Get access to everything we publish when you sign up for Outside+.
If an award were given for “Hyphenate of the Year,” the phrase “plant-based diet” would win by a landslide.
Recommendations abound urging you to eat more plants, which is not a bad idea given the well-documented positive effects of a veggie-full diet — improved body composition, decreased risk of cancer and heart disease, and improved cholesterol, to name but a few. It’s also easier than ever to indulge in plant-based foods, and a recent marketing survey found that sales of plant-based meat and dairy substitutes have increased significantly year over year.
Then … there’s soy.
Once the darling of the vegetarian and vegan movement, soy has been marginalized and even vilified in recent years by conflicting results in clinical studies as well as by a marketplace replete with new-age competitors.
Does soy still have a place at the trending table, or is it time to drop it into the bin with the Shake Weight and those five-fingered shoes?
A Hill of Beans
Nutritionally speaking, the soybean actually has a lot to offer. Like all foods, soy is a collection of several biologically active compounds and contains many beneficial macronutrients and micronutrients. It is one of the few sources of complete protein in the plant world, and when it comes to vitamins and minerals, soybeans get top billing in the vitamin C and folate department, with calcium, iron, phosphorus, potassium, thiamin and magnesium following closely behind.
But the prize behind curtain No. 3 is polyphenols. These antioxidants can help mitigate inflammation and oxidative stress, and according to research published in Oxidative Medicine and Cellular Longevity, they are documented triggers for chronic maladies like heart disease, Alzheimer’s, Parkinson’s and certain forms of cancer. But one prominent polyphenol found in soy is causing all the ruckus: isoflavones.
Soy’s Secret Sauce
Isoflavones have a chemical structure similar to that of estrogen and are thus considered a phytoestrogen (plant-based estrogen). This has raised concerns among many with regards to cancer, specifically the effect isoflavones may have on postmenopausal women as it relates to breast, thyroid and uterine cancer. The American Cancer Society continues to reiterate that soy foods are healthy and safe and that warnings about isoflavones are meant to highlight the potential dangers of consuming large amounts of soy. Most studies to date done on isoflavones have been conducted on animals that metabolize them differently than humans, and identifying if a food is beneficial to people depends heavily on the unique physiology of the individual who consumes said food. Cofactors such as obesity, age and lifestyle further muddy the waters when trying to conjure a clear picture of what something may or may not do in your body.
However, a group of scientists from Loma Linda University in Southern California combed through a mountain of clinical and epidemiological research to determine what benefits, if any, isoflavones offer for women. While the health-promoting powers of soy are more modest than the hype suggests, its merits are very real and remarkably wide-ranging.
HEART DISEASE: Female subjects experienced improvements in arterial health when consuming 40 to 80 milligrams a day of soy isoflavones in tablet form; endothelial function, an indicator of coronary heart disease, improved with an isoflavone intake of 50 grams from soy food sources; and as little as 13 milligrams a day was associated with a reduction in the risk of heart attack and stroke. The U.S. Food and Drug Administration recommends consuming 25 grams of soy protein a day to lower cholesterol and reduce the risk of heart disease, and The European Journal of Preventive Cardiology reported that a soy-rich diet is associated with a 16 percent lower risk of heart disease and a 20 percent lower risk of stroke.
MENOPAUSE: The intensity of hot flashes and night sweats abated with a daily intake of 50 milligrams of soy isoflavones. According to the journal Menopause, isoflavones bind to estrogen receptors in the body and help reduce the severity of menopausal symptoms such as fatigue, vaginal dryness and hot flashes.
OSTEOPOROSIS: A vast number of studies show that bone mineral density improves with a daily isoflavone intake of 90 milligrams from isolated soy protein. Isoflavones also may reduce bone loss, improve markers of bone health and reduce the incidence of endometrial cancer by 19 percent, according to research published in the Journal of the Academy of Nutrition and Dietetics.
The Soy Sweet Spot
The ideal soy/isoflavone intake hovers around 50 milligrams per day for most women, according to the journal Nutrition Today, and most experts agree that isoflavones obtained from whole soy foods are superior to supplements or processed soy products. Fermented soy foods such as miso and natto are among the best options, and a study published in The BMJ found that a higher intake of fermented soy products was associated with a lower risk of early mortality. Choose foods that are minimally processed such as tofu, tempeh, soy milk, soy yogurt and edamame. Soy “burgers” and other faux meats should be eaten in moderation, and you should always check the Nutrition Facts panel and note the sodium and saturated fat content, which are often added to make a product palatable.
Ultimately, soy is best approached like any other food — eaten in its whole form in modest amounts as part of a varied diet. And like so many other nutrition decisions, whether you want to consume it or not is an individual choice. If you enjoy soy and it makes healthy eating more convenient, then go ahead and make it a regular guest at your trending table. If not, no worries: There are plenty of other foods that can easily fill that slot on your dining dance card.
Nutrition facts: A 1⁄2 cup of cooked and shelled soybeans (edamame) contains just 100 calories, 10 grams of protein, 5 grams of fat, 8 grams of carbs and 6 grams of fiber.
Soy contains a substance called phytic acid, which belongs to a class of compounds called anti-nutrients. Anti-nutrients can block the absorption of dietary compounds, which in the case of phytic acid includes iron, zinc, calcium and magnesium. This may sound shocking, but for most people, it should not be a huge concern. For one, mineral deficiencies in Western countries are rare, and a study published in The Journal of Nutrition showed that phytic-acid intake did not disrupt mineral absorption enough to cause an actual deficiency. What’s more, it may actually be good for you: According to research published in the International Journal of Food Science & Technology, phytic acid demonstrated anti-cancer properties, and another study in Nutrition Journal found it helps prevent kidney stones.
Still worried? Then soak, sprout or ferment your soy to reduce its phytic-acid content.
Also, mind your food pairings: Phytic acid only blocks minerals in foods that are consumed with it simultaneously, meaning if you eat soybeans in a spinach salad, you potentially won’t absorb as much of the calcium from the spinach as you would if you ate it without the soybeans.
WTF Is Soy Lecithin?
Produced from raw soybeans, soy lecithin is extracted through chemical or mechanical processing, resulting in a greasy, fat-like substance. This “emulsifier” serves as a catalyst, allowing oil and water to marry and producing a more palatable and stable food product. (For example, it has a longer shelf life.) Soy lecithin is found in countless food products and nutritional supplements, including protein bars and chocolate, and though soy is the most ubiquitous source, lecithin also can be derived from foods such as eggs, sunflower seeds, corn or fish.
However, soy lecithin is found in such tiny amounts in any given food that even those with soy allergies may safely ingest it without feeling any ill effects. And a growing body of research indicates that soy lecithin taken as a stand-alone supplement may improve a number of conditions, including depression, stress, high cholesterol and dementia.
Easy Does It
As with anything, overdoing your intake of soy might not be a great idea.
Check out these unexpected sources of soy to keep your intake in check:
- Infant formula
- Canned broth/soup
- Canned tuna
- Hot dogs
- Energy bars
- Commercial baked goods
- Asian cuisine
- Chicken nuggets
- Low-fat peanut butter
- Deli meat
WARNING: While soy foods are generally considered safe, women who are pregnant or nursing, or those who have survived or are currently battling breast cancer, should check with their doctor before dramatically increasing their intake of soy foods or before starting soy protein or isoflavone supplements.