Index
This food can be eaten whole or in various products, including tofu, tempeh, soy milk, and other dairy and meat alternatives.
It can also be made into soy protein powder.
For vegetarians, vegans, and those who avoid or are allergic to dairy products, soy protein often serves as an essential source of this vital nutrient. However, soy is a somewhat controversial food.
While some view it as a nutritional powerhouse, others view it as an enemy to health.
This article looks at the evidence to tell you if soy protein is good or bad for you.
Nutritional information
Soy protein isolate powder is made from defatted soy flakes washed with alcohol or water to remove sugars and dietary fiber. They are then dehydrated and turned into powder.
This product contains very little fat and does not contain cholesterol.
Soy protein powder is used to make soy infant formulas and a variety of meat and dairy alternatives.
Let’s look at the nutrient content of one ounce (28 grams) of soy protein isolate powder:
- Calories: 95.
- Fat: 1 gram.
- Carbohydrates: 2 grams.
- Fiber: 1.6 grams.
- Protein: 23 grams.
- Iron: 25% of the Daily Value (DV).
- Phosphorus: 22% of the DV.
- Copper: 22% of the DV.
- Manganese: 21% of the DV.
Although it is a concentrated source of protein, isolated soy protein powder also contains phytates, which can decrease mineral absorption.
Summary
Although it is a good source of plant-based protein and rich in nutrients, soy protein, and its powder contain phytates, which decrease the absorption of minerals.
It helps build muscle but may not be the most effective protein option.
Unlike most other plant-based proteins, soy protein is a complete protein.
This means that it contains all the essential amino acids that your body cannot make and needs to get from food.
While each amino acid plays a role in muscle protein synthesis, Branched Chain Amino Acids (BCAAs) are the most important when it comes to muscle building.
One study showed that people who took 5.6 grams of BCAAs after resistance training had a 22% greater increase in muscle protein synthesis than those who received a placebo.
Leucine BCAA activates a particular pathway that stimulates muscle protein synthesis and helps build muscle.
Compared to whey and casein proteins, soy protein falls somewhere in the middle for muscle protein synthesis.
One study showed that soy was inferior to whey protein when protein synthesis for muscles, but it performed better than casein. The researchers concluded that this could be due to the rate of digestion or the leucine content.
Similarly, a review study found that whey protein supports muscle protein synthesis better than soy protein in young and older adults.
Interestingly, soy can benefit you best when combined with other proteins.
Some research suggests that combining dairy and soy proteins may result in higher muscle protein synthesis than whey, casein, or soy alone.
Summary
Although soy protein contains BCAA leucine and improves muscle protein synthesis to some extent, it appears to be inferior to whey protein for muscle building.
It can help you lose weight.
Studies indicate that high protein diets can result in weight loss, even without limiting calories or nutrients.
However, the evidence is mixed regarding the relationship between soy protein and weight loss.
Some studies show that soy protein can increase weight loss just as effectively as animal protein.
In one study, 20 obese men participated in a soy-based high-protein diet and a meat-based high-protein diet. Real food was used instead of soy-based meal replacements.
Appetite control and weight loss were similar in both groups. The researchers concluded that high-protein soy-based diets were as effective for weight loss as high-protein animal-based diets.
Another 12-week weight-loss study found similar results with soy protein powder. Participants received soy-based or non-soy-based meal replacements. Both resulted in an average weight loss of 17.2 pounds (7.8 kg) at the end of the study.
Additionally, a study on people with diabetes and obesity showed that soy protein-based meal replacements, such as shakes, may be superior to standard diets for weight loss.
Those who consumed the soy protein-based meal replacement lost 4.4 pounds (2 kg) more than those who followed the standard diets.
However, while some studies look at the benefits of weight loss, a review of 40 studies that evaluated the effect of soy protein on weight, waist circumference, and fat mass found no significant positive impact.
In general, the evidence for consuming soy protein for weight loss is not as strong as for other proteins such as whey and casein.
Summary
Some research indicates that soy may be effective for weight loss, but the evidence is mixed and does not show that it is more effective than other proteins.
Health benefits
Some research suggests that adding soy protein to your diet can provide various health benefits.
For example, soy foods appear to have positive effects on heart health. In 35 studies, soy consumption lowered “bad” LDL cholesterol and “good” HDL cholesterol.
Another review showed that replacing animal protein with 25 grams or more of soy protein decreased total cholesterol, “bad” LDL cholesterol, and triglyceride levels.
When it comes to cancer, the evidence seems mixed.
Many observational studies have seen a protective effect of a diet high in soy.
However, they note that it is not known if this applies to soy protein isolate powder or other textured plant protein made from soybeans.
Some observational and case-controlled studies link soy intake with a reduced risk of breast cancer.
However, others show no protective benefit of consuming soy for this type of cancer. One study even linked soy intake to stimulated rapid cell production in the breasts of premenopausal women, possibly increasing their potential risk of breast cancer.
When looking at the role of soy in men’s health, some observational studies indicate that consuming soy foods may reduce the risk of prostate cancer in older men.
Although the results of observational studies are encouraging, human clinical trials on the possible cancer-protective effects of soy are inconclusive.
Also, many studies are based on soy foods rather than soy protein powder specifically.
However, soy protein can serve as a good source of plant-based protein for people who do not consume animal protein, including vegetarians and vegans, allowing them to reap the significant benefits of this nutrient.
Summary
Soy foods may provide potential health benefits such as lowering cholesterol and possibly reducing cancer risk, but more research is needed.
Possible drawbacks
Some people have concerns about soy.
As mentioned, soy protein contains phytates, also known as anti-nutrients. These interfere with the absorption of minerals in your body.
There is also some concern that soy intake may affect a person’s thyroid function.
The isoflavones in soy function as goitrogens and can interfere with thyroid function and hormone production.
However, there are a variety of studies showing that soy has no or only a very slight effect on thyroid function in humans.
Also, many people steer clear of soy protein due to its phytoestrogen content, as they fear that phytoestrogens may disrupt natural hormone levels in the body.
Phytoestrogens are chemical compounds that occur naturally in plants and have estrogen-like properties that bind to estrogen receptors in your body. Soy is a significant source of these.
However, soy protein powder is made from soybeans rinsed in alcohol and water, which removes a good portion of the phytoestrogen content.
Similarly, many men are concerned that soy protein may lower their testosterone levels, but research does not support this claim.
An extensive review study indicated that neither soy foods nor soy isoflavone supplements alter testosterone measurements in men.
Many of the potential drawbacks of soy are attributed to soy consumption, not specifically soy protein powder. More research is needed on soy protein powder specifically to see how it affects health.
Summary
While there are some potential drawbacks to eating soy, the evidence is relatively weak and suggests that most people can safely consume soy.
The bottom line
Soy protein is a complete source of protein. It can help muscle development but not as well as whey protein.
In general, soy is safe for most people and may offer health benefits, including weight loss.
