Here’s a secret that you probably won’t hear from your friends at the gym: As long as you’re eating a healthy, balanced diet, there’s a good chance that you don’t need to take supplements at all.

Yes, it’s true. Unless you have a medical condition, the average guy should eat his vitamins in real food—not swallow them in pill form.

“The purpose of a supplement is to correct a deficiency,” says Leslie Bonci, R.D., a nutrition consultant for the Kansas City Chiefs and Pittsburgh Pirates. “You can’t take lot of supplements and eat a crappy diet, which is something that can end up happening.”

While you can’t bottle up a healthy diet, you can plug up the nutritional gaps and give yourself an extra edge in the gym with the best supplements for men. Here are four supplements that can help—but seriously: talk to your doctor before you take them.

Vitamin D

Vitamin D plays a major role in boosting our bone health and warding off osteoporosis by helping the body absorb calcium. It shores up our immune system health, helping to fight off viruses and other bacteria, and may also reduce your risk for prostate and colon cancer. Unfortunately, however, vitamin D is notoriously hard to find in food.

Adults need 600 IUs of D each day, but studies suggest up to 75 percent of us are lacking in this vitamin. Your doctor can measure your levels of D with a blood test; if your numbers are low, you may want to pop a supplement. A follow-up test can tell you how well you’re absorbing the vitamin; different people metabolize D at different rates, says Bonci.

What to look for: A capsule that contains 1,000 IUs is a reasonable starting point, says Bonci. Supplements that contain vitamin D3, which is the same type of vitamin that your body makes after being exposed to the sun, are your best bet.

Creatine

Commonly found in seafood and red meat, creatine is a chemical that can help boost muscle growth and increase short-term athletic performance (think: sprinting, not endurance running), mainly by helping the body generate ATP, or energy stores.

Vegetarians might see more benefits in creatine supplementation than their meat-eating counterparts, says Bonci, since their diets can be lower in creatine-containing foods. She also notes that the effects can vary from person to person: “Some people respond to creatine very well, whereas others don’t, even in higher doses,” she says.

What to look for: The International Society of Sports Nutrition recommends opting for a form of creatine called “creatine monohydrate.” Not only is it the most widely studied form, but is more effective at boosting lean muscle mass and high-intensity exercise performance than the other available types, including creatine citrate, serum, nitrate, and more.

Whey Protein

This protein supplement is made from the watery part of milk that separates from the curds when making cheese. Whey protein powders are commonly used by athletes and weightlifters who are looking to build muscle. Long considered the gold standard of protein powders, whey protein is a complete protein, meaning it contains all the amino acids necessary for muscle growth and repair. It also contains one of the highest amounts of leucine, an amino acid that’s thought to be the most important player in the muscle building process.

What to look for: Whey protein should contain about 2 to 3 grams of leucine for every 30-gram serving. Research suggests that leucine’s muscle-building benefits hit a plateau after we exceed the 3-gram threshold.

Multivitamin

Experts overwhelmingly agree that supplements aren’t a substitute for a healthy diet. That’s because whole foods contain more than just vitamins and minerals—they also contain fiber, protein, and more. But for people who are missing out on certain nutrients—take, for example, someone who avoids the sun and might not be absorbing enough vitamin D—it makes sense to fill in the nutritional gaps with a supplement. “Think of your diet like a symphony,” says Bonci. “You need all the instruments available in the right amounts and tones.”

What to look for: Supplements should contain both vitamins and minerals, says Bonci, mostly in doses that are under 250% to 300% of the daily recommended intakes. “You don’t need mega-doses,” she says. “Our body can only absorb so much of these nutrients at a time.”

Best Multivitamin: One a Day Multivitamin, Men’s Health Formula. With 20 vitamins and minerals, this all-in-one tablet contains (reasonably!) high amounts of nutrients, including 700 IUs of the hard-to-get vitamin D3.