Greetings All! Today we are pondering the subject of soy in an attempt to determine if we should consume it, how much, and which types are best. The reason we are focusing on this today is because during a Forum discussion about canola oil (which is bad!), the subject of soy came up, and there were several opinions about its health benefits, or lack thereof. Someone then suggested that we start a discussion string on the topic of soy specifically. I will therefore report on information that I found and also that Leslie Olsen, a fellow member of the Health and Wellness Networking Group, provided. Okay, here we go…
First, let’s consider recommendations from the AHA. This editorial summarizes the recent American Heart Association (AHA) Science Advisory on soy protein and isoflavones (phytoestrogens) published in the February 21, 2006, issue of Circulation: http://atvb.ahajournals.org/content/26/8/1689.full. I recommend you read the entire article; in summary the authors conclude the following:
– Earlier research indicating that soy protein compared with other proteins has clinically important favorable effects on LDL cholesterol and other cardiovascular disease risk factors has not enjoyed confirmation from many studies reported during the past 10 years.
– No benefit is evident on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure. Thus, the direct cardiovascular health benefit of soy protein or of isoflavone supplements is minimal at best.
– Soy protein or isoflavones have not been shown to improve vasomotor symptoms of menopause, and results are mixed regarding slowing of postmenopausal bone loss.
– The efficacy and safety of soy isoflavones for preventing or treating cancer of the breast, endometrium, and prostate are not established; evidence from clinical trials is meager and cautionary as regards a possible adverse effect.
So the net is that they were not able to identify a significant benefit of soy on CVD, menopause symptoms, or cancers and indicated a possible adverse effect on cancers. Let’s keep going…
Next, consider the 2006 article “The Science of Soy: What Do We Really Know?” by science writer Julia R. Barrett: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1480510/. This article provides good background information on soy, and she concludes by stating that most researchers do agree on is that we are only just beginning to truly understand the nature of soy, and that much more research is needed before it is possible to make firm health recommendations.
Okay, that was informative but did not provide any concrete recommendations. Moving on…
Now, consider the viewpoint from the Harvard School of Public Health: http://www.hsph.harvard.edu/nutritionsource/protein-full-story/. Again I recommend reading the section on soy (I don’t necessarily agree with their sentiments on saturated fat in the other sections); in summary they recommend eating soy in moderation. They state that soybeans, tofu, and other soy-based foods are an excellent alternative to red meat, as in some cultures, tofu and soy foods are a protein staple. They caution that if you haven’t grown up eating lots of soy, there’s no reason to go overboard: Two to 4 servings a week is a good target; eating more than that likely won’t offer any health benefits and we can’t be sure that there is no harm.
So eating it in moderation is ok, but may not offer any health benefits, and may have adverse effects. I’d still like a more meaty (so to speak) explanation, so let’s keep looking…
Let’s check in with Dr Oz. His article is entitled “The Two Faces of Soy – Does it Harm or Help”, which sums up the confusion around this food pretty well: http://www.doctoroz.com/videos/two-faces-soy-does-it-harm-or-help. He notes the following:
“It’s not clear why researchers are having trouble getting dependable findings. It could be inherent in the study; diet research is notoriously difficult to conduct and control. Or the fact that soy comes in many forms with varying components. Or the study population muddies the findings because people around the world have different personal and ethnic physiology.”
He does a nice job going through the currently understood effects of soy on various health conditions and provides recommendations that may be subject to change based upon more learning:
– Limit soy to one serving a day (no more than 30 milligrams of isoflavones)
– Choose good quality soy such as tofu, tempeh and miso
– Skip the “frankensoy” processed soyfoods
– Avoid soy supplements made from isolated soy components such as isoflavones like genistein and daidzein
He also recommends moderation and avoiding the highly processed soyfoods. This is a good start, but he does not mention anything about avoiding GMO soy, which I believe should be included in any recommendation concerning soy. Let’s make one more stop…
Time to check in with trusty Dr. Hyman, who is not afraid to call it as he sees it: http://drhyman.com/blog/2010/08/06/how-soy-can-kill-you-and-save-your-life/. Here also the title captures the duplicitous nature of soy. This is a great article which I suggest you read in its entirety. I appreciate his detailed review of the literature and recommendations the most. Here they are:
– The dangers of soy are overstated (and the benefits may be, too).
– We eat far too much processed soy (and processed foods in general). Stay away from those in your diet including soy protein concentrates or isolates, hydrolyzed or textured vegetable protein, hydrogenated soy bean oil, non-organic sources of soy, and soy junk food like soy cheese and ice cream. Don’t eat them.
– Whole soy foods can be a source of good quality protein and plant compounds that help promote health.
– Eat only organic soy. Stay away from genetically modified versions. (There it is!!)
– Replace soy oil with olive oil, fish oil, nuts, and seeds.
– Breastfeed your child. I prefer that no one feed dairy or soy formula to their babies, but if you have to, try not to worry about it. (Little skeptical about this one, and note that it must be organic, and not, GMO soy!)
– Don’t worry about soy’s effect on breast cancer if you eat it in the forms and amounts I recommend. It has even been shown to protect against breast cancer if you start eating it at a young age. (This is presumably from the Shanghai Study, see reference )
– The effects on the thyroid are not significant or relevant unless you are deficient in iodine (which you can easily get from eating fish, seaweed or sea vegetables, or iodized salt).
His recommendations are consistent with the other references included in this post, and stress moderation and whole ORGANIC soy foods. The only thing I would add is to lean towards fermented soy products because they are easier to digest due to the presence of probiotics. In light of the uncertainty regarding soy, I think this is the best we are going to do.
Thanks for joining us! I’d love to hear other viewpoints because this is an interesting subject. Is the information in this article consistent with your knowledge and experience?
 Abstract of Shanghai study: http://ajcn.nutrition.org/content/89/6/1920.abstract