Which Soy Foods Are Safe?

This is an excerpt from Lesson 26 of The Mastery Program. This lesson is written by Brenda Davis, RD.

Which Soy Foods Are Safe?

Let’s consider the evidence.
Soy has a long history of use in Asia, and within vegetarian populations throughout the world. Two of the healthiest, long-lived populations in the world – the Okinawan Japanese and the Seventh-day Adventists in Loma Linda, California – are frequent soy consumers. The traditional Okinawan diet derives about 5-6% of calories from soy or about two servings a day.[1]
If soy foods were dangerous, its effects would be reflected in the health and longevity of these populations. Soy has been extensively researched. In fact, about 2,000 new studies on soy are released yearly. The value of soybeans for human health depends on the form and quantity eaten.
There is considerable negative press about soy, especially via the internet. There are some legitimate concerns about soy, especially if your thyroid is compromised. Another concern is overuse of soy, particularly in the highly processed forms.
However, the vilification of all soybeans and other soy foods can usually be traced back to groups promoting animal-based diets. These groups are strongly invested in encouraging the consumption of meat, eggs and dairy. They do an exceptional job of convincing consumers to steer clear of soy.
When plant-based enthusiasts jump on the anti-soy bandwagon, they remove a category of food that has the potential to make their diets more nutritious, more healthful and more enjoyable. While it is not necessary to eat soy, it is not necessary to avoid it either. Some individuals need to avoid or limit soy due to allergy or thyroid challenges. However, for most people, soy foods are both safe and nutritious.

What Soy Foods Are The Most And Least Healthful?

Traditional soy foods are generally the most healthful choices. They fall into two categories: fermented (e.g. tempeh, miso and natto) and non-fermented (e. g. tofu, soymilk, edamame soybeans and soy nuts). Both are healthful.
The soaking and cooking that occur when soybeans are prepared for use in non-fermented products – such as soy milk and tofu – reduces anti-nutrients while also improving digestibility and mineral availability. The same came be said for fermented soy products such as tempeh.
The fermentation process has an additional benefit too; it helps to support beneficial gut bacteria. In certain foods, it can even add vitamin B12 (e.g. in tempeh fermented in some Asian countries such as Indonesia) and/or vitamin K2 (e.g. in natto).
More heavily processed soy products, such as veggie meats and protein powders, are rich sources of digestible, high quality protein. However, most veggie meats are much higher in sodium and added fats than traditional soy foods. Read labels, and limit these veggie meats to special occasions. A few soy products, such as soy cheeses, contain partially-hydrogenated oils (trans fats) and should be completely avoided.[2]
In some cases, the soy protein isolates and concentrates used in energy bars and veggie meats (e.g. burgers, sausages, deli slices and wieners) are extracted using a solvent called hexane. Hexane is also used to extract oil from soybeans, corn, nuts, seeds and olives. Why? It’s more cost-effective than squeezing the oil out by pressing. However, hexane is a petrochemical solvent, an air pollutant, and a known neurotoxin!
Negative health consequences associated with hexane have been reported in factory workers with chronic exposure. Although hexane evaporates during food processing, trace residues can remain in food products, and the long term health consequences of these trace amounts are unknown.
The FDA has not set an upper limit for hexane residues in food. The European Union has set an upper limit of 30 ppm (parts per million) in soy products, as they are sold to the consumer. The Cornucopia Institute sent a sample of soy meal and soy grits to the FDA for testing, and these samples contained 21 and 14 ppm hexane respectively.
Some companies that use hexane processed soy claim they only source products which are free of residual hexane (you can search websites online or check with the manufacturer). Although testing for hexane residues in soy foods has been very limited, evidence suggests levels are very low – a small fraction of what one would receive through exposure to gasoline fumes, quick-drying glue or cleaning solvents.[3-5]
But as long as you have a choice, wouldn’t you rather choose products that are free of hexane residues and limit the intake of these products?
To avoid soy protein that has been processed using hexane, purchase certified organic products (in the United States, this means products with the USDA seal). The Cornucopia Institute has a list of hexane-free products on their website: cornucopia.org.

Is Non-GMO Edamame Considered Healthy, Even Though It’s Not Fermented?

Yes, edamame is a very healthy soy food. Edamame are immature, green soybeans. They can be purchased in or out of the pod (usually frozen). Edamame is unprocessed, and has all the benefits of an unprocessed bean, with the added benefit of phytoestrogens.
Many people believe that fermented soy is the only healthful soy. They claim that Asians eat mostly fermented soy. While fermentation increases friendly bacteria and improves digestibility, this doesn’t mean that unfermented soy foods are unhealthy.
In Japan, about half of the soy consumed is fermented (miso and natto); the rest is unfermented (mostly tofu). In the rest of Asia, a much smaller proportion of total soy intake is fermented soy foods.[6]

Is All Conventional Soy GMO?

