Soy Protein

Macronutrient

OVERVIEW

Summary

An alternative to animal sources, this plant-derived protein choice, soy, is a near-complete protein that’s low in fat and calories while high in benefits that women and calorie-restricted dieters may find appealing. While this doesn’t mean we should immediately toss aside our high-quality whey or caseins, it does imply, however, that we should consider including soy in our daily diet. Believe it or not, soy has more protein than meat, eggs, or fish and contains a wide array of essential nutrients, including calcium, iron, potassium, Vitamin E, and fiber.

Other names for Soy Protein

soy, soya, Genistein

Where to find Soy Protein

Soy is produced from soybeans. When its oil is extracted, what is left is a soy-protein residue. Commercially, it can be found in tofu, soy milk, tempeh, textured soy protein, and soy flour.

Conveniently, soy can be added to soups, sauces, and dips, and baked, stir-fried, or blended for increased protein intake.

Powdered forms are often added to drinks, burgers, miso, or even pasta.

PERFORMANCE BENEFITS

Why athletes use Soy Protein

High in the critically important three BCAA’s (branched-chained amino acids) as well as glutamine and arginine, soy is growing in popularity with sports enthusiasts and dieters because it not only supports muscle growth and recovery but promotes an increase in metabolism and fat loss as well. Studies with both male and female athletes have demonstrated that soy may help increase muscle mass and improve performance, while decreasing bodyfat.

Ways that Soy Protein can enhance Muscle Gain & Recovery:
  • Increase dietary protein to help support muscle maintenance and recovery
Ways that Soy Protein can enhance Fat Loss:
  • Indirectly stimulate the metabolism, which may increase the body’s ability to burn fat
Ways that Soy Protein can enhance Longevity:
  • Fight off free radicals to enhance immune functioning due to its isoflavone content
  • Lower levels of blood fats and reduce total cholesterol levels to support a healthy heart

HEALTH BENEFITS

Signs of Soy Protein deficiency

No deficiency conditions are known to exist.

Potential uses for Soy Protein

Research indicates that Soy Protein may be useful in the treatment of:

  • Obesity
  • Cancer, specifically breast and prostate
  • Cardiovascular disease
  • Herpes

DISCUSSION

More about Soy Protein

Even though soy was the first protein powder ever available to consumers searching for a protein supplement, it was considered “substandard” as far as a protein source for decades because it was labeled “incomplete” as compared to animal-source proteins. Now, thanks to science, it’s been vindicated. It is, in fact, a good protein choice, being a near-complete protein that’s low in fat and calories while high in benefits that women and calorie-restricted dieters may find appealing.

Plus, believe it or not, it has more “available” protein than meat, eggs, or fish and contains a wide array of essential nutrients, including calcium, iron, potassium, Vitamin E, and fiber. In fact, in the Protein Digestibility Corrected Amino Acid Score (PDCAAS), which is the method used by the World Health Organization, soy gets the maximum score of ONE, reflecting that it is a complete food for humans.

Is it a worthy choice for athletes?

Studies with both male and female athletes have demonstrated that soy may help prevent the loss of muscle mass and improve performance while decreasing bodyfat, likely by promoting the release of hormones and potentially affecting metabolism.

Soy has also been shown to promote strong bones, connective tissue, and reduce inflammation, helping reduce recovery time. What’s more, studies with Olympic athletes demonstrated that the athletes who used soy experienced less fatigue after training.

Uniquely, some research suggests soy may also help maintain or even boost metabolism, even when calories are decreased. That’s a definite positive for those trying to reach a target weight (a lower weight, that is). You see, when calories are restricted from our daily diet, the body often thinks it’s starving and protects itself by lowering thyroid-hormone levels (responsible for regulating the thyroid). But the phytochemicals in isolated soy protein appear to give our bodies what they need to support thyroid production and keep our metabolisms moving steadily — enhancing the burning of calories for fuel.

While questions have been raised regarding soy’s effects on testosterone, the studies that found a trend toward lower levels of testosterone were done on animals, not humans. Human studies, on the other hand, have revealed that soy may reduce levels of testosterone’s evil counterpart, dihydrotestosterone, which is known for its negative effects. One study showed a reduction of 13% dihydrotestosterone, suggesting soy may inhibit the conversion of testosterone to dihydrotestosterone — this is a good thing, especially for those trying to put on muscle mass!

Of course, we aren’t suggesting reaching for soy and giving up all other quality protein sources, such as whey and caseins, which have been shown to have muscle-building effects. But it looks like it may be beneficial to consume a balance of protein types or at least make sure one-third of your daily protein intake comes in the form of soy isolates.

