Fitness Supplements 101

Here are 4 go-to fitness supplements to help you get better, stronger, and faster.

A variety of fitness supplements

If you’re confused when it comes to fitness supplements, you’re not alone. We’re inundated with online hype, blaring TV infomercials, and glossy magazine ads featuring spokespeople ripped like superheroes pumping the latest and greatest supplements to buff up our workouts. It can be tough to know which ones are right for you, if they’re safe, or whether you actually need them at all.

The notion of a magic-bullet supplement conferring instant strength, weight loss, or athletic performance is really just the stuff of comic books. The truth is, eating right, getting plenty of sleep, and training well are still the not-so-secret secrets. But once that foundation is established, certain nutritional aids may help you excel.

“There are supplements that can enhance performance, plus give you more energy and stamina during training,” explains Tom Nikkola, CSCS, vice president of nutrition and virtual training at Life Time. “They can also reduce muscle soreness so you recover faster from training sessions and are able to train more frequently.”

But several factors — including your goals, gender, and health condition — determine what will work best for you.

Food First

The key to supplement use lies in the very name: They’re designed to supplement the food you eat, not replace it. Experts stress that a healthy diet and lifestyle come first.

“A lot of athletes think of supple­ments as ways to enhance fitness or performance, but you are better off taking a holistic look at what is hindering your performance in the first place,” says Amy Eichner, PhD, special adviser on drugs and supplements for the U.S. Anti-Doping Agency. “Sometimes it’s nutrition, and obviously you should optimize your nutrition. But if you’re not getting enough recovery or sleep and your go-to is a preworkout supplement with stimulants to wake you up, then you’re not dealing with the source of the real problem — you’re just masking symptoms.”

Make certain you’re eating a mostly whole-foods diet that provides ample macronutrients: carbohydrates, healthy fats, and especially high-quality protein, which is key for supporting muscle health.

Nikkola then advises supplementing with micronutrients before even considering fitness supplements. “No supplement is so good that it offsets a lousy diet, and no diet is so good that it doesn’t benefit from the right supplementation,” he explains.

“Bringing insufficient levels of micro­nutrients to optimal doses on a daily basis — which is basically taking you from less than your baseline to a standard optimal baseline — can alone have a performance-enhancing effect,” says Nikkola. “For instance, a micronutrient such as magnesium is key for proper muscle contraction and relaxation. So optimizing your levels can make a significant difference, although magnesium is not specifically thought of as an ergogenic [performance-­enhancing] aid.”

He recommends the Foundational Five for leveling up micronutrients:

  • A multivitamin that includes all-important B vitamins — including thiamin (B1), riboflavin (B2), niacin (B3), and folate (B9) — which are crucial to the release of cellular energy and metabolism.
  • Vitamin D3, which boosts bone health and immunity while fighting inflammation.
  • Magnesium, a key electrolyte that serves as a spark plug for your muscles.
  • Fish oil, which contains omega-3 essential fatty acids that aid nutrient absorption and support overall health.
  • A digestive enzyme to support gut health and immune-system function.

Once that foundation is in place, Nikkola says, “you can start looking at the range of muscle-building, energy-producing, performance-enhancing supplements.”


For two more fitness supplements — and warning signs that you’re having a reaction to a supplement — see below.


What It Is: Carnitine amino acid transports long-chain fatty acids into the mitochondria where it’s burned for energy. Common dietary sources include meat, poultry, fish, and diary. The supplement form — L-carnitine — is available in tablets, liquids, or powders.

What It Does: Due to its strong antioxidant effect, carnitine protects cell membranes from free-radical damage caused by exercise and aging. Studies have primarily evaluated carnitine’s effects on cardiovascular disease, type 2 diabetes, and other medical uses; weight loss has been a secondary aspect in most studies.

Why You Might Use It: If you’re seeking to metabolize more fat and build muscle mass during workouts. The NIH reports that carnitine is typically well tolerated at doses up to 4 grams per day. 

Safety Concerns: The NIH specifies few safety concerns, although it adds that carnitine can cause nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor.

Conjugated Linoleic Acid (CLA)

What It Is: An essential omega-6 fatty acid not produced by your body; it’s found in dairy and animal fats, such as beef, lamb, whole milk, and eggs. Supplemental CLA comes in a powder form.

What It Does: CLA helps boost your body’s metabolism, while supporting your immune system and managing cholesterol levels. Several recent studies have found it helped reduce body fat and preserve muscle tissue in overweight or obese people who did not otherwise change their diet.

Why You Might Use It: If you’re striving to metabolize more fat and build lean muscle mass. Current studies recommend 3.4 to 6.4 grams per day.

Safety Concerns: Side effects may include nausea or upset stomach; these can be reduced by taking the supplements with food. (For more on CLA, see "CLA: Can This Fatty Acid Help You Lose Weight?")

Warning Signs of an Adverse Reaction

Several symptoms indicate that a dietary supplement has caused a reaction, explains liver specialist Herbert Bonkovsky, MD, a professor at Wake Forest School of Medicine. Among the most common:

  • Nausea, vomiting, or diarrhea.
  • Loss of appetite, fatigue, severe joint or muscle pain.
  • Skin rash or hives, severe itching.
  • Swelling of the throat, lips, or tongue.
  • Abdominal pain around the liver.
  • Difficulty urinating, decreased urination, or blood in the urine, stool, vomit, or sputum.
  • Jaundice, which can signal liver injury and hepatitis or cholestasis — the severe failure of bile formation and flow. Symptoms may include yellowing of the eye whites or yellowing skin tone. “People start looking yellow, and it’s usually a family member or friend who notices it,” he says.

If you wish to report an adverse reaction to a supplement, the FDA has an online portal at

is an Experience Life deputy editor.

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