Breaking Research For 1-20-2000

new study leads support to protein supplementation.

Diets low in protein lead to increases in sex hormone-binding globulin in men, potentially reducing the availability of testosterone and causing loss of muscle mass, red cell mass and bone density, according to a report in the January issue of The Journal of Clinical Endocrinology and Metabolism.

The new finding provides more evidence that high-quality protein supplementation can improve health, maintain muscle mass, and enhance quality of life.

Dr. Longcope and colleagues from New England Research Institutes, in Watertown, examined the correlates of sex hormone-binding globulin levels in 1,552 men, ages 40 to 70 years, who were enrolled in the Massachusetts Male Aging Study.

After accounting for sex hormone levels, the team found that age and body mass index were strong determinants of sex hormone-binding globulin levels in the men. In addition, protein and fiber intake were significant contributors to these levels.

The study results suggest that the natural reduction in protein intake with age, and perhaps even the tendency to eat less red meat for health reasons, could result in lower concentrations of active (unbound) testosterone in men. The decrease in bioavailable or free testosterone can result in declines in sexual function, muscle, red cell mass, and contribute to the loss of bone density.

The new data also suggest the converse, that a high-protein diet could increase bioavailable (free) testosterone and potentially "...mitigate the effects of the age-related decrease in that hormone," the researchers observe. Further studies will be needed to test this hypothesis, they say.

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