Protein is responsible for muscle growth and repair, and it plays an important role in any fitness regimen. Most people should get 20 to 35 percent of their calories from protein, but certain athletes place a higher demand on their muscles, requiring a higher capacity for repair. Bodybuilders, for example, should eat up to 0.9 grams of protein per pound of body weight. It can be difficult for some, especially vegetarians, to meet protein needs from food alone, so many turn to protein supplement shakes. Whey protein is the heavyweight of the protein supplements, but soy is rising in popularity.
Sources
Soy protein comes from the soybean, a legume that has been a kitchen staple for thousands of years. It can be eaten whole and raw, known as edamame, or it can be processed into a variety of foods like tofu, meat substitute, and even cooking oil. Whey is a milk byproduct of cheese making, and you can see it as the liquid portion of cottage cheese. Supplement manufacturers either isolate or concentrate the whey and sell it in a powdered form to be mixed with milk. Many of those same manufacturers also offer powdered soy protein that can be used the same way.
Benefits
A 2004 paper in the "Alternative Medicine Review" stated that whey protein possesses a number of immune-enhancing properties, and can act as an antioxidant, antibacterial, antiviral and antihypertensive agent. Research physicians have used whey protein to treat cancer, heart disease and osteoporosis, and it can also enhance athletic performance. The University of Maryland Medical Center notes that soy has been shown to reduce menopause symptoms and the risk of heart disease and osteoporosis. There is also evidence to show that soy can help lower blood lipid levels and prevent hormone-related cancers.
Drawbacks
A 2004 study in the "Nutrition Journal" found that whey protein did not preserve the body's total antioxidant function as well as soy. Additionally, people who are lactose-intolerant may experience some digestive issues, since whey is a milk protein. Soy is an allergen to some people, but those who are not allergic are unlikely to experience anything more serious than mild stomach upsets and irregularity. People with kidney disease should not eat soy because it is high in phosphorus and potassium, and it has also been linked to the growth of breast cancer cells, although more research is needed.
Shakes vs. Whole Food
Both soy and whey are available as shakes or in whole foods. If you are allergic to soy, whey is naturally the way to go. If you are vegan, soy is the better option because whey comes from milk. It is unhealthy to get all of your protein needs from milk and cheese because the nutrient balance includes too much fat, and you would need a lot of it to meet your protein requirements. If you would rather use whey protein, a whey isolate shake is the better option. If you prefer to get your protein from whole foods, soy is the better option because it is found in so many different foods with different nutrient profiles. If you use protein as a pre-workout meal, both proteins will digest more quickly in shake form.
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