Although not all conventional soy is GMO, the vast majority is. In 2013, 93% of the soy grown in the United States was genetically modified.[7] Globally, about 6% of soy crops are used directly as human food (mostly in Asia), and most of the balance is used as animal feed.[8]
Many people who avoid soy due to concerns about GMO do not stop to consider that the beef, pork, chicken and dairy products they are eating came from animals raised on GMO soy!

Can Soy Be Trusted To Be Non-GMO When Organic?

The U. S. National Organic Standards Board prohibits the use of GMOs, and processors cannot accept GMO-contaminated ingredients to be used in organic products. However, they have not established thresholds for adventitious GMO presence. Nor have they introduced testing requirements.
Contamination of “organic” crops can result from drifting pollen and other natural forces while they are still in the fields, or during the harvest, storage or shipment of the product. However, the extent of this contamination is unknown.
Until routine testing is required, we cannot be certain. However, choosing certified organic is our best bet for minimizing exposure to genetically modified crops. Some companies do their own testing for GMO. One example is Eden Foods. The bottom line is that it’s possible for certified organic products, including soy, to be contaminated by GMO crops.[9-11]

Is Soy Allergenic?

Yes, soy is allergenic. Soy is among the top eight foods that cause 90% of allergic reactions. The other seven foods are milk, eggs, peanuts, tree nuts, wheat, fish and shellfish. The prevalence of soy allergy is estimated at about 0.4% of children in the United States.
It is estimated that 10-14% of infants who are allergic to cow’s milk develop an allergy to soy when provided soy infant formula. Soy allergy tends to be a transient allergy of infancy and childhood, which is commonly outgrown by the age of ten years. The prevalence of soy allergy among adults is unknown, but is thought to be very small.[12]
The most common symptom of soy allergy is eczema. In infants, soy allergy can trigger diarrhea, vomiting, abdominal distress, irritability, intestinal blood loss and failure to thrive. Some people also react with respiratory symptoms such as cough, asthma, wheezing or rhinitis. Anaphylactic reactions to soy are extremely rare.
If you are allergic to soy, you will need to be diligent about label reading, since soy is used extensively in processed foods. In the United States, all foods that contain soy must list it in the ingredients or in a “contains soy” statement. TVP (textured vegetable protein) and HPP (hydrolyzed plant protein) are derived from soy. Some people who are allergic to soy can tolerate soy lecithin and soy oil.[12,13]

What Benefits Does Soy Have?

