Soy protein muscles in on whey

BY JULIE SEAMER
THURSDAY, JULY 05, 2007

A recent study comparing the efficacy of different protein sources on skeletal muscle protein synthesis has seen whey and soy come in equal winners.

Unlike carbohydrate only meals, both carbohydrate/whey protein mix and carbohydrate/ soy protein mix have performed favourably by promoting general protein synthesis of the skeletal muscle ¹. These finding are a good reminder that skeletal muscle is acutely responsive to physiological variations in dietary amino acids, and that the two preferred sources of these are whey and soy protein, alike.

In fact, despite controversy around soy being oestrogenic, soy is a high quality protein comparable to milk protein, containing all the essential amino acids including two key components for sports performance:

Arginine plays a key role in stimulating hormone release for the promotion of muscle formation. It is also required for creatine phosphate formation, which is one for the most important sources of energy for muscles ². For athletes, arginine may contribute to blood vessel health and in the maintenance of a healthy immune system ³.

Glutamine is essential during metabolic stress and promotes protein synthesis supporting adequate hydration in cells and buffering lactic acid build up during exercise ⁴. It therefore impacts positively on recovery.

Soy protein foods also provide amino acids leucine, isoleucine and valine, which are used as an energy source during exercise ⁵.

A common problem experienced by many athletes is sports anaemia, as a result of intense training, and iron loss, via sweat and urine and the actual destruction of red blood cells due to temperature increases within the body ⁶. Every 100mg soy protein provides 18mg of iron, making it particularly beneficial for female athletes who have even further iron loss through menstruation.

Research supports the virtues of soy protein in sports nutrition in 3 key ways:

Improving physical strength and performance
Young elite badminton players given a soy protein based beverage demonstrated improved levels of 'VO2 Max' and iron. VO2 Max is the maximum amount of oxygen taken up by a person under set conditions – improvement of which is generally accompanied by enhanced output. In this study, the greatest improvement in VO2 Max was after four months of consuming the soy protein whereby the player's physical strength and performance increased significantly ⁷.

Reducing post-exercise fatigue
Researchers from the Institute of Sports Medicine in Romania found that when Olympic athletes consumed soy protein at 1.5g per kg of body weight, in addition to their regular intake of dietary protein (2g per kg body weight), fatigue after exercise sessions was reduced ⁸.

Improving recovery through anti-oxidation
The naturally occurring isoflavones in soy act as antioxidants in the body ⁹, neutralising unstable compounds such as free radicals that develop during periods of oxidative stress, such as exercise. These compounds may contribute to fatigue, soreness and muscle injury ¹⁰. A study of 20 athletic college males who consumed either 40 grams of soy protein or 40 grams of whey protein, showed that the total antioxidant status (TAS) increased only in the soy fed group. The rise in the body's TAS from the isoflavone content was associated with reduced enzymes in the blood that indicate muscle inflammation and damage ¹¹. These findings suggest a protective role of isoflavones in soy, by decreasing acute exercise-induced injury, which may have implications after training long and hard, shortening recovery time.

Aussie Bodies offer two soy protein powder supplements. Soy Protein Plus is boosted with essential fats, vitamins and extra antioxidants for general immunity and well-being. Perfect Soy Protein in an unflavoured powder, enjoyed for its purity, offering a high-quality, low-carbohydrate source of protein. Even if you are not dairy intolerant, it may be time you gave soy a try!

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