The main difference between protein supplements is that whey protein comes from a cow (it is a protein extracted from milk) and soy protein comes from a legume (the soy bean). Vegetarians prefer to supplement their diet with soy protein and athletes use a combination of various protein supplements.

Protein supplements have gained popularity as they often contain a higher biological value than ordinary food protein sources such as meat. The biological value reflects indicates the digestibility of the protein and how available the protein is for use by the body. A whole egg was rated at 100% nitrogen absorbed, but as protein powders became better sources of protein, the percentage became a number and now a whole egg is has a biological value of 100. This allows some processed proteins to have biological values greater than 100, such as whey at 104. Soy protein concentrate has a biological value of 74.

The amino acid score (AAS) measures essential amino acids in a protein compared to a reference protein. The AAS rates the protein on the most limiting amino acid found in the protein, but it does not consider the digestibility of the protein. A value greater than 1 (whey protein contains a value of 1,14) indicates that the protein being considered contains a greater amount of essential amino acids than humans require and soy protein concentrate has a value of 0.99 so both protein supplements have an AAS close to 1, which is optimal to the body.

Protein digestibility percentage measures the percentage of protein consumed against the amount absorbed in the body as many of the nutrients and nitrogen elements get lost, dissolved or excreted in the body. Soy Protein Concentrate has a 95% digestibility rate, while whey has a 99% digestibility.

Glutamine is a non-essential amino acid that transports nitrogen to the body’s tissues and increases muscle cell volume through cellular hydration. Glutamine supplementation also increases hormone levels, which leads to the muscle using fatty acids for fuel rather than blood sugar. Soy protein contains higher levels of glutamine than whey. It also contains higher levels of arginine, a non-essential amino acid that combats fatigue, facilitates muscle growth through promoting the release of both growth hormone and insulin in the body during intense exercise. Arginine produces nitric oxide, which increases blood flow, and thus delivers more nutrients to the muscles and increases lipid (fat) metabolism.

Soy protein is very low in fat, contains no cholesterol and contains phytochemicals. The main phytochemicals in soy protein are isoflavones, saponins and phytc acid that are strong antioxidants. Soy protein and its associated phytochemicals seem to reduce heart disease, osteoporosis and risk of cancer.

Whey is considered to be the most popular protein supplement among bodybuilders. It is usually recommended to take whey before and after your workouts (a fast acting protein). Whey protein may be slightly more expensive than soy, but it is still cheaper than meat. It has a great flavour and both supplements can be used with many types of food to increase protein content and nutritional value.

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