Benefits for females

Soy appears to be particularly beneficial for active women because of the isoflavones it contains; namely, daidzein. These estrogen-like compounds have been found to be especially helpful for women going through menopause — helping reduce the hot flashes, irritability, and discomfort associated with this transition. Soy appears to be so effective for some women that some doctors are suggesting it may become an alternative to traditional estrogen-replacement therapy.

Important for not only women but men as well is that soy has also been shown to help the body hold on to calcium and retain bone strength, which may help prevent osteoporosis.

Cancer-fighting potential?

As yet, the results aren’t officially in on soy’s direct effects on cancer or on its potential anti-carcinogenic attributes. But the evidence is mounting. You see, soy provides the body with three potential cancer-fighting compounds — the powerful antioxidant phytic acid; protease inhibitors, which have been shown to block the enzymes that may lead to cancer; and finally, the isoflavones genistein and daidzein (referred to earlier), which may compete with the hormone estrogen and minimize the damage it can inflict. Studies have shown soy may be especially beneficial for people at risk for hormone-dependant cancers, such as those in the breast and prostate.

Heart-healthy nutrition

While it’s still unknown exactly how soy may help lower cholesterol levels, what is known is that it does, in fact, appear to be effective. Some research has shown consuming soy protein may lower total cholesterol levels by 23 mg per deciliter, which may significantly diminish the likelihood of related illnesses, including heart disease and stroke.

In fact, the science is so strong in this case, the FDA (Food and Drug Administration) has allowed a health claim to be posted on products containing the suggest serving of soy protein (4 servings at 6.25 grams per day) that reads: “Soy protein may reduce cholesterol and the risk of heart disease.”

In conclusion

As the research continues to pile up for soy as a plant-derived alternative to animal-source proteins, a possible cancer and heart-disease fighter, and antioxidant, scientists continue to debate what other potential uses they may find for this little bean. One thing is certain, though, more and more researchers and experts are recommending incorporating soy into our nutrition plans as part of our daily protein intake for greater health today and far into the future.

NOTES ON USAGE

Amount

Between 1 and 1.5 grams of protein per pound of bodyweight per day is often recommended for active males; .75 to 1 gram per pound of bodyweight per day for women. Thus, a 180-lb man would consume between 180 and 270 grams of protein per day. And a 125-lb woman would consume between 95 and 125 grams of protein a day.

Specific ranges for soy isoflavones, contained in soy proteins, range from 50 to 100 mg per day.

Timing

Soy protein can be consumed anytime throughout the day to increase protein intake and is often found as a powered drink or shake and in many meal-replacement products (or MRP’s, for short).

Important tip

If you decide to use a soy powder to get more soy in your diet, look for soy isolate listed first or second on the ingredients list. This helps ensure you’re getting a higher quality product, as soy isolates are 90% protein, as opposed to concentrates, which are a mere 70% protein.

Synergists of Soy Protein

No synergists have been noted.

Toxicity of Soy Protein

No known toxicity.

Bans and restrictions

None reported.

RELATED RESEARCH

  • Barnes, S., “Evolution of the Health Benefits of Soy Isoflavones,” Proc Soc Exp Biol Med 217.3 (1998) : 386-92.
  • Crouse, J.R., 3rd, et al., “A Randomized Trial Comparing the Effect of Casein with that of Soy Protein Containing Varying Amounts of Isoflavones on Plasma Concentrations of Lipids and Lipoproteins,” Arch Intern Med 159.17 (1999) : 2070-6.
  • Dragan, I., et al., “Studies Regarding the Efficiency of Supro Isolated Soy Protein in Olympic Athletes,” Rev Roum Physiol 29.3-4 (1992) : 63-70.
  • Istfan, N., et al., “The Nutritional Value of a Soy Protein Concentrate (STAPRO-3200) for Long-Term Protein Nutritional Maintenance in Young Men,” J Nutr 113.12 (1983) : 2524-34.
  • Messina, M., and Barnes, S., “The Role of Soy Products in Reducing Risk of Cancer,” J Natl Cancer Inst 83.8 (1991) : 541-6.
  • Slavin, J., “Nutritional Benefits of Soy Protein and Soy Fiber,” J Am Diet Assoc 91.7 (1991) : 816-9.
  • Wahlqvist, M.L., and Dalais, F.S., “Phytoestrogens: Emerging Multifaceted Plant Compounds (editorial),” Med J Aust 167.3 (1997) : 119-20.