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Pre-Workout Supplements: My Take as a Dietitian

Note: Since most of my content is about fertility and pregnancy, I want to clarify that I do not recommend these products for pregnancy.

A few days ago, my ultra-fit friend asked me how I felt about pre-workout. I could tell from her wording that she knew I would probably have some qualms about this kind of supplement. I immediately did my typical dietitian thing and told her I had to do more research before making any statements. First, to answer this question, I feel it's important to underscore two primary considerations in sports nutrition. One is performance, and the other is health. Sports dietitians must be aware of how supplements and nutrients affect health and performance. Unfortunately, supplements and nutrients that enhance performance may not be healthy (i.e., nutritious or safe). Some foods and supplements that are healthy may not help improve performance. I am not a sports dietitian or much of a sports fan. I exercise casually and have never worried much about my performance. Because of my dispassionate attitude for performance, I pretty much only worry about health outcomes when it comes to supplements.

If I only consider health outcomes, my sentiments toward pre-workout are simple. I think it's unnecessary. All supplements come with health risks, so it's best to avoid supplements that aren't necessary. In my mind, if you're too tired to work out, don't take a supplement; take a nap!

That being said, I know this is not a realistic answer for many people, including my friend. My friend seems to love working out (I don't get it). Given her busy career and her bustling personal life, it makes sense that she'd probably enjoy an energy boost before her workout- not to mention a reduction in soreness and increase in muscle mass. To answer her question more realistically, I looked at the ingredients in typical pre-workout supplements.

Pre-workout supplements have extremely variable ingredients. Products have a variety of active ingredients. I chose three 3rd party tested supplements and briefly reviewed the safety and efficacy of components that seemed to pop up the most frequently: caffeine, creatine, branched-chain amino acids (BCAAs), beta-alanine, and nitric oxide precursors. Please remember that this is a complicated subject that is evolving every day.

Caffeine is a standard ingredient in pre-workouts. I adore caffeine, though I know it is a compound with risks in addition to benefits. The three supplements I investigated ranged in caffeine from 175 mg to 350 mg. Up to 400 mg of caffeine is known to be safe in adults, but pregnant women should cap it at 200 mg. This amount is approximately equivalent to 2 cups of coffee, though one cup can vary drastically from another. The amount of caffeine in one serving of most pre-workout is safe. Still, it's essential to consider other sources of caffeine in your diet when taking pre-workout. Someone who drinks a cup of coffee at breakfast, a caffeinated soda at lunch, and dark chocolate after dinner should probably scale back before adding a supplement with caffeine into the mix. Some individuals experience side effects of caffeine at lower doses than others. These side effects can include fast heart rate, nervousness, insomnia, headache, and irritability, among others. If caffeine affects your sleep, it would be healthier to skip the pre-workout supplement (and even the workout if necessary). Sleep is just as important as exercise when it comes to overall health.

Although most individuals experience increased athletic performance when consuming caffeine, not everyone does. Some people even experience worsening performance. Always pay attention to your body, and remember that just because it works well for someone you know does not mean you will experience the same effects. One commonly recommended dose of caffeine for performance enhancement is 3-6 mg/kg body weight 60 minutes before exercise.

If you want to calculate the suggested dose for yourself, divide your weight in pounds by 2.2 to get your weight in kilograms. Then multiply that number by 3 and 6. For example, a woman weighing 125 lbs weighs ~57 kg. 57x3= 170 and 57 x 6=342, so this woman could consider consuming between 170 and 342 mg of caffeine 1 hour before exercise to improve performance. The pre-workout supplements I recommended seem to adhere to these recommendations well.

How can you get it from food? Coffee, tea, chocolate

Creatine is a compound typically found in supplements in the form of creatine monohydrate. Some studies have shown that it effectively increases endurance and strength in high intensity and short bursts of exercise (think powerlifting and sprinting). The supplement is generally considered safe when taken in reasonable amounts (<20 g/day). Too much creatine could hurt the kidneys and the heart. Fortunately, the pre-workouts I reviewed contained 0, 1, and 3 g. So, why does one of the supplements not have any creatine if it's so helpful? My guess is that this brand is cognisant of the interaction between creatine and caffeine. Caffeine may decrease the efficacy of creatine, so it may not be advantageous to take them in the same supplement. If I were super into athletic performance, I might consider taking creatine as a separate supplement at a different time of day than my caffeine.

Although creatine is not found in vegetarian sources, it can be synthesized by amino acids arginine, glycine, and methionine which are found in plant foods. Vegetarians or vegans don't need to supplement with creatine, but they may experience more benefits from supplementation than their fellow meat-eaters.

How can you get it from food? A variety of protein sources. It can be found in meat, poultry, fish, and dairy; but it can also be synthesized from amino acids found in plant-based foods.

Branched-chain amino acids include the essential amino acids isoleucine, leucine, and valine. They are considered "essential" because the body cannot make them but instead must be ingested. BCAAs may inhibit or postpone muscle soreness following exercise and may enhance recovery. A standard dose is between 1-5 g per day and is considered safe. Only one of the supplements I looked at contained BCAAS, containing 1 g total. It included the most leucine (500 mg), consistent with the research that leucine is likely the most critical BCAA for protein synthesis.

