Soy Myths

Fact or fiction?

There’s no denying that soy is quite the wonder-bean. It’s a source of complete protein and has a host of other healthful properties. But with so much information available about soy, it’s not always easy to be sure what’s accurate. So we’ve done our research to help you distinguish the truth from the tall tales.

There’s no denying that soy is quite the wonder-bean. It’s a source of complete protein and has a host of other healthful properties. But with so much information available about soy, it’s not always easy to be sure what’s accurate. So we’ve done our research to help you distinguish the truth from the tall tales.

General nutrition

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Reality: Soymilk such as Silk® delivers many of the same important nutrients as cow's milk, including calcium, vitamin D and protein. In addition, unlike many types of cow's milk, soymilk is very low in saturated fat and cholesterol-free. Find out more about Silk vs. milk.

 

Reality: Soy protein is one of the eight most common food allergens; a list that also includes proteins in milk, eggs, peanuts, tree nuts, fish, shellfish and wheat. However, these foods are not equally allergenic. In fact, soy allergy is relatively rare and much less common than milk and peanut allergies.1,2 If you know or suspect you are allergic to soy, consult your doctor for dietary guidelines and always read labels with care.

 

Reality: Soybeans—like other legumes and whole grains—contain phytate; a naturally-occurring plant compound that can reduce the absorption of minerals such as calcium and iron. However, research shows that calcium from soymilk is absorbed as well as calcium from cow's milk.3 In addition, new research indicates that in contrast to older thinking, iron absorption from soy is also very good.4

 

Reality: Unlike most plant proteins, soy protein is "complete," meaning that it contains all of the essential amino acids—the building blocks of protein—in sufficient quantities to meet the body's requirements.5 The medical and nutrition communities, as well as the FDA, recognize soy protein as equal in quality to animal protein.

 

Reality: Whole soybeans are a nutritious source of protein, fiber, beneficial omega-3 fats and a variety of vitamins and minerals such as folate and potassium. However, not all foods made from the soybean provide all of these beneficial components. Soymilk made from whole soybeans, soynuts, tempeh and edamame are examples of whole soyfoods which better preserve the nutritional attributes of the soybean. Most processed products such as soy supplements and isolated soy protein do not.

 

Reality: There are two types of soymilk commonly found on the market: those made from whole soybeans and those made from isolated soy protein. Whole bean soymilk, such as Silk, is made by crushing the bean and removing the indigestible fibrous portions, then blending the resulting "base" with water, flavoring and nutritious fortifications such as calcium. This whole bean process preserves not only the protein but also other important components of the original soybean including isoflavones, essential fatty acids including an omega-3 fat and some fiber. Soymilk made from isolated soy protein is highly processed, made by chemically extracting the protein from the bean, then reconstituting the isolated protein with water and other additives.

 

Reality: Soy flour (used in some Silk Light products) is a minimally processed ingredient made by mechanically grinding soybeans. Soy protein powder (isolated soy protein) is a highly processed substance, made by chemically extracting and isolating the protein from the bean.

 

Reality: While any food can cause sensitivity in some people, clinical studies don't show soy causes more gastrointestinal disturbances than other commonly consumed foods. Furthermore, soymilk is a wholesome and delicious milk alternative for those who can't drink milk due to lactose intolerance. If you know or suspect you are allergic to soy, consult your doctor for dietary guidelines and always read labels with care. Find out more about Silk vs. milk.

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Pregnancy and fertility

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Reality: Human clinical studies show that soy does not impair male or female fertility.6,7,8

 

Reality: There is no clinical data indicating soy consumption adversely affects sperm quality or quantity.6,7

 

Reality: For centuries, Asian women have consumed soy while pregnant. Many human studies have also confirmed that soy is safe for pregnant women. In fact, fortified soymilk like Silk is a delicious and convenient source of many nutrients that are important in pregnancy, including calcium and high-quality protein. Soymilk is also lactose-free, which may be helpful to some pregnant women with lactose sensitivity. If you are pregnant, ask your doctor for advice about a healthy diet. Find out more about Silk vs. milk.

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Children

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Reality: Soymilk like Silk and other soyfoods can be a nutritious addition to a child's diet. For most children, soymilk can be introduced around the same time dairy milk is typically introduced (usually around age one). Since all children are different, Silk recommends consulting your doctor before changing your child's diet. Silk soymilk is a good source of high-quality protein and provides many of the same nutrients found in milk including calcium, vitamin D, potassium, riboflavin and vitamin B12. Soymilk and other milk alternatives should not be used as infant formula. Find out more about Silk vs. milk.

 

Reality: The medical and nutrition communities, as well as government agencies, agree that soy can play a valuable role in a healthy balanced diet for men, women and children alike. Soy is a complete plant protein, meaning that it contains all of the amino acids necessary for optimal human health. Soymilk such as Silk is also an excellent source of calcium and vitamin D: two nutrients especially important for growing kids. Find out more about Silk vs. milk.

 

Reality: There is no human evidence showing that soy affects sexual development. Soy does not affect hormone levels nor does soy contain the hormone estrogen.9,10

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Hormones and sexuality

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Reality: There is no human clinical evidence showing that soy affects sexual development. Soy contains isoflavones, also known as phytoestrogens or "plant estrogens." However, isoflavones are different from the hormone estrogen.

