Don’t Judge this Wonder-Bean Too Quickly
Soy protein can be as nourishing as most other protein sources. Soybeans
(Glycine soya) are an important part of the daily diet in many Asian countries.
They have high protein content and have been consumed in times of food shortage.
Humans can survive and thrive on soy protein when animal protein is scarce or
How Does Soy Protein Stack Up?
Soy protein is a complete protein—it contains all of the essential amino
acids required for human growth and maintenance. Proteins are evaluated by a
“protein digestibility corrected amino acid score” (PDCAA). This score rates
proteins on their amino acid content and the body’s ability to digest and absorb
these amino acids when compared to a standard: egg whites. Egg whites have a
PDCAA score of 1. Soy protein, whey protein and milk (casein) also have a PDCAA
Soy protein offers heart-health benefits. In October 1999, the FDA issued its
final rule allowing claims that 25 grams of soy protein per day is associated
with a lower risk of coronary heart disease.1,2 The basis of this ealth claim is
that lower blood levels of total cholesterol and low density lipoprotein (LDL)
can be achieved by substituting soy protein for animal protein.3,4
The Isoflavones in Soy Protein Offer Health Benefits
Soy protein naturally contains compounds called isoflavones. These
phytoestrogens (plant estrogens) can bind to estrogen receptors in the body and
exhibit weak estrogen-promoting and estrogen-inhibiting activity.5 Isoflavones
also provide antioxidant activity.
- Population studies suggest that the consumption of soy protein is
associated with a lowered risk of breast cancer.6,7 Women of Asian descent
have a lower incidence of breast cancer than women in Western countries.
- Isoflavones in soy protein may offer a protective effect against
hormonally regulated cancer.8
- Soy isoflavones are reported to help reduce menopausal symptoms.9,10 In
fact, this aspect of soy protein has been favorably compared to estrogen
hormone replacement therapy (HRT) in reducing menopausal symptoms but
without the negative side effect of increasing breast cancer risk.11
- Soy isoflavones appear to modestly protect bone loss. Studies show isoflavone-rich soy protein can increase bone mineral density (BMD) while reducing BMD loss.12,13
- Isoflavones also offer a protective benefit to men. Studies show that supplementing with soy isoflavones appears to reduce the risk of developing prostate cancer and may also help reduce symptoms associated with prostate cancer.14, 15
- Soy isoflavones have also been shown to reduce side effects in children receiving either chemotherapy or radiation treatments.16
While it is clear the phytoestrogens in soy protein offer protective health
benefits, people with serious medical conditions, including cancer of the
breast, ovary or prostate, should consult their health care practitioner before
using soy protein supplements.
The Importance of Proper Processing of Soy
Like all legumes, soybeans must be processed by soaking, heat, steam,
pressure, or mechanical extraction to facilitate digestion of the protein
contained in the bean. Heating and mechanical extraction (soaking, milling and
fermenting) perform three important functions in soy preparation:
- Soaking inactivates phytate (phytic acid), an indigestible form of inositol that
can hinder the absorption of minerals in the diet.
- Heating degrades and
inactivates trypsin inhibitors.17 These are found in all legumes in small
amounts, and they prevent normal digestive processes in the body.
- Heating and
fermenting deactivates agglutinins. Agglutinins in foods can promote blood
clotting. Soy products generally do not contain agglutinins because they are
deactivated during heat processing. Soy flour that has not been heated may
Putting Rumors to Rest
Thyroid function is not
impaired by soy protein.
18,19 Soy protein does not impede iodine absorption by
the body. Clinical trials show that soy protein rich in isoflavones (19 g soy,
36 mg isoflavones) did not have any effect on thyroid-stimulating hormone (TSH)
or thyroxine in men or women.20,21 People who are predisposed to hypothyroidism
do not need to avoid soy protein, but they should ensure adequate intake of
iodine and thyroid hormone medications.19
Soybeans have been subjected
to extensive genetic modification to improve crop yields. No data suggests such
modification is harmful to human health.
Consumers who wish to avoid risks can
be assured that NSP uses only non-GMO soy to create soy protein supplements.
Soy protein is a safe and healthful dietary supplement. The pharmacological
properties of isoflavones are strongly supported for their health benefits. Soy
protein is a sustainable source of protein and a healthful solution to meeting
daily energy needs.
