Veganist_ Lose Weight, Get Healthy, Change the World - Kathy Freston [31]
KF: But what about the hormones? I’ve heard it said that soy acts like estrogen in the body and adds to problems like girls starting their periods too soon and the development of certain types of cancers?
NB: It is true that there are hormones in soy products. The phytoestrogens found in soybeans (phyto means “plant”) are much weaker than the estrogens (female sex hormones) in a woman’s bloodstream. One common explanation for soy’s beneficial effects is that phytoestrogens reduce the effects of a woman’s natural estrogens. Think of the estrogens in a woman’s body as a fleet of jumbo jets. They land at an airport and pull up to the jetways where they will discharge their passengers and baggage. But what if the jetways were already occupied by small private planes? The jumbo jets would be unable to dock, and would be left sitting idle on the tarmac.
When phytoestrogens attach to the estrogen receptors on cells, they are like little private planes. They partially block a woman’s natural estrogens from attaching. From a health standpoint, that’s good. Many women have too much estrogen in their blood. And since estrogens tend to fuel the growth of cancer cells, anything that reduces estrogen effects helps cut cancer risk.
But recent research has shown that this explanation is almost certainly inadequate; soy’s effects are much more complicated, but it illustrates how foods can temper the negative effects of hormones.
KF: Does soy increase your risk of fibroids?
NB: It might even reduce the risk. Fibroids are knots of muscle tissue that form within the thin muscle layer that lies beneath the uterine lining. Estrogens can encourage these muscle cells to overgrow. Fibroids are not cancerous, but sometimes they become large and painful.
A study of Japanese women found that the more soy women ate, the less likely they were to need a hysterectomy, suggesting that fibroids were less frequent. In a study of women in Washington State, soy did not seem to help or hurt, perhaps because American women eat very little soy, compared with their Japanese counterparts. What did have a big effect in this study were lignans, a group of phytoestrogens found in flaxseed and whole grains. The women consuming the highest amounts of these foods had less than half the risk of fibroids, compared with the women who generally skipped these foods. So, again, phytoestrogens seem beneficial, countering the effects of a woman’s natural estrogens, although in this case the benefit comes from foods other than soy.
KF: What if you have hypothyroidism?
NB: Some studies have suggested that soy isoflavones take up some of the iodine that would normally be used to make thyroid hormone. The same is true of fiber supplements and some medications. In theory, then, people who consume soy might need slightly more iodine in their diets (iodine is found in many plant foods, and especially in seaweed and iodized salt). However, clinical studies show that soy products do not cause hypothyroidism.
Soy products do seem to reduce the absorption of medicines used to treat hypothyroidism. If you take these medicines, your health-care provider can easily check to see if your dose needs to be adjusted.
KF: Okay; back to diabetes; can it be reversed?
NB: Yes. When people begin a healthful diet, most see big improvements in weight, cholesterol, and their blood sugar. Their need for medications diminishes, and some may not need medications at all. In some cases, you would never know they had had diabetes. However, I caution people not to simply throw their medications away. They need to speak with their doctors so they can alter their medication regimens only when and if it is appropriate.
Let me describe a case: A man named Vance joined our study. His father was dead by age thirty, and Vance was thirty-one when he was diagnosed with diabetes. As our study began, he started a low-fat, vegan diet and gradually lost