Labdoor tested 51 best-selling pre-workout supplements in the United States for active and inactive ingredient content and heavy metal (arsenic, cadmium, lead, mercury) contamination.
Tested products often cited “proprietary blends” without specified quantities of active ingredients. Key active ingredients tested in this batch include creatine, beta-alanine, tyrosine (as L-tyrosine and N-acetyl-L-tyrosine (NALT)), arginine (as L-arginine HCl and arginine alpha-ketoglutarate (AAKG)), caffeine, and taurine. For products with specified quantities, actual active ingredient content ranged from being 81.2% less to 89.0% more than its respective label claim. Only 2 of 51 products tested had formulations in which all of their claimed active ingredients were measured to meet levels established in research to be effective. 46 products measured caffeine, but only 22 specified actual quantities. Of the 24 products that did not specify caffeine content, 5 exceeded 300 mg per serving, more than 3 times the caffeine content in an average cup of coffee.
Pre-workout supplements were generally heavy on potentially harmful ingredients. 40 of 51 products recorded some combination of flagged ingredients including artificial sweeteners, coloring agents (FD&C Blue 1, Blue 2, Red 40, Yellow 5, Yellow 6), and benzoate preservatives with cancer-causing potential. 1 product, Train CriticalFX (beverage), was found to contain BMPEA (beta-methylphenethylamine), an amphetamine analog classified as a doping agent.
Collective data for this batch analysis relied on analytical chemistry methods including HPLC (High Performance Liquid Chromatography) to quantify amounts of individual amino acids and caffeine, and ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) to determine heavy metal (arsenic, cadmium, lead, mercury) load. Products from manufacturers previously cited by the FDA for using illicit stimulants were also screened by HPLC for illicit stimulants.
Pre-workout supplement labels citing “proprietary blends” often did not specify quantities of active ingredients. Those products that did specify ingredient quantities still varied greatly in their labeling accuracy.
CAFFEINE: 46 products measured caffeine, but only 22 specified actual quantities. Of the 24 products that did not specify caffeine content, 14 exceeded 200 mg per serving, equivalent to more than 2 times the caffeine in some popular energy drinks. Label accuracy was an issue even for those products that specified caffeine content. Products ranged from having only 18.8% of the caffeine claimed on a label to having 47.3% more than its label claim.
21 of 33 products measuring creatine did not specify creatine content. For products with specified creatine amounts, creatine content ranged from being 26.4% less than its label claim to 25.1% more.
Of the amino acid ingredients (tyrosine, beta-alanine, arginine, taurine), arginine had the largest range of label accuracy. In the 4 products that specified arginine quantity (out of 24 products with measureable arginine), products ranged from only having 27.6% of a label claim to having 77.0% more than a label claim. Overall, actual content measurements for active ingredients (caffeine, creatine, tyrosine, beta-alanine, arginine, taurine) in products specifying quantities of those ingredients deviated an average of 16.6% from their label claims, ranging from 81.2% less to 89.0% more than its respective label claim.
SUGAR: According to FDA guidelines, food products with less than 0.5 g of sugar per serving can claim to be sugar free. In this batch analysis, 22 products measured 0.5 g or more sugars per serving, but only 5 actually specified the quantity of sugar present. For these 5 products, sugar content ranged from being 3% less than its label claim for sugar to being 89.0% more.
All products in this report were screened by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) for the presence of 4 key heavy metals: arsenic, cadmium, lead, and mercury. The following proposed and established daily intake limits for these heavy metals, taken from California Proposition 65’s Safe Harbor Levels for chemicals that can cause cancer, birth defects, or reproductive harm, were used to assess product purity: no more than 0.1 mcg of inorganic arsenic, 4.1 mcg of cadmium, 0.5 mcg of lead, or 0.3 mcg of mercury per day.
All of the tested products passed heavy metal screens for cadmium, lead, mercury, and inorganic arsenic. 1 product, Human Evolution Supplements Extreme Override, reached, but did not exceed, the upper limit of 0.5 mcg/day of lead intake in a single serving.
