When you turn to a supplement to boost your performance, you usually know the results you’re after: bigger muscles, quicker gains, more reps. So the easy thing to do would be to mindlessly take the popular pre-workout supplements. But if you’ve ever worked hard for anything, you know that easy isn’t always right. And knowing what you’re putting in your body—and whether or not it actually works—is important.
In part, that’s because while medications give a laundry list of side effects associated with that drug, supplements don’t. The Food and Drug Administration only loosely regulates its labels, in fact, allowing it to make what’s called structure/function claims: promises like “supports increased metabolism”. Dangerous ingredients do, too, make their way into these products—as shown by recent research in the journal Drug Testing and Analysis, which found that of 21 products tested, 11 contained an amphetamine-like stimulant called BMPEA. And sometimes stuff that winds up in supplements just flat out doesn’t work.
So before you load up on a popular pre-workout supplement, know what you’re really consuming. We did the digging on eight common ingredients.
Beta-alanine acts as something called an acidity buffer: The amino acid-derivative increases the amount of carnosine—a buffer that helps prevent declining pH and fatigue in your muscles, says Lonnie Lowery, Ph.D., R.D., a sports nutrition professor at the University of Mount Union in Akron, OH, and co-host of the "Iron Radio" podcast. “That helps you work out about 3-5% harder or longer,” he adds. Think of a supplement with beta-alanine as a couple of extra reps and a bit more muscular endurance. Expect to see some performance increase after a month or so of using 5 or 6g a day, says Lowery. And know that high doses can lead to a nervous system reaction that causes flushing and tingling; it’s harmless, but weird, says Lowery.
L-arginine is an amino acid found in red meat, poultry, fish, and dairy products, and it's necessary for your body to make proteins, increase growth hormone, promote muscle protein synthesis, and relax blood vessels: These are just some of the claims made about arginine, says Jessica Crandall, R.D., spokesperson for the Academy of Nutrition and Dietetics, of Denver Wellness and Nutrition. But, beware: “There’s little evidence that it increases growth hormone levels in healthy adults, and can be dangerous for those with heart conditions.”
You may not realize it, but coffee’s main ingredient and your a.m. stimulant is added to almost all thermogenic and pre-workout supplements because everyone knows it “works,” says Lowery. Ever see a "proprietary blend" listed on a label? That almost always contains some amount of caffeine, he says, adding that the ingredient boosts metabolism, reduces fatigue, raises adrenaline levels, and improves muscle function. Some research even suggests up to 50% jumps in reflexive power output if you time and dose the caffeine correctly, he says.
Try a dose of around 3-5mg per kilogram of bodyweight, says Lowery. The general limit for caffeine is 400mg, or about 5 cups, a day. Overdoing it (more than 500mg/day per day) could have side effects including insomnia, nervousness, stomach upset, fast heartbeat, and muscle tremors, he says.
Introduced in the early '90s, there’s a lot of misinformation about creatine—like that it’s a steroid (which it’s not). There’s also a lot of research on it—with about a 75% consensus that it works in boosting repeat explosive performance, says Lowery. So what is it? Creatine is a non-essential nutrient, says Lowery. “Your body already has it, so essentially, you top off your gas tank with it.” (You can also find creatine in meat and fish, but you'd need to eat a lot to get the same effect.) And it’s worth the top off: You can see a 20 or 25% increase in muscle creatine content if you supplement enough, says Lowery, who adds that similar to beta-alanine, creatine can help you work out longer and boost anaerobic performance. “Just like carb-loading helps endurance performance, creatine helps power athletes perform,” he says.
The main effect of creatine is that it’s an immediate energy pool, says Lowery. Instead of the body working through various pathways to make ATP—an energy-carrying molecule—it can tap the extra creatine.
There are two ways to dose with creatine: The classic way would be 20-30g a day at no more than one tablespoon (5g) at a time, four to six times a day. “You load it fast and hard,” Lowery says. Later studies suggest that 1 tablespoon a day over the course of a month works as a slower approach, he says. Creatine can cause fluid retention—it hyper hydrates the cells, making your muscles feel bigger—but this route causes less rapid fluid retention. Studies have also found an actual increase in muscle mass.
Take a supplement with betaine in it and you’ll find that the creatine content in your muscles goes up. Think of it as a weaker, second-string creatine, Lowery says. Like creatine, betaine also hyper-hydrates the muscle, but researchers aren’t clear about the mechanism by which, or to what extent, it helps performance; there’s not as much research on it,” he says. That said, betaine could have other benefits. “It’s a methyl donor, which means, among other things, it could interact with DNA and thus may do all sorts of things, like potentially turn genes on and off,” says Lowery. While betaine may be a good thing when it comes to performance, methyl donors might do things scientists can’t yet pinpoint—which could make them do unforeseen things.
Yohimbine affects the way adrenaline works in the body, says Lowery. It blocks a type of adrenaline receptor and that can enhance the effect of some stimulants. “It’s often added to stimulants, mostly for fat-loss purposes,” he says. Adrenaline (epinephrine) mobilizes stored fat, and yohimbe helps it act more selectively. But consider this: Playing with the way adrenaline works in your body can bring symptoms. If you block adrenaline’s ability to constrict peripheral blood vessels, such as in your legs, blood doesn’t always get pushed up to the head upon standing, and this can make you dizzy, causing orthostatic hypotension—a temporary form of low blood pressure, Lowery cautions.
Nitric oxide causes your blood vessels to dilate. When we’re at rest, more than half of our capillary beds in muscle are closed, says Lowery. So the idea with nitric oxide as a supplement is that when you start to exercise, you need to open up those capillaries for nutrient delivery or waste removal—and the molecule does just that. The problem is, the supplements that may stimulate nitric oxide just give you amino acids like arginine—which supposedly becomes nitric oxide—hoping this will open up blood vessels, says Lowery. “Any benefits are really debatable, and most research is not very impressive,” he adds. If you want to open up your vascular bed (muscle blood vessels) and garner benefits like increased protein synthesis, 20-30g of whey protein and a banana are probably a better bet, he adds.
Niacinamide may sound familiar—and that’s because it’s a form of the B vitamin Niacin, says Crandall. “It claims to enhance performance of your joints and muscles, and decrease muscular fatigue, but there’s no scientific evidence that suggests it is beneficial for muscle fatigue,” she says. Paradoxically, niacin may actually blunt fat mobilization, making it an odd choice to put in stimulant fat-burner products, Lowery adds.