Supplements are super popular. One recent survey estimates that more than half of Americans use them, and we spend billions of dollars on them each year. The truth is, though, most people don’t need any supplements unless they’re deficient in a vitamin or mineral. And even if they are, they should probably switch up their diet instead of buying pills or powders. That’s because when these chemicals are eaten in food, your body can absorb and use them better. Plus, it’s much harder to overdose.

A surprising number of supplements have actually been shown to hurt us. In fact, every year, about 23,000 Americans head to ERs because of adverse reactions. All that being said, there are a few supplements in the right situations that might be worth it.

Before you take anything, though, you should definitely talk to a doctor, who will look at your personal situation and help you make an informed choice. We’re not doctors.

Creatine

It’s a molecule that you naturally make in your liver and kidney, and mostly stored in your muscles.

And besides workout supplements, you can get it from foods like beef and fish. Not everyone responds to extra creatine, but studies have shown that many people see improvements in sports that require short bursts of power, like sprinting. People can run faster, lift heavier weights, and build more muscle.

Creatine can also help with muscle recovery from intense workouts but doesn’t seem to help with endurance sports, like long-distance running or swimming.

Scientists think that the extra creatine gets modified by your body and helps make the main molecule that cells use for energy: ATP. That extra available energy lets muscles work harder than they normally would, especially in bursts.

Outside of weightlifting competitions, creatine also can help people with muscular dystrophy, a genetic disease that causes progressive muscle loss and weakness. These patients tend to have lower levels of natural creatine. And, in certain forms of the disease, supplements increase muscle strength and let patients go about their daily lives more easily.

Beet juice

Didn’t think we’d mention a trendy juice, did you? But beet, or beetroot, juice seems to actually do something! It’s made from beets.

And in multiple studies, researchers have found that it can improve athletic performance, specifically for aerobic sports, like running or swimming. While the juice has a lot of potentially good stuff in it, scientists think the part that’s most beneficial for exercise is the nitrate.

Beets are chock full of it, and our bodies will turn it into nitric oxide, which triggers blood vessels to get wider. This allows more blood to flow, so more oxygen gets to your muscles. Your muscles use oxygen to break down food to create energy to contract. So, with more oxygen around, you don’t tire out as quickly.

At least, that’s the working theory. For those same reasons, beet juice might also help lower blood pressure. If you drink a lot, though, just be prepared for some pink or red pee.

Antioxidant multivitamins

Now, as we said, you typically don’t need supplements unless you have a deficiency, so there’s no real good reason to take multivitamins. And non-food antioxidants generally don’t help either. But there is one exception, for people with age-related macular degeneration, or AMD. People with this condition are usually over the age of 50. They slowly lose their vision, because of damage to the macula, which is the central part of the retina — the light-sensitive cells at the back of your eye.

The basic idea is that because cells in the retina absorb light, which can excite electrons and create reactive molecules called free radicals, they could get damaged. So antioxidants, which sop up free radicals, might help. And some of the most familiar vitamins, including vitamin C and E, are antioxidants.

There’s been quite a bit of scientific debate and lots of clinical trials to pin down which vitamins and antioxidants are actually helpful. The general consensus is that certain combinations do work well enough to slow the progression of AMD. They don’t prevent eye damage, but slowing it down is still good.

You’ve probably heard about this one, but it’s worth mentioning because it’s one of the few cases where we have pretty indisputable evidence that a supplement does some good.

Folic acid

Vitamins are compounds that your body needs to work and grow that you can’t make on your own, so you have to get them from somewhere else, like food.

Specifically, folic acid is important for making red blood cells, and thymine and cytosine, two of the four bases that make up DNA. You can’t make new cells without it. So, while everyone needs folic acid, pregnant people really need it, because they’re rapidly growing a whole new human inside them. That means the usual folic acid that we eat, either naturally in leafy vegetables and other foods, or in fortified things like breakfast cereal, may not be enough.

Doctors advise pregnant people to take folic acid supplements, both before and during the pregnancy. Without enough folic acid, they can develop anemia, or too few healthy red blood cells. That can mean their tissues don’t get enough oxygen, making them tired.

