If you’ve been reading recently you know I’ve been on a hormone kick recently. That sexy looking molecule to the right and the hormone du jour: testosterone. Testosterone is the principal anabolic and sex hormone in humans, responsible for sexual desire and function, muscular hypertrophy, densification of bones, and hair growth. Compared to females, males famously produce about ten times the amount of testosterone, but females are far more sensitive to its effects. Though testosterone is largely responsible for those traits and characteristics that are considered “masculine” – physical strength, body hair, dominance, and virility – both sexes require it for proper sexual and physical development. In mammals, males secrete it primarily from the testicles (about 95% of the total amount, in fact) and women secrete it from the ovaries. A modicum is produced in the adrenal glands in both sexes.
Testosterone plays an important role throughout every stage of a person’s life:
Prenatally, testosterone – along with dihydrotestosterone, a more potent anabolic hormone – is partly responsible for the formation of the male genitalia. It helps determine gender identity (with society bringing up the rear later in life, of course) and it spurs development of the prostate and seminal vesicles.
In early infancy, boys’ testosterone levels rise, almost to puberty levels, only to plummet at 4-6 months. We’re still not entirely sure what the rise means and what all that testosterone is doing, but it’s definitely doing something. One theory is that the brain is being “masculinized.”
Immediately prior to puberty, testosterone begins to rise in both boys and girls. Childhood is departing, replaced by budding pubic hair, the beginnings of body odor, growth spurts, oily hair and skin, and that ridiculous peach fuzz above the lips that every eleven year-old male tries to cultivate and claim as facial hair. Bones mature and the arm pits grow hair.
During puberty, testosterone enjoys a massive increase. Most of you reading this probably recall those awkward, exciting change-filled times: new odors, inconvenient fluctuations in the functionality and appearance of certain organs, strange new outlooks on the opposite sex. Good times. Thanks, testosterone!
In adults, testosterone’s effects on growth and development have largely manifested and maintenance becomes its province. Libido is preserved for both men and women and erection strength and frequency are regulated by testosterone. Muscles resist wasting thanks to T (and even grow larger).
I would be remiss if I failed to mention testosterone’s chief antagonist: cortisol . Cortisol, as you know, is one of the stress, fight-or-flight hormones. It kept us alive and our wits about us under short-term life-or-death situations for much of our evolution. Unfortunately, when cortisol is constantly elevated – as it often is in the sleep-deprived and chronically-stressed – testosterone is muted. Cortisol is catabolic  (breaks tissue down), while testosterone is anabolic . Excessive levels of cortisol produce insulin resistance, fat gain, and muscle wasting, while testosterone promotes muscular hypertrophy and lean mass gains. Cortisol contributes to metabolic syndrome, while testosterone helps alleviate it.
Ironically, serum testosterone status seems to predict the cortisol response  of people faced with victory or defeat. High T men and women who “lost” released more cortisol, the stress hormone; when they “won,” less cortisol was released. Low T folks’ cortisol changes did not depend on winning or losing. I guess that’s a downside to high T levels, technically, but it’s to be expected. I’m reminded of the Jimmy Cliff classic , “The bigger they come, the harder they fall”.
Low serum concentrations of testosterone are also independently associated with higher mortality rates in men , even when you consider other risk factors and preexisting health conditions.
Testosterone is important in the formation of bones, as I mentioned earlier, but it’s also crucial for the maintenance of bone density, especially in the elderly .
Testosterone aids in protein synthesis, effectively helping rebuild muscle fibers with amino acids. It can preserve existing mass or build upon it, creating more.
So, testosterone is important, and even vital, if you want to build (and keep) strong bones and muscles, maintain a healthy, active sex life, and live long and well into old age – but how do we make sure we’re making enough?
In 1889, a Harvard University professor by the name of Charles-Édouard Brown-Séquard injected himself with a “rejuvenating elixir” containing the extract of dog and guinea pig testicle, reporting increased vigor and feelings of well-being. Traditional Chinese herbalists would often prescribe dried tiger’s penis for impotence, and ancient Greek Olympians feasted on goat and lamb testicles to boost stamina and athletic performance. Clearly, even before testosterone was specifically identified, the ancients (and not-so-ancients) knew that the loins were involved in vigor, strength, and stamina.
