Muscle-building supplements should be simple: Take them and build muscle. Unfortunately, today’s market is filled with a lot of confusing products. As a general rule, the simpler and more natural the supplement, the better it works. Here are the proven top options for building muscle—along with two products you should avoid.

Muscle-Enhancing Supplements

Protein

It may be boring, but protein is simply the best substance for building muscle. The biology is clear: Protein is the raw material, the natural resource that cells use to repair themselves and to build new cells. Without protein, your muscles have nothing to work with. Fortunately, you can find protein in all kinds of places, from nuts and chicken to powders and shakes.

RELATED: The Truth About Muscle-Enhancing Supplements

Casien Protein

Casien protein is different from whey protein in that takes your body longer to digest. This is ideal for building muscle overnight after an intense workout session, and it makes an excellent companion to fast-acting whey protein.

Creatine

Creatine is an organic acid that gives muscle cells more energy to put protein to good use. Creatine can help build muscle faster, but only if you take it right before you work out and use its energy boost to push yourself harder. If you’re willing to work hard during your workout, this supplement can work for you.

Nitric Oxide (NO) and L-Arginine

NO is a tricky supplement. On one hand, nitric oxide gas has been proven to increase blood flow, which in theory can help muscles work harder and heal faster. However, the supplements on the market do not necessarily do a good job of actually giving your body NO it can use, and the overall benefits are not apparent. This supplement is not necessary to strong muscle growth, despite its relentless marketing, so you’re better off saving your money on this one.

L-Arginine frequently appears in pill form and as part of muscle powders. It is an amino acid that basically functions as NO under a different name, since it is chosen based solely on its ability to increase nitric oxide production. Most supplements that claim to increase NO use L-Arginine, but again, the benefits remain dubious.

Prohormones

Prohormones, which are designed to increase testosterone and similar hormones for muscle growth, have such a troubled history that most are outlawed in the United States, except in unproven natural “herb” guises. DHEA is one of the few that is still legal, but despite its many supporters, the science simply isn’t there. DHEA supplements can affect prohormone levels, but they have not been connected with muscle growth. They have, however, been associated with an increase in estrogen and related issues.

Read more about safe muscle-enhancing supplements on STACK’s Supplement, Protein and Creatine pages.