Soy - References

 
Soy

Soy, a staple food in many Asian countries, contains valuable constituents, including protein, isoflavones, saponins, and phytosterols. Soy protein provides essential amino acids. When eaten with rice, soy provides protein comparable with that found in animal products. Soy is low in fat and cholesterol-free.

What Are "Star" Ratings?

a7_3star Reliable and relatively consistent scientific data showing a substantial health benefit.

a7_2star Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

a7_1star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

This supplement has been used in connection with the following health conditions:


Used for AmountWhy
High Cholesterol
25 grams soy protein per day3 stars Soy supplementation has been shown to lower cholesterol. Soy contains isoflavones, which are believed to be soy’s main cholesterol-lowering ingredients.

3 stars High Cholesterol

25 grams soy protein per day

Soy supplementation has been shown to lower cholesterol in humans.1 Soy is available in foods such as tofu, miso, and tempeh and as a supplemental protein powder. Soy contains isoflavones, naturally occurring plant components that are believed to be soy’s main cholesterol-lowering ingredients. A controlled trial showed that soy preparations containing high amounts of isoflavones effectively lowered total cholesterol and LDL (“bad”) cholesterol, whereas low-isoflavone preparations (less than 27 mg per day) did not.2 However, supplementation with either soy3 or non-soy isoflavones (from red clover)4 in pill form failed to reduce cholesterol levels in a group of healthy volunteers, suggesting that isoflavone may not be responsible for the cholesterol-lowering effects of soy. Further trials of isoflavone supplements in people with elevated cholesterol, are needed to resolve these conflicting results. In a study of people with high cholesterol levels, a soy preparation that contained soy protein, soy fiber, and soy phospholipids lowered cholesterol levels more effectively than isolated soy protein.5


Used for AmountWhy
Hypertension
10 grams soy protein or 16 ounces soy milk twice per day3 stars Supplementing with soy protein may significantly lower blood pressure.

3 stars Hypertension

10 grams soy protein or 16 ounces soy milk twice per day

In a double-blind study of postmenopausal women, supplementing with 10 grams of soy protein twice a day for six weeks significantly reduced diastolic blood pressure by an average of 5 mm Hg, compared with a diet not containing soy protein.6 In another study, men and women with mild to moderate hypertension consumed 500 ml (approximately 16 ounces) of soy milk or cow's milk twice a day for three months. After three months, the average systolic blood pressure had decreased by 18.4 mm Hg in the soy group, compared with 1.4 mm Hg in the cow's milk group. The reductions in diastolic blood pressure were 15.9 mm Hg with soy milk and 3.7 mm Hg with cow's milk.7 In another study of people with hypertension who were consuming a low-protein, low-fiber diet, supplementing with a combination of soy protein and psyllium (a fiber source) lowered systolic blood pressure by an average of 5.9 mm Hg.8 The blood pressure reduction with soy protein alone or with fiber alone was less pronounced than that with combination treatment. Other research has also shown a blood pressure–lowering effect of soy protein.9 , 10


Used for AmountWhy
Athletic Performance and Exercise Recovery
33 to 40 grams daily2 stars In one study, elderly men participating in a strength training program who took a supplement containing protein (part of which was soy protein) immediately following exercise saw significant gains in muscle growth and lean body mass.

2 stars Athletic Performance and Exercise Recovery

33 to 40 grams daily

In one preliminary study, elderly men participating in a 12-week strength training program took a liquid supplement containing 10 grams of protein (part of which was soy protein), 7 grams of carbohydrate, and 3 grams of fat either immediately following exercise or two hours later.11 Men taking the supplement immediately following exercise experienced significantly greater gains in muscle growth and lean body mass than those supplementing two hours later, but strength gains were no different between the two groups. A controlled study of female gymnasts found that adding 0.45 grams of soy protein (0.45 grams per pound of body weight per day) to a diet that was adequate in protein during a four-month training program did not improve lean body mass compared with a placebo.12 No research has compared different sources of protein to see whether one source, such as soy protein, has a better or more consistent effect on exercise recovery or the results of strength training.


Used for AmountWhy
Obesity
Refer to label instructions 1 star Soy appears to have several effects on the body that might help with weight loss.

