- Milk and peanut allergies are each 5-6 times more prevalent than soy allergies. In fact, the true incidence of soy allergy - as confirmed by double blind, placebo-controlled food challenges - is quite low. Research indicates that allergic reactions to soy occur predominately in children less than four years of age, and most estimates agree that <1.0% of children (probably 0.2-0.4% of children) have true soy allergies. Moreover, 90% of children who have reactions to soy outgrow the allergy by age four. Given these statistics, it is safe to assume that <0.1% of adults (fewer than 1 in 1,000) are allergic to soy.
- Food allergen reaction thresholds, or the minimum oral dose of protein that elicits an allergic response, tend to be several orders of magnitude (more than 100-1000 times) higher for soy than for milk and peanut proteins. In other words, it takes 100-1000 times more soy protein than milk or peanut protein to initiate an allergic response in sensitive people.
- Soy allergies tend to produce mild symptoms relative to other food allergies. In a summary report of clinical food challenge studies, it was noted that in 80% of reported cases, symptoms of soy allergies were minimal to mild, with the remaining 20% being moderate. No severe allergic reactions to soy were reported. In comparison, milk and peanut allergies produced minimal-to-mild symptoms in 50-70% of cases, moderate symptoms in 20-30% of cases, and severe symptoms in 10-15% of cases.
Phytate Content (%)
|Soy Protein Isolates|
|Small White Beans|
|Great Northern Beans|
- Soy foods containing isoflavones appear to have protective effects against breast cancer, particularly when consumed lifelong (e.g. when consumed as part of a healthy, balanced diet beginning in childhood).
- Healthy dietary intakes of soy isoflavones, as reflected in Asian diets, appear to be in the range of 20-80 mg per day.
- High rates of soy isoflavone intake (>150 mg per day) through consumption of isoflavone-fortified foods and supplements should be avoided, particularly by menopausal and post-menopausal women who are at risk for estrogen dependent breast cancer and who have not regularly eaten soy foods in their pasts.
- Fermenting soy foods increases isoflavone bioavailability. However, it also decreases the actual isoflavone content of the food. Typical intakes of non-fermented soy foods are higher than fermented soy products and would contribute a much larger percentage of dietary isoflavones.
- Fermented soy may be easier for some people to digest, although digestion of non-fermented products is not a common problem and can generally be resolved.
- Fermented products have lower phytate levels. Again, this is not a major issue since mineral levels of people eating a typical mixed diet are not significantly affected by the phytic acid content in non-fermented soy. Additionally, phytic acid intake has been linked to a reduced risk of certain cancers.
- Fermented soy products can be quite high in sodium. A review of soy intake and stomach cancer indicated that risk increased with intake of fermented soyfoods (mainly miso), but decreased with intake of non-fermented soyfoods (mainly tofu). The increased cancer risk may be related to high sodium intake in those eating fermented products. Sodium intake is a well-known risk factor for stomach cancer.
- Statements that non-fermented soy is inferior to fermented soy are misleading. In a review of 26 animal studies of experimental carcinogenesis in which diets containing soy or soybean isoflavones were used, 17 (65%) reported protective effects. No studies reported that soy intake increased tumor development. The epidemiological data are also inconsistent, although consumption of non-fermented soy products (such as soymilk and tofu) tended to be either protective or not associated with cancer risk; however, no consistent pattern was evident with the fermented soy products (such as miso). Protective effects were observed for both hormone- and non-hormone-related cancers.
- Soybean plants fix nitrogen from the atmosphere and require little (if any) nitrogen fertilizer. In addition, by alternating soybeans with corn and other crops on a given piece of land, soy production can reduce the amounts of nitrogen fertilizer needed by those alternating crops.
- Soy offers a primary plant-based source of protein that is complete, balanced, and as nutritionally rich as most animal proteins - and it does this at a fraction of the environmental cost. Consider that a very high percentage of the corn and soybeans produced in the
each year are fed to cattle, pigs, and chickens, and that the conversion of these grains into meat is inefficient. In fact, it requires 20 pounds of corn and soybeans to produce a single pound of beef. In comparison, it requires 4.5 pounds to produce a pound of chicken meat and 7.3 pounds to produce a pound of pork. U.S.