NOTE: Currently, intake limits for total arsenic have only been established for drinking water. The only available guideline for arsenic in supplement products is a proposed limit from CA Prop 65 on the inorganic component of total arsenic. Generally, inorganic arsenic species (tri- and penta-valent arsenic) are considered more toxic than their organic counterparts. Chemical analysis of this batch of products measured arsenic in total. Since research has shown that the contribution of inorganic arsenic to total arsenic is ~80% (in rice), an 80% assumption was used to project and then compare inorganic arsenic content in these products to the CA Prop 65 proposed limit of 0.1 mcg per day.
The majority of the pre-workout products in this batch recorded similar nutritional value scores, with only minimal variation in calorie, fat, carbohydrate, and sugar content.
Except for Vega Sports Pre-Workout Energizer, all products measured less than 6 g of added sugars per serving. At 11.7 g of added sugars and 70 calories per serving, Vega Sports Pre-Workout Energizer recorded the highest values for both attributes. 11.7 g of added sugars is almost half of the World Health Organization’s recommended limit of 25 g of added sugars per day, or 5% of daily caloric intake based on a 2000 calorie per day diet.
While some research evidence suggests that carbohydrates increase creatine uptake by muscle cells, we discourage excessive intake of added sugars for this purpose.
BETA-ALANINE: There is no established UL value for beta-alanine intake, but clinical studies recommend repeated small doses of 2 g throughout the day compared to single 4-6 g bolus doses to avoid the side effect of paresthesias, or tingling, in the arms, head, and neck. Of the 42 products with measurable beta-alanine content, 8
products contained more than 2 g of beta-alanine per serving.
CREATINE: Gastrointestinal discomfort can occur when creatine is taken without enough water or if too much creatine is taken at once. Water weight gain is also a possible side-effect. Otherwise, research notes no clinically significant adverse effects of acute creatine supplementation up to 10 g. All products measuring any creatine content had less than 5 g of creatine per serving.
L-ARGININE: There is no established UL value for L-arginine, but clinical study has noted that acute doses exceeding 10 g of L-arginine can cause gastrointestinal distress and diarrhea. All 24 products with measurable arginine content (in the form of L-arginine HCl or arginine alpha-ketoglutarate (AAKG)) recorded less than 10 g of arginine per serving.
L-TYROSINE: There is no established UL value for L-tyrosine and minimal side effects have been documented. Large doses of L-tyrosine can be split into 2 smaller doses at half-hour intervals if digestive discomfort arises.
CAFFEINE: 6 of 46 products with measureable caffeine exceeded 300 mg of caffeine in one serving, more than 3 times the caffeine content in an average cup of coffee. The FDA has cited that 400 mg (~5 cups of coffee) per day is the highest level at which caffeine is still considered safe for healthy adults.
TAURINE: Although adverse effects are not notable for taurine even at high doses, research states that the highest observed safe level for taurine is currently 3000 mg per day. 1 of the 16 products with measureable taurine, Gaspari Nutrition SuperPump Max, exceeded this guideline with 3601 mg in one serving.
Pre-workout supplements were generally heavy on potentially harmful ingredients. 38 products recorded sucralose and 27 products recorded acesulfame potassium (AceK), both of which are artificial sweeteners. AceK is currently being studied for its potential carcinogenicity, and possible effects on prenatal development and neurological function. 26 products had some combination of controversial artificial colors (FD&C Blue 1, Blue 2, Red 40, Yellow 5, Yellow 6). 1 product, Gaspari Nutrition SuperPump Max, was found to have carmine, a red coloring agent linked to severe allergic reactions.
Products whose manufacturers were previously cited by the FDA for using illicit stimulants were screened for illicit substances, including DMAA, DMBA, BMPEA, DEPEA, DMPPA, and ephedra. Of those 16 products, 1 product, Train CriticalFX (beverage), was found to contain BMPEA (beta-methylphenethylamine), an amphetamine analog classified as a doping agent with extreme cardiovascular risks.
BETA-ALANINE: Beta-alanine supposedly works through its conversion to carnosine, which buffers acid build-up in muscle tissue during high-intensity exercise lasting 60-240 seconds when acidosis is most limiting. To effectively raise carnosine concentrations, research recommends 4-6 grams of beta-alanine per day in divided doses of 2000 mg or less throughout the day for at least 2 weeks. Of the 42 products with measurable beta-alanine, 34 contained less than 2000 mg of beta-alanine per serving. Beta-alanine content ranged from 108.4 mg to 5541.4 mg.
