If you frequently hit the gym, chances are you’ve encountered pre-workout supplements. Often in powder form, these drinks are meant to be consumed right before exercise for an energy boost that may lead to a more intense, more effective sweat session. Some everyday athletes even swear by them as a workout “must-have.” But are they really necessary for the average exerciser? And what do sports nutrition pros think about them? Here’s what they had to say:

WHAT’S ACTUALLY IN PRE-WORKOUT SUPPLEMENTS?

Before we can evaluate whether pre-workout supplementation is necessary, we need to know what’s in it. Here’s what’s most commonly included in these supplements:

CARBOHYDRATES

Some pre-workout supplements include carbohydrates, which can be beneficial before any type of workout. “Even 15–25 grams may help with endurance,” says Heidi Skolnik, a certified dietitian nutritionist and sports nutritionist in the Women’s Sports Medicine Center at the . “Even for a spin class, it can help you push harder,” she adds. At the same time, carbs are especially easy to get from food sources, she points out.

CAFFEINE

Most pre-workout supplements contain caffeine. In fact, it’s the main active ingredient. “Caffeine is a well-known ergogenic aid, meaning that it can enhance performance,” says , a registered dietitian who specializes in sports dietetics. “Most research suggests it is most effective for workouts 0–20 minutes and over an hour, but many feel they benefit in general. Because it provides a boost to the central nervous system, it can help energize a workout.”

CREATINE

“Many pre-workout supplements contain creatine with the goal of improving strength in a workout,” Goodson says. “This is likely more beneficial in a strength-training workout over a cardio based one.”

BETA-ALANINE

“When taken consistently, beta-alanine can help buffer lactic acid in the muscle allowing you to work harder longer,” Goodson explains. “However, beta-alanine typically must be consumed for a month to reap the benefits. A one-time dose usually won’t do much.”

ARGININE

“Arginine is a precursor to nitric oxide, which is a vasodilator,” Goodson says. “This means it helps dilate the veins and, in theory, delivers more oxygen and nutrients to the working muscle.” That means you might be able to work harder, longer and see better results from your workouts.

THE BENEFITS OF PRE-WORKOUT SUPPLEMENTS

IT CAN HELP IMPROVE PERFORMANCE

While its not guaranteed, taking pre-workout supplements may help you work harder, longer. That’s a pretty major “pro.” “Potential benefits include a boost in performance, improved strength, speed, endurance and focus,” Skolnik says. “It also lessens perceived exertion so you can work harder with less perceived effort.” In other words, your workout might feel easier.

IT MAY HELP YOUR MENTAL GAME

“Caffeine can improve mental performance and alertness by acting on the central nervous system,” says Julie Stefanski, certified sports dietitian and spokesperson for the . In addition to feeling your workout is easier than it really is, you may also feel more focused on the task at hand.

HOW YOUR BODY RESPONDS DEPENDS ON YOUR GENES

New  has shed light on the fact that not everyone responds to caffeine in the same way in an active setting. “The study found a significant gene-caffeine interaction, meaning the effect that caffeine has on performance depends on your genes, which determines the rate at which you metabolize caffeine,” Skolnik explains. For those who are quick metabolizers of caffeine, it can aid performance, but for those who are slower metabolizers, it can cause jitters and anxiety, which could actually harm performance.

IT COULD CAUSE STOMACH TROUBLES

“Caffeine can stimulate gastrointestinal movement for some, so for outdoor athletes like runners and cyclists, that needs to be taken into consideration,” Goodson notes.

IT’S NOT ALWAYS A GOOD CHOICE FOR RACE DAY

“If you compete in any form of competition or race, it is important to note that you will have more adrenaline pumping through your veins, which also speeds up heart rate,” Goodson says. “Adding caffeine to this could exacerbate that and make you feel uncomfortable.” This may not be true for everyone, but it’s worth considering if you’re thinking about taking pre-workout supplements before a big race or sports event.

IT COULD MESS WITH YOUR SLEEP

“Caffeine can interfere with the normal sleep cycle,” Stefanski points out. “This can start a vicious cycle in which caffeine becomes a crutch for chronic sleepiness and fatigue but reducing sleep quality and duration at the same time.”

SOME SUPPLEMENTS MIGHT NOT BE EFFECTIVE

“Some products may contain dietary supplements backed by valid research, but not in a dose that will actually enhance performance,” Stefanski says. For example, while some pre-workout products contain beta-alanine, the dose shown to be of benefit to athletes is normally not included in a combination product.

Most sports nutrition pros are on the same page here: For recreational exercisers, pre-workout supplementation isn’t necessary. “There is no ‘need’ for a pre-workout supplement,” Goodson says. “While some consider them beneficial, for many a cup of coffee and granola bar can provide the same benefits to energy.”

Stefanski also looks elsewhere before suggesting pre-workout supplements. “I always ask my clients to pinpoint issue that they’re trying to correct by using a certain product. Lack of energy can occur from insufficient calories or carbohydrates, overtraining, anemia, dehydration or simply a lack of sleep. Identifying and correcting the issues that are the source of the fatigue would be better than using a product which may or may not help you reach your fitness goals.”

That said, they’re not against using it if it feels beneficial. But if you’re going to use a pre-workout supplement, it’s crucial to choose carefully, Goodson says. “It is important to note that if you choose to take a pre-workout supplement, you should look for a third-party certified product like  or .” Since supplements are unregulated, this can help ensure the purity and quality of the supplement.