogen, known as isoflavones. Not all isoflavones work in the same manner. Some act in the same way that natural estrogens in the body do; others work as anti-estrogens that inhibit estrogen activity.

Soy and Menopause

Menopausal women and those who are at risk of breast cancer benefit from soy through isoflavones that act as a mild form of estrogen in the body or as anti-estrogens that lower the amount of estrogen in the body. For women trying to fall pregnant this estrogen element may contribute towards a reduction in fertility according to scientists.

The Science Around Soy and Fertility

According to Parenting Weekly, the biggest problem concerning the current information on how soy influences fertility is that there simply have not been enough studies conducted.  However, it is still worth looking at the discoveries in order to discern whether soy has an impact on fertility.

Increasing Menstrual Cycles

According to a study done in 1994 that was cited in the American Journal of Clinical Nutrition, high soy levels in a woman’s body can decrease FSH (a hormone which stimulates follicles) and LH (the luteinizing hormone) and can lengthen her menstrual cycle by an average of 2.5 days. The same study reveals that most women should not worry, as the amount of soy needed to accomplish this would be the same as drinking three glasses of soymilk a day. However, most women that that have multiple risk factors for infertility may be more sensitive to soy.

Soy and Sperm

Another study done in 2005 at King’s College in London showed that the likelihood of human sperm losing its acrosomes (caps which allow the sperm to penetrate the egg) increased threefold after exposure to the isoflavone genistein which is found in soy.

Conflicting Results

The biggest problem faced by scientists and health experts when trying to ascertain whether soy has an effect on fertility is the amount of conflicting results. Other studies have shown that the amount of soy ingested has little or no negative effect on fertility. For instance, the American Journal of Clinical Nutrition mentions a study by the Department of Pharmacology and Toxicology, at the University of Alabama at Birmingham in 1998, where genistein was given to prepubescent rats. The results proved that there were no changes to fertility in the animals. Most scientists who are not convinced that soy affects fertility often point to countries where large amounts of soy is ingested and the fertility rate is high, such as Asian nations that consume a lot of soy and have high fertility rates. Ultimately, doctors are reluctant to prohibit soy intake because of all of its other health benefits. As an inexpensive and healthy source of protein, many medical practitioners, especially those in developing countries, would rather have patients consuming soy than suffering from malnutrition, which is far worse for fertility.

Soy In Your Diet

If you are experiencing fertility issues, try to limit the amount of soy in your diet so that you can rule out any possibilities that it is negatively affecting your fertility. Limit your intake of tofu, soymilk, tempeh, TVP, and soy nuts. As it does not contain phytoestrogens, you can safely use soy sauce.

  • Danielle Wyman

    If you have grown up a lactose intolerant person and have had soymilk present in your diet on a daily basis since basically birth, how does that effect your fertility? If I stop drinking soymilk now, will that improve my odds of possibly having a child?

  • earthsmagic

    Based on what I have been reading, long term soy usage can cause hormonal imbalances that can lead to unexplained infertility. The operative word is CAN. You will find people out there who drink soy milk on a daily basis and who have gotten pregnant right away. If you find that you are having a difficult time getting pregnant, you might want to cut back on your soy milk and change to another type of milk like almond or coconut milk. The soy can cause an imbalance in your hormones so you might also want to take a fertility supplement like Fertilaid to help balance your hormones before you start actively trying to get pregnant. Good luck!


Last modified: March 19, 2014


The information provided here should not be considered medical advice. It is based on the average experience of women trying to conceive and may not be what you may be experiencing. It's not meant to be a replacement for any advice you may receive from your doctor. If you have any concerns about your cycle or our ability to get pregnant, we advise you to contact your doctor.