CREATINE: Creatine most likely enhances exercise performance by increasing the body’s energy in the form of ATP (adenosine triphosphate), thereby improving peak power output and lean mass. Caffeine and beta-alanine have both been found in research to enhance creatine’s effects.
9 of the 38 products with measureable creatine content contained more than 2000 mg of creatine per serving. Creatine content ranged from 126.58 mg to 4264.01 mg per serving. Research recommends starting with loading doses of 300 mg per kilogram of body weight daily for a week, followed by maintenance doses of 30 mg per kilogram daily thereafter. For a 150 lb (68 kg) individual, maintenance doses should be 2040 mg per day; loading doses should be 20.4 g per day (in 4-5 separate doses throughout the day). In those with high amounts of muscle mass and high activity levels, some research evidence posits that doubling the maintenance dose recommendation can be more effective.
Creatine monohydrate is the most popular form of creatine used in supplements, but creatine nitrate, magnesium-chelated creatine, and creatine hydrochloride are other variants with some research evidence for equivalent efficacy to creatine monohydrate. 31 of the 38 products with creatine had one or more of these creatine variants in their formulations. 3 products used creatine ethyl ester, a less effective form of creatine. Creatine ethyl ester is 82.4% creatine by weight and is more easily directed towards being converted into a byproduct, creatinine, rather than increasing muscle levels of creatine. 2 products used sodium creatine phosphate, only 51.4% creatine by weight. Research is limited on its efficacy.
L-ARGININE: Arginine made in the body increases levels of nitric oxide, which acts as a vasodilator, allowing the heart to pump equivalent volumes of blood with less effort. These effects, however, have been shown in research to be unreliable for supplemental arginine. As such, there is no established value for suggested daily intake of L-arginine. As a pre-workout supplement, L-arginine is usually taken in 3-6 g doses. Of the 27 products that measured any L-arginine HCl or arginine alpha-ketoglutarate (AAKG) content, only 1 had more than 3 g per serving - SNI Nitric Shock recorded 3858.5 g of AAKG per serving.
L-TYROSINE: L-tyrosine is suspected to increase physiological levels of adrenaline and may help attenuate cognitive decline during acute stressors like cold, sleep deprivation, study, and exercise. However, pre-workout supplementation with 150 mg per kilogram body weight of L-tyrosine has not been found to help aerobic endurance, anaerobic power, or muscle strength. Still, for cognitive purposes, L-tyrosine tends to be most effective at doses of 150 mg per kilogram body weight taken an hour before exercise. This equates to 10 g for a 150 lb. individual. All 29 products with measureable tyrosine content had less than 3 g of L-tyrosine or N-acetyl tyrosine (NALT) per serving, ranging from 10.2 mg to 2880.7 mg.
CAFFEINE: Clinical study supports caffeine’s use for improving strength performance, short and high-intensity anaerobic exercise, and endurance-based aerobic exercises. In endurance exercises, a 1.2-1.4 fold improvement via caffeine was seen regardless of youth or old age and can last for 6 hours, but effects were only noted in individuals not yet adapted to caffeine usage. Some proposed mechanisms for caffeine’s efficacy include reducing perceived effort and pain and increasing muscle cell contractility. 6 mg per kilogram body weight is the most commonly studied effective dose of caffeine, but 3 mg was found to be equally effective for aerobic performance. 3 mg per kilogram body weight equates to about 200 mg in a 150 lb. individual. 21 of 41 products with caffeine measured at least 200 mg per serving. Caffeine content ranged from 58.9 mg to 376.6 mg per serving.
TAURINE: Taurine is an amino acid involved in heart contraction and antioxidant activity Standard dosing has not been established, and research is inconclusive about the benefits of taurine for energy or exercise performance.
Almost all products tested had at least one claimed active ingredient that did not meet the quantity recommended for effective dosing. Only 2 products met recommended doses for all of their claimed actives - Legion Pulse Pre-Workout Drink with caffeine and beta-alanine, and Six Star Pro Nutrition Pre-Workout N.O. Fury with caffeine, creatine, and taurine.