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Story at-a-glance

  • Men who received one dose of testosterone performed more poorly on the Cognitive Reflection Test, which estimates a person’s capacity to override incorrect intuitive judgment
  • Reducing cognitive reflection may be one mechanism by which testosterone affects judgment
  • Testosterone may also enhance confidence, leading men to have less self-doubt and be less likely to correct mistakes

By Dr. Mercola

Supplemental testosterone is a $3 billion industry,1 and millions of American men use testosterone in the form of prescription gels or injections under the assumption that it will increase energy and sex drive and generally make them feel younger. It’s true that in most men, testosterone levels begin to fall after the age of 30. So perhaps it’s not surprising that men in their 40s are the fastest-growing group of testosterone users2 — especially when direct-to-consumer drug ads tout its reported benefits.

There’s no doubt that testosterone is an important hormone. It helps maintain muscle mass, bone density, red blood cells and a general sense of vigor and well-being, not to mention plays a role in libido. However, hormone replacement therapy shouldn’t be taken lightly, and that includes testosterone supplementation. Before taking the plunge, there are a number of factors to consider, not the least of which are potential side effects.

A Single Dose of Testosterone May Impair Cognitive Reflection

In a revealing study, 243 men received a single dose of either testosterone or placebo, then took the Cognitive Reflection Test (CRT), which estimates a person’s capacity to override incorrect intuitive judgment or, in other words, realize when they’re wrong and take steps to fix it.3

Men who received testosterone performed more poorly on the CRT, which suggests they were more likely to go with their gut instincts and had reduced cognitive reflection. Colin Camerer, chair of the T&C Chen Center for Social and Decision Neuroscience at Caltech, said in a press release:4

“What we found was the testosterone group was quicker to make snap judgments on brain teasers where your initial guess is usually wrong … The testosterone is either inhibiting the process of mentally checking your work or increasing the intuitive feeling that ‘I’m definitely right.'”

Past research has linked testosterone with aggression and poor impulse control, as well as fighting between males. The researchers suggest that reducing cognitive reflection may be one mechanism by which testosterone affects judgment, noting that it may also enhance confidence, leading men to have less self-doubt and be less likely to correct mistakes.5 It’s the first time a study has shown testosterone may affect cognition in just one dose.6

Before Considering Testosterone, Be Sure You Really Need It

Signs of low testosterone are varied and range from depression and difficulty concentrating to increased body fat, fatigue and lower sex drive. Disturbed sleep, increased body fat and declining muscle and bone mass can also occur. What you’ll notice is that all of these symptoms can be signs of many health conditions, not just low testosterone.

Drug companies have been aggressive in their marketing of “low T,” which likely explains why prescriptions for testosterone are on the rise. Dr. Michael O’Leary, a senior urologist at Brigham and Women’s Hospital, told Harvard Men’s Health Watch:7

“Virtually everybody asks about this now because the direct-to-consumer marketing is so aggressive … Tons of men who would never have asked me about it before started to do so when they saw ads that say ‘Do you feel tired?’ General fatigue and malaise is pretty far down my list [to prescribe testosterone] … But if they have significant symptoms, they’ll need to have a lab test. In most men the testosterone level is normal.”

Average testosterone levels in men range from 300 to 1,000 nanograms per deciliter of blood, but this can vary widely depending on time of day, medications you’re taking and even sleep and stress levels.

Testosterone therapy is approved for treating hypogonadism, or low testosterone levels (a total testosterone level below 150 ng/dL is indicative of hypogonadism), but research published in JAMA Internal Medicine suggests most men taking it do not have a true deficiency.8 In addition, once you start taking testosterone, your body will stop producing it on its own. This means it can be difficult to stop, and many men end up taking testosterone indefinitely.9

What Are the Risks of Testosterone Therapy?

The risks of long-term testosterone therapy are not entirely clear, but some research suggests that men aged 65 and older who took testosterone doubled their risk of heart attack within the first three months of use, even if they did not have heart disease prior to starting the therapy.10

The result was similar in younger men diagnosed with heart disease. Jacques Baillargeon, Ph.D., lead author of the JAMA Internal Medicine study, told the Times, “I think these relatively healthy men who are starting testosterone at age 40 are potentially going to be exposed for a very long time, and we don’t know what the risks are.”11

On the other hand, some research has shown benefits. For example, one study using data from 83,000 U.S. veterans found that men with low testosterone who used testosterone gels, patches or injections had a reduced risk of heart attack, stroke and even all-cause mortality, compared to untreated men.12

For now, however, there are more questions than answers, physically and mentally speaking. As Camerer, author of the featured study, put it, “If men want more testosterone to increase sex drive, are there other effects? Do these men become too mentally bold and thinking they know things they don’t?”13

How to Increase Your Testosterone Naturally

Certainly, before taking a risk via synthetic testosterone, it makes sense to explore the options to increase your levels naturally — and of this there are many. The video above describes nine helpful strategies, including:

Weight loss. Researchers found that weight loss reduced the prevalence of low testosterone levels in middle-aged, overweight men with prediabetes by at least 50 percent.14 High-intensity exercise Strength training
Limit or eliminate sugar from your diet, as insulin spikes sabotage production of testosterone.