1 star Obesity

Animal and human studies have suggested that when soy is used as a source of dietary protein, it may have several biological effects on the body that might help with weight loss.15 A preliminary study found that people trying to lose weight using a meal-replacement formula containing soy protein lost more weight than a group not using any formula.16 However, controlled studies comparing soy protein with other protein sources in weight-loss diets have not found any advantage of soy.17 , 18 , 19 When soy protein is used for other health benefits, typical daily intake is 20 grams per day or more.

Used for AmountWhy
Premenstrual Syndrome
Refer to label instructions 1 star Supplementing with soy protein may help relieve premenstrual swelling and cramping.

1 star Premenstrual Syndrome

In a double-blind trial, supplementing with soy protein (providing 68 mg of isoflavones per day) for two menstrual cycles was significantly more effective than a placebo at relieving premenstrual swelling and cramping.20 The placebo used in this study was cow's milk protein. Some doctors believe that cow's milk, because of its estrogen content, can worsen premenstrual symptoms. If that is the case, then the beneficial effect of soy protein may have been overestimated in this study.

Also indexed as:
  • soy protein

About this treatment

1. Carrol KK, Kurowska EM. Soy consumption and cholesterol reduction: review of animal and human studies. J Nutr 1995;125:594–7S.

2. Crouse JR 3rd, Morgan T, Terry JG, et al. A randomized trial comparing the effect of casein with that of soy protein containing varying amounts of isoflavones on plasma concentrations of lipids and lipoproteins. Arch Intern Med 1999;159:2070–6.

3. Nestel PJ, Yamashita T, Sasahara T, et al. Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women. Arterioscler Thromb Vasc Biol 1997;17:3392–8.

4. Samman S, Lyons, Wall PM, et al. The effect of supplementation with isoflavones on plasma lipids and oxidisability of low density lipoprotein in premenopausal women. Atherosclerosis 1999;147:277–83.

5. Hoie LH, Morgenstern EC, Gruenwald J, et al. 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;44:65–71.

6. Washburn S, Burke GL, Morgan T, Anthony M. Effect of soy protein supplementation on serum lipoproteins, blood pressure, and menopausal symptoms in perimenopausal women. Menopause1999;6:7–13.

7. Rivas M, Garay RP, Escanero JF, et al. Soy milk lowers blood pressure in men and women with mild to moderate essential hypertension. J Nutr 2002;132:1900–2.

8. Burke V, Hodgson JM, Beilin LJ, et al. Dietary protein and soluble fiber reduce ambulatory blood pressure in treated hypertensives. Hypertension2001;38:821–6.

9. He J, Gu D, Wu X, et al. Effect of soybean protein on blood pressure: a randomized, controlled trial. Ann Intern Med 2005;143:1–9.

10. Welty FK, Lee KS, Lew NS, Zhou JR. Effect of soy nuts on blood pressure and lipid levels in hypertensive, prehypertensive, and normotensive postmenopausal women. Arch Intern Med 2007;167:1060–7.

11. Esmarck B, Andersen JL, Olsen S, et al. Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. J Physiol 2001;535:301–11.

12. Stroescu V, Dragan J, Simionescu L, Stroescu OV. Hormonal and metabolic response in elite female gymnasts undergoing strenuous training and supplementation with SUPRO Brand Isolated Soy Protein. J Sports Med Phys Fitness 2001;41:89–94.

13. Casini ML, Marelli G, Papaleo E, Ferrari A, D'Ambrosio F, Unfer V. Psychological assessment of the effects of treatment with phytoestrogens on postmenopausal women: a randomized, double-blind, crossover, placebo-controlled study. Fertil Steril 2006;85:972-8.

14. Upmalis DH, Lobo R, Bradley L, Warren M, Cone FL, Lamia CA. Vasomotor symptom relief by soy isoflavone extract tablets in postmenopausal women: a multicenter, double-blind, randomized, placebo-controlled study. Menopause 2000;7:236-42.

15. Bhathena SJ, Velasquez MT. Beneficial role ofdietary phytoestrogens in obesity and diabetes. Am J Clin Nutr2002;76:1191–201[review].

16. Allison DB, Gadbury G, Schwartz LG, et al. Anovel soy-based meal replacement formula for weight loss among obeseindividuals: a randomized controlled clinical trial. Eur J Clin Nutr2003;57:514–22.

17. Bosello O,Cominancini L, Zocca I, et al. Short- and long-term effects of hypocaloric dietscontaining proteins of different sources on plasma lipids and apoproteins ofobese subjects. Ann Nutr Metab 1988; 32:206–14.