 

Reality: Soy does not contain the hormone estrogen. It does contain isoflavones, which are naturally occurring plant compounds. Isoflavones are classified as plant estrogens but isoflavones are very different from the hormone estrogen.

 

Reality: There is no human evidence that soy consumption affects sexual orientation.

 

Reality: The overwhelming amount of clinical research shows that soyfoods do not adversely affect thyroid function in people with normal-functioning thyroids.11 Soy protein may inhibit the absorption of thyroid medication taken by hypothyroid patients, but soyfoods are not contraindicated for individuals who are hypothyroid.12 Patients using thyroid medication should work closely with a doctor to ensure consistent and effective dosing.

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Cancer and other diseases

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Reality: In fact, studies show that among those who consume higher amounts of soy, such as Asian populations, cancer is less likely than in those who consume relatively little soy.13,14 Intriguing evidence in particular suggests that soy reduces risk of breast and prostate cancer. Find out more about the health benefits of soy.

 

Reality: According to the American Cancer Society, breast cancer patients can consume soyfoods like soymilk, tofu and edamame.15 In fact, a recently published study involving nearly 10,000 breast cancer patients found that higher soy consumption was associated with a 25% reduction in cancer recurrence.16 Find out more about the health benefits of soy.

 

Reality: In fact, according to the FDA, consuming 25 grams of soy protein per day, as part of a healthy diet low in saturated fat and cholesterol, may help reduce the risk of heart disease.17 Clinical research shows that soy protein directly lowers LDL ("bad") cholesterol.18 Soy also contains omega-3 fatty acids, which have been studied for their role in heart health. Furthermore, plant-based foods like soymilk are often lower in saturated fat and cholesterol than their animal-based counterparts, making them an especially smart choice for a heart-healthy lifestyle. It is clear that soyfoods work through many ways to promote heart health. Find out more about the health benefits of soy.

 

Reality: Clinical evidence shows that soyfoods do not adversely impact the immune system.19

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1 Vierk KA, Koehler KM, Fein SB, Street DA. Prevalence of self-reported food allergy in American adults and use of food labels. J Allergy Clin Immunol 2007;119(6):1504-10.

2 Gupta RS, Springston EE, Smith B, Warrier MR, Pongracic J, Holl JL. Geographic variability of childhood food allergy in the United States. Clin Pediatr (Phila) 2012.

3 Zhao Y, Martin BR, Weaver CM. Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow's milk in young women. J Nutr 2005;135(10):2379-82.

4 Lonnerdal B, Bryant A, Liu X, Theil EC. Iron absorption from soybean ferritin in nonanemic women. Am J Clin Nutr 2006;83(1):103-7.

5 Hughes GJ, Ryan DJ, Mukherjea R, Schasteen CS. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chem 2011;59(23):12707-12.

6 Mitchell JH, Cawood E, Kinniburgh D, Provan A, Collins AR, Irvine DS. Effect of a phytoestrogen food supplement on reproductive health in normal males. Clin Sci (Lond) 2001;100(6):613-8.

7 Beaton LK, McVeigh BL, Dillingham BL, Lampe JW, Duncan AM. Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men. Fertil Steril 2010;94(5):1717-22.

8 Hooper L, Ryder JJ, Kurzer MS, Lampe JW, Messina MJ, Phipps WR, et al. Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis. Hum Reprod Update 2009;15(4):423-40.

9 Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil Steril 2010;93(7):2095-104.

10 Hamilton-Reeves JM, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina MJ. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertil Steril 2010;94(3):997-1007.

11 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;16(3):249-58.

12 Zeitler P, Solberg P. Food and levothyroxine administration in infants and children. J Pediatr 2010;157(1):13-14.

13 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.

14 Wu AH, Yu MC, Tseng CC, Pike MC. Epidemiology of soy exposures and breast cancer risk. Br J Cancer 2008;98(1):9-14.

15 Rock CL, Doyle C, Demark-Wahnefried W, Meyerhardt J, Courneya KS, Schwartz AL, et al. Nutrition and physical activity guidelines for cancer survivors. CA Cancer J Clin 2012;62(4):242-74.

16 Nechuta SJ, Caan BJ, Chen WY, Lu W, Chen Z, Kwan ML, et al. Soy food intake after diagnosis of breast cancer and survival: an in-depth analysis of combined evidence from cohort studies of US and Chinese women. Am J Clin Nutr 2012;96(1):123-32.

17 Food labeling: health claims; soy protein and coronary heart disease. Food and Drug Administration, HHS. Final rule. Fed Regist 1999;64(206):57700-33.

18 Messina M, Messina V, Jenkins DJ. Can breast cancer patients use soyafoods to help reduce risk of CHD? Br J Nutr 2012:1-10.

19 Ryan-Borchers TA, Park JS, Chew BP, McGuire MK, Fournier LR, Beerman KA. Soy isoflavones modulate immune function in healthy postmenopausal women. Am J Clin Nutr 2006;83(5):1118-25.