Answers to the Myths of the Dangers of Soy

BY Laura H. Hatton, M.S., C.C.N., C.P.T., ACHS Instructor

Recently there has been a lot of information being published purporting the evils of soy. I have been very concerned about this information and responded to a specific set of myths that were published on a popular website. The following is a summary of that research.

Myth #1―High levels of phytic acid in soy reduce the assimilation of calcium, magnesium, copper, iron, and zinc. Phytic acid is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets cause growth problems in children.

First off, all beans and grains have phytates. We understand this and are instructed to cook our beans and grains well and never eat raw. Second, assimilation is only potentially compromised in zinc and iron, as well as some calcium and magnesium. It has never been shown to interfere with copper absorption. However, though the possibility of this occurring is seen to interfere with the growth and mineral status of animals, it has never been seen in humans. In several studies done on humans there was no evidence of compromised absorption of any of these metals.

Sprouting has been shown to reduce phytate levels and fermentation is very helpful in this. Tempeh has ½-⅔ the phytate content of regular soybeans.[1] Also, cooking, germination, fermentation, soaking, and autolysis have been shown to decrease the inhibitory effect of phytic acid on mineral absorption.[2] Another important study noted that prebiotics and probiotics promote degradation of phytates in the gut.[3] Thus, it is very important to have very healthy gut flora to improve digestion of soy.

Myth #2―Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals soy containing trypsin inhibitors caused stunted growth.

Although studies have shown these adverse effects in rats, other studies showed no effect on mice or hamsters. Trypsin inhibitors are sensitive to heat. Therefore, most of their activity is lost when raw soybeans are exposed to heat.

As Liener explains, “Most commercially available soybean products intended for human consumption, such as tofu, soy milk, soy-based infant formula, soy protein isolates and concentrates, and textured meat analogs, have received sufficient heat treatment to cause inactivation of at least 80% of the trypsin inhibitor activity present in raw soybeans. This level of trypsin inhibitor destruction is well above the threshold level of 50-60% inactivation found to be necessary for eliminating significant growth inhibition and pancreatic hypertrophy."[4]

In addition, “All antinutritional factors such as phytic acid, tannin, trypsin inhibitor.. are decreased during soaking in 0.5% sodium bicarbonate.” In other words, soaking beans in a little baking soda will help reduce these things. “Human trypsin is more resistant to inhibition than is the trypsin of other mammalian species. The effect on human trypsin of soybean trypsin inhibition in soy protein does not appear to be a potential hazard to man.”

>> For information about more soy myths, download the full-length article in the March edition of the ACHS holistic health eNewsletter, the ACHS Reporter: http://www.achs.edu/newsletter.aspx?id=7

References:
[1] Liener IE. (1994). Implications of Antinutritional Components in Soybean Foods. Crit Rev Food Sci Nutr, 34(1):31-67.
[2] Urbano G. (2000). Lopez-Jurado M, et al. The Role of Phytic Acid in Legumes: antinutrient or beneficial function. J Physiol Biochem, 56(3):283-94.
[3] Scholz-Ahrens KE; Ade P; et al. (2007). Prebiotics, probiotics, and synbiotics affect mineral absorption, bone mineral content, and bone structure. J Nutr, 137(3 Suppl 2):838S-46S.
[4] Liener IE. (1994). Implications of Antinutritional Components in Soybean Foods. Crit Rev Food Sci Nutr, 34(1):31-67.

Image (c) http://upload.wikimedia.org/wikipedia/commons/8/82/Soybean.USDA.jpg

Soy fact vs soy fiction

The FDA has allowed the following claim to be made concerning soy products: “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.”

To qualify food must: Contain 6.25 G of soy protein, have less than 3 g fat and 1 g saturated fat, and less than 20 mg of cholesterol and less than 480 mg of sodium. This claim is based on whole soy protein food, not isolated soy constituents. Asian diets contain typically 6-11 g of soy protein/day, which includes 25-50 mg of isoflavones.

Soy is a complete protein. Not really, but that might not be a bad thing.

The FDA claims that soy protein can be a good substitute for animal protein because it contains all the necessary essential amino acids. Soy is high in the non-essential amino acids, but is low in cysteine, methionine, and lysine. However, soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. (This could help with insulin resistance.)

An unnecessarily high intake of essential amino acids—as in high-meat diets—may prove to be as grave a risk factor for “Western” degenerative diseases as is excessive fat intake.

Soy prevents cancer. Maybe.