18. Yamashita T, Sasahara T, Pomeroy SE, et al. Arterial compliance, bloodpressure, plasma leptin, and plasma lipids in women are improved with weight reduction equally with a meat-based diet and a plant-based diet. Metabolism1998;47:1308–14.

19. Jenkins DJ, Wolever TM, Spiller G, et al. Hypocholesterolemic effect ofvegetable protein in a hypocaloric diet. Atherosclerosis 1989;78:99–107.

20. Bryant M, Cassidy A, Hill C, et al. Effect of consumption of soy isoflavones on behavioural, somatic and affective symptoms in women with premenstrual syndrome. Br J Nutr 2005;93:731–9.

21. Messina M. To recommend or not to recommend soy foods. J Am Diet Assoc 1994;94:1253–4.

22. Teixeira SR, Potter SM, Weigel R, et al. Effects of feeding 4 levels of soy protein for 3 and 6 wk on blood lipids and apolipoproteins in moderately hypercholesterolemic men. Am J Clin Nutr 2000;71:1077–84.

23. Divi RL, Chang HC, Doerge DR. Antithyroid isoflavones from soybean. Biochem Pharmacol 1997;54:1087–96.

24. Ishizuki Y, Hirooka Y, Murata Y, Togashi K. [The effects on the thyroid gland of soybeans administered experimentally in healthy subjects.] Nippon Naibunpi Gakkai Zasshi 1991;67:622–9. [in Japanese].

25. Forsythe WA. Soy Protein, thyroid regulation and cholesterol metabolism. Forsythe WA. Soy protein, thyroid regulation and cholesterol metabolism. J Nutr 1995;125:619S–23S.

26. Bennink MR, Mayle JE, Bourquin LD, Thiagarajan D. Evaluation of soy protein in risk reduction for colon cancer and cardiovascular disease: Preliminary results. Second International Symposium on the Role of Soy in Preventing and Treating Chronic Disease. September 15–18, 1996. Brussels, Belgium.

27. Jabbar MA, Larrea J, Shaw RA. Abnormal thyroid function tests in infants with congenital hypothyroidism: the influence of soy-based formula. J Am Coll Nutr 1997;16:280–2.

28. Messina MJ, Persky V, Setchell KD, Barnes S. Soy intake and cancer risk: a review of the in vitro and in vivo data. Nutr Cancer 1994;21:113–31.

29. Rao CV, Wang C-X, Simi B, et al. Enhancement of experimental colon cancer by genistein. Cancer Res 1997;57:3717–22.

30. Barnes S. The chemopreventive properties of soy isoflavonoids in animal models of breast cancer. Breast Cancer Res Treat 1997;46:169–79 [review].

31. Hilakivi-Clarke L, Cho E, Onojafe I, et al. Maternal exposure to genistein during pregnancy increases carcinogen-induced mammary tumorigenesis in female rat offspring. Oncol Rep 1999;6:1089–95.

32. Lu L-JW, Anderson KE, Grady JJ, Nagamani M. Effects of soya consumption for one month on steroid hormones in premenopausal women: implications for breast cancer risk reduction. Cancer Epidemiol Biomarkers Prev 1996;5:63–70.

33. Nagata C, Takatsuka N, Inaba S, et al. Effect of soymilk consumption on serum estrogen concentrations in premenopausal Japanese women. J Natl Cancer Inst 1998;90:1830–5.

34. Hargreaves DNF, Potten CS, Harding C, et al. Two-week dietary soy supplementation has an estrogenic effect on normal premenopausal breast. J Clin Endocrinol Metab 1999;84:4017–24.

35. Petrakis NL, Barnes S, King EB, et al. Stimulatory influence of soy protein isolate on breast secretion in pre- and postmenopausal women. Cancer Epidemiol Biomarkers Prev 1996;5:785–94.

36. McMichael-Phillips DF, Harding C, Morton M, et al. Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast. Am J Clin Nutr 1998;68(suppl):1431S–6S.

37. Unfer V, Casini ML, Costabile L, et al. Endometrial effects of long-term treatment with phytoestrogens: a randomized, double-blind, placebo-controlled study. Fertil Steril 2004;82:145–8.

38. Marini H, Minutoli L, Polito F, et al. Effects of the phytoestrogen genistein on bone metabolism in osteopenic postmenopausal women: a randomized trial. Ann Intern Med 2007;146:839–47.


Last Review: 05-11-2011

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2011.

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