Soybean is a superfood rich in various nutrients, including protein. According to one study, a soybean’s composition includes 40% crude protein.
Therefore, soybean is the raw material for soy protein and soy protein isolate. Soy protein refers to any soy-derived food, including tofu, tempeh, and soy milk. On the other hand, soy protein isolate is a product of defatted soy meal and contains approximately 90% protein when in powder form.
However, soy protein is a controversial food product, with multiple US soy articles describing excessive soy protein consumption as harmful. So, how much soy protein can you consume safely? Keep reading to learn more.
Soy Nutrient Profile
As stated earlier, soy has a high nutrient density, hence its popularity. Soy is particularly popular among individuals on a meat-free diet because it is a plant-based complete protein. Complete proteins contain all nine essential amino acids the body cannot produce independently.
Most complete proteins are from animal sources like red meat, white meat, eggs, and dairy products. Therefore, soy is a rare plant-based complete protein that can substitute meat or function as a meat extender.
However, besides proteins, soy is also rich in other macronutrients, including vitamins, minerals, and fatty acids. Such macronutrients include polyunsaturated fats (20% omega-3 fatty acids), soluble and insoluble fiber, potassium, manganese, calcium, magnesium, zinc, folate acid, B vitamin complex, and vitamin E.
Therefore, besides soy protein and soy protein isolate, consumers can take soy to meet the daily reference intake for other macronutrients. Also, soy protein is more affordable and readily available than animal protein.
Soy Phytochemical Profile
As mentioned earlier, soy is a superfood. Superfoods are a fresh produce with benefits beyond meeting the body’s nutrient intake requirements and feature phytochemicals that interact with the body to promote health. Soy protein has a complex phytochemical profile, although its most dominant phytochemicals are isoflavones and antioxidants.
Isoflavones are plant-based phytochemicals or compounds primarily found in legumes, although the soybean has the highest isoflavone content of all foods. One report shows that isoflavones or phytoestrogens may have estrogen-like or antiestrogenic effects.
Besides estrogen-like effects, isoflavones also have antioxidant properties. One research study identifies other antioxidants in soy protein as chlorogenic acid isomers, caffeic acid, and ferulic acid. The polyphenolic compounds highlighted above are bioactive and induce antioxidant activity to counter oxidative stress in the body.
Why Eat Soy? Soy Protein Health Benefits
Besides its outstanding protein profile, prevailing research links soy with preventative effects against certain health conditions, thanks to its phytochemicals. Moreover, phytochemicals also have symptom-reduction effects against certain health conditions. Below is an overview of the research-backed health benefits associated with soy protein.
Promotes Cardiac Health
Soy protein has a favorable effect on blood cholesterol levels. According to one clinical review report, various studies concluded that consuming 25mg-50mg of soy protein daily lowers the body’s total low-density lipoprotein (LDL) cholesterol levels.
Cholesterol is a risk factor for various cardiac conditions, including elevated blood pressure, coronary heart disease, stroke, and heart attack. Consequently, the FDA approved labeling soy foods as protective against coronary disease.
Bone And Muscle Health
Soy protein is also effective for lean muscle growth and optimal bone health. According to one study, the isoflavone content in soy protein tends to stimulate osteoblastic bone formation while inhibiting osteoclastic bone resorption.
Osteoblastic bone formation is the generation of a new bone layer, entailing the formation of a matrix over the older bone’s surface. On the other hand, osteoclastic bone resorption is the degradation of bone tissue.
Osteoblastic bone formation and osteoclastic bone resorption are essential to bone homeostasis, and bone diseases like osteoporosis inhibit this balance. The study referenced above showed an improvement in osteoblastic bone formation among postmenopausal women who incorporated soy protein in their diet. Postmenopausal women are at a higher risk of developing osteoporosis.
Moreover, a second study established a link between soy protein and muscle strength, endurance, and power among osteoporotic postmenopausal women. The lean muscle development and strength gains increased when the study subject combined soy protein supplementation with exercise.
Reduced Hormonal Cancer Risk
Breast and prostate cancer are the dominant hormonal cancers. Although early evidence linked the isoflavones in soy protein to increased breast cancer risk, recent research shows the opposite.
According to one study review, a lifelong soy-based diet reduces breast cancer risk among women. Also, women who take soy after a breast cancer diagnosis have a reduced risk of cancer recurrence.
Moreover, a second study showed that soybean antioxidants had a cytotoxic (death-inducing effect on prostate cancer cells. However, the research on soy and its effects on prostate cancer are preliminary.
Is There Anything Like Too Much Soy Protein?
While soy protein has multiple nutritional and health benefits, excessive soy consumption could have the opposite effect. For starters, one study shows that excessive isoflavone consumption hampers normal thyroid function by impeding thyroid peroxidase activity. The thyroid hormone regulates multiple metabolic activities, and its dysfunction can cause elevated cholesterol levels and insulin resistance.
Second, soy protein contains antinutrients, including phytic acids, lectin, and trypsin inhibitors. Antinutrients are plant-based competitive compounds that bind to specific minerals, inhibiting the body’s capacity to absorb such macronutrients.
Antinutrient effects, while typically mild, can lead to malnutrition for individuals on an exclusively plant-based diet. For example, trypsin inhibitors in soy protein inhibit trypsin function, which is necessary for protein breakdown and absorption in the small intestines.
How Much Soy Should I Consume Daily?
According to one study, the recommended dietary allowance for proteins is 0.8 grams per pound of body weight per day. However, unlike most complete proteins, soy protein has a high isoflavone and antinutrient content.
Therefore, one government report recommends taking no more than 30mg-50mg of isoflavones daily. Check your soy product packaging to determine the isoflavone quantity you are taking per soy protein serving.
Alternatively, a second report recommends taking no more than 25 grams of soy daily, translating to 2-4 soy servings per day. It gives serving recommendations for various soy products as a guide for distributing the recommended 25 grams throughout the day.
Soy Products
The US soy market has various protein products, including whole soy foods like Tofu, Tempeh, edamame, and Miso. Moreover, second-generation soy products like soy milk, yogurt, cheese, and textured soy meat substitutes like soy sausages and burger patties are available.
Consider eating more soy whole foods because the traditional processes used to prepare such foods help reduce the soy protein’s antinutrient levels. Also, avoid highly processed soy foods like soy protein isolate.
Conclusion
Soy protein is somewhat controversial, albeit its associated benefits outweigh its disadvantages. Moreover, as directed above, you can maximize soy’s benefits by consuming the protein in moderation.
