Illustration: Elena Scotti/Gizmodo

Dietary supplements don’t need to do anything, by definition. Tons of them don’t. That might sound strange, since half of Americans take a vitamin or mineral supplement daily. But there are in fact, reasons to take some of them. Let’s say you eat nothing but ground beef, Cheerios and Dr. Pepper every day. My nutritionist sister once saw a patient who lived this life. The human body, a machine that evolved over millions of years requiring a variety of different molecules to work best, was not optimized with a ground beef, Cheerios and Dr. Pepper-only diet in mind.

This person might require some sort of supplement or daily multivitamin, unless they plan on adding more diversity to their diet. What is a balanced diet? It’s certainly not the average American’s diet, which contains too few vegetables and too little dairy, according to data from the National Health and Nutrition Examination Survey. This causes us to lose out on the vitamins and minerals those foods usually supply.

A balanced diet involves a diverse combination of plant and animal products, processed only as much as required for your body to digest them, eaten in quantities that make you full but not sick. Eggs and a glass of milk for breakfast, a whole wheat bread with meat and cheese sandwich and a side salad for lunch, fruit and some nuts for a snack, and a piece of chicken with vegetables for dinner is probably a good day of meals for the average person (though I am speculating). Such a menu would be very difficult for some, especially those on a tight budget or those easily tempted by the infinite number of cheap, processed choices available at the supermarket.

Advertisement

Advertisement

That’s where folks believe that supplements come in. Some popular supplements are for molecules our bodies need that are especially difficult to get, like vitamin D, which is contained naturally in only a few foods like fish, meats and mushrooms unless producers put it in, as is the case with milk. Other supplements are simply unregulated medications in disguise, Edward Saltzman, Academic Dean for Education at the Tufts University Friedman School of Nutrition Science and Policy, tells Gizmodo. The problem is, the FDA doesn’t need to determine whether dietary supplements work provide a nutritional benefit before they’re sold. And, Saltzman adds, “There are very few supplements of the thousands marketed for which there is really solid evidence [of efficacy].”

So, here is a list of supplements that repeated scientific studies have proven do something. Do not take this as medical advice. If you are worried, please talk to your doctor or dietician, who will hopefully recommend you change your diet before taking a supplement.


Vitamin D

WHAT IT DOES: Helps promote bone growth.
WHO SHOULD TAKE IT: People with vitamin D deficiencies (after speaking with a doctor).

Advertisement

Advertisement

Milk, fish, and a few other foods contain molecules collectively known as vitamin D, which your body can also produce through exposure to the Sun. That means folks who don’t head outside much, or don’t eat a balanced diet, might be at risk for vitamin D deficiency or even rickets, a bone disease, if things get bad enough. Possibly ten percent or as many as three quarters of Americans have the D deficiency, depending on who you ask, according to an article in Scientific American. “It’s the deficiency that can increase the risk to common illnesses,” Michael Holick, Professor of Medicine, Physiology and Biophysics at Boston University School of Medicine, told Gizmodo. “That’s why I think it’s the most important supplement people could be aware of.” Holick is a vitamin D superfan—he has published a ton on the vitamins, and he said it’s the only supplement he takes aside from a daily multivitamin.

There’s fairly robust data pointing to the D vitamins’ importance to back Holick up. One meta-analysis combining almost 100,000 patients found that vitamin D and calcium together slightly reduce the chances of bone fractures in post-menopausal women and older men. Another found that vitamin D supplements had no benefit for healthy children, but could possibly help bone development in children with a vitamin D deficiency. And another found that it’s probably sound advice to offer vitamin D to malnourished children in underdeveloped countries at risk of developing nutritional rickets, which can also stem from a vitamin D deficiency.

The National Institute of Health recommends we get between 400 and 800 international units of vitamin D, and most American dairy producers fortify their milk with about 10 micrograms, or 400IUs, per quart. Less than half of Americans get more than 30 nanograms of vitamin D per milliliter of blood according to that Scientific American article, the amount doctors think is healthy but around twice the amount used to diagnose a true vitamin D deficiency. Older folks, those with certain disorders, those with darker skin and obese people might have trouble getting enough vitamin D, and should maybe consider taking a supplement after speaking to their doctor.

Holick is a big fan of vitamin D for other reasons, too. One meta analysis found that when taken early in life, it could reduce the risk of type 1 diabetes, for example. The results of another 25,000-person vitamin D study will come out this year and offer more evidence (or not) towards whether larger doses of vitamin D have long term benefits. But do you need to take it as a supplement? If you feel like spending extra money on a pill, you can do whatever you want. If you’re drinking enough milk and getting enough sun, though, you probably don’t need it. This is the nicest I will ever treat a dietary supplement.


Calcium

WHAT IT DOES: Promotes bone growth, helps reduce premature births
WHO SHOULD TAKE IT: Pregnant people or teenagers if they aren’t getting enough in their diet (after speaking with a doctor)

Advertisement

Advertisement

Vitamin D helps your body absorb calcium, so the two are frequently found in the same fortified foods and supplements. Calcium also promotes healthy bone growth—combined with collagen, that’s what makes up your bones. That means people need to eat it, but still, adolescent boys and girls have trouble meeting their calcium requirements according to the NIH’s Office of Dietary Supplements, as do older men and women. Vegans and lactose intolerant people also might have trouble getting enough calcium, since they’re avoiding dairy.

