Debunking the anti-soy myths

Despite the abundance of scientific evidence demonstrating the benefits of whole soy foods, many people have been scared off from healthful foods like edamame by the anti-soy propaganda (lacking responsible scientific integrity) that continues to float around the internet.

Edamame. Flickr: cl_03

It is true that the nutrient-depleted isolated soy in protein powders and processed foods is likely problematic. And of course, I recommend steering clear of genetically modified soy, as its safety, phytochemical value, and environmental impact remain questionable.

However, research has shown overwhelmingly that whole and minimally processed soy foods (like edamame, tofu and tempeh) provide meaningful health benefits. The presence of isoflavones, a class of phytoestrogen, has sparked much of the controversy around soy. There were concerns that these plant estrogens could potentially promote hormonal cancers, such as breast and prostate cancers; however, those fears were unfounded. I have previously discussed the large body of evidence that convincingly suggests that whole and minimally processed soy foods protect against breast cancer. In addition, a 2009 meta-analysis of studies on soy and prostate cancer found that higher soy intake was associated with a 26% reduction in risk.1 In addition, it appears that isoflavones have a number of anti-cancer effects that are unrelated to their ability to bind the estrogen receptor. Accordingly, soy foods are not only associated with decreased risk of hormonal cancers, but also lung, stomach, and colorectal cancers.2-4 (For further discussion of soy foods and health, see the May 2012 member teleconference.)

An article posted by John Robbins seeks to finally put the soy misinformation to rest. He provides a balanced review of the available information, addressing all the common concerns about soy, from cancer and osteoporosis risk to protein digestibility and mineral absorption.

Soy is not a magic pill or a poison; it is simply a bean.

One can’t argue with the data – the associations between minimally processed soy intake and reduced risk of cancers has been reported over and over again. There is no real controversy here.  However, one still should not eat lots of soy products, to the exclusion of other valuable foods. Variety is crucial for obtaining diversity in protective phytochemicals, and a variety of beans are health promoting, along with many other foods.  So use good judgment, avoid processed foods, GMO foods and eat a variety of whole natural plant foods including beans such as black beans, chickpeas, lentils and enjoy some edamame, tofu and tempeh as well.

 John Robbins: The truth about soy

 

Image credit - Flickr: cl_03

References:

1. Hwang YW, Kim SY, Jee SH, et al: Soy food consumption and risk of prostate cancer: a meta-analysis of observational studies. Nutr Cancer 2009;61:598-606.
2. Yang WS, Va P, Wong MY, et al: Soy intake is associated with lower lung cancer risk: results from a meta-analysis of epidemiologic studies. Am J Clin Nutr 2011;94:1575-1583.
3. Kim J, Kang M, Lee JS, et al: Fermented and non-fermented soy food consumption and gastric cancer in Japanese and Korean populations: a meta-analysis of observational studies. Cancer Sci 2011;102:231-244.
4. Yan L, Spitznagel EL, Bosland MC: Soy consumption and colorectal cancer risk in humans: a meta-analysis. Cancer Epidemiol Biomarkers Prev 2010;19:148-158.

Walnuts may promote male fertility

Infertility affects 10-15% of couples trying to conceive, and it is estimated infertility is at least in part due to the male in at least one-third, and up to 60% of these cases.1,2  Several dietary factors affecting fertility have been identified in women. Can men also improve their diet to improve their fertility?

 Walnuts

Certain micronutrients are thought to contribute to male reproductive fitness. Oxidative stress can damage sperm, and accordingly higher blood antioxidant capacity, carotenoids, and vitamins C and E have been associated with higher sperm count and motility. Infertile men have been shown to have lower circulating levels of these antioxidant nutrients compared to fertile men.3,4 Adequate folate, abundant in green vegetables, may also promote fertility by preventing DNA damage in sperm.5 In contrast, higher saturated fat consumption, and cheese specifically, have been linked to lower semen quality.2,6,7

Omega-3 fatty acids may also contribute to semen quality. Previous observational studies had shown that higher omega-3 fatty acid intake associated with higher rate of favorable sperm morphology (shape), and that fertile men tend to have higher blood omega-3 levels than infertile men.2,8 Deficiency in the omega-3 fatty acid DHA was shown to produce infertility in male mice, adversely affecting sperm count, morphology and motility. DHA supplementation restored these parameters to normal.9 Similarly, in a study of infertile men, DHA+EPA supplementation improved sperm counts compared to placebo.10

A latter study built on this previous omega-3 data by testing the effects of regular walnut consumption on semen quality in healthy young adult men (21-35 years old). Walnuts are rich in ALA, an essential omega-3 fatty acid and the precursor to DHA and EPA. However, there are many anti-inflammatory and beneficial compounds in walnuts that could be collectively responsible for the health benefits found in walnuts.  They contain more than a dozen phenolic acids, numerous tannins (especially ellagitannins), and a wide variety of flavonoids. The control group maintained their usual diet and was instructed to avoid eating nuts. The intervention group added about 3 ounces (75 grams) of walnuts to their usual diets each day for 12 weeks. Blood omega-3 ALA concentrations increased in the walnut group. Sperm vitality, motility and number of normal-morphology sperm were enhanced compared to baseline in the walnut group, whereas there were no changes in the control group.11 This study suggests that ALA (found in walnuts and flax, chia and hemp seeds) in conjunction with other beneficial nutrients in walnuts makes them a valuable food for  male fertility.

