Welcome to the first in a series of nutrition and health science journal reviews from the Biolent team! Strap in, firmly affix your learnin’ caps, and get ready for an open discussion of the peer-reviewed literature on such exciting topics as GMO foodstuffs, soy isoflavones, and the ups and downs of the glycemic index. Any questions, counterpoints, or shower thoughts can be discussed in the comments section. Please include sources for any factual claims, as we’re all learners here and we value scientific rigor.
We’ll kick things off today with a discussion of an article published in Circulation, a scientific journal of the American Heart Association (AHA). The article is “Soy Protein, Isoflavones, and Cardiovascular Health”. It’s a part of the AHA’s science advisory series, which is intended to provide a comprehensive summary of the scientific consensus on various topics. These are the articles that doctors, dietitians, and other health professionals use to determine best practices for counselling and treating patients, and they represent the best work of the scientific community to date on the topics they cover.
A bit of background: soy products are of interest to the powdered meal replacement community because of their high protein content, low cost, and oh-so-delicious taste and texture. We use soybean oil in Biolent preparations as a healthy source of polyunsaturated fats. It is the position of the Food and Drug Administration that soy products may benefit cardiovascular health, and so advertisers are allowed to state this benefit so long as their product contains at least 7.5g of soy protein per serving. Other health claims have been made regarding soy products, including reduced risk of certain types of cancer, osteoporosis, and menopausal hot flashes. In order to simplify things for busy readers, the American Heart Association conducted a review of a number of randomized controlled trials and collected these results into a single summary document available to the public, and intended for use by healthcare professionals in their practice.
Results were predictable mixed, but here’s the TL;DR in bold, followed by a bit of explanation:
1. Soy protein consumption has been shown to reduce LDL (bad cholesterol) by an average of about 3%, and up to 20% in some people. Reductions in LDL have been shown to reduce risk of heart attack, stroke, and other such things would just plain ruin Christmas dinner. These reductions were generally compared against a standard animal protein such as casein. Daily soy protein consumption in these studies varied from 18g/day to 50g/day, but above the minimum cutoff of 18g/day, there was no extra benefit from consuming more soy. Instead, the benefits of soy protein seem linked to initial LDL concentrations. If an individual had a very high LDL to start, they were more likely to see a greater LDL reduction from consuming soy than someone who had mildly elevated or average blood LDL at the start of the study period.
2. Soy protein has no appreciable effect on HDL (good cholesterol), triglycerides, lipoprotein(a) or blood pressure. These are all risk factors for heart attack and other cardiovascular diseases, and despite multiple randomized controlled trials, soy protein consumption has not been found to provide any benefits here. This doesn’t take away from the heart-protecting effects of soy on LDL, it just means that these other risk factors haven’t been linked to soy, for better or for worse.
3. Soy protein consumption has no appreciable effect on cancer risk, bone loss, or hot flashes. It has been suggested that isoflavones (phytoestrogens) in soy might be able to reduce risk of prostate, breast, and endometrial (uterine) cancer, as well as reducing postmenopausal osteoporosis and menopausal hot flashes in humans. No strong link has yet been established between soy consumption and any of these conditions, and not for lack of study- it appears the concentration of phytoestrogens in soy products simply isn’t high enough to change our physiology in a noticeable way. This is especially true of soy protein isolate, which is washed with alcohol during processing, effectively stripping away all isoflavones from the finished product.
4. Soy products should be generally beneficial to cardiovascular and overall health “because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Using soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health”.
I think it’s worth closing on point number four because it hints at a pretty simple principle that underlies much of the convoluted food science that we all love to dig around in. Plants are good for you! Your mom was right, and the prevailing Western diet high in saturated fat, salt, and sugar isn’t doing our hearts or our healthcare system any good. Based on the current science, soy protein could provide a heart-healthy alternative as an ingredient in soylent or as part of a more traditional diet.
Thankfully for those of us who don’t have the time to stalk the financial interests of every author of every paper they’ve ever read, or the money to hire a private investigator, the AHA has a standard policy of avoiding actual or potential conflicts of interest by requiring all their authors and reviewers to submit a Disclosure Questionnaire to highlight any sneaky lobby money or private interests that might bias their reporting of the literature. This information is available in table format at the end of the study. I won’t harp on it too much, but disclosure of conflicts is like, crazy important when evaluating research papers. If you don’t know what kinds of biases the authors might have, it’s really tough to critically appraise the conclusions they draw.
On that note, keep in mind that this review is being published by a private company that markets a product containing soy. This isn’t necessarily a bad thing, but we’re committed to transparency, so for your own sake, read the original article! Here’s another link to it, because google is too much work.
Hope you enjoyed entry one in this journal review series, or if you hated every minute of it I hope it at least got you worked up enough to do some reading of your own. If it just plain bored you to death and you still managed to make it all the way through, congratulations, you sadistic beauty, here’s a link to four-freaking-hundred hundred pictures of baby animals for your trouble. Once again, rather than just preaching the Word of Science here, we’re hoping to actually get a discussion going, so feel free to comment with further reading, corrections, or rebuttals- just please please please, cite any factual claims. There’s a lot of pseudoscience out there, but we’ll all be better off if we can stick to the real deal.
Nick from Biolent