Their (our) fixation on consumption of genitalia and genitalia extractions to correct deficiencies in strength, vigor, sexual stamina, and general “well-being” sounds intuitive, in a folksy, endearing sort of way. Does it make sense to eat bull testicles to restore one’s manhood and increase available testosterone?
Not really. Testosterone doesn’t pool up in one’s testicles. It’s not a static reservoir waiting in reserve to be disseminated throughout the body. It’s a hormone that the testicles (in men) and ovaries (in women) produce. That mouthful of fluid you got when biting into a roasted sheep’s testicle on your Greek vacation wasn’t pure, liquid testosterone – sorry. In order to get testosterone, you have to produce it (or inject it, but that’s an entirely different post) endogenously. And if you want to manipulate the amount of testosterone you have available, you can do it the same way you manipulate other hormones, like insulin , leptin , growth hormone , and cortisol . You tinker with your diet, your exercise, and your basic daily lifestyle.
Lift Heavy Things
Resistance training is a potent stimulant of testosterone production, so be sure to lift heavy things every now and again. If you want to tinker even further, messing around with rest intervals between sets can stimulate different hormonal responses. In one study , resting 90 seconds between squat and bench press sets boosted post-workout T levels the most, followed by rest periods of 120 seconds. Resting 60 seconds increased growth hormone the most and T the least.
In young men, a short six-second bout of sprinting increased serum total testosterone levels . Levels remained elevated during recovery. Interestingly, testosterone was also correlated with lactate levels in the blood. It would be even more interesting to know if any training that causes lactate levels to rise would also increase testosterone.
Avoid Excessive Cortisol
Since cortisol antagonizes and reduces free testosterone levels, and stress promotes the release of cortisol, avoiding stress becomes crucial for maintaining or boosting T levels. Make sure you get a good night’s sleep, every night (which in and of itself increases testosterone levels ). Avoid overtraining , especially in the Chronic Cardio  arena, which may affect T levels and reproductive function . And be sure to take time to chill out and relax (read a book, go for a walk, play ).
Get Sun, or Take Vitamin D Supplements
Vitamin D , already associated with bone and muscular strength, also positively correlates with testosterone levels in men . Back in February, the vitamin D/T link got a decent amount of media attention .
Eat Clean, Pastured Animal Products
Toxic substances called dioxins have been shown to interfere with the male reproductive system , including production of testosterone. While concentrated sources of dioxins include Agent Orange (which I’m sure you’re already avoiding), we obtain most of our dietary dioxins through conventionally-raised animal products , especially animal fats  and dairy  (dioxins accumulate in fat). If you’re going to be eating fatty cuts of meat or using dairy, try to go for pastured, grass-fed  animals to reduce your exposure and lessen the negative impact on your testosterone levels.
Eat Saturated and Monounsaturated Fat
A low-fat, high-fiber diet reduced serum and free testosterone levels  in middle-aged men. T usage wasn’t affected, but T production was reduced. Another look at male athletes found that both saturated fat , monounsaturated fat , and cholesterol  intakes were positively correlated with resting testosterone levels . PUFA  intake was barely associated with increased levels.
Avoid Foods that Regularly Spike Your Blood Glucose Levels
Researchers found  that 75 grams of pure glucose – and the resultant spike in blood sugar – was enough to drop testosterone levels by as much as 25% in a random grouping of healthy, prediabetic, and diabetic men. Now keep in mind how rapidly many SAD carb choices (pasta, cereal, bread, etc) convert to glucose upon digestion…
Get Adequate Zinc Intake
A zinc deficiency predicts lowered testosterone in men  (eat your shellfish), but heroic supplementary doses of the mineral don’t boost T levels beyond normal  in men with adequate dietary intake.
All in all, testosterone is an incredibly important hormone for health, longevity, and vitality – in both men and women. Leading a Primal life, free of excessive stress and peppered with smart, intense workouts, full of healthy animal fats and plenty of vitamin D, should be enough to promote adequate amounts of testosterone coursing through your veins. It may sound a bit redundant at times (advice: live Primal!), but what can you do when a common, uniting thread seems to run through almost every aspect of human health. It almost writes itself.