Men beef up on soy, study finds

SATURDAY, NOVEMBER 09, 2002

New research suggests soy protein is as good as beef in contributing to muscle size and strength.

Researchers at the Kansas State University tested the effects of two diets on 21 men aged 65 and over. The men had been placed on a lacto-ovo-vegetarian diet (a diet including eggs and dairy but no meat) for two weeks.

Then, having started a resistance training program, 10 men were switched to a diet with beef (0.6g per kg body weight) while the remaining 11 stayed on the other diet which contained soy protein (also 0.6g per kg body weight).

Muscle size and strength increased by about the same rate in both groups, leading researchers to conclude that the source of protein was not an issue.

The research comes despite skepticism among bodybuilders of the benefits of soy protein for muscle growth and testosterone production.

"In assessing the merits of soy, many people base their reservations on hearsay and misinterpreted studies, some tested on animals rather than humans," nutritionist Leigh Blashki says.

"In the past two decades there have been several studies on humans which not only support the case for soy protein as a healthy muscle builder, but also as a contributor to antioxidant status and the reduced risk of prostate cancer."

The Kansas study echoes a report from late last year which found there was no significant difference between the merits of soy protein and whey protein.

Presented at last year's annual meeting of the Canadian Society for Exercise Physiology, the study was based on 48 men, aged 18 to 35, who were divided into groups and randomly given either 60g soy protein, 60g whey protein or a placebo. The subjects participated in a six-week weight-training program.

Tests done before and after the program showed that the subjects who got either soy or whey protein had increases in lean mass that were 3 to 5 percent more than those who took the placebo. The men taking the protein supplements also showed less muscle breakdown after training than the placebo group.

Researchers found that neither the whey or soy protein supplements showed any superiority in promoting muscular gains and decreased muscle breakdown.

"Soy protein is excellent for tissue growth because it contains a higher proportion of several amino acids than animal proteins, including glutamine, arginine, lysine and the branched-chain amino acids. Arginine is crucial for muscle development and is also associated with improved immune response.

"In soy protein isolates such as Solae™, you also get the added benefits of naturally occurring soy isoflavones which greatly improve the antioxidant levels diminished after intense training."