Soy protein forms a great protein source for vegetarians and vegans. Still, many controversies surround it, and you may wonder if it’s good or bad for you.

There are many protein powders, and soy protein isolate is one of them. It is prepared from soybean flakes and is widely consumed as a meat and dairy alternative for people who are either allergic to or avoid animal products and vegans and vegetarians. Besides, it is used to make a healthy milk formula for infants. Despite all these uses, some consider it as a foe of health. If you want to know whether soy protein is good or bad for you, peer into this article.

The basics about soy protein

Soybeans are a great protein source, consumed immaturely as edamame and mature as soybeans. Soybean flakes are used to prepare many dietary products, including soy protein, tempeh, tofu, and soy milk. The flakes are thoroughly washed with water or alcohol in making soy protein, and all the fiber, cholesterol, and sugars are eliminated. The final product is then processed into powder and marketed as soy protein powder.

Soy protein nutritional information

Most health experts, nutritionists, and dietitians rely on a food’s nutritional profile to gauge what it offers to the body. Generally, soy protein isolate powders are made from defatted soybean flakes, which have undergone processing; hence they have no cholesterol and little to no fats. Below is their general nutritional profile;

  •  1 gram
  •  1.6 grams
  •  95
  •  2 grams
  •  22% of the DV
  •  23 grams
  •  21% of the DV
  •  25% of the Daily Value (DV)
  •  22% of the DV

The breakdown above shows how soy proteins are nutritionally rich and a good protein source. However, most of the nutrients are covered in phytates (phytic acid), making nutrient absorption hard.

Soy protein is good for muscle synthesis, but it’s not the best

Most vegans, vegetarians, people who are allergic to or avoid animal proteins find soy protein a good alternative because it’s a complete protein. This means that it has all the nine essential amino acids which the body cannot synthesize and must come from the diet. However, soy protein may not be the best for muscle building. Of course, all amino acids are great at muscle building; however, branched-chain amino acids (BCAAs), especially leucine, are the best. In a study examining the role of various amino acids in muscle building, leucine improved boosted muscles by 22%, hence the popularity of leucine supplements among body-builders.

When compared against other protein powders like casein and whey, soy lies in between. While it does better than casein, whey protein is more effective than it. The effect was the same in adults and children working out. In explaining this observation, various mechanisms have been applied, with phytate affecting digestion and low leucine content as the main ones. However, combining whey and soy protein results in a synergistic effect that builds more muscles than whey in isolation. The result is expected to be the same when soy protein works in combination with other proteins.

It May be good for weight loss

Proteins are among the best foods for weight loss because they help a person remain full for longer and reduce the secretion of ghrelin, a hunger-inducing hormone. However, when it comes to soy protein, studies have mixed findings, and the relationship is not one-sided. For instance, a 12-week study examining the effect of soy powder and non-soy powder food replacements in weight established that both were effective at shaking pounds, with all participants losing an average of 7.8kg. Furthermore, it’s thought that diabetics and obese people would lose more weight by consuming soy powder since they lost at least 2kg more.

Another study examined weight loss in 20 men eating normal protein sources and soy-based real foods at different times. At the end of the research, the two periods resulted in similar weight loss effects, showing that soy powder and soy-based meal replacements are as effective as other proteins in weight loss. Still, other studies say otherwise. For example, in a recent analysis, more than 40 studies on soy powder found no significant connection between the powder and weight loss, calling for further research on the same.

Potential health benefits of soy protein consumption

Even with the mixed opinions about the role of soy protein in weight loss and muscle synthesis, health experts agree that adding it to your diet is beneficial. For instance, some studies have shown that the protein can lower and raise bad and good cholesterol, respectively. Another study confirmed the same and added that soy protein could lower triglyceride levels. These two effects lower the risk of heart disease since they are its risk factors. In addition, some studies indicate that soy protein could reduce breast cancer risk, yet others reveal that it can promote the replication of breast cancer cells, especially in postmenopausal women. Regarding men, study results are equally mixed, with some claiming that it can reduce prostate cancer risk, while others are showing no relationship at all.

Health concerns about soy protein consumption

Despite the rich nutritional profile and the potential health benefits of soy proteins, there are drawbacks linked to their consumption. The first one has to do with the phytate presence, which limits the availability of zinc and iron nutrients. Still, this is a less serious concern, especially if your diet is diverse (usually the case) and you don’t rely on soy protein as your main protein source. Secondly, some people are worried that it might interrupt thyroid function due to isoflavones’ presence, but research shows that the effect is little to none at all. While women might be concerned about soy protein’s phytoestrogens that could imitate estrogen, they have the defatted soy protein powder, washed and has no phytoestrogen. In addition, some men are concerned about soy protein decreasing their testosterone levels, but the claims are not science-based.


Soy protein is a good protein alternative, especially for vegans, vegetarians, and people who avoid or are allergic to animal proteins. Its potential health benefits include weight loss and may also aid in muscle synthesis, although not as effective as whey proteins. Of course, there are health concerns linked to its consumption, including interference with thyroid function linked to phytoestrogen, but soy protein powder is a suitable alternative with no phytoestrogen due to defatting.

MS, University of Tartu
Sleep specialist

Using the acquired academic and professional experience, I advise patients with various complaints about mental health - depressed mood, nervousness, lack of energy and interest, sleep disorders, panic attacks, obsessive thoughts and anxieties, difficulty concentrating, and stress. In my free time, I love to paint and go on long walks on the beach. One of my latest obsessions is sudoku – a wonderful activity to calm an unease mind.

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