We started with a list of 214 testosterone boosters, found in their natural habitats on websites like Bodybuilders.com, BroScience, and The Art of Manliness. These supplements are marketed almost exclusively to men looking for that extra edge in the weight room, the bedroom, and the mirror. One problem: A big chunk of those on the hunt for the best testosterone supplements are looking to compensate for a more serious condition.

Men who suspect they are suffering from a true deficiency in testosterone (“low T”) are advised to bypass over-the-counter supplements and make an appointment with a doctor to get tested. “At the very least, it’s important to get a baseline assessment with a blood draw,” Dr. Mehran Movassaghi, director of the Providence St. John’s Men’s Health Center told us. “A lot of the symptoms of hypogonadism have overlap with depression and other medical conditions. If you don’t know where you’re starting from on a hormonal level, self-medicating with these supplements can be very dangerous.”

If you’re an otherwise healthy guy just looking for a little boost, read on. We’re about to give some ingredients a real hard look.

At the very least, any products we recommended had to include fenugreek or D-aspartic acid.

Testosterone boosters typically pack in a whole mess of ingredients. We wanted evidence that at least one of them can actually boost T — and frankly, we found very little confirming that any do.

Herbs like Tribulus terrestris and stinging nettle have cool-sounding names, and there are a handfulofstudies that show longjack and maca can improve libido and erectile dysfunction, but they are all about as useful as water when it comes to increasing testosterone levels. Horny goat weed, the ole devil, has boosted testosterone — but only in rats. N-Methyl-D-aspartate (NMDA), a synthetic amino acid derivative, failed to make any impact.

The only agents clinically proven to increase testosterone in healthy men at all are the amino acid D-aspartic acid (DAA) and the herb fenugreek. Don’t get too excited: Each has studies showing an increase in testosterone, as well as studies showing no effectwhatsoever. Dr. Darryn Willoughby, a professor of health, human performance and recreation and the director of the Exercise and Biochemical Nutrition Laboratory at Baylor University, has conducted some of the most commonly cited studies on agents in testosterone supplements, including the fenugreek study showing a boost and the DAA study showing none. He told us flat out if any of these products had some effect, it would be “minimal at best in ‘boosting’ testosterone.”

“The body tightly regulates its own levels of testosterone so that anything that boosts the body’s natural production of it will not be large-fold,” he explained. “This is where anabolic steroids can be effective, as a person is actually taking synthetic testosterone, not trying to induce the production of it. Steroids bypass the tightly regulated testosterone axis in the body.”

The distinction between taking anabolic steroids and testosterone boosters is key: With the former, you’re putting more testosterone in your body. With the latter, you’re trying to trick your body into pumping out more.

These are not exactly inspiring results, but compared to the rest of the bunch, a couple of positive clinical studies went a long way. That’s not to say that all those extra goodies are worthless — maca and longjack can’t increase testosterone, but they are bothshown to increase sex drive in healthy men.

We cut formulas containing harmful, counterproductive, or banned substances.

Testosterone boosters, like all dietary supplements, are not approved by the Food and Drug Administration prior to marketing. This lack of oversight dates back to the 1994 Dietary Supplement Health and Education Act (DSHEA), which stipulated that purveyors of supplements weren’t required to prove the safety of their products or the veracity of what’s on the labels to the FDA before listing them for sale.

The controversial law was pushed by lobbyists from health food companies reacting against the Nutrition Advertising Coordination Act of 1991, which sought to tighten FDA regulation of dietary supplements. Under DSHEA, it’s only after supplements hit the marketplace that the FDA can exercise its “safety monitoring responsibilities,” which include reviewing labels and evaluating reports of “adverse events” by consumers or health care professionals. As such, the FDA advises you consult with a doctor before taking any given dietary supplement, and warns of potential risks associated with taking them improperly, in combination with other medicines, or if you have certain medical conditions.

With this disclaimer in mind, we looked for any red flags. We cut formulas containing caffeine anhydrous (pure caffeine powder) after news came out that it can be lethal even in small doses. We also cut ingredients that aren’t necessarily unsafe, but might interfere with a supplement’s potentially testosterone-boosting effects. Calcium D-glucarate poses no known health risks, but can reduce the body’s production of steroid hormones, which include testosterone. Additionally, agmatine sulfite can block the body’s NMDA receptors, which aid in testosterone synthesis.

We also flagged substances banned by the National Collegiate Athletic Association (NCAA) and the World Anti-Doping Agency (WADA). Granted, these agencies are notoriously hard-nosed when it comes to supplements. Their prohibited lists are long and include catch-all asterisks: Substances that are at all chemically related to a banned drug are also banned by proxy, as are any substances that “violate the spirit of the sport.” That said, many are banned for good reason, and we cut out formulas containing glaring offenders: the pro-hormone DHEA, which carries risks when used long-term, and growth factors like HGH and IGF-1, which have been linked to heightened cancer risk and earlier death in adults.

We cut all proprietary blends.

Posing as a trade secret, proprietary blends can act as a ruse for manufacturers to bulk up their products with cheap, unsafe, or ineffective junk. This is also thanks to a protection established under the DSHEA, which only requires manufacturers to list the total mass amount of the proprietary blend and its ingredients in descending mass order, but not the individual amounts of each ingredient.

Shawn Wells, a diet and nutrition expert and chief scientific officer at BioTRUST Nutrition, says, “Ninety percent of the time, proprietary blends are about listing things for marketing purposes and saving a lot of money.” He explained that “people think they are getting all these listed ingredients, but out of a total of 4,000 mg of a supplement, 3,999 mg could be, say, creatine, and only 1 mg could be BCAAS, which is what you really want. There’s no way to know.” He added that proprietary blends can also pose a danger when they contain certain ingredients, say, stimulants like caffeine or synephrine, which can be unsafe in larger doses.

At left, one of the contenders we cut features a proprietary blend that lists included ingredients, but not their respective amounts. In contrast, our top pick, Hypertest XTR, offers detailed amount info.

Ultimately, the T-boost industry has more false promises than actual results.

According to Dr. Willoughby, even in studies where there was an increase in testosterone, it was only around 15–20 percent. “In men with clinically normal testosterone levels, this modest increase will most likely not be anabolic enough to improve exercise performance,” he says.

There you have it: These do not work. So to make our top picks, we looked for the best balance of other vitamins, herbs, and minerals that have proven results: zinc and vitamin D, for example, which can help replenish a dip in T levels, and maca and longjack, which are reported to amplify libidos. If these supplements aren’t going to guarantee a boost in your T, at the very least our favorites will boost your good health.