Can soy isoflavones help me get pregnant?
Unfortunately, there's no clear-cut answer. Some women claim that taking soy isoflavones helped them conceive, but scientists haven't studied it and there's no data to say whether it's effective – or safe.
In fact, some experts caution that ingesting highly concentrated soy products may actually inhibit fertility, especially in women who have a "normal" menstrual cycle, meaning under 35 days and regular. In those women, taking soy supplements could throw a functioning cycle out of whack.
The idea is that soy isoflavones – a type of phytoestrogen, or plant-derived estrogen – may work similarly to the fertility drug clomiphene (brand names Clomid and Serophene). Both act on estrogen pathways in the body and can be used to manipulate the menstrual cycle. If you ovulate irregularly or not at all, this could kick-start ovulation. If your fertility problems are due to something else, the remedies won't help.
In theory, here's how it would work. The soy isoflavones block the estrogen receptors in your brain and fool your body into thinking its natural estrogen levels are low. In response, your body starts a cascade of events to boost estrogen production. (As part of this process, a group of eggs matures so that one will be ready for release during ovulation.) After five days, you stop taking the isoflavones. Once their receptor-blocking effect wears off, your body says, "Oh, we've got lots of estrogen now – time to ovulate" and releases a hormone that triggers ovulation.
The problem is that not all soy isoflavones necessarily act this way.
"Some soy isoflavones work as an estrogen blocker but others mimic estrogen – meaning the body thinks it is estrogen. This can cause health problems and make a hormone imbalance worse," says Jill Blakeway, a licensed acupuncturist and clinical herbalist and co-author of Making Babies: A Proven Three-Month Program for Maximum Fertility. "Someone with uterine fibroids, for example, may find that her condition gets worse after taking soy isoflavones."
The drug clomiphene doesn't present this risk because it's specifically designed to act as an estrogen blocker. Soy isoflavones are more varied and unpredictable in their impact.
Furthermore, certain tissues in your body that are sensitive to estrogen, such as the breasts, uterus, and ovaries, may not fare well when exposed to estrogen-like soy isoflavones. There's some evidence that large doses of soy may encourage cancerous cells to grow in these tissues. There's also evidence that eating too much soy can harm the thyroid and lead to hypothyroidism.
Plus, says Blakeway, if you take soy isoflavones in the first half of your cycle to boost estrogen production, but take nothing in the second half to boost progesterone levels, you can end up with a hormone imbalance that hurts fertility. That's because the hormones involved in the menstrual cycle rise and fall in a finely coordinated dance. If you alter one, it can affect the others.
Finally, soy isoflavones are sold as dietary supplements, which means they're not regulated by the U.S. Food and Drug Administration (FDA). As a result, they aren't subject to the same rigorous testing that prescription or over-the-counter medications are.
"There's just no way to tell that what you're taking contains the amount of soy (or other ingredients) you think it does," says nutritionist Hillary M. Wright, director of nutrition counseling at the Domar Center for Mind/Body Health at Boston IVF and author of The PCOS Diet Plan: A Natural Approach to Health for Women With Polycystic Ovary Syndrome. Clomiphene, in comparison, is regulated by the FDA, has a long track record of safety, and is prescribed in precise amounts.
Soy isoflavones aren't significantly cheaper than clomiphene, so saving money probably isn't a good reason to use them. The supplements typically run about $10 to $20 for one cycle. Clomiphene is covered by most insurance plans, so the cost would usually consist of the co-pay (often in the range of $5 to $20). If you don't have prescription drug coverage, one cycle of the brand-name drug Clomid costs around $60, and one cycle of the generic version (sold as clomiphene citrate or Milophene) costs around $30. Of course, using any form of clomiphene requires a prescription and care from a health professional.
If you still want to try soy isoflavones for fertility, consider the following advice:
- Women over 35 should seek medical intervention right away rather than spending time exploring an option like soy that may not be effective, says Shari Brasner, an ob-gyn and professor at Mount Sinai School of Medicine and author of Advice From a Pregnant Obstetrician.
- Try soy isoflavones only if you ovulate irregularly or not at all. Don't use them if you have any health issues that could be made worse by taking concentrated phytoestrogens, such as uterine fibroids, uterine polyps, endometriosis, fibrocystic breasts, or thyroid disease.
- If you have polycystic ovarian syndrome (PCOS), it's wise to avoid soy isoflavones – even though clomiphene is often prescribed for women with this condition. Phytoestrogens can aggravate PCOS, says acupuncturist Blakeway. Clomiphene is a better bet for women with PCOS, since experts know exactly how the drug works and it has more predictable results.
- Take a dose of 80 to 200 mg per day on cycle days 3 to 7 or 5 to 9 (just as you would if you were taking clomiphene), advises Blakeway. Use the lowest dose possible, and don't change it during the five-day course. Also, stick to supplements – it's not realistic to try to get the suggested amount through food alone.
- Talk with your doctor about possible interactions between soy and any medications you're taking, including antibiotics, thyroid medications, and clomiphene.
- Be aware that you may experience short-term side effects, including headaches, fatigue, breast tenderness, and digestive disturbances. Taking the supplements at bedtime may help minimize the impact of these side effects.
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