Chapter 102
Testosterone Levels and Nutrition
Exercise can increase testosterone levels, but it depends on the type of training. Contrary to the popular belief that weightlifting raises testosterone levels, a systematic review of training studies in older men found that only aerobic and interval training did anything. Interestingly, music during exercise can lower testosterone levels. After half an hour of listening to music, testosterone levels in men drop by 14 percent. Does all music have this effect, or only certain genres? While half an hour of silence had no effect, 30 minutes of Mozart, jazz, pop, or Gregorian chants (neither related nor connected to me by marriage) suppressed testosterone about as much. And half an hour of one’s own favorite music? That cuts testosterone levels in half! What does that mean? Since testosterone in men is associated with dominance and aggression, perhaps we evolved to use music to soothe the wild beast, like a melodious cold shower to calm down.
What else can lower testosterone levels? Sleep deprivation. In an experiment in which men were allowed to sleep only five hours per night for a week, their testosterone levels fell by 10 to 15 percent. Alcohol can, too. While two or three drinks can produce an acute, temporary rise in testosterone that peaks after about two hours, the blood testosterone levels of men randomized to drink three beers a day for three weeks decreased by about 7 percent (compared with nonalcoholic control beverages). Men who drink a lot of coffee seem to have higher testosterone levels, and when subjects were randomized to drink five small cups (180 ml) daily for eight weeks, an increase in testosterone was found after a month, but it was gone again after the second month.
And “testosterone-boosting” supplements? An analysis of the best-selling “T-boosters” on Amazon.com found that 70 percent of products contained ingredients that had either no effect or an equivocal effect. 10 percent of the products actually lowered testosterone levels. One of the few ingredients you would expect to raise levels is fenugreek.
Fenugreek seeds have long been used as an aphrodisiac and for reduced male fertility. In rats, it can increase testicular weight and testosterone production, but what about in humans? In clinical trials with fenugreek at a daily dose of a quarter to two thirds of a teaspoon, testosterone levels increased within three months by about 10 percent, accompanied by an increase in sex drive and arousal. Positive side effects include an improvement in LDL cholesterol, triglycerides, and short- and long-term blood sugar regulation (with fenugreek powder working better than fenugreek extract products). Also, your armpits will smell like maple syrup (really!).
Testosterone Levels and Nutrition
Can people who suffer from reduced libido due to low testosterone increase it through a change in diet? I cover this topic in detail in see.nf/tdiet. High-fat meals can dramatically affect testosterone levels. The testosterone levels of men who ate a Sausage & Egg McMuffin from McDonald’s for breakfast dropped by 25 percent within an hour and stayed down for as long as four hours. That was not just due to higher inflammation levels, since testosterone fell before inflammation from the saturated fat rose. Testosterone levels can drop significantly within 15 minutes after eating a ham-and-cheese sandwich, which hardly leaves enough time for the sandwich to be digested. So the scientists turned to digestive hormones like GLP-1, which is released within 15 minutes after consuming a high-fat meal and appears to have a suppressive effect on testicular function. The researchers recommended that men should “minimize their fat intake, … to optimize their testicular function.”
High-protein diets can also suppress testosterone, contrary to what Men’s Health claimed under “blatant misuse of scientific information.” When overweight men were randomized to receive a few spoonfuls of whey protein powder (from milk), their testosterone level dropped by 100 points within an hour, which explains why a high-protein, low-carbohydrate diet can lead to a marked decline in testosterone levels. That doesn’t mean junky carbohydrates are better. The amount of sugar water equivalent to two cans of soda can also sharply lower testosterone levels.
Can phytoestrogens have feminizing effects?
I cover the findings on this in see.nf/phyto, but not even substantially higher doses than the one or two servings of soy phytoestrogens per day that Asian men typically eat have feminizing effects on men, and they also do not affect testosterone levels in humans. What about the phytoestrogens in flaxseed? In men who were given six slices of bread daily with two added tablespoons of ground flaxseed, testosterone levels did not change over six weeks compared with weeks without flaxseed. There was one case in which a man grew breasts (gynecomastia) when he regularly consumed one tablespoon of flaxseed oil per day, but he was also taking a statin drug, which itself already increases the risk of gynecomastia.
Testosterone and Mortality
Big Pharma portrayed low testosterone as a serious health problem. “It’s one thing to tell men that ‘Low T’ can make them grumpy,” says a commentary in JAMA Internal Medicine, “but quite another to claim that it kills them.” Most observational studies found an association between low testosterone levels and increased mortality, but that is not surprising, because obesity and chronic diseases—even acute illnesses like heart attacks or infections—lower testosterone, whereas healthy older men can maintain their levels. Low testosterone can therefore serve as a barometer of health status and is far more likely to be a consequence than a cause of disease.
In the largest observational study of men who had increased cardiovascular risk and received testosterone replacement, it turned out that testosterone recipients had a significantly higher risk of heart attack, stroke, or premature death once the researchers accounted for the confounding factors mentioned. Testosterone could explain why women live an average of seven years longer than men, because it is a powerful immunosuppressant.
Men are less able to fight off infections and, compared with women, respond worse to vaccinations. However, lower immune activation can have the advantage of fewer autoimmune diseases. Testosterone could be the reason women more often suffer from conditions like lupus, rheumatoid arthritis, and multiple sclerosis, whereas men have higher morbidity and mortality from infectious diseases. The lower infection risk is one reason castrated cats live years longer than “intact” tomcats. In fact, there are rare mammals with “semelparous” reproductive strategies in which the males experience only a single mating frenzy, fueled by a surge of testosterone, before dying shortly afterward from a total collapse of their immune system. So do human eunuchs live longer?
In rodents, castration actually extends life span. (On the other hand, hundreds of 10,000-volt electric shocks have the same effect on them. I’m not trying to tell anyone what to do.) A historical study of Korean eunuchs found that they lived 14 to 19 years longer than non-castrated men of similar socioeconomic status, and the proportion of centenarians among them was more than 100 times that of modern societies. Still, doubts arise about the accuracy of the records when you read that one of the eunuchs is said to have lived to 109 years old, which is close to the longest life span recorded in men. A similar report about castrati (singers who were castrated before puberty to preserve their high voice) from the 15th century observed no survival advantage compared with “intact” male singers over the same period.
More recent data exist in the history of American eugenics, under which developmentally disabled people were mass-sterilized into the 1930s—a practice upheld by the U.S. Supreme Court. In a psychiatric hospital in Kansas, the hundreds of castrated patients lived an average of 13 years longer than those who were not castrated. The fact that the main difference between the two groups was death from infection is consistent with the testosterone hypothesis. Be that as it may, testosterone replacement therapy is not a viable anti-aging strategy. An editorial in the Journal of the American Medical Association lamented: “Testosterone abuse will not simply stop because of faulty logic or lack of evidence, since neither was needed to get it started—rejuvenation fantasies thrive on hope and require no facts …”