Regrettably, there is simply no clear-cut answer. There are women who claim that taking soy isoflavones did indeed help them to conceive. However, scientists have not studied the efficacy, and there isn’t any data to say whether it’s effective – or if it is safe.
Some experts even caution that ingesting highly concentrated soy products may hinder fertility, especially in ladies who have a “normal” menstrual cycle, meaning regular and under 35 days. In those women, soy supplements added to the diet could cause a woman’s natural cycle to go off-kilter.
The idea behind the theory is that soy isoflavones, which are a type of phytoestrogen (plant-derived estrogen), may work similarly to the fertility drug clomiphene (brand names Serophene and Clomid). They act on estrogen pathways in a woman’s body and can be used to manipulate the menstrual cycle. If your ovulation is irregular or non-existent, this could jump-start it. That being said, the remedies won’t help if your fertility problems are due to something else.
Theoretically, it works like this: estrogen receptors in your brain are blocked by the soy isoflavones, and your body thinks its estrogen levels are low. The body then kicks estrogen production into high gear. During this process, a group of eggs matures to prepare for one to be released during ovulation. After five days of taking the isoflavones, you stop. When this occurs, your body believes there is plenty of estrogen and so signals for ovulation.
Unfortunately, not all soy isoflavones react with the body in 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.”
Clomiphene does not present this danger because it is explicitly designed to act as an estrogen blocker, whereas soy isoflavones are more unpredictable in their impact.
On top of this, estrogen-like soy isoflavones may wreak havoc on other areas of the body, such as the ovaries, uterus and breasts. Research has shown that large doses of soy may cause cancerous cell overgrowth in these tissues. Eating too much may also lead to hypothyroidism.
Plus, says Blakeway, taking soy isoflavones in the first half of your cycle to boost estrogen production, then taking nothing in the second half to boost progesterone levels, may cause a hormone imbalance that damages fertility. That’s because the hormones linked in the menstrual cycle ebb and flow in a finely coordinated dance. If one is altered, it can affect the others.
Finally, soy isoflavones are sold as dietary supplements, which means they are not regulated by the U.S. Food and Drug Administration (FDA). Because of this, they are not subject to the same meticulous testing that prescription or over-the-counter (OTC) medicines 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, on the other hand, is governed by the FDA, has a long track record of safety, and is prescribed in specific amounts.
Soy isoflavones aren’t significantly more affordable than clomiphene, so saving money alone isn’t a good motivation to use them. The diet supplements generally cost $10 to $20 for one cycle. Clomiphene is covered by most insurance policies, so the expense would usually consist of just the co-payment (often in the range of $5 to $20). Without prescription drug coverage, one cycle of the brand-name drug Clomid costs around $60, while a cycle of the generic version (clomiphene citrate or Milophene) costs approximately half that – around $30. Of course, clomiphene does require a prescription and monitoring from a health professional.
If you are still interested in soy isoflavones to help with fertility, please consider the following advice:
• Any women over the age of 35 should seek medical intervention right away rather than exploring alternative options like soy that may not be practical or effective, says Shari Brasner, a professor and ob-gyn at Mount Sinai School of Medicine and author of Advice From a Pregnant Obstetrician.
• Soy isoflavones should be utilized only if you ovulate irregularly or not at all. Do not use them if you have any health issues such as uterine fibroids, uterine polyps, endometriosis, fibrocystic breasts, or thyroid disease, as those could be made worse by taking concentrated phytoestrogens,
• Likewise, it’s wise to avoid soy isoflavones if you have polycystic ovarian syndrome (PCOS)– even though clomiphene is in fact often prescribed for women with this condition. Phytoestrogens can aggravate PCOS, says acupuncturist Blakeway. Clomiphene is a safer bet for women with PCOS since specialists know exactly how the drug acts and it has better-expected results.
• The recommended dose to take is 80 to 200 mg per day on cycle days 3 to 7 or 5 to 9 (just as you would if you were taking prescription clomiphene), advises Blakeway. Always use the lowest dose possible, and don’t change it during the five-day period. Moreover, stick to supplements – it is simply not realistic to try to get the advised amount through food alone.
• Always speak with your doctor about possible interactions between soy and any medications you’re taking, including thyroid medications, antibiotics and clomiphene.
• You may experience short-term side effects. These include fatigue, headaches, breast tenderness, and digestive disorders. Taking the supplements before going to bed may help decrease the impact of these side effects.