Testosterone is the male sex hormone; it is found in both genders and throughout many different species. Testosterone serves a variety of functions in the body such as sexual and bodily development, metabolic and behavioral influence, and much more. It is important to know what increases and decreases this hormone, as well as when levels are too high or low in your body.

What is Testosterone?

Testosterone (T) is the male sex hormone. It is produced primarily in the testicles in males and the ovaries in females. This steroid hormone has extensive effects on sexual development, body composition, and behavior. This hormone in excess or deficiency can cause a variety of diseases, and both dietary and behavioral factors affect T levels.

Testosterone Effects

1) Advances Puberty

While testosterone grows throughout age before puberty, a significant jump occurs at around age 10 [1]. Testosterone increases are correlated with early stages of puberty [2, 34].

Increasing testosterone can cause early puberty and also hasten the onset of puberty in children with delayed puberty [56, 7].

Testosterone leads to increases in insulin-like growth factor 1 (IGF-1) and growth hormone, which are both pivotal in childhood growth [89, 10].

The hormone causes men to grow beards and increase the size of the skull and face [1112].

Testosterone can improve body composition, in combination with a minimum level of growth hormone [8].

Experimental research in non-human mammals suggests that testosterone is necessary for proper neurobehavioral development, especially before birth and in early infancy [13].

Furthermore, a study on Chinese boys found a correlation between T levels and fluid intelligence (problem-solving skills) during certain stages of puberty [14].

2) Improves Body Composition and Metabolic Health

Low testosterone is associated with obesity, metabolic syndrome, type 2 Diabetes and insulin resistance [15, 16].

Testosterone is associated with fat loss, and testosterone treatment can decrease fat percentage [17].

T treatment decreases total fat mass while increasing fat-free mass [18].

In men with lowered bioavailable T levels and Type 2 diabetes, testosterone replacement therapy improved body composition [19].

In men with low testosterone, testosterone replacement improves the metabolic profile [20].

3) Increases Sexual Function

A baseline T level (~12 nmol/L [21]) allows for healthy intercourse, sexual drive, and induced nocturnal erections in men [22].

Adding testosterone beyond the apparent baseline does not continue to increase these characteristics [21, 23].

However, treating men with low testosterone helps to repair these functions, and promoting other functions such as bone mineral density and body composition (see above) [24, 25, 26].

Testosterone therapy improves well-being, mood, and sexual function in premenopausal women with low libido and low testosterone [27].

Oral and vaginally applied testosterone & estrogen have been shown to improve sexual function in postmenopausal women [2829].

In women who had their uterus removed, testosterone treatment resulted in better sexual function, leaner body mass, and increased strength [30].

Men with sexual dysfunction (ED) associated with Type 2 diabetes reported improved sexual function and mood when treated with testosterone replacement [31].

High volume, moderate-intensity aerobic exercise for at least 200 minutes a week showed great improvements in sexual function and T levels [32].

Testosterone has been shown to increase the expression of dopamine transporters (DAT) and vesicular monoamine transporter (VMAT), both of which allow dopamine to promote sexual desire. This neurotransmitter is a possible mechanism for testosterone’s effects [33].

4) Increases Bone Mineral Density

Low testosterone is associated with osteoporosis [34, 35].

Testosterone increases bone mineral density in the spine [17].

T treatment can prevent bone loss and hip bone mineral density [36].

5) Improves Cardiovascular Health

Testosterone reduces total cholesterol [17].

T levels and cholesterol levels have always been shown to be inversely proportional. In pigs fed high fat and cholesterol diets, those that were castrated for T deficiency developed much higher levels of LDL, as well as the PCSK9 enzyme (an enzyme that binds to an LDL receptor). This presents a possible mechanism for the reason behind this inverse relationship [37].

The hormone also might prevent atheroma formations (plaque -induced degeneration of arteries) and progression to acute coronary syndrome [38].

6) Increases Attraction to Femininity

Changes in salivary testosterone levels in men contribute to the strength of men’s reported attraction to femininity in women’s faces [39].

7) Increases Muscle Strength

Testosterone can increase muscle strength [17].

8) May Increase Monogamy in Men

In male mice who are in relationships, testosterone decreases their desire for other females [40].

9) Increases Red Blood Cells

Via the 5α-reductase enzyme, testosterone becomes dihydrotestosterone. This hormone increases red blood cell creation and maintains proper blood iron levels. Testosterone completes these functions as well [41].

