Testosterone Molecules

Anastrozole (Arimidex) is a prescription aromatase inhibitor and testosterone booster which requires a doctor’s prescription; getting a prescription can be inconvenient, especially considering most doctors won’t prescribe it. Also, not every man is a candidate for it, for instance if your estradiol level is in the normal range. However, there are a number of natural aromatase inhibitors and therefore natural testosterone boosters.

Recall that aromatase is an enzyme in the testosterone synthesis pathway. It converts testosterone into estradiol, the most potent estrogen, and androstenedione into estrone, another potent estrogen. Estrogens exert negative feedback on luteinizing hormone (LH), which signals the gonads to make testosterone. Hence when estrogen is high, less LH is made, and testosterone decreases.

By inhibiting aromatase, less testosterone is converted to estrogens, so there’s less negative feedback on LH, which rises, then more testosterone is made. Aromatase inhibitors can boost testosterone while leaving estrogens in the normal male range.

Natural aromatase inhibitors

A number of natural products can inhibit aromatase.

One of them is red wine. While alcohol itself has a weak inductive effect on aromatase, i.e. it increases it, the chemicals in red wine overcome this effect, and in fact are powerful inhibitors of aromatase. This may be the mechanism of action, at least in part, on the potent inhibitory action of red wine on breast cancer cells. The chemical in red wine doing much of the inhibiting of aromatase may be resveratrol.

Since red wine has this effect, it’s not surprising that grape seed extract also inhibits aromatase, and also suppresses aromatase expression. The authors of this study described the effects of grape seed extract as “potent”.

Over 300 natural products have been tested for aromatase inhibition activity.

Among the most active products included green tea, cocoa, coffee, and collard greens.

Being lean and muscular is the best testosterone booster

TRT (testosterone replacement therapy) has become a hot topic among men in general and readers on this site, understandably given the secular decline in testosterone levels. The causes of this secular decline are unknown, but speculation centers on obesity and xenoestrogens in water, personal care products, and plastics.

Obesity is certainly a cause of low testosterone. In turn, low T can cause obesity by lowering muscle mass. It’s a vicious cycle.

Fat tissue generates aromatase, so being overweight or obese lowers T and increases estrogens. More precisely, body composition, the proportion of fat vs muscle mass, matters a lot.

If you’re concerned about your testosterone level, lose fat and gain muscle. Do this by lifting weights and cutting out refined carbohydrates and sugar. That’s the best natural testosterone booster.

Vitamin D raises testosterone

Vitamin D deficiency is rampant in the U.S. and Europe. Among healthy adolescents in a northern city (Boston), 42% were vitamin D insufficient. Vitamin D insufficiency is more common in northern latitudes, in winter, and in people with dark skin.

If 42% of healthy teenagers were vitamin D insufficient, then the figure among adults who may be less healthy, don’t get outside in the sun as much, and are overweight may be much higher.

Men who took ~3000 IU of vitamin D for a year had a significant and substantial increase in testosterone, from 20 to 30%.



To increase testosterone, the following steps are suggested.

  • Get lean and muscular if you’re not already
  • Consider vitamin D. The gold standard is getting a blood test for it, then supplementing as/if appropriate.
  • Consider natural aromatase inhibitors. These include red wine, grape seed extract, resveratrol, DIM, cocoa, coffee, and black or green tea.


PS: Learn how to get lean and muscular with my book, Muscle Up.

PPS: You can support this site by purchasing through my Supplements Buying Guide for Men. No extra cost to you. It lists most of the supplements discussed above.

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  1. Jim says:

    What is your take on using Propecia (finisteride)? I have been using it for about 4 years and have not noticed any bad effects on my T levels. Could it inhibit testosterone production?

    • P. D. Mangan says:

      I can’t say I know a lot about it, although when I was in blood banking, that drug was one of the few that made someone ineligible to donate, which is a red flag for me. Also, I’ve read anecdotes about it affecting sex drive. All that said, it appears that it may actually increase T:

      Finasteride treatment led to a generally modest increase relative to placebo in serum testosterone, with the greatest increases occurring in men with low baseline testosterone levels. The physiologic significance of these changes in men with low baseline testosterone levels is unclear, but the associated reduction in BMI is intriguing and may be related, because BMI is known to be negatively correlated with serum testosterone levels in men.


  2. Blixxa Burzum says:

    “TRT (testosterone replacement therapy) has become a hot topic among men in general and readers on this site, understandably given the secular decline in testosterone levels.”

    I will emphasize though that T levels in developed nations are already much higher than they are in traditional societies and are likely way higher than they were across our entire evolutionary history. This is because the natural environmental stressors and hardships of our natural forager ecology suppressed this hormone in favor of immunity and lower metabolic demand.

    Elevated “normal” population T levels are thus a modern novelty and a marker of domesticity: office workers are higher T than farmers, and zoo animals have higher T than wild populations. One negative result of this evolutionary novel hormonal surplus appears to be prostate cancer, which is high among developed populations and a unique condition for our similarly domesticated (un-neutered) high T pets.

    • P. D. Mangan says:

      I’d like to see some references for all of that before I buy into it. I did find one saying that T levels in US men were higher at younger age than for men in Nepal, Paraguay, and Congo, but no difference after age 45. T could be lower in undeveloped countries due to higher parasitic load. But as for prostate cancer, I don’t believe T is involved, or if it is, it’s a minor factor. Obesity, insulin resistance, and free iron (related to the first 2) are far more important.

      Added: Evidence linking testosterone to lower immunity is surprisingly weak. See also here.

  3. louis sir says:

    so was there dosing information for grape seed extract in that study?

    • P. D. Mangan says:

      louis, all the testing of natural products as aromatase inhibitors was done in cell culture. So one could get the concentration and figure out a dose using body weight.

  4. Joshua says:

    That link for the vitamin D study just leads to a login page. Maybe you linked to the full-text of a study where only you have access? Any way you could link to a free abstract for it? Thanks for all you do.

  5. Lot of interesting points brought up in this article. I can’t attest for the wine and grape seed extract, but I can definitely feel a difference after losing 20 pounds. Like you said, body composition is going to be one of the biggest factors. Keep up the great work.

  6. Greg says:

    What are your thoughts on natural T boosters like Longjack, Ashwagandha for boosting T and Pine sterols for DHEA

    • P. D. Mangan says:

      I honestly can’t say I know a lot about them. Natural aromatase inhibitors like DIM may work, but probably magnesium, zinc, fish oil, vitamin D are your best bets.

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