Soy Protein: Benefits, Side Effects & Dosage


What is Soy Protein?

Soybean is a popular cooking ingredient. It is also commonly developed into other products, such as soy milk and tofu. Additionally, soy protein is also a popular supplement powder because it provides a large amount of protein compared to other meat protein alternatives.

Patients who are allergic to dairy can consume soy protein, which is a major factor in the debate between soy protein versus whey protein. Soy protein can be very helpful for those planning to start a vegetarian or vegan lifestyle. There are many benefits, but there are few side effects related to over consumption (x).

Soybean is a high-protein legume that converts into soybean powder to include in food or protein shakes. Because of its high protein and low carbohydrate nutritional profile, there are many people who may benefit from soy protein in their diet. This nutritional profile makes it a popular supplement for those trying to lose weight, build muscle or maintain an adequate protein intake without meat or dairy-based proteins (x).

Soy Protein vs. Whey Protein

The biggest argument in the soy protein versus whey protein debate is that soy protein is far more accessible than other varying dietary lifestyles. Whey protein is made from cow’s milk, which presents a significant barrier to anyone who is lactose intolerant, as well as anyone following a vegan or dairy free diet for health reasons. Further, even those without an intolerance or related health concern can suffer side effects from too much dairy.

Soy Protein vs. Pea Protein

Pea protein is another good option, but its amino acid profile is not complete, meaning that the person would need to get amino acids from other sources. It is also just as good as whey protein for those trying to gain muscle (x). Pea protein powder is also a great choice for anyone with an allergy to soy.

Benefits of Soy Protein 

In addition to being vegan, dairy-free and low in cholesterol, soy protein has plenty of potential benefits for a wide range of health concerns.


Studies state that soy protein powder may help reduce blood sugar levels in patients with diabetes. Consuming this dairy free powder as soy fiber or as soybean will still yield results (x, x).


Feeding infants and toddlers formula with fiber or soy protein may help relieve diarrhea, compared to a formula with cow’s milk (x, x).

High Cholesterol

Consuming soy protein instead of other sources can reduce total cholesterol intake. It can also reduce LDL cholesterol, labeled “bad cholesterol.” Even though soy does not increase HDL—“good” cholesterol—it may help reduce LDL cholesterol (x).

High Blood Pressure

Including soy protein in the diet may help reduce systolic blood pressure by as much as 4 to 8 mmHg. It may also reduce diastolic blood pressure by about 3 to 5 mmHg (x, x).

Breast Cancer

There is a lot of speculation between medical researchers surrounding the correlation between soy and breast cancer. Researchers once believed that soy in the diet may increase the risk of breast cancer, but now research shows that a moderate intake (1 to 2 servings a day of whole soy products) does not actually increase the risks of any type of cancer. Additionally, studies show that a lifelong diet rich in soy products may even reduce the risk of breast cancer, compared to patients who eat less soy or add it to their diets later in life (x).

Kidney Disease

Consuming soy protein may reduce protein in urine for patients with kidney disease. This reduces the levels of certain elements, such as creatinine, which may build up over time and cause health problems (x, x).


Research suggests that soy protein may help increase bone mineral density, particularly in women, which can increase the risks for osteoporosis. It contains isoflavones that may help reduce the risk of fractures. This quality is extremely beneficial for older female patients because bone density declines with age. However, research has not noted the same effects for younger female patients (x, x).

Irritable Bowel Syndrome (IBS)

Consuming soy-based components with isoflavones can help patients manage symptoms of irritable bowel syndrome (IBS), which include stomach pain and diarrhea (x).

Menopausal Support

Including soy in the diet can help manage menopause symptoms. For example, soy protein may help reduce hot flashes, better control mood and regulate body weight and blood sugar levels in menopausal women (x, x).

Metabolic Syndrome

Patients with metabolic syndrome may find that including soy protein in their diets may help reduce blood sugar levels. Metabolic syndrome is a collection of conditions that increase the risk for chronic conditions such as diabetes or heart disease (x, x).

Benefits of Soy Protein

Side Effects of Soy Protein

Soy proteins offer a lot of benefits for the human body in proper dosages. However, despite its potential benefits, consuming it in excess can cause side effects. Continuous, long-term use in high dosages can eventually cause health complications. It may cause abnormal tissue growth in the uterus. This complication specifically results from soy protein. Consuming soy in its original form does not seem to cause this issue (x).

