Soy Protein: A Complete Source Of Essential Amino Acids? (2025)

Soybeans contain all nine essential amino acids, making them a complete source of protein. This is unusual for a plant-based food, as most plant proteins are low in at least one essential amino acid. Soy is therefore a great option for people looking to add more plant-based proteins to their diet.

Soybeans contain all the essential amino acids necessary for human nutrition

Soy has been grown and harvested for thousands of years. Populations with diets high in soy protein and low in animal protein have lower risks of prostate and breast cancers than other populations. Increasing dietary whole soy protein lowers levels of total cholesterol, low-density lipoproteins, and triglycerides. It may also improve menopausal hot flashes and help maintain bone density and decrease fractures in postmenopausal women.

The specific nutrient makeup of soy depends on the form. For instance, soy protein isolate has much more protein per serving than tofu or soy milk. However, all plants contain all nine essential amino acids, but some only offer very limited amounts. For example, lysine only occurs in small amounts in most grains and cereals.

Soy may aid heart health, cancer risk, and blood sugar levels. These benefits are largely attributed to soy’s health-promoting compounds like phytosterol, saponins, lecithin, phytic acid, and isoflavones, in addition to its nutrition profile.

Soy is one of the few plant-based complete proteins

Soy has been grown and harvested for thousands of years. Populations with diets high in soy protein and low in animal protein have lower risks of prostate and breast cancers than other populations. Increasing dietary whole soy protein lowers levels of total cholesterol, low-density lipoproteins, and triglycerides. It may also improve menopausal hot flashes and help maintain bone density and decrease fractures in postmenopausal women.

The benefits of soy are largely attributed to its health-promoting compounds like phytosterol, saponins, lecithin, phytic acid, and isoflavones, in addition to its nutrition profile. For example, in one review of 35 studies, soy intake lowered LDL (bad) cholesterol and raised HDL (good) cholesterol.

The specific nutrient makeup of soy depends on the form. For instance, soy protein isolate has much more protein per serving than tofu or soy milk. However, all soy foods, including tofu, edamame, tempeh, and soy milk, are considered complete proteins.

Soy protein isolate has more protein per serving than tofu or soy milk

Soybeans contain all nine essential amino acids necessary for human nutrition. Populations with diets high in soy protein and low in animal protein have lower risks of prostate and breast cancers than other populations. Soy may also aid heart health, blood sugar levels and menopausal hot flashes.

Soy is generally a good source of protein, though the specific nutrient makeup depends on the form. For instance, soy protein isolate has much more protein per serving than tofu or soy milk. Soy protein isolate is processed to be a concentrated source of protein. Tofu is made by curdling and pressing soy milk solids, and has a higher protein content per serving than soy milk. One cup (or 240ml) of unsweetened soy milk contains around 7g of protein, while the same amount of firm tofu contains around 20g. However, it's worth noting that soy milk is often fortified with additional nutrients, such as calcium and vitamin D, which are important for bone health. Tofu is a good source of iron and calcium, but it may not be as versatile in cooking as soy milk.

Populations with diets high in soy protein and low in animal protein have lower risks of prostate and breast cancers

Soybeans contain all nine essential amino acids, which are necessary for human nutrition. Soy is one of the few plant-based foods to be considered a complete protein. This includes soy foods such as tofu, edamame, tempeh, and soy milk.

In addition, studies among prostate cancer survivors indicate that eating soy foods may lower PSA levels. Among men in various stages of prostate cancer, those who consumed soy milk or isolated soy isoflavones saw their PSA levels rise at a slower rate.

Some studies also show that a diet high in soy may reduce the risk of breast cancer. However, there are not enough data to make recommendations concerning soy intake in women with a history of breast cancer. The refined soy isoflavone components, when given as supplements, have not yielded the same results as increasing dietary whole soy protein.

Soy may aid heart health, cancer risk, and blood sugar levels

Soybeans contain all nine essential amino acids, making them a complete source of protein. Soy is one of the few plant-based foods to be considered a complete protein, with other plant proteins often lacking in at least one essential amino acid.

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