- Bakhit RM, Klein BP, Essex-Sorlie D, et al. Intake of 25 g of soybean protein
with or without soybean fiber alters plasma lipids in men with elevated
cholesterol concentrations. J Nutr 1994;124:213-22.
- Potter SM, Baum JA, Teng H, et al. Soy protein and isoflavones: their effects on blood lipids and
bone density in postmenopausal women. Am J Clin Nutr 1998;68:1375S-9S.
- Wong WW, Smith EO, Stuff JE, et al. Cholesterol-lowering effect of soy protein
in normocholesterolemic and hypercholesterolemic men. Am J Clin Nutr
- Hendler SS Ph.D., M.D., Rorvik D M.S. PDR for
Nutritional Supplements 1st Edition. New Jersey: Medical Economics Company,
- Keinan-Boker L, van Der Schouw YT, Grobbee DE, Peters PH.
Dietary phytoestrogens and breast cancer risk. Am J Clin Nutr 2004;79:282-8.
- Sartippour MR, Rao JY, Apple S, et al. A pilot clinical study of short-term
isoflavone supplements in breast cancer patients. Nutr Cancer 2004;49:59-65.
- Trock BJ, Hilakivi-Clarke L, Clarke R. Meta-analysis of soy intake and breast
cancer risk. J Natl Cancer Inst 2006;98:459-71.
- Washburn S, Burke GL,
Morgan T, et al. Effect of soy protein supplementation on serum lipoproteins,
blood pressure, and menopausal symptoms in perimenopausal women. Menopause
- Albertazzi P, Pansini F, Bonaccorsi G, et al. The effect of
dietary soy supplementation on hot flushes. Obstet Gynecol 1998;91:6-11.
- Barnes S. Phyto-oestrogens and osteoporosis: what is a safe dose? Br J Nutr.
2003 Jun;89 Suppl 1:S101-8.
- Ho SC, Chan SG, Yi Q, et al. Soy intake and
the maintenance of peak bone mass in Hong Kong Chinese women. J Bone Miner Res
- Cassidy A, Albertazzi P, Lise Nielsen I, Hall W,
Williamson G, Tetens I, Atkins S, Cross H, Manios Y, Wolk A, Steiner C, Branca
F. Proc Nutr Soc. 2006 Feb;65(1):76-92.Critical review of health effects of
soyabean phyto-oestrogens in post-menopausal women.
- Kumar NB, Cantor A,
Allen K et al. The specific role of isoflavones in reducing prostate cancer
risk. Prostate 2004;59:141-7.
- Jacobsen BK, Knutsen SF, Fraser GE. Does
high soy milk intake reduce prostate cancer incidence? The Adventist Health
Study. Cancer Causes Control 1998;9:553-7.
- Hernández-Infante M, Sousa V,
Montalvo I, Tena E. Impact of microwave heating on hemagglutinins, trypsin
inhibitors and protein quality of selected legume seeds. Plant Foods Hum Nutr.
- Tacyildiz N, Ozyoruk D, Yavuz G, Unal E, Dincaslan
H, Dogu F, Sahin K, Kucuk O. Soy isoflavones ameliorate the adverse effects of
chemotherapy in children.Nutr Cancer. 2010;62(7):1001-5.
- Hampl R,
Ostatnikova D, Celec P, Putz Z, Lapcík O, Matucha P. Short-term effect of soy
consumption on thyroid hormone levels and correlation with phytoestrogen level
in healthy subjects. Endocr Regul. 2008 Jun;42(2-3):53-61
- Messina M,
Redmond G Effects of soy protein and soybean isoflavones on thyroid function in
healthy adults and hypothyroid patients: a review of the relevant literature.
Thyroid. 2006 Mar;16(3):249-58.
- Zhou Y, Alekel DL, Dixon PM, Messina M,
Reddy MB. The Effect of Soy Food Intake on Mineral Status in Premenopausal
Women. J Womens Health (Larchmt). 2011 Apr 12. [Epub ahead of print]
- Dillingham BL, McVeigh BL, Lampe JW, Duncan AM. Soy protein isolates of varied isoflavone content do not influence serum thyroid hormones in healthy young men.
Thyroid. 2007 Feb;17(2):131-7