It may cause allergic reactions, such as rashes, itching and even anaphylaxis in more severe cases. Individuals with hay fever or asthma are more likely to have a food allergy to soy elements (x).

Some patients may also experience extreme fatigue (x, x). Soy proteins can cause digestive issues as well, like an upset stomach, stomach pain, bloating, nausea and constipation (x, x). In large doses, soy may also affect thyroid function. Patients who are iodine-deficient are more prone to experience this. On the other hand, if a patient has hypothyroidism, consuming soy proteins can potentially make the condition worse (x, x).

Other Potential Side Effects

Soy products may also increase the risk for kidney stones because they contain large amounts of oxalates, which are the main component of kidney stones. Patients with serious kidney problems will have difficulty digesting certain elements in soy. If the body cannot digest them, it will store them and this could cause health complications (x, x). Phytoestrogens is an ingredient in soy may be toxic in large doses. Those with kidney failure may be at risk for phytoestrogens levels in the blood (x, x).

Long-term use of soy proteins with isoflavone can also potentially increase the chances of precancerous changes developing in the tissues along the uterus lining (x). It may also increase the risk for bladder cancer. Patients with cystic fibrosis may also find have difficulties processing protein (x, x). Speak to a doctor about the possibility of these risks. Despite these possibilities, this supplement is most likely safe in proper doses in the short-term (x, x, x).


Pregnancy & Breastfeeding

Generally, soy protein is usually safe to consume during pregnancy and breastfeeding. However, consuming large amounts could cause developmental complications for the baby, so it’s best to consult a doctor before taking this supplement.


In most cases, it is most likely safe for children to use. However, children require different dosages and instructions. Soy milk may cause health issues or nutrient deficiencies. Keep in mind that children with cow’s milk protein allergy may also be allergic to soy products (x).

Is Soy Protein Safe for Men?

Because soy protein contains phytoestrogens, some male patients avoid it with the assumption that it affects male sex hormones. However, a review of several clinical studies show that consuming soy products in normal, healthy doses does not affect testosterone levels or availability in male participants (x).

Why Take Soy Protein Powder?

Cardiovascular Benefits

Increasing plant protein in the diet can also promote cardiovascular health. This includes reduced blood pressure as well, since it is low in carbohydrates and saturated fat and it is completely free of cholesterol (x). Consuming soy proteins or following a soy-based diet can also help increase fiber intake. Fiber may help promote a healthy gastrointestinal system, as well as lower cholesterol levels in the body (x). It contains polyunsaturated fat which also helps lower cholesterol and generally supporting a healthy heart (x).

Vitamins and Minerals

Soy proteins contain a multitude of vitamins and minerals. It has omega-3 fatty acids, B vitamins, zinc, antioxidants and iron along with vitamin D and calcium. All these elements help the human body function properly (x).

Lactose Intolerance

Soy protein is a great alternative for those with lactose intolerance. Parents can also use soy-based formula for infants who cannot tolerate lactose as well (x, x).


Galactosemia is a condition in which the patient has trouble digesting the sugar galactose. Again, children or adults suffering from galactosemia can use soy protein to maintain a healthy nutritional profile (x).

Dosage for Soy Protein Powder

As a dietary supplement, the recommended dosage for soy protein isolate powder is 15 to 30 grams per day with permission from a medical professional. Individual needs may vary, so it is best to consult a doctor before taking this supplement.

The Bottom Line

Soy protein is a plant-based protein that comes from soybeans. A popular alternative to meat, it is popular with people who follow a vegan and vegetarian diet. It is also an excellent alternative for those who are allergic to milk or other dairy products.

Research shows that it may help improve heart and bone health, offer cardiovascular benefits and reduce the risk of cancer. Besides this, soy protein may also be able to help individuals with diabetes, high cholesterol, kidney disease and those experiencing menopausal symptoms.

However, despite the benefits, consuming large amounts of soy protein over a long period could result in digestive trouble, higher chance of diabetes and kidney diseases. It may also cause allergic reactions in patients with an allergy to soy or lactose. Overall, it is a generally safe and potentially effective supplement in proper dosages. Always consult a doctor before taking this supplement. They are not a replacement for medical conditions or a substitute for medical advice. Instead, supplements aim to support overall health.

About the author

Sukriti Taneja

Let's Be Friends