Yes, the nutritional benefits of soy are similar to other legumes, although soybeans are higher in protein and fat, and lower in carbohydrates. Soybeans derive 25-38% of their calories from protein, compared with about 20-30% for other legumes.
The quality of protein in soy is similar to that of animal products, and is better than that of other legumes. (See Lesson 14, on Protein, in The Mastery Program for details.) Soy foods provide an excellent, easy way for children and adults to reach recommended intakes of the amino acids lysine and tryptophan.
While most legumes are generally low in fat (2-15% of calories), soybeans derive about 40% of calories from fat. (This is why tofu is such a useful ingredient for creamy salad dressings and other creamy recipes.)
The fat in soybeans is mainly polyunsaturated, including 7% alpha-linolenic acid (an omega-3 fatty acid). Whole soybeans are a rich source of fiber, but processing diminishes fiber content. Soybeans are high in B-vitamins, especially niacin, pyridoxine and folic acid. They are also good sources of minerals such as calcium, iron, magnesium and copper.
Calcium is often added to soymilk, and tofu is commonly set with calcium, so these products are particularly rich calcium sources. For many years, experts thought iron was poorly absorbed from soy. However, more recent evidence suggests absorption is quite high.[14, 15]
When you consume them with fruits and vegetables rich in vitamin-C, iron absorption is further enhanced. Nutrient absorption is also improved when soy is soaked, cooked or fermented. Soy products can contribute very significantly to nutritional needs of people during every stage of the lifecycle.[16]
Evidence suggests that regular soy consumption may provide a variety of health benefits, including lower risk of coronary heart disease, reduction in hot flashes, protection against some forms of cancer, and possible protection against osteoporosis.
In addition, compared with animal protein, soy protein may protect kidney function.[17, 18] (If you have compromised kidney function, many studies show that soy preserves renal function better than meat.)
Coronary heart disease (CHD) – Both clinical and epidemiologic evidence suggest that soy foods favorably alter CHD risk, and reduce risk of heart attacks.[19, 20] A 2011 meta-analysis of randomized controlled trials assessing the effects of soy protein on serum lipid levels estimated that a median intake of 30 grams of soy protein per day was associated with a reduction in LDL cholesterol of about 5%. Soy intake also increased HDL cholesterol levels and reduced triglycerides.
The authors concluded that one to two servings of soy protein (15-30 grams) has a significant, favorable impact on serum lipoprotein risk factors.[21] Research suggests that soy intake is inversely associated with an emerging risk factor called carotid IMT (carotid intima-media thickness). [22, 23] Carotid IMT is a test that measures the thickness of the intima and media in coronary arteries, and when carotid IMT is thicker, CHD risk is elevated.
Reduction in Hot Flashes – Experts have long speculated that the lower incidence of hot flashes in Asian women, especially Japanese women, could be explained, at least in part, by their more generous and consistent intake of soy foods.
Although data has been somewhat inconsistent, the weight of the evidence is favorable. A 2012 systematic review and meta-analysis of 19 trials reported that isoflavone supplements reduced the frequency of hot flashes by 21% and the severity of hot flashes by 26%.
Isoflavone supplements containing at least 18.8 mg of genistein were more than twice as potent as lower dose supplements.[24] Evidence to date is stronger for isoflavone supplements than for soyfoods.[25] So if you are a women who experiences very frequent hot flashes, you may receive the greatest benefit.
Reduced Risk of Prostate Cancer – Evidence suggesting that soy intake reduces risk of prostate cancer is encouraging. Prostate cancer is significantly lower in soy-consuming Asian populations, compared to North American or European populations. However, people who migrate from Asia to America and adopt Western diets quickly forfeit their advantage. [26, 27]
Asian men who consume about two servings of soy foods per day are about 30 -50% less likely to develop prostate cancer than Asian men who are not soy consumers.[28] A 2009 meta-analysis of 14 studies reported a 26% reduction of prostate cancer risk in the highest compared to lowest categories of intake.
It’s interesting to note that when fermented and non-fermented soy foods were analyzed separately, the non-fermented products cut risk by 30% while fermented soy foods did not affect risk.[29] A 2013 meta-analysis found a 51% risk reduction with intake of soy foods/soy isoflavones in men with clinically-identified risk of prostate cancer. [30]
Possible Protection Against Osteoporosis – Evidence from epidemiologic studies suggests that consumption of soy foods is protective against fractures.[31, 32] Results of clinical trials have been less encouraging, with most trials finding no benefit of soy intake.[33] However, a two year trial from Italy reported a 5.8% improvement of bone mineral density in postmenopausal osteopenic women given 54 mg genistein per day (about four servings of soy), compared to a 6.3% decrease of bone mineral density in the placebo group.[34]
Although the evidence to date has been disappointing, it is possible that soy benefits bone health over the long term, and the exposure time in short term clinical studies is insufficient to produce significant changes in bone density. It is also possible that the benefits of soy are due to components other than the isoflavones, and that long term interventions using traditional soy foods would yield better results.

Garlic Vegannaise

Makes 1 pint.
  • 10½ ounces (1 carton) silken tofu
  • 2 Tablespoons tahini
  • ¼ cup lemon juice
  • 1 clove garlic
  • 1 Tablespoon brown rice syrup, maple syrup or date paste
  • 1 teaspoon nutritional yeast
  • 1 teaspoon Dijon-style mustard
  • 1 teaspoon sea salt
1. Combine ingredients in a blender and puree until smooth, using as much water as needed to achieve desired consistency.

