A friend sent through an article the other day, which had been tweeted by Dave Asprey (@bulletproofexec) to his 36,000 followers.
Its a perfect example of why you need to check your sources, and how badly science can be misrepresented on the internet.
The article, entitled “Is Soy Poisoning your Body?“, was full of anxious hand-wringing about the dangers of soy:
“Over the past two decades, soy has been widely promoted as a miracle food that can prevent heart disease, fight cancer and reduce hotflashes. Today, studies reveal the truth. The soybean is now being linked to cancer (4), thyroid disease (7), menstrual and fertility issues (6), compromised immunity (5) and even brain damage (3).”
The article’s author is Wendy Myers (@IwillLiveto110), who is a “Certified Holistic Health Coach”, and was published on the website of Ameer Rosic (@AmeerRosic), who is a “Biohacking Expert and Optimal Health Warrior”.
I eat a bit of soy (mainly tofu and soy milk), and was delighted to see that the article included references. I have absolutely no qualifications in Nutrition, Health, or science of any kind, but I can read, and generally trust the system of peer reviewed science to help me make informed decisions about my health.
So, with my health so obviously threatened by the evil soy, I figured I had to check out the articles.
What I found was hard to believe:
The articles she cited were generally not supportive of Wendy Myer’s claims, and in fact a few of them actually argued against them!
Unfortunately, most people would have read the headline, skimmed the article, seen that it was referenced, and assumed that she had scientific backing for what she was saying.
She does not, and most reputable science argues the opposite: soy can be a healthy part of your diet, and may in fact provide health benefits greater than their basic nutritional value.
This is not good enough
I believe that Ameer Rosic , as publisher of this article, had a responsibility to ensure the accuracy of the claims the article was making.
I also believe that Dave Asprey, as a promoter of this article, also had a responsibility to his followers to give this article more than a cursory glance. If you are going to set yourself up as an adviser on subjects like nutrition, you need to ensure that your advice has at least an element of legitimacy.
Let the buyer beware
If you’d like to have a look at what I mean, I’ve outlined below how the published, peer-reviewed articles relate to Wendy’s claims. I’d encourage you to read them.. its pretty interesting.
Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic
http://humrep.oxfordjournals.org/content/23/11/2584.full
Wendy Myers said:
“In men, soy lowers testosterone levels, and reduces the quantity and quality of sperm.”
The study had absolutely nothing to do with testosterone.
With regards to sperm quantity, the study said:
“there was a statistically significant trend toward decreasing sperm concentration with increasing soy foods intake”
which supports her point about sperm quantity. But it also said,
“the association between soy food intake and sperm concentration was more pronounced among overweight and obese men than among lean men”
which indicates that there might be something more complex at play here than just soy intake.
With regards to sperm quality, the study said:
“Soy food and soy isoflavone intake were unrelated to sperm motility, sperm morphology or ejaculate volume”.
So, no effect on sperm quality.
But the study’s authors themselves cautioned against drawing any conclusions from just this one study:
“The clinical significance of these findings remains to be determined. Owing to the scarcity of human data in this area, it is very important that this issue is examined further, ideally in randomized trials.”
US Food And Drug Administration. FDA Poisonous Plant Database.
http://checkoutthechallenge.com/blog/wp-content/uploads/2013/08/soypoisonPDF.pdf
Not sure why this is in her references, because she doesn’t actually reference this. It is the output of a keyword search on a database, which doesn’t really have anything to do with her article.
Brain aging and midlife tofu consumption.
http://www.ncbi.nlm.nih.gov/pubmed/10763906
Wendy Myers said:
“The soybean is now being linked to … brain damage”
The abstract said:
“higher midlife tofu consumption was independently associated with indicators of cognitive impairment and brain atrophy in late life”
So, point taken.
But..
This is a single, non-controlled study, published 14 years ago. I haven’t been able to find a single study which was able to reproduce these results. The study also only found an effect on men, not their wives, which once again indicates that something more complex than simple soy intake may be occurring here.
This is also supported by this study:
Does phytoestrogen supplementation affect cognition differentially in males and females?
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3677816/
which stated:
“In males, the data are sparse and equivocal, and more studies are needed to determine whether the effects will be beneficial or deleterious.”
In contrast, I submit these (double blind, controlled) studies:
Eating soya improves human memory.
http://www.ncbi.nlm.nih.gov/pubmed/11605103
Results:
“Those receiving the high soya diet showed significant improvements in short-term … and long-term memory … and in mental flexibility …. These improvements were found in males and females.”
Long-term soy isoflavone supplementation and cognition in women: a randomized, controlled trial.
http://www.ncbi.nlm.nih.gov/pubmed/22665144
Results:
“long-term dietary soy isoflavone supplementation in a dose comparable to that of traditional Asian diets has no effect on global cognition but may improve visual memory”
Isoflavones and cognitive function in older women: the SOy and Postmenopausal Health In Aging (SOPHIA) Study.
http://www.ncbi.nlm.nih.gov/pubmed/12792289
Results:
“isoflavone supplementation has a favorable effect on cognitive function, particularly verbal memory, in postmenopausal women.”