10) May Improve Cognitive Function and Mood

Testosterone is associated with risk-taking, which is in turn associated with abstract reasoning ability and fluid intelligence (Raven matrices). One study showed that a substantial part of the effect of T on attitude to risk is mediated by abstract reasoning ability [42].

Sex hormones have an effect on the memory of facts and knowledge. Testosterone is shown to be correlated with activation of the left prefrontal lobe of the brain [43, 44].

Low testosterone is associated with depression [45].

11) May Help Autoimmune Disease and Pain

Androgens such as testosterone could have an influence on T cell differentiation [46].

Testosterone inhibits the binding of Substance P to its receptor. Substance P is associated with inflammation and pain [47].

Autoimmune diseases may be associated with low blood testosterone concentrations [48].

Testosterone can reduce temporomandibular joint (connecting the cheekbone to the jaw bone) pain [49].

12) Increases Risk-Taking

Various measures of risk-taking propensity have shown that high testosterone and low cortisol led to risk-taking in financial markets for both sexes [50, 5152, 53, 54].

Changes in salivary testosterone can predict future risk-taking behavior [55].

More specifically, some studies suggest that risk-taking increases in certain situations, and not others – namely, in those of known possibilities and strategic decision making [56].

Another study finds no relation in adolescent females between testosterone and risk-taking, but a strong association between estradiol (E2) and risk-taking (E2 is aromatized from testosterone) [57].

Similar to aggression, it is believed that the orbitofrontal cortex (impulse control) could be responsible for the relationship between testosterone and risk-taking [58].

13) Increases Competitiveness, Aggression, and Protectiveness

Male rats without proper androgen levels show less rough/competitive play behaviors than those who do [59].

Studies show a strong association between testosterone levels and physical and verbal aggression/dominance [60].

Women with high testosterone have shown a strong sense of intrasexual competitiveness [61].

While testosterone is known to be linked to aggressive behavior, one possible mechanism is reduced activity in the orbitofrontal cortex of the brain, which handles impulse control [62].

Beyond inherent testosterone levels, it is difficult to predict the effects of external testosterone on qualities such as aggression [63].

Mice studies suggest that the timing of peak plasma testosterone during pregnancy and the first few days of birth can predict possible aggressive behavior in adulthood [64].

14) Cancer

Low testosterone is associated with prostate cancer [65].

High Testosterone Side Effects

  • Adverse Effects on the Cardiovascular System, such as High Blood Pressure (66, 67, 6869)
  • Polycystic Ovary Syndrome in Women [70, 71]
  • Borderline Personality Disorder (BPD) [72]
  • Non-gender specific cancer aggressiveness [73]
  • Anxiety disorders in children of mothers exposed to excess androgens [74]

Anabolic Steroid Side Effects

  • Testicular Shrinking/Atrophy [67, 68]
  • Gynecomastia (Breast Development) in males [67, 68]

Testosterone Circadian Rhythm

Testosterone is higher in the morning than at night according to a study of 66 men [75]. It’s about 32% higher in the morning for 30-year-olds, but the cycle becomes more constant as men age, getting to only 8% higher in the morning at 70 years old.

Thus, Testosterone levels should be tested in the morning [76].

This Testosterone cycle is also found in women, and young girls (even as young as 5) and boys experience an increase in testosterone on their way to puberty [77, 78].

Daily rhythms of testosterone are associated with parenting [79]. 341 parents with two children (per couple) were tested and higher evening Testosterone in mothers was associated with more sensitivity to the oldest and youngest child.

Also for mothers, more daily changes in Testosterone was associated with less sensitivity to both children and less respect for the youngest child.

What Decreases Testosterone?

  • Increasing age [17]
  • Stress [80]
  • Heavy acute alcohol drinking [81]
  • Sleep disorders [82]
  • Obesity [83]
  • Injury to the testes
  • Prostaglandins (fats that act like hormones in the body) A1 and A2 and E2 [84, 85]
  • Dibutyryl cAMP (increases aromatase) [85]
  • Severe traumatic brain injury affecting the pituitary gland [86]
  • Diabetes, hemochromatosis, HIV/AIDS, mumps, meningitis, syphilis, and other infections are all known to have a negative effect on T levels [87]
  • Methadone (opioid-dependence medication) [88]
  • Grade B and C nonalcoholic liver disease [89]
  • Soy-phytoestrogens (molecules that imitate estrogens), decreased T levels in rats [90]
  • IL-6 (increases aromatase) [91]
  • Broad beans [92]
  • Anything containing Quercetin, Genistein, and Flavone (but we don’t know how much needs to be taken before they start lowering Testosterone) [93]
  • Statins (HMG-CoA reductase inhibitors) lower cholesterol which is a precursor to testosterone, so taking statins has a side effect of lowering testosterone [94].

