By David Liu, and editing by Stacey Sexton

Sunday Jan 8, 2012 (foodconsumer.org) -- Testosterone levels decline as men age, which explains why elderly men are not as sexually active as younger ones.   A study published in late 2011 in Biological Trace Element Research suggests that both exercise and magnesium supplements may increase the free and total plasma testosterone in men.

Testosterone, which is also found in women but at lower levels, is very important for men.  Low testosterone, or testosterone deficiency, medically known as hypogonadism, can lead to a decrease in muscle mass, changes in cholesterol levels, a decrease in hemoglobin and possibly mild anemia, fragile bones and a decrease in body hair.

A study led by V. Cinar of Slcuk University in Karaman, Turkey assessed how 4 weeks of magnesium supplementation and exercise may affect the free and total plasma testosterone levels in sportsmen practicing tae kwon do.  The control group was sedentary individuals tested at rest and after exhaustion.

The testosterone levels were determined in three study groups at four different settings: resting and exhaustion before supplementation, and resting and exhaustion (exercise) after supplementation.

Group 1 included sedentary controls supplemented with 10 mg. magnesium per kilogram body weight.  Group 2 were tae kwon do athletes practicing 90–120 minutes per day supplemented with 10 mg. magnesium per kilogram body weight. Group 3 were tae kwon do athletes practicing 90–120 minutes per day receiving no magnesium supplements.

The free plasma testosterone levels increased in the groups who exercised before and after supplementation as compared to levels in resting groups.   Exercise also boosted testosterone levels in exhaustion groups, relative to sedentary subjects.

Similar increases were observed for total testosterone.

The researchers concluded, "Our results show that supplementation with magnesium increases free and total testosterone values in sedentary individuals and in athletes. The increases are higher in those who exercise than in those who are sedentary.”

Another benefit of exercise is increased circulation, which helps men engage in an intimate relationship with their partners.