Couples who plan on becoming pregnant should follow a healthful, high-nutrient diet (including plenty of ALA-rich nuts and seeds), not only to better their chances of conceiving, but also to protect the future health of their children. Children’s health is influenced by their parents’ diets even before conception.12

In addition to focusing on whole plant foods, maintaining a healthy weight and minimizing exposure to agricultural pesticides (by eating organic produce when possible and minimizing animal foods) and endocrine disrupting chemicals (such as BPA and phthalates) are additional factors that can help to maintain favorable semen quality.13-19

 

References:

1. FamilyDoctor.org: Male Infertility [http://familydoctor.org/familydoctor/en/diseases-conditions/male-infertility.html]
2. Attaman JA, Toth TL, Furtado J, et al: Dietary fat and semen quality among men attending a fertility clinic. Hum Reprod 2012;27:1466-1474.
3. Benedetti S, Tagliamonte MC, Catalani S, et al: Differences in blood and semen oxidative status in fertile and infertile men, and their relationship with sperm quality. Reprod Biomed Online 2012;25:300-306.
4. Minguez-Alarcon L, Mendiola J, Lopez-Espin JJ, et al: Dietary intake of antioxidant nutrients is associated with semen quality in young university students. Hum Reprod 2012;27:2807-2814.
5. Boxmeer JC, Smit M, Utomo E, et al: Low folate in seminal plasma is associated with increased sperm DNA damage. Fertil Steril 2009;92:548-556.
6. Afeiche M, Williams PL, Mendiola J, et al: Dairy food intake in relation to semen quality and reproductive hormone levels among physically active young men. Hum Reprod 2013.
7. Jensen TK, Heitmann BL, Jensen MB, et al: High dietary intake of saturated fat is associated with reduced semen quality among 701 young Danish men from the general population. Am J Clin Nutr 2013;97:411-418.
8. Safarinejad MR, Hosseini SY, Dadkhah F, et al: Relationship of omega-3 and omega-6 fatty acids with semen characteristics, and anti-oxidant status of seminal plasma: a comparison between fertile and infertile men. Clin Nutr 2010;29:100-105.
9. Roqueta-Rivera M, Stroud CK, Haschek WM, et al: Docosahexaenoic acid supplementation fully restores fertility and spermatogenesis in male delta-6 desaturase-null mice. J Lipid Res 2010;51:360-367.
10. Safarinejad MR: Effect of omega-3 polyunsaturated fatty acid supplementation on semen profile and enzymatic anti-oxidant capacity of seminal plasma in infertile men with idiopathic oligoasthenoteratospermia: a double-blind, placebo-controlled, randomised study. Andrologia 2011;43:38-47.
11. Robbins WA, Xun L, FitzGerald LZ, et al: Walnuts improve semen quality in men consuming a Western-style diet: randomized control dietary intervention trial. Biol Reprod 2012;87:101.
12. Ng SF, Lin RC, Laybutt DR, et al: Chronic high-fat diet in fathers programs beta-cell dysfunction in female rat offspring. Nature 2010;467:963-966.
13. Juhler RK, Larsen SB, Meyer O, et al: Human semen quality in relation to dietary pesticide exposure and organic diet. Arch Environ Contam Toxicol 1999;37:415-423.
14. Swan SH: Semen quality in fertile US men in relation to geographical area and pesticide exposure. Int J Androl 2006;29:62-68; discussion 105-108.
15. Bonde JP: Male reproductive organs are at risk from environmental hazards. Asian J Androl 2010;12:152-156.
16. Nordkap L, Joensen UN, Blomberg Jensen M, et al: Regional differences and temporal trends in male reproductive health disorders: semen quality may be a sensitive marker of environmental exposures. Mol Cell Endocrinol 2012;355:221-230.
17. Pflieger-Bruss S, Schuppe HC, Schill WB: The male reproductive system and its susceptibility to endocrine disrupting chemicals. Andrologia 2004;36:337-345.
18. Mocarelli P, Gerthoux PM, Needham LL, et al: Perinatal exposure to low doses of dioxin can permanently impair human semen quality. Environ Health Perspect 2011;119:713-718.
19. Jensen TK, Andersson AM, Jorgensen N, et al: Body mass index in relation to semen quality and reproductive hormones among 1,558 Danish men. Fertil Steril 2004;82:863-870.