The Health Benefits of Soybeans

By on November 23, 2008
soybeansThe soybean (Glycine max) originated in China and has been cultivated there for over 13,000 years. It was first introduced into Japan before becoming popular in other Asian countries.

Soy food products come in many forms such as the traditional miso, tempeh, tofu, soy sauce and the more recently developed soy milk, soy flour, soy hot dogs, soy burgers and soy cheese.

The simple sugars raffinose and stachyose found in unfermented soy foods are not digestible and can cause flatulence and abdominal discomfort.

The health benefits of soybeans and soy foods include reduced LDL cholesterol, cancer prevention and reduced coronary artery disease risk.

Health Benefits of Soybeans

  • Nutrients
    Soybeans are an excellent source of protein and molybdenum. They are a very good source of iron, calcium, phosphorus, and dietary fiber. They are a good source of vitamins B1, B2, B6, and E and folic acid. They also contain other health promoting compounds, including phytosterols, lecithin, isoflavones, phytoestrogens, and protease inhibitors. The amino acid profile of soy is a little low in methionine and tryptophan, but is still regarded as an excellent source of protein, soybeans (38% protein), soy flour (40 to 50% protein), soy protein concentrates (70% protein), and soy protein isolates (90 to 95% protein).

  • Reduce LDL Cholesterol
    Increased consumption of soy foods has been associated with reduction in LDL cholesterol in both clinical and observational studies. Human studies have also shown that soy protein is effective in lowering plasma cholesterol, LDL cholesterol and triglyceride concentrations.

    In one 8-week randomized, placebo-controlled trial in 117 patients with high cholesterol levles, LDL cholesterol was significantly reduced by 5.9% after consuming 15-25g/day of soy protein.

    A meta-analysis of thirty studies concluded that a daily dietary intake of 25g of soya protein resulted in small, highly significant reductions in total and LDL cholesterol (-6%)

    A preparation combining isolated soy protein with soy fibers and phospholipids has been shown to have twice the lipid-lowering effect of a preparation containing isolated soy protein alone.

  • Cancer Prevention
    Soybean consumption is thought to be one of the major reasons for the relatively low rates of breast cancer and prostate cancer in Asian countries.

    The isoflavones daidzein and genistein, found in soybeans and soy products have been shown in epidemiological studies to be protective against breast cancer and prostate cancer.

    These two isoflavones act as phytoestrogens (dietary estrogens) that reduce the effects of estrogen, neutralizing some of estrogen’s cancer causing potential.

    Although there no studies demonstrating an increase in the risk of breast cancer among women eating soy, there is suggestion that soy phytoestrogens can behave like estrogen and potentially increase breast cancer risk. Test tube studies have shown that genistein stimulates the growth of estrogen-positive breast cancer tumors, and women with this type of breast cancer tumor should avoid soy.

    Results of numerous studies are suggestive of a possible relationship between phytoestrogen intake and reduced prostate cancer risk.
    The results of the Japan Collaborative Cohort Study suggest that a high intake of soy bean curd (tofu) might have preventive effects against the risk of ovarian cancer.

  • Testosterone
    There has been some evidence suggesting a mild inverse relationship between soy protein intake and testosterone levels in males. A study published in the Journal of the International Society of Sports Nutrition concluded that a 12-week supplementation with soy protein did not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.

    Another study suggests that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration. Population statistics are however contradictory to this result.

  • Coronary Artery Disease
    In a study of forty-one hyperlipidemic men and postmenopausal women it was concluded that consumption of soy products reduces coronary artery disease risk because of both modest reductions in blood lipids and reductions in LDL cholesterol, homocysteine, and blood pressure.
1. Soy contains amounts of oxalate and individuals with a history of oxalate-containing kidney stones should consume soy in moderation.
2. Genetically modified soybeans should be avoided if possible.
3. Women with estrogen-sensitive breast tumors should restrict or avoid consumption of soy.

