Wednesday, May 14, 2008

The Great Soy Conspiracy and A Word on Accountability

So here's my analysis of the article I mentioned last time, of which this is excerpted and edited from the email:

I can see why you’re concerned about soy after reading the article. I read it and it lulled me into a false sense of objectivity before smacking me with its biased and inflammatory statements. It’s child abuse to give an infant soy formula? Seriously? (Breast milk is best for an infant, actually, and normally all he or she needs nutritionally.) The article is the antithesis of how I would like people to approach science and nutrition, especially when it comes to looking at primary research. Marc Leduc, the article’s author and creator of the website, presents an absolutely one-sided argument against soy. Here’s one of the many problems I have with what Leduc wrote:

Some sources claim that "soy has demonstrated powerful anticancer benefits...the Japanese, who eat 30 times as much soy as North Americans, have a lower incidence of cancers of the breast, uterus and prostate."(7)

Indeed they do. But the Japanese, and Asians in general, have much higher rates of other types of cancer, particularly cancer of the esophagus, stomach, liver and pancreas.(8) Asians throughout the world also have high rates of thyroid cancer.(9) The logic which links low rates of reproductive cancers to soy consumption requires attribution of high rates of thyroid and digestive cancers to the same foods, particularly as soy causes these types of cancers in laboratory rats. [Emphasis mine]
Why the sudden lack of citation(s) here? He doesn’t point to any studies that would support this last statement, and he doesn’t cite any research dated after 2002, the year the article was written, even though the website seems to have been last updated in 2006. There are also limitations with looking at rat studies and cancer that he doesn’t address. (Consider the amount of soy that would need to be given to rats and the fact that no one can ever conduct an intervention study on humans where they are fed possible carcinogens, at least, not without breaking several laws.) Speaking of citations, the fact that he only highlights links to other parts of his website is somewhat disconcerting. If those articles follow a similar standard as this one on soy, then I’m even more troubled.

Oh wait. Here’s something troubling. An article from the Complementary Alternative Medicine Association:
The second main "anti-nutrient" soybeans contain is phytic acid. Present to some degree in all types of beans, phytic acid blocks the uptake of important minerals, such as iron, magnesium, calcium and especially zinc. Soybeans have the highest phytic acid levels of any legume, and as such have an extraordinary ability to cause mineral deficiencies. Third World countries with diets high in grains and soy have the most profound deficiencies of these minerals. []
From Leduc’s article:
Soybeans also reportedly contain an anti-nutrient called "phytic acid", which all beans do. However, soybeans have higher levels of phytic acid than any other legume. Phytic acid may block the absorption of certain minerals, including magnesium, calcium, iron and zinc. Epidemiological studies have shown that people in 3rd World Countries who have high consumption of grains and soy also commonly have deficiencies in these minerals. It must also be noted that this may be of particular concern with regard to babies who are using soy-based infant formulas. [Paragraph 5]
To me, the wording is a little too similar to go without a citation. (Plagiarism…) Also, notice that Leduc says phytic acid (or phytates) “may” interfere with some mineral absorption, but then when he restates this fact three paragraphs later, he declares that phytic acid does indeed block this absorption. (As a writer, he should have noticed that.) To be clear, phytates can hinder the overall absorption of the above minerals by binding to them, but most cooking and preparation methods can reduce the amount of phytates to varying levels. In the case of nonheme (plant) iron and phytates, simultaneously consuming vitamin C or a little meat with the phytates can counteract some of phytates’ binding effects.

When I wrote to you about soy, I didn’t cite any primary research articles to you for a few reasons. Unlike Leduc, for each study that presents a conclusion one way, there can be a handful or more of other studies that present the opposite conclusion. For example, here’s the link to a full text of a meta-analysis from a 2002 Journal of Nutrition issue that looks at data from studies on the possible effects of soy on premenopausal women and men: Here’s the abstract for a study from the most recent issue of Topics in Clinical Nutrition that looks at soy and postmenopausal women: (Unfortunately, the full article is only available to subscribers or through database access to the journal.) I could keep going with similar citations and counterexamples, but then it would be inappropriate overkill here and counterproductive as well. Unless you want to know where my information comes from (lectures, nutritional science textbooks, journal databases, primary and secondary sources, and some computer searches) or you want to know the scientific details behind what I say, I see no reason to write that way to you. You’re a person asking my informed opinion about something related to food and nutrition, and that’s the context to which I’ll respond.


And this is how I see my site here. As I've mentioned before when I started developing this blog, I am learning nutrition as a student. There's no RD after my name nor do I claim to be offering any health advice in any capacity beyond that of another person on the street. What I will endeavor to do here, however, is to write responsibly, especially when it comes to nutrition.

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