Testosterone is a vital hormone your body desperately needs. More muscle, less fat, greater strength—there’s a lot to like about T if you’re a hard-training gym rat. It is what defines you, not only as a lifter, but as a man. And while your soaring levels of this miracle hormone may be at peak levels in your teens and early 20s, it’s important to wrap your brain around one lamentable truth: nothing lasts forever. Though your testosterone levels are what define your virility, they start to decline 1.6 percent per year after 30. And with that decline comes a decline in other areas (that may or may not include the bedroom). Decreased strength, lower libido, unshakeable fatigue…the list goes on.

While these symptoms may be cause for a doctor’s visit, there are ways that you can start making up that 1.6 percent via supplementation. Training hard with heavy weight is one way to keep your test tanks topped off. But before you let your brain start wandering to supplemental solutions like tribulus terrestris—so long the go-to T-booster for the M&F crowd—read on to find out exactly what testosterone is, what it does for you, what you need to avoid and what you can take to keep those levels set to “beast.”

Testosterone Basics

The truth about testosterone is that it’s the blue print to male vitality and it’s an essential androgen in your body for normal reproductive and sexual function. At the base of the brain is the pituitary gland and hypothalamus; both control the production of male hormones and sperm. To spark testosterone production, luteinizing hormone (LH) and follicle stimulating hormone (FSH) are sent from the pituitary glands to the testes. All that to say that it then gets put to work during your next session with the iron.

What are the different types of testosterone?

Two types of testosterone become established: free and bonded. Bonded testosterone attaches to protein globulins and albumins but free testosterone effortlessly binds to androgen receptors to increase sex drive, build and maintain muscle mass, reduce fat, and enhance your performance in the gym. Testosterone is also made in the body by cholesterol and in a study in Journal of Clinical Endocrinology and Metabolism, men consumed more than 100 grams of “good fat” a day for two weeks. The results were that the men had higher levels of free testosterone. So don’t be a hater when it comes to downing your healthy fats—load up on the nuts, seeds and avocado to support T production.

What Causes Low Testosterone?

T levels are at their peak during the awkward puberty years, hence why you’ve developed a deeper voice, facial hair and larger muscles. The most common cause of low testosterone results from problems in the pituitary gland and hypothalamus. That area of the brain may be unable to release an adequate amount of LH and FSH. As mentioned earlier, your T starts to dip 1.6 percent each year after you hit 30, so you may experience some of the less desirable effects: noticeable weight gain, lower sex drive, decreased muscle mass and even depression.

How to Raise Testosterone?

So should you just hang up your lifting belt after 30? Or are there things you can do to forestall your decline into fitness purgatory? According to the Journal of Clinical Endocrinology & Metabolism, five percent of all men experience clinically low testosterone. Hormone replacement therapy for men should only be considered if blood levels confirm low testosterone. Replacement therapy must be prescribed by a doctor, and it will come in the form of gels, pills, injections, or patches. We know…this sounds complicated and, to some, maybe even embarrassing. But as you may have gathered by now, you’re not alone and you’re not without simpler solutions.

Before dropping money on a commercially available T-booster, you want evidence that the ingredients are living up to their standards. Tribulus terrestris has been a highly noted ingredient in this category for quite some time, but does it actually work? Well, in a 2007 study published in the Journal of Strength and Conditioning Research indicated that tribulus terrestris doesn’t produce any huge gains in strength or lean muscle like manufacturers claim and that testosterone levels don’t increase. Anecdotally, tribulus supplementation seems to be hit-or-miss.

Keep reading for five natural ingredients to look for when you choose a T-boosting supplement.