 About 1 in 4 women will eventually suffer from fibroids. Most commonly manifesting is excessively heavy periods in pain or pressure. Why might you feel pressure? Because you may be carrying around 26 pounds of tumors in your uterus. Fibroids are the most common reason women get hysterectomies, having their uterus removed completely, a major surgery associated with disability and death. All surgery carries risk. The chances of dying within a month of surgery may only be about 1 in 1200, which makes it among our safest surgeries, safer than getting your gallbladder removed, for example. But of course you lose the ability to bear children and cost billions of dollars a year. Yet despite the high prevalence, significant pain and suffering and huge economic impact, relatively little is understood about the cause and disease process that lead to fibroid tumors. Avoiding atomic bomb blasts whenever you can is probably a good idea in terms of decreasing fibroid risk. What about more easily modifiable risk factors? Well, alcohol consumption is associated with increased risk, particularly beer. Whenever you hear that, whenever you hear beer specifically, you think of the hormonal effects specific to beer, specifically the powerful phytoestrogen found in hops. Well, if that phytoestrogen is increasing fibroid risk, what about the phytoestrogens in soy? Well, this was looked at in the Black Women's Health Study. Fibroids are two to three times more prevalent among African-American women, so they thought maybe dairy intake might be contributing to the disparity, given their higher levels of lactose intolerance. And indeed, dairy consumption was associated with reduced risk. They figured it was the calcium content, or maybe the vitamin D, but perhaps the women were drinking soy milk instead, and that was increasing their risk? No, soy intake was found to be unrelated. Same finding in a group of predominantly white women, though they did note a protective association with the amount of lignans flowing through their bodies. Lignans are another class of phytoestrogens found predominantly in flax seeds, but throughout the plant kingdom. Hard to make any generalizations about soy phytoestrogens, though, as soy consumption was rather low across the board. This was done in Washington state. If you go to Japan, where they have the highest per capita soy consumption in the world, you get a bigger spread of intakes. The researchers had previously found that soy intake was inversely associated with the risk of hysterectomy, meaning women who ate more soy had lower hysterectomy rates, suggesting a potentially protective effect of soy against uterine fibroids. Since that's the main reason women have their uterus removed, this would be consistent with in vitro studies. It found that the main soy phytoestrogens seemed to inhibit fibroid tissue proliferation in a petri dish. But when they specifically looked, there was no evidence of a linked soy at all, protective or otherwise. The same was found in one study out of China. Fruit and vegetable intake was associated with significantly lower risk of fibroids. Soy food consumption was not, but a second study out of China published the same year found a significant association between soy milk intake and fibroids. That's consistent with the three alarming case reports of women with symptomatic fibroids reporting an unusually high intake of soy milk, or regularly consuming excessive amounts of soy, or extremely high intakes of soy every day for decades. It's hard to take these cases seriously when nowhere do they actually say how much they were consuming. The only quantitative mention was 40 grams of isoflavones, which roughly translates to 400 gallons of soy milk every day. That would be excessive, but also impossible. The only way to know for sure is to put it to the test, not just a population study or anecdotal reports, but randomized women to two years of soy phytoestrogens, the amount found in three to five cups of soy milk a day, and no significant effect on the frequency or growth of fibroids was found.