When you eat protein, it is broken down into amino acids. In addition to helping you build muscle, amino acids are the building blocks for every cell, tissue, and organ in your body. Of the 20 different kinds of amino acids, your body can make 11, which means you do not need to get them from food. The remaining nine amino acids that your body can not produce are referred to as "essential" amino acids, and are acquired through the food that you eat. When looking at soy vs. whey protein, it is important to consider all the factors regarding your body's use of a protien supplement.
Biological Value
One factor regarding your body's use of a protien supplement that needs to be considered is how well that supplment can be broken down and used by your body. Proteins are ranked according to biological values. Biological values, or BV, are arbitrary numbers that are given to protein sources to show comparisons in their availability within the body. Looking a protein's BV is an easy way to assess the quality of the protein. The easier a protein supplement absorbs, the faster your body can put it to use. At the time this system was initiated, eggs were given the highest BV of 100 because they are the most bio-available natural protein. In time, whey, a common protein supplement, was isolated from milk and given a higher BV. The BV of whey protein, depending on how it's processed, can yield anywhere from a 104 to 154 on the BV scale, while the BV of soy protein is only 74. Based on the BV scale, whey protein can be absorbed and utilized by your body more quickly.
Protein Efficiency Ratio
Another factor regarding your body's use of a protien supplement that needs to be considered is how well that supplment can help you reach your fat loss or muscle building goal. The FDA used the protein efficiency ratio, or PER, to derive the recommended daily allowance of protein seen on food labels. This number was created to measure the gain in body weight divided by the weight of the protein consumed for infant laboratory rats. Because rats utilize protein differently than humans, there are some doubts about using the PER due to potential calculation errors, but this is still a number to look at in the whey vs. soy debate. Keep in mind that these errors cause a minor overestimation of animal protein and a slight underestimation of plant protein. Another factor to keep in mind is that PER does not measure maintenance of muscle, but rather growth, so if you're using protein supplements as a way to burn fat rather than build muscle, the PER may not be the best way to determine the best supplement source. Nonetheless, according to the FDA, any protein having greater than a 2.7 PER calculation is considered an excellent source of protein. Soy protein has a PER of 2.2, while whey protein has a PER of 3.2, making whey protein more effective for gaining muscle.
Amino Acid Score
Of the 20 amino acids, your body can make 11. The remaining nine amino acids that your body can not produce are referred to as "essential" amino acids, and are acquired through food and supplementation. When comparing protien supplements, you must also take into account the amino acids that the supplment will provide. Although the amino acid score, or AAS, of a protein does not take into account the digestibility of the measured protein, it is still a quick, reliable, and low-cost way to compare protein sources and supplements by assessing essential amino acid. The AAS measures essential amino acids in a protein compared to a reference protein. Each protein being tested is rated based on its most limiting amino acid found. A value greater than 1 indicates that the protein being considered contains a greater amount of essential amino acids than humans require. Soy protein has an AAS score of .99 while whey protein has an AAS score of 1.14, showing that whey protein has a significantly greater concentration of amino acids.
Glutamine
The last factor to consider is a protein supplement's glutamine content. Glutamine is a non-essential amino acid that can be found in protein. Glutamine is used by the body to transport nitrogen to tissues. Glutamine has also been shown to increase muscle cell volume through cellular hydration. Glutamine supplementation also increases growth hormone levels, which leads to the muscle using fatty acids for fuel rather than blood sugar. For individuals looking to build muscle, 3 g to 5 g of glutamine should be consumed three times per day. When looking at glutamine concentration, soy protein has 10.5 g of glutamine per 100 g of protein, while whey protein only contains 4.9 g of glutamine per 100 g of protein, showing soy to be a more significant source of glutamine.
Soy vs. Whey
Soy vs. whey is a protein supplement debate that has gone on for decades. Soy and whey protein are both healthy additions to a balanced diet and both bring different qualities to the table. No matter which protein supplement you choose, it is important that you are, in fact, using a protein supplement to get the protein necessary to give your body what it needs. Remember, protein helps to build every cell, tissue, and organ in your body. The Institute of Health's Dietary Reference Intake, or DRI guidelines state that normal, healthy adults can safely consume protein anywhere from 10 percent to 35 percent of their total calories. For example, on a 2,000 calorie diet you could safely consume anywhere from 50 g to 175 g of protein -- 10 percent to 35 percent of calories -- per day.
References
- The Simple Soybean and Your Health; Mark Messina, PhD; Virginia Messina, RD; Ken Setchell, PhD; 1994.
- "Nutrition and Dietetics"; Role of protein and carbohydrate sources on acute appetite responses in lean and overweight men; J Bowen; 2008
- "Institute of Medicine"; Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fatty Acids, Cholesterol, Protein and Amino Acids; September 2002
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