Soy contains isoflavones that are phytoestrogens, which may have both benefits and risks. Phytoestrogens interact with many receptors, including estrogen hormone receptors, but the type of interaction and the type of receptor dictates the biologic response. For instance genistein, one of the main soy isoflavones, interacts differently with estrogen receptor alpha and estrogen receptor beta. Genistein was shown to inhibit the growth of MCF-7 breast cancer cells.

Epidemiological studies show that women with traditional diets high in soy have a lower incidence of breast cancer those women with Western diets. There are no studies that show eating high amounts of soy later in life can decrease a women’s risk of breast cancer however.

Soy is safe for breast cancer survivors. Probably NOT.

Currently neither the animal data nor human data is conclusive as to whether soy is safe for breast cancer survivors. Women who are estrogen positive breast cancer survivors are frequently told to restrict their intake of soy products because of the phytoestrogen content.

GMO soy is healthy. If you don’t mind herbicides on your food!

Genetically modified soy is “Roundup Ready”, MEANING Roundup can be sprayed on the crop for weed control. Roundup Ready (RR) varieties of soybean has increased the use of glyphosate for weed control and glyphosate residues were found in soybean leaves and stems, and metabolites of the herbicide were found in the grain. Applications of glyphosate have no effects on phytoestrogen levels in glyphosate-resistant soybeans.

Fermented soy is better for you. Not really.

There is a difference in the isoflavones in non-fermented vs. fermented soy food, but the effect of enzymes and flora activity in the digestive tract makes the difference unimportant.

Soy is a common food allergen. True!

Soy is one of the top food allergens, along with cow’s milk, citrus, nuts, wheat, seafood and egg. Allergenicity of GMO soy may be altered. Hydrolyzed soy protein may not be as antigenic and there may be cross-reactivity with birch pollen and soy.

Soy inhibits the thyroid. Not True!

In 14 human studies, most found little change in thyroid function tests of normal subjects ingesting isolated soy protein. There are a few case studies of soy impacting hypothyroid patients, by reducing thyroid medication absorption. Always also consider iodine deficiency. Iodine deficiency lead to goiter and soy may make an iodine deficiency worse. An interesting not is that Asian soy consumption is often coupled with seaweed, which is naturally high in iodine.

Soy inhibits protein digestion. Possibly.

Raw soy contains Bowman-Birk (BBI) inhibitor of chymotrypsin and trypsin and the Kunitz inhibitor of trypsin (KTI). Heating and processing of the soybean removes most but not all of these inhibitors. On the other hand, several studies suggest that BBI can also function as an anticarcinogen, possibly through interaction with a cellular serine protease.

Soy is safe for infant formulas. Caution is needed.

Infants consuming soy formulas had 10 times higher isoflavone levels in their blood than women receiving soy supplements who show menstrual disturbances. Small, physiologically relevant phytoestrogen exposure levels can alter estrogen-dependent gene expression in the brain and affect complex behavior in a wide range of species. The implications for these findings in humans, and particularly in infants, largely remain uninvestigated but are a subject of increasing public interest.

Soy infant formulas contain BBQ and KTI, protein enzyme inhibitors; infants on soy formula consume about 10 mg of KTI plus BBI per day. The impact of reduced protein digestion due to these enzyme inhibitors in infants is not known.

Soy is a good food. Most likely.

Whole soy foods are a good source of fiber, B vitamins, calcium and omega-3 essential fatty acids. Replacing some high fat animal protein with soy foods is beneficial. Soy can be part of a healthy diet, along with fruits, vegetables, and whole grains, fish and lean meats Introduce soy slowly to the daily diet. Avoid if you have soy allergies.

Soy is a nutraceutical. Most likely.

Soy isoflavones may be helpful for modest cholesterol lowering effects. Soy isoflavones effect on breast cancer is unclear. Soy isoflavones may be helpful for menopausal symptoms. Soy isoflavones may be supportive for postmenopausal bone health.

>> By Dr. Arianna Staruch, ND, ACHS Dean of Admissions

Soy fact vs soy fiction

The FDA has allowed the following claim to be made concerning soy products: “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.”

To qualify food must: Contain 6.25 G of soy protein, have less than 3 g fat and 1 g saturated fat, and less than 20 mg of cholesterol and less than 480 mg of sodium. This claim is based on whole soy protein food, not isolated soy constituents. Asian diets contain typically 6-11 g of soy protein/day, which includes 25-50 mg of isoflavones.

Soy is a complete protein. Not really, but that might not be a bad thing.