What Increases Testosterone?

Best Testosterone Booster

A high protein diet and supplementing Oleuropein together increases testosterone by 300% in rats while halving rat cortisol [95]. 40% casein protein and around 100 mg/kg of body weight per day of Oleuropein. Although, that’s a lot of Oleuropein.

Doing 4 hours of exercise per week increases testosterone by 250% compared to doing ~2 hours of exercise. This was found while studying 90 obese men at a moderate intensity (55 – 70% of maximum heart rate) [96]. Administering pure lactate (a by-product of exercise) has a similar effect [97].

Supplementing with DHEA increases testosterone by 200% in middle-aged men and by about 180% in young men [98]. There were 16 people in the study doing high-intensity interval training and only 50 mg was needed to increase testosterone within 24 hrs (DB-RCT).

Vitamin D increases testosterone by 25% in overweight men that are deficient in Vitamin D [99]. 3,000 IU per day over a year worked for 165 young-to-middle-aged men.

Too much testosterone is said to shrink testicles, but when this happens the testicles return to normal size after testosterone lowers again [100].

  • Dietary Fat: one of the side effects of a low-fat diet is significantly reduced testosterone levels; one study showed a reduction of 12% after 8 weeks on a low-fat diet [101, 102]
  • DHEA [103] – DHEA appears to boost testosterone most of the time in people older than 40 years of age, but not often not in younger men.
  • Lactate [104]
  • Zinc – In human studies of zinc deficiency supplementation of zinc is able to increase circulating testosterone concentrations [105], but some studies don’t show a testosterone increase when there’s an adequate amount [106].
  • Boron supplements in diet increases both testosterone and 17β-estradiol [107]
  • Forskolin (free test) (mild increases in total) [108]
  • Aerobic exercise [32]
  • Low-dose amount of alcohol (short term) [81]
  • Getting enough sleep [82]
  • Vitamin D3 – increases free and total testosterone in clinical trials when 3,000 IU is taken if it’s under 50nmol/l [109, 110]
  • Porn [111, 112, 113] – The increase when sexually aroused is minor and transient.
  • Social interaction with attractive females – After a 5-minute conversation with an attractive woman, male testosterone levels can increase up to 30% from baseline (relative to an increase of 13% for conversing with males) (114115).

Other methods with less evidence


  • Clomiphene in hypogonadal men and men with ED [160, 161]
  • Sildenafil [162]
  • Varicocelectomy [163]
  • Pathways: inhibiting aromatase, prolactin, increasing 17beta-HSD, CYP17A1

Boost Bioavailable Testosterone

Testosterone is converted into estrogen by aromatase [164]. This can be stopped with aromatase inhibitors.

These were all taken from one super study taking extractions and testing against aromatase in a test tube [164].

Here are 5 of the best foods that boost bioavailable Testosterone by inhibiting aromatase (20 – 90% inhibition) [164]:

Others include:

  • Chaparral (greasewood)
  • Damiana
  • Fermented Pomegranate (non-fermented skin is half as good)
  • Feverfew
  • Willowherb (Epilobium)
  • Willow bark
  • Cat’s Claw (Uncaria tomentosa)
  • Mistletoe (Viscum album)
  • Propolis

Then there are ones that inhibit it, but were measured differently:

  • Mushrooms (button, lion’s mane, portobello, almond, shiitake, oyster)
  • Peppers (bell – particularly the leaves)
  • Coffee
  • Asparagus
  • Mustard (greens)
  • Collards
  • Kale
  • Lemons
  • Grapefruit
  • Strawberry
  • Mangosteen
  • Chicory
  • Tomato (leaves)
  • Parsley
  • Eggplant (‘fruit’ and leaves)
  • Spinach
  • Cocoa
  • Beer and Wine
  • Chamomile (contains apigenin)
  • Myosmine and Nicotine (both found in tobacco and others)

Irregular Testosterone Levels?

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