Most of us know soy as a high-protein vegetable source, once most visible in health food stores but today as mainstream an ingredient as corn or wheat. Today's supermarket shelves stock the bean in every form, from soymilk and other dairy alternatives to miso, tofu and tempeh.
It's the key ingredient in the high-protein bars and drinks that line the "performance aisle." Soy-based vegetarian meats are in the frozen sections of small-town grocery stores. Even phony cheese and ersatz mayo from soy can be had anywhere these days.
Long an Asian staple, soy first became popular in the West for very practical reasons -- its versatility. Soy is high in both protein (a complete protein) and fat (containing both classes of essential fatty acids, omega-3 and -6), with most of its carbohydrates in the form of fiber.
Soy's Western health food "career," according to the Harvard Health Letter, was launched by a meta-analysis published in the New England Journal of Medicine linking soy protein intake of 47mg per day with a 13 percent reduction in LDL cholesterol, which is associated with increased risk of heart disease. This prompted the FDA to approve a "heart health" claim in 1999 for foods containing 25g or more of soy protein.
While soy protein's potential to lower cholesterol may have been the launch pad, soy's status as a health food resulted from a "perfect storm" convergence of events that drew attention to several of its components. Protein is not soy's only weapon against cholesterol. Soy also has phytosterols, plant chemicals structurally similar to cholesterol that can inhibit absorption of dietary cholesterol.
Probably soy's most important component are the isoflavones genistein and daidzein. These are classed as phytoestrogens, compounds structurally similar to the hormone estrogen. The big questions: Could soy, by providing estrogen-like compounds, reduce the incidence of estrogen-sensitive cancers like breast cancer? Could soy decrease bone loss by making up for age-related drop in estrogen?
A complete protein that can imitate meat supports the growing attention to vegetarianism and its more strict faction, veganism. Almost anything can be imitated with soy because of its unique texture. Meanwhile, the persistent low-carb enthusiasm means attention to soy as an alternative to starchy foods deemed off-limits by the followers of Dr. Atkins. Breads and tortillas, chips and other snacks can fill in the blanks of a diet formerly dominated by meat and cheese.
With all that reputation and promise; with that level of market penetration, some contrarians felt it necessary to "slow the soy train." Results of new studies on soy and cholesterol declared soy's benefits as not quite as promising as once thought. In fact the American Heart Association asked the FDA to rescind its allowance of a heart health claim. Then some animal studies raised the question about whether soy isoflavones might actually increase the recurrence of breast cancer by promoting the growth of estrogen-sensitive cells.
Even though these concerns didn't show up in human studies with people eating realistic levels of soy foods, the soy slam by mainstream media was on. (The studies on bone health are still promising but by no means conclusive.) Soy contains more phytic acid than other grains and beans, which may inhibit the absorption of iron, zinc, calcium and magnesium. Reportedly some people in third-world countries and who eat a lot of grains and soy may have some mineral deficiencies. Rarely mentioned in such criticisms is that nutrient deficiencies among people with restricted diets are not unusual.
Research is ongoing in all of these areas, which means that neither exaggerated claims of health benefits nor exaggerated claims of the dangers of soy are justified at this time. Will all questions about soy as the king of health food ever be conclusively resolved? And if not, what are we to do?
The problem isn't whether soy lives up to its full promise; the problem isn't with soy at all. One superfood can't cure cancer and heart disease and at the same time solve the global obesity crisis and free us all from diabetes … in the process giving us stronger bones and sharper minds.
So what should processors do until all the questions about soy are resolved? How about just enjoying soy's availability and adaptability as an ingredient unequivocably useful in products designed to be part of a healthy, nutrient-dense, well-balanced diet. Just a suggestion.