Having good insulin sensitivity is positively correlated with healthy testosterone concentrations15

Optimize your vitamin D level. To produce testosterone, your body requires several different nutrients.

Among the nutrients more often depleted are vitamin D3 and zinc

Reduce stressStress, when chronic and unaddressed, can result in hypercortisolemia, which inhibits testosterone production16
Increase zinc and magnesium intakeZinc is one of the nutrients required for testosterone production, and magnesium has also been shown to improve sex hormone levels, including testosterone and human growth hormone Eat healthy fats, and do not shun cholesterol-rich foods as your body cannot produce testosterone without cholesterol.

Research shows a diet with less than 40 percent of energy as fat (mainly from animal sources, i.e., saturated) leads to a decrease in testosterone levels17

Boost intake of branch chain amino acids. This is best accomplished by whole foods like whey protein concentrate (not isolate)

In particular, pay attention to getting plenty of vigorous exercise and be mindful of your sugar intake. When men consumed a glucose (sugar) solution as part of a glucose tolerance test, the amount of circulating testosterone in their blood was reduced by as much as 25 percent. Even two hours later, their testosterone levels remained much lower than before the test.18

Consider whey protein both before and after exercise. Research from Finland found people who took 15 grams of whey isolate both before and after resistance exercises had an increase in testosterone production of up to 25 percent, which was maintained for 48 hours.19

What to Eat and Other Strategies to Give Testosterone a Boost

Beyond what’s listed above, another effective strategy for enhancing testosterone is intermittent fasting. It helps boost testosterone by improving the expression of hormones like insulin, leptin, adiponectin, glucacgon-like peptide-1 (GLP-1), cholecystokinin (CKK) and melanocortins, which are linked to healthy testosterone function, increased libido and the prevention of age-induced testosterone decline.

Unbeknownst to many, having sex will also increase your testosterone and “sexual activity affects testosterone more than initial testosterone affects sexual activity.”20 In other words, testosterone levels get a boost after sex, and not necessarily the other way around. What you eat also plays a role, including:

Pomegranate. One glass of pomegranate juice per day increased testosterone levels between 16 percent and 30 percent in one study21 Authentic extra-virgin olive oil. In research, participants who consumed olive oil daily experienced an increase in testosterone levels between 17 and 19 percent over a three-week period22
Zinc-rich foods such as oysters, sardines, anchovies, cashews, wild-caught Alaskan salmon and raw pumpkin seeds Coconut and coconut oil will improve your body’s ability to make cholesterol, which is necessary for testosterone production
Cruciferous vegetables such as broccoli and cauliflower will help a man’s body excrete excess estrogen, thereby increasing available testosterone23 Garlic. While it does not contain any necessary nutrients to produce testosterone, it does contain allicin, a compound that lowers cortisol.

With your cortisol levels lowered, your body can more effectively and efficiently use the testosterone that is produced24

Finally, the three supplements that follow may also support healthy testosterone levels. Personally, I’ve successfully raised my hormone levels into the healthy young adult range using the protocols described in this article.

  • Saw palmetto. Besides addressing symptoms of low testosterone, this herb may also help to increase testosterone levels by inhibiting up-conversion to dihydrotestosterone.25
  • Astaxanthin in combination with saw palmetto. There is also solid research indicating that if you take astaxanthin in combination with saw palmetto, you may experience significant synergistic benefits. A 2008 study found that an optimal dose of saw palmetto and astaxanthin decreased estrogen while simultaneously increasing testosterone.26
  • Ashwagandha. This ancient Indian herb is known as an adaptogen, which can help boost stamina, endurance and sexual energy. Research published in 2010 found that men taking ashwagandha experienced a significant increase in testosterone levels.27

Bioidentical Hormones Are Best

With the lifestyle strategies above, it’s likely that your testosterone levels will stay within the normal range. However, if you do choose to use hormones, it is really crucial to use bioidentical hormones like DHEA. DHEA is a hormone secreted by your adrenal glands and is one of the most abundant precursor hormones in your body. It’s crucial for the creation of sex hormones, including testosterone.

However, it’s important to monitor your levels and work with an experienced professional before you start using DHEA (or any other hormone, bioidentical or not.) The preferred routes of administration to most closely mimic normal levels are trans mucosal applications (intrarectal or intravaginal), as this allows for the most effective absorption and inhibits the production of unwanted metabolites of DHEA.

You will likely only need a few milligrams (mg) a day, not the 50 mg to 100 mg or more that is typically used. Keep in mind, though, that there are still questions about long-term safety, and there’s still the potential for side effects.

In addition, I do not recommend prolonged supplementation of DHEA and other hormones, even bioidentical ones. Doing so can trick your body into halting its own DHEA production and could potentially impair your adrenal function. It is also best to regularly monitor hormone levels if you choose to use hormone administration. My favorite and recommended is the DUTCH test that I discussed in-depth with Mark Newman, the founder of this test.