Breast, colorectal, and prostate cancer risk in the European Prospective Investigation into Cancer and Nutrition–Norfolk in relation to phytoestrogen intake derived from an improved database
http://ajcn.nutrition.org/content/91/2/440.full
Wendy Myers said:
“The soybean is now being linked to cancer”
Her inclusion of this study is probably the most surprising of all of her references. The point of difference for the study is that they were actually able to measure other sources of phytoestrogens (other than soy) including “fruit and vegetables, nuts, seeds, oils and beverages, cereals, and, for the first time in a large-scale study, foods of animal origin”.
Their findings:
“breast cancer risk was not associated with phytoestrogen intake”, in fact “greater intake of phytoestrogens during adolescence is associated with a reduction in breast cancer risk”
“For men, colorectal cancer risk was not associated with the intake of any of the phytoestrogens under study”, but “phytoestrogens may be a contributory measure through which prostate cancer is associated with dairy intake” ( No dairy, no problem )
“Among women, the risk of colorectal cancer was not associated with phytoestrogen intake”
In their conclusion, the authors stated that there is “little evidence that baseline intakes of most phytoestrogens are associated with subsequent risk of breast or prostate cancer. However, equol and enterolactone, found at high concentration in eggs and dairy products, may influence the risk of prostate cancer and colorectal cancer among women”
The phytoestrogen genistein induces thymic and immune changes: A human health concern?
http://www.pnas.org/content/99/11/7616.short
Wendy Myers said:
“The soybean is now being linked to … compromised immunity”
So, this is a 2002 non-controlled study carried out on mice, attempting to ascertain whether soy-based infant formulas could have an effect on thymic and immune systems.
Their results “raise the possibility that serum genistein concentrations found in soy-fed infants may be capable of producing thymic and immune abnormalities”.
But, they also said “extrapolation of results obtained with one species to another must be done with great caution, and clearly important questions still need to be addressed in the mouse model”
Two years later, a study entitled “Safety of Soy-Based Infant Formulas Containing Isoflavones: The Clinical Evidence” (http://jn.nutrition.org/content/134/5/1220S.full) reviewed studies actually carried out on humans, and concluded:
“Modern (Soy-Based Infant Formulas) were shown to support immune system development in young, growing infants”, and “infants fed (Soy-Based Infant Formulas) demonstrated immune cell status similar to infants fed human milk and weaned to cow’s milk and that their responses to immunization were consistent with normal immune system development”
Effects of phytoestrogens genistein and daidzein on production of human chorionic gonadotropin in term trophoblast cells in vitro
http://informahealthcare.com/doi/abs/10.1080/09513590500282273
Wendy Myers said:
“The soybean is now being linked to … menstrual and fertility issues”
So, now we’re getting into molecular science, which is a little deeper than I feel capable of commenting, except to say a couple of things:
1. Human chorionic gonadotropin (hCG) is only produced after conception, so any effect that soy has on its production really doesn’t have anything to do with menstrual issues, as she suggests (http://en.wikipedia.org/wiki/Human_chorionic_gonadotropin)
2. This is a study “in vitro” ie: outside of the normal biological context, on cells harvested from full term placentas.. a long way from actual living humans.
It seems to me that the authors are drawing a pretty long bow when they conclude “exposure to these estrogen-like compounds during sensitive periods of development may have the capacity to alter the function of the reproductive system and thereby influence fertility.”
I’d think that a more reasonable conclusion would be that “much more epidemiological data are required to interpret current molecular studies”
(The impact of dietary oestrogens on male and female fertility – http://journals.lww.com/co-obgyn/Abstract/2007/06000/The_impact_of_dietary_oestrogens_on_male_and.3.aspx)
Effects of Soy Protein and Soybean Isoflavones on Thyroid Function in Healthy Adults and Hypothyroid Patients: A Review of the Relevant Literature
http://online.liebertpub.com/doi/abs/10.1089/thy.2006.16.249
Wendy Myers said:
“The soybean is now being linked to … thyroid disease”
This study actually has a conclusion that is in direct opposition to her claim. You don’t even have to ready the study.. just look at the abstract:
“With only one exception, either no effects or only very modest changes were noted in these trials. Thus, collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function.”
This study’s author has also published an article entitled “Insights Gained from 20 Years of Soy Research” (http://jn.nutrition.org/content/140/12/2289S.full), where he states:
“Soyfoods represent first and foremost a healthful means by which to obtain protein and to add diversity to the diet, because most Americans consume legumes to a very limited extent. Independent of nutrient content, evidence in support of soyfoods providing health benefits such as reducing the risk of various chronic diseases ranges from very speculative to very encouraging. Overall, with the exception of those who are allergic, there is little evidence soyfoods are contraindicated for any individual.”
Nutrient Content of the U.S. Food Supply, 1909-2004: A Summary Report
http://www.cnpp.usda.gov/publications/foodsupply/foodsupply1909-2004report.pdf
Wendy Myers said:
“In the US, soy amounts to 20% of the calories consumed”
The report states that soy contributed to a higher level of selenium, dietary fibre, protein, vitamin E, copper (used in the formation of hemoglobin) in the American diet, none of which could be argued to be detrimental.
But the report also states that only about 3.1% of food energy comes from the combination of Legumes, Nuts and Soy.. which is nowhere near the 20% she claims.