The FDA claims that soy protein can be a good substitute for animal protein because it contains all the necessary essential amino acids. Soy is high in the non-essential amino acids, but is low in cysteine, methionine, and lysine. However, soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. (This could help with insulin resistance.)

An unnecessarily high intake of essential amino acids—as in high-meat diets—may prove to be as grave a risk factor for “Western” degenerative diseases as is excessive fat intake.

Soy prevents cancer. Maybe.

Soy contains isoflavones that are phytoestrogens, which may have both benefits and risks. Phytoestrogens interact with many receptors, including estrogen hormone receptors, but the type of interaction and the type of receptor dictates the biologic response. For instance genistein, one of the main soy isoflavones, interacts differently with estrogen receptor alpha and estrogen receptor beta. Genistein was shown to inhibit the growth of MCF-7 breast cancer cells.

Epidemiological studies show that women with traditional diets high in soy have a lower incidence of breast cancer those women with Western diets. There are no studies that show eating high amounts of soy later in life can decrease a women’s risk of breast cancer however.

Soy is safe for breast cancer survivors. Probably NOT.

Currently neither the animal data nor human data is conclusive as to whether soy is safe for breast cancer survivors. Women who are estrogen positive breast cancer survivors are frequently told to restrict their intake of soy products because of the phytoestrogen content.

GMO soy is healthy. If you don’t mind herbicides on your food!

Genetically modified soy is “Roundup Ready”, MEANING Roundup can be sprayed on the crop for weed control. Roundup Ready (RR) varieties of soybean has increased the use of glyphosate for weed control and glyphosate residues were found in soybean leaves and stems, and metabolites of the herbicide were found in the grain. Applications of glyphosate have no effects on phytoestrogen levels in glyphosate-resistant soybeans.

Fermented soy is better for you. Not really.

There is a difference in the isoflavones in non-fermented vs. fermented soy food, but the effect of enzymes and flora activity in the digestive tract makes the difference unimportant.

Soy is a common food allergen. True!

Soy is one of the top food allergens, along with cow’s milk, citrus, nuts, wheat, seafood and egg. Allergenicity of GMO soy may be altered. Hydrolyzed soy protein may not be as antigenic and there may be cross-reactivity with birch pollen and soy.

Soy inhibits the thyroid. Not True!

In 14 human studies, most found little change in thyroid function tests of normal subjects ingesting isolated soy protein. There are a few case studies of soy impacting hypothyroid patients, by reducing thyroid medication absorption. Always also consider iodine deficiency. Iodine deficiency lead to goiter and soy may make an iodine deficiency worse. An interesting not is that Asian soy consumption is often coupled with seaweed, which is naturally high in iodine.

Soy inhibits protein digestion. Possibly.

Raw soy contains Bowman-Birk (BBI) inhibitor of chymotrypsin and trypsin and the Kunitz inhibitor of trypsin (KTI). Heating and processing of the soybean removes most but not all of these inhibitors. On the other hand, several studies suggest that BBI can also function as an anticarcinogen, possibly through interaction with a cellular serine protease.

Soy is safe for infant formulas. Caution is needed.

Infants consuming soy formulas had 10 times higher isoflavone levels in their blood than women receiving soy supplements who show menstrual disturbances. Small, physiologically relevant phytoestrogen exposure levels can alter estrogen-dependent gene expression in the brain and affect complex behavior in a wide range of species. The implications for these findings in humans, and particularly in infants, largely remain uninvestigated but are a subject of increasing public interest.

Soy infant formulas contain BBQ and KTI, protein enzyme inhibitors; infants on soy formula consume about 10 mg of KTI plus BBI per day. The impact of reduced protein digestion due to these enzyme inhibitors in infants is not known.

Soy is a good food. Most likely.

Whole soy foods are a good source of fiber, B vitamins, calcium and omega-3 essential fatty acids. Replacing some high fat animal protein with soy foods is beneficial. Soy can be part of a healthy diet, along with fruits, vegetables, and whole grains, fish and lean meats Introduce soy slowly to the daily diet. Avoid if you have soy allergies.

Soy is a nutraceutical. Most likely.

Soy isoflavones may be helpful for modest cholesterol lowering effects. Soy isoflavones effect on breast cancer is unclear. Soy isoflavones may be helpful for menopausal symptoms. Soy isoflavones may be supportive for postmenopausal bone health.

>> By Dr. Arianna Staruch, ND, ACHS Dean of Admissions