COVID Update: Masks are still required in health care settings, even if you’re fully vaccinated. Also, Scripps does not provide COVID-19 tests for asymptomatic patients. See FAQs.

Setting the Record Straight About Soy

Find out if it is healthy or harmful

A physician from Scripps Health in San Diego offers insights into whether eating soy is safe.

Soy — such a small plant to cause so much controversy. Some say it is a wonder food, while others may see it as a detrimental to health. So what’s a health-conscious consumer to believe?

Some soy facts

Soy is a subtropical plant — a legume — that is native to southeastern Asia and is toxic if eaten raw. Many consumers are unaware that forms of soy can be found in a plethora of foods, from baked goods and cereals to energy bars and vegetarian meat alternatives. And don’t forget soy milk and even soy infant formula.

In the 1970s and 1980s, soy was a health-food darling, purported to prevent certain cancers, lower cholesterol, support cardiovascular health and promote strong bones. In 1999, based on early research showing that soy protein lowered levels of LDL cholesterol, the U.S. Food and Drug Administration even approved a health claim that soy may reduce the risk of heart disease. But in recent years, soy is earning a reputation as an unsafe food to be avoided. In 2007, the FDA announced it was reevaluating the evidence in support of its 1999 assertion, in light of the many new research studies in the ensuing decade.

Soy foods

The confusion may stem from the differences between whole soy and the processed soy found in so many foods in the U.S.

“Whole soy can be a fine addition to diets,” says Hai Le, MD, an internal medicine physician at Scripps Coastal Medical Center, Vista. “It can be a valuable alternative to animal proteins, but soy derivatives are highly processed and can be overconsumed.”

Whole soy is a complete protein with all nine essential amino acids and is a source of fiber, vitamins and minerals, such as folate and potassium. Whole soy food options use the entire bean in its natural state and include edamame (large soybeans harvested when the beans are still green) and soybeans.

Processed soy — which is soy that has been dehulled and defatted — lacks the nutritional value of whole soy and may include unhealthy additives, such as sodium. Soybean oil, extracted using a chemical solvent, has become the base for most vegetable oils; soy lecithin, the waste product left over after the soybean is processed, is used as an emulsifier; soy flour appears in baked and packaged goods; and different forms of processed soy protein are added to everything from veggie burgers to protein powders and animal feed.

“When you read the ingredient labels, if you see glycine max, hydrolyzed vegetable protein, textured vegetable protein, monodiglyceride or monosodium glutamate listed, then the product contains processed soy,” says Dr. Le. “Just because something is vegetarian doesn’t mean it’s necessarily nutritious. Soy-based imitation-meat products often contain overly processed soy.”

Good soy choices

Fermented whole soy products — produced by a host of yeast and beneficial bacteria — can also be healthy. Fermentation neutralizes some of the compounds found in soybeans, such as phytic acid, that can cause difficulty with digestion and creates some beneficial compounds, such as vitamin K and fatty acids. Your refrigerated section of the grocery story contains fermented soy products.

  • Tempeh
    Tempeh is a type of fermented soybean found in solid, cakelike sheets that can be cut to size. It can be used with vegetables in a stir-fry or baked and grilled for a sandwich. Crumble it up and add to soups, salads, pasta sauce and casseroles.
  • Miso
    Miso is a thick, fermented paste made from soy beans and usually prepackaged in a plastic tub. Brownish in color, it tastes salty and tangy. The most common use of miso is in soup, but it can also add flavor to sauces and marinades.
  • Natto
    Natto is a sticky paste made by adding healthy bacteria to lightly cooked soybeans and fermenting. Natto is a good addition to soups and broths, as well as a topping for rice dishes. Natto can be an acquired taste because of its strong smell and distinct taste.
  • Fermented tofu
    Fermented tofu is made from cooked soybeans formed into a custard-like cake, and then fermented to make a white, creamy food resembling semisoft cheese.