How can you get it from food? Meat, poultry, fish, dairy, beans, whole wheat, brown rice, soy, lentils

Beta-alanine was included in all three pre-workout supplements I investigated. Doses included 1.5, 2, and 3.6 grams. Beta-alanine is considered safe at standard doses in healthy individuals, though tingling is a possible side effect. A typical, effective amount is between 4-6 grams per day.

Beta-alanine is important because it is a rate-limiting precursor for carnosine. This limitation means that if there is not enough beta-alanine, the body cannot make carnosine. Carnosine reduces fatigue and oxidative stress and may improve performance during high-intensity exercise.

How can you get it from food? Meat, poultry fish

Nitric oxide precursors are a trendy addition to many sports supplements because of nitric oxide's role as a vasodilator. This means that nitric oxide causes the blood vessels to widen, allowing more blood flow. Sports enthusiasts and those trying to conceive may both be familiar with the importance of adequate blood flow. Athletes need blood flow to the muscles they are exercising. Individuals with endometriosis and poor egg quality may experience better pregnancy outcomes with adequate blood flow to the uterus and ovaries.

But can a supplement increase the body's nitric oxide production? Supplements claiming to do this typically contain L-arginine, which is an amino acid that is helpful in the production of nitric oxide. L-citrulline is also commonly found in these supplements because the body can convert it into L-arginine. Unfortunately, studies haven't provided much evidence that L-arginine or other nitric oxide precursors actually work to increase the body's nitric oxide or improve exercise performance in elite athletes. There is a small amount of evidence that recreational athletes may benefit more than professional athletes.

Overall, L-arginine is safe in healthy individuals, but as always, it does interact with some medications. People who have had a heart attack have an increased risk of death when taking L-arginine, so they should avoid the supplement.

How can you get it from food? White meat, dairy pumpkin seeds, soy, spirulina, peanuts, chickpeas, lentils

Given all of this information, I understand why many people enjoy taking pre-workout.

If you are a professional or elite athlete, you should see a sport's dietitian to discuss which supplements will be the most helpful. Your performance will improve more if the supplement is tailored to your specific needs and sport.

I am reluctant to recommend a pre-workout supplement for individuals simply trying to maintain adequate health. Here's why:

  1. The ingredients are inconsistent. Because the ingredients in different pre-workouts vary so much from brand to brand, it isn't easy to make a generalized recommendation. Some ingredients may be more helpful and appropriate than others.

  2. Supplements can be tainted with heavy metals or excess amounts of active ingredients. My biggest concern with all supplements is that they are regulated differently than food and medications. It's possible that a supplement can contain a completely different dose of the ingredient than what is listed on the bottle. They can also be laced with dangerous contaminants. These concerns are why I always recommend purchasing supplements that have been third-party tested. This testing means that a separate company tests the supplements for contaminants and label accuracy. The three supplements I looked at were all 3rd party tested.

  3. The long-term effects of many of these supplement ingredients are unknown. Sometimes seemingly innocuous ingredients are not as harmless as they seem. There are many examples of "healthy" ingredients that can be toxic or carcinogenic when taken in excess. Unfortunately, many supplements have not been around long enough for long-term effects to be known.

  4. Because poor outcomes are always a risk of dietary supplements, I always recommend nutrients be obtained from food first. Athletes should focus on eating nutrient-dense foods before focusing on supplementation. Supplements are only intended to fill in small gaps in the diet.

  5. $$$$ Supplements are expensive, and your money may be better spent elsewhere. Many of the beneficial ingredients in these supplements can be found in meat, dairy etc. Why not spend that money on higher quality meat and dairy?

The 3 Supplements I Looked at and Their Active Ingredients (This is not an endorsement)

Gold Standard Pre-Workout from Optimum Nutrition:

3rd Party Tested by Informed Choice

175 mg caffeine "from natural sources"

3 g creatine monohydrate

1.5 g beta-alanine

Pulse Pre-Workout from Legion

3rd Party Tested by Labdoor

8 g Citrulline Malate

3.6 g beta-alanine

350 mg caffeine

350 mg l-theanine

300 mg alpha gpc

2.5 g betaine

Sweetened with Swerve and Stevia

Do Vitamins Pure Pump Pre-Workout

3rd Party Tested by Labdoor

Alpha- lipoic acid (ALA)


500 mg L-arginine

2000 mg L-citrulline

200 mg Caffeine

2000 mg Beta-alanine

B vitamins

Vitamin C


Creatine monohydrate 1000 mg

No sweetener


Caffeine: How much is too much? Mayo Clinic. Published March 6, 2020. Accessed January 29, 2022. L-Arginine Supplements Review & Top Picks. Published January 5, 2022. Accessed January 29, 2022. Muscle & Workout Supplements Review & Top Picks. Published June 19, 2021. Accessed January 29, 2022.

Creatine. Mayo Clinic. Published February 9, 2021. Accessed January 29, 2022.

Martins GL, Guilherme JP, Ferreira LH, de Souza-Junior TP, Lancha AH. Caffeine and exercise performance: Possible directions for definitive findings. Frontiers in Sports and Active Living. 2020;2. doi:10.3389/fspor.2020.574854

Sureda A, Pons A. Arginine and citrulline supplementation in sports and exercise: ergogenic nutrients?. Med Sport Sci. 2012;59:18-28. doi:10.1159/000341937

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