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Nutrition Pre-Workout Supplements: What Are the Benefits and Side Effects?

Many fitness enthusiasts swear by pre-workout supplements, but some experts urge caution. 

Man stretching next to a shaker bottle  with pre-workout supplements.

Between pro athletes, nutrition influencers, and that person at the gym who’s always rattling a drink shaker, pre-workout supplements get a lot of hype. Some proponents claim that the benefits include improved focus and concentration, while others swear that a single serving is worth extra reps, faster times, and heavier PRs. 

For ambitious athletes who want to optimize their training, pre-workout supplements seem like an easy win. But do they really deliver on their promises and, more importantly, are pre-workout supplements safe? Some experts have doubts. 

“Pre-workout formulas aren’t for everyone, and if supplements are substituted in place of whole foods on a regular basis, they can deprive an athlete of a well-balanced diet,” explains Danielle Gaffen, MS, RDN, LD, founder of Eat Well Crohn’s Colitis. “Research also hasn’t proven pre-workout to be more effective than whole foods that provide the same nutrients.” 

Before you crack open a canister and dig around for that little plastic scoop, it’s important to understand what’s in a typical pre-workout supplement and what the potential benefits and side effects are. 

What Are Pre-Workout Supplements?

Typically sold in powdered drink form, pre-workout supplements are designed to be ingested 30 to 60 minutes before exercising. Their intended purpose is to make you feel strong and energized so you can make the most of your workout. Ingredients vary from brand to brand, but most pre-workouts contain some or all of the following:  

Caffeine 

Caffeine is the common denominator for pre-workout supplements; it’s tough to find a formula that doesn’t contain this plant-based stimulant. And according to The International Society of Sports Nutrition’s 2021 position stand, the benefits of caffeine can extend beyond alertness. 

“Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies,” the article states. “Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions.” 

Carbohydrates 

One of three macronutrients, carbohydrates are the body’s preferred energy source, as they are most easily metabolized to create glucose. Glucose is what fuels your movement (as well as your daily activities, brain activity, and bodily functions). 

Branched-Chain Amino Acids (BCAAs)

First, a quick human biology refresher: Amino acids are molecules that serve as the “building blocks” of protein. Of the 20 amino acids used by the body, 11 non-essential amino acids are manufactured by the body, and nine essential amino acids must be sourced from food. When we eat protein, the digestive system breaks it down into amino acids, which are processed by the liver and used by the body for protein synthesis (muscle building and repair). 

Leucine, isoleucine, and valine, three of the nine essential amino acids, are considered branched-chain amino acids (BCAAs), due to their unique chemical structure. While all essential amino acids are critical to protein synthesis, BCAAs are distinguished for their role in “signaling” or initiating the process. However, some research indicates that leucine is the primary driver of protein synthesis, and isoleucine and valine have less of an effect. 

Beta-Alanine 

Beta-alanine, a non-essential amino acid, supports the synthesis of carnosine, a compound found in skeletal muscle tissue that helps regulate intramuscular pH levels by buffering exercise-induced acid that leads to muscle fatigue. “The proposed benefit (of supplementing with beta-alanine) would help increase an athlete’s capacity for training and increase time to fatigue,” Gaffen says.

Creatine 

Creatine is a compound formed within the body using the amino acids arginine, glycine, and methionine. It can also be consumed through animal-based protein sources and supplements. Creatine helps provide energy to the muscles, allowing them to perform more muscle-building contractions, explains Gaffen. 

“Creatine monohydrate is one of the most popular supplements used by strength and power athletes,” she says. “Supplementation elevates muscle creatine levels and facilitates the regeneration of creatine phosphate, which helps to regenerate adenosine triphosphate (the body’s primary energy source at the cellular level).”  

Nitric Oxide 

“Nitric oxide is a vasodilator, which means that it increases the diameter of your blood vessels and helps increase blood flow to the muscles,” explains Todd Buckingham, PhD, Chief Exercise Physiologist at The Bucking Fit Life. It’s often found in pre-workout supplements in the form of beetroot juice or l-citrulline. 

Buckingham points out that performing a five-minute warm-up has similar vasodilating effects, as it causes the body to release nitric oxide into the blood vessels. 

Should You Take Pre-Workout Supplements?

While the pros of pre-workout supplements sound promising, both Buckingham and Gaffen argue that most of the proposed benefits can be obtained through real food. “In my opinion, I don’t think anybody needs to take a pre-workout,” Buckingham says. 

Regulation is one concern. Because the supplement industry is not overseen by a governing body, pre-workout supplements do not always disclose every ingredient in their formula, nor do they include optimal dosages of each ingredient. This can be problematic and potentially dangerous, especially when it comes to caffeine. 

“Four hundred milligrams of caffeine a day is pretty much the upper limit for adults, but some pre-workout supplements have over 400 milligrams in one scoop,” Buckingham says. 

Additionally, pre-workout supplements may include filler ingredients—many of which are amphetamine-like banned substances—that aren’t explicitly listed on the packaging. “Athletes who are getting drug tested need to be cognizant of what they’re ingesting at all times and making sure that their supplement is safe to take,” Buckingham says. 

“It would be just as advantageous to drink coffee and eat a banana before working out,” he adds, and you would know exactly what you were consuming. 

Flavoring agents, while seemingly innocuous, can also cause unnecessary problems during a workout.

 “Pre-workout supplements frequently contain artificial sweeteners (like sucralose) or sugar alcohols (like sorbitol),” Gaffen says. “While these ingredients enhance flavor without adding calories, some sweeteners may contribute to intestinal distress—gas, bloating, diarrhea—and discomfort.”

Bottom line: The potential benefits of pre-workout supplements probably aren’t worth the risks or side effects. (Nor the expense—a one-month supply of reputable pre-workout powder can cost over $50.) You’re more likely to experience meaningful and long-lasting improvements from lifestyle changes, Buckingham says.

 “If you have low-energy levels and feel like you need a pre-workout, get extra sleep. Drink more water. Eat a healthier diet. Those things are going to have a much better impact, not only on your workouts, but also on your energy levels and your life on a daily basis,” he says.

A chart listing the pros and cons of pre-workout supplements.

How to Take Pre-Workout Supplements Safely 

If you’re still interested in experimenting with pre-workout supplements—maybe you don’t drink coffee or struggle with eating before a workout—use these guidelines when vetting and using products. 

  • Look for an NSF certification label. NSF (National Sanitation Foundation) is a third-party organization that tests products to ensure they meet basic safety standards. 
  • Monitor your caffeine intake. Remember that the upper limit for caffeine consumption is 400 milligrams a day. Be sure to account for other foods or beverages containing caffeine, like coffee, soft drinks, and chocolate. 
  • In some cases, avoid creatine. Adolescents under the age of 18, pregnant or nursing people, and individuals with kidney problems should not take any supplements containing creatine. 
  • Pay attention to your gut. As mentioned, artificial sweeteners such as sucralose and sorbitol can cause intestinal distress, so keep a look out for them and evaluate how you feel when you take pre-workout supplements that contain them.
  • Don’t wait for a high-stakes situation to try pre-workout. “Overall, athletes should always use what works best for them by experimenting with pre-workout before practice sessions and planning ahead to ensure they have it available when they compete,” Gaffen says. Remember: nothing new on competition days. 

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