References

1. B J Willcox, et al. Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Ann. NY Acad Sci. 2007; 1114(1):434 – 455.
2. Davis, B and Melina, V. Becoming Vegan: Comprehensive Edition. The Book Publishing Co. Summertown TN. 2014.
3. Directive 2009/32/EC of the European Parliament and of the Council of 23 April 2009 on the approximation of the laws of the member states on extraction solvents used in the production of foodstuffs and food ingredients. Official Journal of the European Union.
4. Berkeley Wellness. May 1, 2012. berkeleywellness.com
5. Cornucopia Institute. Behind the Bean. 2009. cornucopia.org
6. Zhang X, et al. Soy food consumption is associated with lower risk of coronary heart disease in Chinese women. J Nutr. 2003; 133: 2874-8.
7. USDA. Adoption of Genetically Engineered Crops in the U.S. ers.usda.govx
8. Soy Facts. Soyatech. soyatech.com
9. Gillam, Carey. U.S. organic food industry fears GMO contamination. Reuters. 2008. reuters.com
10. National Organic Standards Board GMO ad hoc Subcommittee Discussion Document GMOs and Seed Purity. Feb. 6, 2013. ams.usda.gov
11. Riddle, Jim. University of Minnesota. Southwest Research and Outreach Center. GMO Contamination Prevention. What does it take? 2012. swroc.cfans.umn.edu
12. Vickerstaff Joneja J. The Health Professional’s Guide to Food Allergies and Intolerances. Academy of Nutrition and Dietetics. 2013
13. Food Allergy Research and Education (FARE). Soy Allergy. http://www.foodallergy.org/allergens/soy-allergy
14. Murray-Kolb LE, et al. Women with low iron stores absorb iron from soybeans. Am J Clin Nutr. 2003; 77: 180-4.
15. Lonnerdal B, et al. Iron absorption from soybean ferritin in nonanemic women. Am J Clin Nutr. 2006; 83: 103-7.
16. Davis, B and Melina, V. Becoming Vegan: Comprehensive Edition. The Book Publishing Co. Summertown TN. 2014.
17. Anderson JW. Beneficial effects of soy protein consumption for renal function. Asia Pac J Clin Nutr. 2008;17 Suppl 1:324–8.
18. Bernstein AM, et al. Are high-protein, vegetable-based diets safe for kidney function? A review of the literature. J Am Diet Assoc. 2007;107:644–50.
19. Zhang X, et al. Soy food consumption is associated with lower risk of coronary heart disease in Chinese women. J Nutr. 2003; 133(9):2874–2878.
20. Kokubo Y, et al. Association of dietary intake of soy, beans, and isoflavones with risk of cerebral and myocardial infarctions in Japanese populations: the Japan Public Health Center-based (JPHC) study cohort I. Circulation. 2007;116(22):2553–2562.
21. Anderson JW, Bush HM. Soy protein effects on serum lipoproteins: a quality assessment and meta-analysis of randomized, controlled studies. J Am Coll Nutr. 2011 Apr;30(2):79-91. Review.
22. Zhang B, et al. Greater habitual soyfood consumption is associated with decreased carotid intima-media thickness and better plasma lipids in Chinese middle-aged adults. Atherosclerosis. 2008;198(2):403–411.
22. Hodis HN, Mack WJ, Kono N, Azen SP, Shoupe D, Hwang-Levine J, Petitti D, Whitfield-Maxwell L, Yan M, Franke AA et al: Isoflavone soy protein supplementation and atherosclerosis progression in healthy postmenopausal women: a randomized controlled trial. Stroke. 2011; 42(11):3168–3175.
23. Taku K, et al. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012;19(7):776-90.
24. Levis S, Griebeler ML. The role of soyfoods in the treatment of menopausal symptoms. J Nutr. 2010;140:2318S-21S.
25. Shimizu H, et al., Cancers of the prostate and breast among Japanese and white immigrants in Los Angeles County. Br J Cancer. 1991;63(6): p. 963-6.
26. Cook LS, et al., Incidence of adenocarcinoma of the prostate in Asian immigrants to the United States and their descendants. J Urol. 1999;161(1): p. 152-5.
27. Yatani R, et al., Trends in frequency of latent prostate carcinoma in Japan from 1965-1979 to 1982-1986. J Natl Cancer Inst. 1988;80(9): p. 683-7.
28. Yan L, Spitznagel EL. Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis. Am J Clin Nutr. 2009;89:1155-63.
29. Yan L, Spitznagel EL. Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis. Am J Clin Nutr. 2009;89(4):1155-63.
30. van Die MD, et al. Soy and soy isoflavones in prostate cancer: a systematic review and meta-analysis of randomised controlled trials. BJU Int. 2013 Sep 5. doi: 10.1111/bju.12435. [Epub ahead of print]
31. Zhang X, et al. Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women. Arch Intern Med. 2005;165:1890–5.
32. Koh WP, et al. Gender-specific associations between soy and risk of hip fracture in the Singapore Chinese Health Study. Am J Epidemiol. 2009;170:901–9.
33. Marini H, et al. Breast safety and efficacy of genistein aglycone for postmenopausal bone loss: a follow-up study. J Clin Endocrinol Metab. 2008;93:4787–96.
34. Lagari VS, Levis S. Phytoestrogens in the prevention of postmenopausal bone loss. J Clin Densitom. 2013;16(4):445-9.

4 Comment(s)

  1. Thanks for this great garlic vegannaise recipe! I primarily use hummus as a sandwich spread and for dipping with veggies, but I have missed the old comfort of a more “dairy” like spread. This will make a tasty ingredient for potato and pasta salads as well!

    Heather | Reply

  2. I found this information interesting — thank you.

    Is there any way to avoid GMO contamination? I, for one, would like as little contaminated food in my diet as possible.

    Cornelia Bryant | Reply

  3. Thanks very much. This was a helpful article!

    Margaret Day | Reply

  4. Thank you! Very informative article.

    Oksa Pron | Reply

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