And deficiencies can affect the baby’s growth too, since they’re getting the vitamin from their parent. Not enough folic acid can cause a neural tube defect early in development, which can be serious. In one defect, known as spina bifida, the baby’s spinal column doesn’t close all the way, which can damage nerves and sometimes leaves kids paralyzed.

In another, called anencephaly, the baby doesn’t fully develop its brain or skull. Most of these babies die before or just after birth.

Melatonin

Melatonin is sometimes marketed as a cure-all for sleep-related problems. Its track record is a little spotty, but studies have found small benefits in certain cases. It may be most useful for people who have abnormal or disrupted circadian rhythms — like people with jet-lag, night shifts, or a condition called delayed sleep phase syndrome, which is when your biological clock is perpetually several hours behind.

And that’s because melatonin is a hormone that helps control our cycling in and out of sleep. As it gets later and dark outside, the pineal gland in your brain starts to release the hormone, and it binds to receptors deep in the brain to help usher you into dreamland.

So when your body isn’t naturally making melatonin — like if you’ve changed time zones — taking some could help ‘reset’ your internal clock, and let you get more rest than you otherwise would. And some studies support this idea, while others find barely any improvement.

Also, melatonin might help people with insomnia fall asleep faster, and increase the total amount of time they sleep. It’s typically only about 10 extra minutes, though, and in some experiments, those gains aren’t there.

Last year, the American Academy of Sleep Medicine even revised its guidelines to say that they don’t recommend melatonin for insomnia. Although they also admit that’s based on relatively weak evidence. So the scientific community isn’t positive about this one.

Part of the problem is that even though melatonin is relatively well studied, researchers have tested different dosages at different times and for different things. So we can’t be too confident about what it can do.

The other big thing worth mentioning is that even though people may use melatonin like a drug, basically to treat or prevent a condition, the FDA doesn’t classify it as one. So it’s regulated in the US like a supplement.

A study published in 2017 found that 70% of melatonin supplements have 10% more or less melatonin in them than their labels say, with some falling in an enormously wide range. The supplements can also have other things that aren’t listed on the label, like the neurotransmitter serotonin.

And this could get dangerous, like too much serotonin can lead to overactive nerves and a bunch of potentially severe symptoms, like seizures.

St. john’s wort

The saintly name comes from the fact that the plant’s yellow flowers bloom around the birthday, and feast day, of John the Baptist. It’s been used for lots of maladies, going back at least to the ancient Greeks. But it’s most famous for its effects on mood.

Modern scientists think that’s because of the chemical hyperforin. Hyperforin prevents neurons from taking up certain neurotransmitters, like serotonin, norepinephrine, and dopamine, which leaves more of them in synapses between cells.

Scientists aren’t sure why this helps, but having more of these neurotransmitters around may let neurons communicate better, and strengthen the circuits in the brain responsible for controlling mood.

Many standard antidepressants do the same basic thing, even if their mechanisms are slightly different.

Now, St. John’s wort has been tested in multiple placebo-controlled trials. These are clinical trials in which some people get the substance being tested, and others get a placebo, like a sugar pill. That way, researchers can tell if a drug or supplement does anything. And those experiments showed that it helped people with mild to moderate depression.

The best case for St. John’s wort is a 2008 meta-analysis that included 29 different studies. It concluded that the supplement does better than a placebo and is just as effective as standard antidepressants, but with fewer side effects.

But that meta-analysis also included a lot of studies from Germany, where St. John’s wort is popular and tends to do well in trials. And other studies, especially those outside Germany, have sometimes failed to see St. John’s wort doing much more than a placebo.

A huge downside of St. John’s wort is that it interacts with a lot of other drugs and makes them less effective — like HIV antiretrovirals, birth control, and organ transplant rejection drugs. And we’re not even close to listing them all.

Researchers think hyperforin triggers the liver to make more of an enzyme that breaks down certain medicines, so you go through them more quickly.

And you most definitely should not combine St. John’s wort with other antidepressants, because those drugs can also increase serotonin levels, which can lead to a serotonin overdose. Because of other mechanisms, St. John’s wort can also make you more sensitive to the sun, and it can lead to miscarriages, so pregnant people should avoid it. Not to mention, some people are straight-up allergic.