Testosterone is the principle male hormone in the human body. It is a steroid hormone from the androgen group of hormones. In humans testosterone is primarily secreted by the testes in men and by the ovaries in women. Testosterone is highly anabolic and has a dose response relationship with skeletal muscle mass which means the more testosterone there is the more muscle mass there is. This is evident with the amount of muscle men have compared to women as well as the excessive muscle mass bodybuilders can build when they use testosterone based drugs. Testosterone is also highly responsive to different lifestyle factors, including how much protein you eat on a daily basis.
In men, testosterone plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass and the growth of body-hair.
Men care about testosterone because deficiencies in the hormone can lead to muscle weakness or sexual disorders, such as erectile dysfunction. Testosterone use in the form of anabolic steroids results in an increase in skeletal muscle mass, strength and athletic performance. The amount that athletes and bodybuilders use to achieve their impressive levels of performance and size is much higher than the amount used in testosterone replacement therapy. The difference being that replacement therapy is for men who have low testosterone levels are only given enough to return them back to normal levels. Bodybuilders and athletes already have normal levels and take even more to push them past what is possible naturally. This is how they achieve seemingly super human feats of strength and muscle mass levels.
Testosterone at ’proper’ amounts is responsible for the normal growth and development of male sex organs, and the maintenance of secondary sex characteristics such as male pattern skeletal muscle.
Without enough of it, you can feel anxious, depressed, become intellectually muddled, and develop a low sex drive. Also, low levels of testosterone may result in a decline in muscle mass and strength, and an increase in upper body and abdominal fat.
Testosterone levels are widely believed to fall with age, however recent research has disputed this claim, suggesting that the testosterone decrease from aging is mostly associated with an ’aged lifestyle’.
Interestingly it seems as though testosterone levels may be declining in north American men. In one of the largest study of its kind, Travison et al. report a population-wide decline in Massachusetts’s men’s testosterone levels during the last 20 years that is not related to normal aging or to health and lifestyle factors known to influence testosterone levels.
They found that testosterone concentrations dropped about 1.2% per year, or about 17% overall, from 1987 to 2004. The downward trend was seen in both the population and in individuals over time.
The strongest association was observed in same-aged men from different sampling years. For example, a 65-year-old in 2002 had lower testosterone levels than a 65-year-old in 1987.
So what can cause increases or decreases in Testosterone?
We do know that muscle building workout programs also increase salivary testosterone measures. However, improper training program design can actually decrease testosterone levels as large unaccustomed increases in training volume can decrease testosterone levels.
Testosterone is also influenced by psychological factors, for example during sports competition Testosterone increases, this effect is seen even in sports similar to chess (shogi). It could be suggested that competition itself increases testosterone regardless if it is a mental or physical competition. Testosterone even rises when a group of men in a social setting are competing for the attention of women. It appears that competition between men, regardless of the arena, will have an effect on testosterone. Now that we’ve seen testosterone is sensitive to your external social environment it’s also worth noting that it’s sensitive to the internal environment of your body and specifically to your nutritional environment.
There is a significant negative correlation between testosterone and protein intake in men. People with protein intake that is 12-15% of their daily caloric intake have higher serum testosterone levels then people with a protein intake of 20, 25 and 30% of their caloric intake.
So there is evidence that a chronic high protein diet can decrease testosterone levels. Research has also found that taking a supplement containing 50 grams protein and 100 grams of carbohydrates right before and immediately after heavy strength training can lower the testosterone response to training.
And the protein load doesn’t have to be as high as 50 grams of protein. Another study found that as little as 25 g of protein taken before a workout can significantly lesson the testosterone and GH response to strength training.
In fact, in a test of whole food (protein 38 g; carbohydrate 70 g; fat 7 g), a supplement drink (same protein , carbs and fat as the whole food), an isocaloric carbohydrate beverage (same amount of calories but all carbs), or a placebo beverage (flavored water) immediately, 2 and 4 hours after a standardized weight training protocol, it was the placebo that had the highest testosterone response to exercise.
This research indicates that there seems to be a negative correlation between overall protein intake and testosterone levels as well as post workout protein and testosterone levels.
The evidence that protein and even carbohydrate post-workout can blunt testosterone response may be overstated as it does not seem to blunt increases in muscle mass. It would appear that while long term high protein diets may decrease testosterone they seem to do so without negatively influencing muscle mass. In fact, people on low calorie diets or following an Intermittent Fasting routine seem to maintain more muscle mass when protein intake is slightly higher than normal.
In summary while testosterone levels are influenced by protein, the degree of change does not seem to be enough to cause changes in muscle mass.
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