Soybeans: Protein, Phytoestrogens, Glycemic Index & Nutrition Facts

The misunderstood bean

Soybeans are one of the world's most important crops, but you probably know them best as edamame, tofu, tempeh, or soy milk. They are, without a doubt, the king of plant proteins. Unlike most other plants, soy provides a 'complete' protein, meaning it has all nine of the essential amino acids our bodies can't make on their own. It's basically a steak, but a bean.

Despite this, soy has a reputation problem. For years, people have worried about its 'phytoestrogens' and potential effects on hormones. We'll get into that, but the short version is this: the science has moved on. For most people, whole soy foods are not just safe, they're incredibly good for you.

Soybean nutrition facts

Here's the nutritional breakdown for a 100-gram (about 2/3 cup) serving of mature, cooked soybeans. That's a pretty hefty portion, so you might eat less in a single meal.

The numbers speak for themselves. That protein content — 36.5 grams! — is staggering for a plant food. It's more protein than you'd find in 100g of steak. It's also delivering nearly 10 grams of fiber, which is fantastic for your gut and for feeling full. The fat is mostly unsaturated, the heart-healthy kind. It's a truly balanced, nutrient-dense food.

The real story on phytoestrogens

This is the source of 90% of the confusion around soy. Soy contains compounds called isoflavones, which are a type of phytoestrogen (meaning 'plant-estrogen'). Because their chemical structure looks a bit like human estrogen, people worried they might act like it in the body.

Here's the key: they don't. Phytoestrogens are much, much weaker than human estrogen and can actually have a balancing effect. In some cases they block stronger, human estrogen from binding to cells; in others, they provide a very mild estrogenic effect. Decades of research, including large human studies, have concluded that moderate soy consumption doesn't cause feminizing effects in men or increase cancer risk. In fact, it's consistently linked with a lower risk of certain hormone-related cancers like breast and prostate cancer.

Soybean's glycemic index

Glycemic index (GI) ranks how fast a food raises blood sugar. Foods under 55 are 'low'. While there isn't one single, universally cited GI number for soybeans (it's not a sugary food people test often), they are unequivocally a low-GI food. With so much protein, fiber, and fat, and very little sugar, the carbohydrate it contains is absorbed very slowly. This makes it an absolute winner for blood sugar control.

The best ways to eat soy

You'll get the most benefit from soy by eating it in its less processed forms. Here's a quick guide.

What soybeans are good for

What to pair soy with

Soy's savory, nutty flavor makes it a brilliant team player in the kitchen. Use it as a protein base to build a balanced meal.

Eat freely — or be mindful?

Three ways with soy

Here are three simple ways to get whole soy foods into your week, focusing on flavor and minimal processing.