Pros and cons of soy foods

What’s good about Soy?

It’s heart-healthy. Soy protein has been shown to slightly reduce levels of LDL cholesterol, the “bad” kind. A landmark 1995 study that looked at nearly 40 controlled clinical trials found that replacing 50 grams of animal protein a day with 50 grams of soy protein lowered LDL cholesterol by nearly 13 percent. But a subsequent American Heart Association update found that the reduction is actually closer to 3 percent.

Replacing even a small amount of your daily animal protein with soy protein is smart for your heart and blood vessels, as it’s leaner than many animal protein sources—plus the fat it does contain is the heart-healthy type. Soy also supplies fiber, vitamins, and minerals. If a food contains at least 6.25 grams of soy protein per serving and is low in saturated fat and cholesterol.

It’s a stellar protein source. One cup of unshelled edamame, for example, packs 17 grams of protein, almost as much as three ounces of 70 percent lean ground beef and about the same as a hard-boiled egg. Soy is also unusual in that it’s a complete protein source, meaning it contains all of the essential amino acids rather than just some of them, as most plant sources do.

It’s high in fiber. One cup of cooked edamame contains 8 grams of fiber, as much as a dozen prunes.

It’s an alternative to cow’s milk. One cup of soy milk offers nearly as much protein as the same amount of dairy milk and, if fortified with calcium, supplies up to 30 percent of your daily calcium requirement. Note that not all soy milk is fortified. Also check the label for sugar content, since some soy milk has a lot of added sugar.

What’s maybe good about Soy?

The isoflavones in soy may strengthen your bones… Isoflavones are a type of phytoestrogen, meaning they are plant-derived compounds that weakly mimic the effect of estrogen. Because estrogen plays a role in bone health, it’s been suggested that soy isoflavones may reduce osteoporosis risk. But the evidence for this is mixed.

It helps with hot flashes. Research on soy’s effect on hot flashes has been similarly mixed. The North American Menopause Society’s 2015 position statement on nonhormonal treatment of hot flashes says that supplements containing soy isoflavones may help, but more research is needed. And some evidence suggests that the supplements may increase breast cancer risk, as discussed below, so for now we think it’s prudent to avoid them.

Safety concerns about soy

Because soy can mimic the activity of estrogen in the body, there has been some concern that it might increase breast cancer risk. The type of soy that’s potentially worrisome is supplemental soy and soy protein isolates, the kind used in nutritional bars and supplements. In fact, the phytoestrogens (estrogen-like compounds) in whole soy foods mayactually help protect against breast cancer. The American Cancer Society says that more research is needed to understand the relationship between specific forms of soy and cancer risk.

Hexane in processed soy foods is another concern. Hexane is a solvent used to extract oil from soybeans. If your bar or meat substitute has soy protein isolate, soy protein concentrate, or textured vegetable protein listed on its label, it likely has undergone hexane processing. Hexane is classified as a neurotoxin by the CDC, and chronic exposure in factory workers has been linked to neurological conditions. But it’s unclear whether consuming trace residues is hazardous. Whole soybeans (edamame) are always a hexane-free and healthy option.

Top food sources of soy

Soy “burger” 1 patty around 14
Tempeh 3 oz 13
Edamame 1/2 cup cooked 11
Meatless soy crumbles 1/3 cup 10
Soy yogurt 1 cup 9
Tofu 3 oz 8
Soy milk 1 cup 7
Soy nut butter 2 Tbsp. 7


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