References:
1. The Encyclopedia of Healing Foods by Michael Murray, Joseph Pizzorno, and Lara Pizzorno.
2. Benders’ Dictionary of Nutrition and Food Technology.
3. USDA National Nutrient Database for Standard Reference.
4. Sakauchi F, Khan MM, Mori M, Kubo T, Fujino Y, Suzuki S, Tokudome S, Tamakoshi A; JACC Study Group. Dietary habits and risk of ovarian cancer death in a large-scale cohort study (JACC study) in Japan. Nutr Cancer. 2007;57(2):138-45. PMID: 17571946.
5. Høie LH, Graubaum HJ, Harde A, Gruenwald J, Wernecke KD. Lipid-lowering effect of 2 dosages of a soy protein supplement in hypercholesterolemia. Adv Ther. 2005 Mar-Apr;22(2):175-86. PMID: 16020407.
6. Høie LH, Morgenstern EC, Gruenwald J, Graubaum HJ, Busch R, Lüder W, Zunft HJ. A double-blind placebo-controlled clinical trial compares the cholesterol-lowering effects of two different soy protein preparations in hypercholesterolemic subjects. Eur J Nutr. 2005 Mar;44(2):65-71. Epub 2004 Apr 5. PMID: 15309422.
7. Jenkins DJ, Kendall CW, Jackson CJ, Connelly PW, Parker T, Faulkner D, Vidgen E, Cunnane SC, Leiter LA, Josse RG. Effects of high- and low-isoflavone soyfoods on blood lipids, oxidized LDL, homocysteine, and blood pressure in hyperlipidemic men and women. Am J Clin Nutr. 2002 Aug;76(2):365-72. PMID: 12145008.
8. West SG, Hilpert KF, Juturu V, Bordi PL, Lampe JW, Mousa SA, Kris-Etherton PM. Effects of including soy protein in a blood cholesterol-lowering diet on markers of cardiac risk in men and in postmenopausal women with and without hormone replacement therapy. J Womens Health (Larchmt). 2005 Apr;14(3):253-62. PMID: 15857272.
9. Jenkins DJ, Kendall CW, Jackson CJ, Connelly PW, Parker T, Faulkner D, Vidgen E, Cunnane SC, Leiter LA, Josse RG. Effects of high- and low-isoflavone soyfoods on blood lipids, oxidized LDL, homocysteine, and blood pressure in hyperlipidemic men and women. Am J Clin Nutr. 2002 Aug;76(2):365-72. PMID: 12145008.
10. Harland JI, Haffner TA. Systematic review, meta-analysis and regression of randomised controlled trials reporting an association between an intake of circa 25 g soya protein per day and blood cholesterol. Atherosclerosis. 2008 Sep;200(1):13-27. Epub 2008 Apr 15. PMID: 18534601.
11. Strom SS, Yamamura Y, Duphorne CM, Spitz MR, Babaian RJ, Pillow PC, Hursting SD. Phytoestrogen intake and prostate cancer: a case-control study using a new database. Nutr Cancer. 1999;33(1):20-5. PMID: 10227039.
12. Akaza H, Miyanaga N, Takashima N, Naito S, Hirao Y, Tsukamoto T, Mori M. Is daidzein non-metabolizer a high risk for prostate cancer? A case-controlled study of serum soybean isoflavone concentration. Jpn J Clin Oncol. 2002 Aug;32(8):296-300. PMID: 12411567.
13. Habito RC, Montalto J, Leslie E, Ball MJ. Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males. Br J Nutr. 2000 Oct;84(4):557-63. PMID: 11103227.
14. Kalman D, Feldman S, Martinez M, Krieger DR, Tallon MJ. Effect of protein source and resistance training on body composition and sex hormones. J Int Soc Sports Nutr. 2007 Jul 23;4:4. PMID: 17908338.
15. Chavarro JE, Toth TL, Sadio SM, Hauser R. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum Reprod. 2008 Nov;23(11):2584-90. Epub 2008 Jul 23. PMID: 18650557.
16. Image by unite

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2 Comments

  1. Pingback: Case Study: Soy Beans' Impact on the World | Globalization101

  2. s.d.de

    May 31, 2012 at 11:46 pm

    curing effect of soabean.

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