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Advantages and disadvantages of protein supplements with soy protein
Advantages and disadvantages of protein supplements with soy protein
08 Oct 2024
Posted By: Mateusz Durbas Times Read: 554 Comments: 0

It is indicated that vegans consume less protein than those on a traditional diet. That's why many athletes who follow a plant-based diet regularly turn to protein supplements, including soy protein isolate. Let's check out the main advantages and disadvantages of protein nutrients based on soy protein isolate.

Soy protein - what is it?

Soy protein, as the name suggests, comes from soybeans(Glycine max L. Merrill), which are an important source of protein in the diets of vegans and vegetarians. Soy protein has been shown to have a good amino acid composition, making it of high biological value. Soy protein is a rich source of lysine and has very good digestibility and assimilability. The literature reports that soy protein has a PDCAAS (protein amino acid digestibility index) of 1.0 and appears to be comparable to whey protein isolate (WPI - Whey Protein Isolate). However, when one considers the naturally contained anti-nutrients in soy (e.g., phytic acid and trypsin inhibitors), which limit the absorption of some nutrients, whey protein isolate appears to be superior to soy protein using DIAAS, an index of digestible essential amino acids. Soy protein, on the other hand, tends to be cheaper than whey protein (WPC and WPI) and is therefore often added to protein bars for physically active people in the form of soy protein isolate.

Soy protein - health-promoting properties

Studies have suggested that soy protein may contribute to improving blood lipid profile and reducing the risk of cardiovascular disease, especially ischemic heart disease). It has been shown that replacing 13 or 50 grams of animal protein (e.g., fatty red meat) in the diet with an identical amount of soy protein can lead to a reduction in LDL fraction cholesterol (the so-called "bad" cholesterol) by 3.6% and 6.0%, respectively. It is indicated that adherence to a diet providing at least 25 grams of soy protein each day can favorably affect cardiovascular outcomes, mainly lipidogram (blood cholesterol and triglyceride testing). The results of a meta-analysis of 46 studies involving postmenopausal women showed that soy protein containing isoflavones (phytoestrogens) significantly reduces blood concentrations of the following parameters:

  • triglycerides (by an average of 5.04 mg/dl),

  • Total cholesterol (by an average of 3.02 mg/dl),

  • LDL fraction cholesterol (by an average of 3.27 mg/dl),

  • apolipoprotein B (Apo B).

Recent scientific reports also show that soy and soy products can reduce blood CRP (a marker of inflammation) and fasting glucose levels in patients with type 2 diabetes, and lower systolic blood pressure in people with hypertension (above 135 mmHg).

Soy protein - does it help build muscle mass?

Protein supplements based on soy protein isolate are now readily available, quite attractively priced and popular among athletes on a vegan diet. Soy protein isolate is widely used for oral nutritional formulations due to its high protein content, neutral taste and excellent emulsifying properties. Soy protein isolate powder contains an average of 80 grams of protein (24 grams per serving) and small amounts of carbohydrates, fat and dietary fiber. Compared to whey protein, soy protein contains a lower amount of essential amino acids (EAAs) per 1 g, especially fewer branched-chain amino acids(BCAAs) - leucine, isoleucine and valine. Recent findings have shown that the use of soy or whey protein containing 2 g of leucine for three months in non-weight-trained (beginner) subjects contributed to significant increases in muscle strength and lean body mass, with no significant differences between groups. Soy protein can support the development of strength and muscle mass to the same extent as whey protein, especially when consumed in amounts that provide sufficient leucine. Therefore, it is advisable to consume slightly more soy protein to produce a similar physiological effect (development of skeletal muscle strength and mass) as whey protein.

Mężczyzna na siłowni patrzący w lustro i trzymający hantle w rękach

Soy protein may interact with drugs

It is well known that soy protein can impede the absorption of levothyroxine, a drug commonly used to treat hypothyroidism. Therefore, patients taking levothyroxine should take a minimum 4-hour break between taking the drug and eating a meal containing soy and its products. In addition, soy protein may interact with iron, warfarin (an anticoagulant) and monoamine oxidase inhibitors (drugs mainly used to treat atypical depression and Parkinson's disease).

Soy protein may adversely affect the thyroid gland

Soy protein can have adverse effects on thyroid function, mainly in people with known hypothyroidism and in those who do not provide the body with adequate amounts of iodine with their diet. The results of conducted studies have shown that soy isoflavones affect thyroid function by inhibiting the activity of thyroid peroxidase (TPO), which is involved in the formation of thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4). Frequent consumption of soy protein is not recommended in people with iodine deficiency and thyroid dysfunction, as well as in pregnant women and patients taking levothyroxine.

Soy protein is classified as a potent allergen

Soyprotein can sensitize people with soy allergies, so they should not consume soy and its products (including protein supplements based on soy protein isolate)at all. Regular inclusion of soy protein in the diet by people with a soy allergy can cause various side effects, the most common of which are:

  • diarrhea,

  • abdominal pain,

  • nausea and vomiting,

  • urticaria,

  • angioedema,

  • eczema,

  • breathing difficulties,

  • oral allergy syndrome,

  • headache and dizziness,

  • musculoskeletal complaints,

  • menstrual cycle disorders (in women).

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