Dr. Oz on Soy
I have never watched the Dr. Oz show, but two days ago I got a phone call from my mother saying that Dr. Oz was telling people that processed soy can mess up your hormones.
Nerdles.com provides a run down on the show that includes:
“Now the #1 thing to avoid to keep your hormones in balance is processed soy. Processed soy is stripped of all the healthy omega-3s, fiber, and are ultimately left with carbs and soy protein isolate. Inside soy protein isolate, you’re finally left with estrogen and high-levels of this will interrupt your cycle….The gold standards of soy are miso, natto, and tempeh – get these into your diet instead for healthy hormone levels.”
But processed soy does not contain more isoflavones (the “soy estrogens”) per serving than unprocessed soy, so this doesn’t make much sense. Processing soy protein concentrates the protein, not the isoflavones.
And on Dr. Oz’s website, in the article, 4-Week Cyclical Hormonal Health Plan, they bring out the old Weston Price Foundation talking points, “Traditionally, Asian cultures consume no more than two teaspoons of fermented soy a day, which has been shown to be health-promoting, while more than that quantity becomes problematic.”
The idea that Asians limit their soy to two teaspoons a day, and that it is all fermented, is not backed up by the research as reviewed in my article, Soy: What’s the Harm? – Asian Intakes. By the way, two teaspoons of soy is only 1/12 of a typical 1/2 cup serving of tempeh – not even a serving per week.
Nor is there any evidence that more than two teaspoons a day is problematic. The entire article, Soy: What’s the Harm? is a discussion of how much soy is safe (or you can see the much abridged version, Response to Not Soy Fast).
Since I have not reviewed the large amount of research on soy and menstrual cycles in any rigorous way, I asked Dr. Mark Messina, one of the world’s leading soy experts, to comment on the statement that soy will interrupt your menstrual cycle and he said:
“Soyfoods and the phytoestrogens in soy have relatively minor effects on reproductive hormone levels in women. There is evidence indicating that soy may increase the length of the menstrual cycle by approximately one day. However, when only high-quality studies are considered, the effect of soy is no longer statistically significant. Whether a possible effect of soy on menstrual cycle length has clinical implications is unclear although longer cycles are associated with a lower risk of breast cancer.”
In addition to the information on soy, that entire article, 4-Week Cyclical Hormonal Health Plan, sounds pretty far-fetched.