Ocassionally, my family eats tofu, tempeh and miso.  I also put soy milk in my tea once in a while, because cow’s milk doesn’t agree with me and nut or rice milks don’t taste right, mixed in with the tea. While occasional consumption of soy products is unlikely to cause health problems, too much soy is not the healthiest choice. Just like with everything else, I believe the less processed foods you consume, the better.

Average consumption of soy foods in Japan and China is 10 grams (about 2 teaspoons) per day.  Unlike Western vegetarians, the Asians consume soy foods in small amounts as a condiment, and not as a replacement for animal foods.

Processed foods containing soy, include soy protein isolate, which has been linked to cancer and vitamin deficiencies, among other things. Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein.You can find soy protein isolate in many health bars, diet drinks, school lunches and baked goods.  If you’re going to consistently consume soy, I would recommend staying away from processed soy products, such as “fake” meats and leaning towards the fermented soy products, which have had their anti-nutrients neutralized. These products are tempeh , tamari sauce and miso.

Here’s why soy is not the optimal food:

Soy  is one of the most pesticide-sprayed crops.  Soy foods contain high levels of aluminum, which is toxic to the nervous system and the kidneys. Aluminum content of soy goes up dramatically as a result of  processing. Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines as well as MSG, which is a potent neuro-toxin. Additional MSG is quite often added to many soy products.

Protein Trypsin inhibitors in soy interfere with protein digestion. They can cause multiple pancreatic disorders. In test animals  trypsin inhibitors in soy caused stunted growth. Like all legumes, soy beans are deficient in sulfur-containing amino acids methionine and cystine. In addition, modern processing denatures fragile lysine.

Blocking vitamin and mineral absorption Soy has a high content of phytates, which can  inhibit mineral absorption.   High phytate diets have caused growth problems in children. It is possible to neutralize phytic acid in soy through methods such as soaking, sprouting and long, slow cooking. Meat consumption blocks phytates as well.

Phytates in soy appear to be not very harmful, however,  if one’s diet does not revolve around soy products. According to Dr. Weil: “Phytates in your everyday meals should not be an issue for you as long as you’re eating a balanced diet. Most of us consume enough minerals in common foods to more than make up for the small amounts of these micronutrients that might be tied up by phytates. The only individuals who might need to be careful are vegetarians who consume a lot of wheat bran, which is a concentrated source of these substances. Phytate-associated deficiencies of iron and zinc do occur in some third-world countries where people mostly eat grains.”

The compound that resembles vitamin B12 in soy cannot be used by the human body. Soy foods cause the body to require more B12, which could be a problem for vegetarians, who consume a lot of “fake meat” type of products. Personally, I get most of my B12 through spirulina and other sea vegetables, as well as through eggs. Soy foods increase the body’s requirement for vitamin D, as well. Since latest research has linked vitamin D consumption with increased immunity, it is possibly safe to say that soy foods decrease immune function as well.

Both  calcium and vitamin D are needed for healthy bones. Unlike common belief, soy foods do not prevent osteoporosis in Asia. Calcium from bone broths and vitamin D from seafood, lard and organ meats prevent osteoporosis in Asian countries.

Phytoestrogens. Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women. Megadoses of phytoestrogens in soy infant formula have been blamed in the current trend toward increasingly premature sexual development in girls and delayed sexual development in boys.

Hypothyroidism. Soy contains goitragens  (compounds, leading to hypothyroidism (“slow thyroid”. ) “Slow thyroid” leads to weight gain and other health issues. Consumption of soy-based formula for infants has been linked to autoimmune thyroid disease as well. Soy based infant formulas contain 80 times more manganese than breast milk. Too much manganese content is linked to neurotoxicity.

for more info:

Weston A Price Foundation – Myths and Truths about soy

Mothering Magazine – The Whole Soy Story