A meta analysis found that calcium paired with vitamin D could help mitigate the bone loss effects that come with taking certain infection treatments, like corticosteroids—in fact, the study recommends that all patients receiving corticosteroids also receive vitamin D and calcium supplements. Calcium supplements also reduced the risk of a disorder which causes high blood pressure during pregnancy, and other symptoms called pre-eclampsia. Calcium supplements taken by pregnant women even seemed to reduce premature births and maternal death, according to the same study.

Calcium, like the vitamin D, seems to be a supplement helpful for people who are teens, pregnant, or both, or if they aren’t getting enough calcium in their diet. But, “certain populations, like those with kidney disease and someone prone to certain kidney stones wouldn’t want to take calcium in excess,” since calcium supplements, rather than calcium in food, can lead to kidney stones, Lauren McGill, registered dietician at the University of Texas at Austin’s Fitness Institute of Texas, told Gizmodo. Calcium supplements can also have side effects like constipation.

Advertisement

Calcium supplements can benefit those not getting enough calcium in their diet. But maybe consider drinking more milk to get your calcium and vitamin D before taking a pill.

Iron

WHAT IT DOES: Helps reduce anemia in menstruating people
WHO SHOULD TAKE IT: People who lose blood (like pregnant or menstruating people or those who donate blood) with iron deficiencies who can’t get enough from their food

Advertisement

Advertisement

Iron has an important function in hemoglobin, the protein in blood cells that helps carry oxygen all over your body. Meat and vegetables generally contain enough iron for your diet, but the iron in meat presents itself in the molecule called heme, while the iron in vegetables is usually on its own. Our bodies are typically better at using the heme form of iron.

Iron is an easy mineral for humans to have a deficiency in, especially those who lose or share blood. Those who can’t get enough iron in their diet risk developing anemia, the condition where blood isn’t as good as carrying oxygen. That doesn’t mean these people should take an iron supplement, though—it means they should talk to a doctor or dietician about how to get more iron into their bodies.

Still, there’s lots of evidence that shows iron supplements at least do something. One meta analysis found they could help reduce anemia, fatigue, and iron deficiency in menstruating women, for example. Another found it’s helpful for pregnant women to take supplements, while another found it’s probably best for those supplements to come intermittently, rather than daily. One other also found daily iron supplements important to reducing childhood anemia.

Advertisement

Supplementing iron over the recommended daily amount of 18 milligrams could have side effects, though, like constipation or diarrhea, reports the Office of Dietary Supplements. And there are a lot of foods that contain iron, like breakfast cereals, oysters and meats. “It’s a mineral you wouldn’t want to blanket supplement because it can cause damage” and build up to a toxic level, said McGill. “That’s something you would want a healthcare professional to monitor.”

This seems like a good pit stop to explain why I’m only using meta analyses to motivate this post, and not single studies. Single studies usually have dozens to a few hundred patients. Sometimes, they’re funded by companies who are trying to sell a product or pharmaceutical, which could lead to intentional or unintentional bias. Plus, single studies generally just find a correlation between a thing, say, iron, and an outcome, say, not having anemia. One might be causing the other, or maybe the researchers just got lucky and a bunch of people taking iron supplements’ anemia went away for unrelated reasons. Therefore, while single studies might be exciting tools to understand the progress of science, and sometimes they really do contain definitive, groundbreaking discoveries, it’s best not to use them for medical advice. After all, another study might come along and completely refute the study before it.

Advertisement

So, onwards!


Creatine

WHAT IT DOES: Boost muscular performance
WHO SHOULD TAKE IT: Athletes or those with muscular dystrophy (after speaking with a doctor)

Advertisement

Advertisement

We’re now approaching the part of the list with the supplements that are basically just drugs. Creatine is one of those supplements. Most healthy people get enough creatine in their diet just fine, but athletes who need or want more protein might use it. McGill explained that creatine can improve athletes’ performance and strength, including enhancing muscle mass, but it can also cause muscles to retain water and make athletes feel heavy. Jenny Senecal, registered dietitian and nutritionist with Gourmet Dining Services at Manhattan College, agreed with McGill’s philosophy, that these molecules should really be coming from food. If athletes are running out of time and feel like drinking a protein shake, “make sure the source is reputable,” she said.

But this is an article about what supplements work, and creatine does seem to have performance-enhancing abilities. A small meta analysis covering 14 trials and almost 400 patients found that creatine seemed to make folks with muscular dystrophy, the disease where muscles get weaker over time, feel better.

That’s actually pretty cool! Except again, if you’re thinking about taking creating supplements, you should talk to your doctor first.


Melatonin

WHAT IT DOES: Helps the body regulate its daily cycle
WHO SHOULD TAKE IT: Shift workers or folks suffering from jet lag

Advertisement

Advertisement

Taken right before bed, melatonin has probably delivered you a batch of wild dreams and made you feel groggy the next day. Your brain produces the hormone naturally as a part of the daily cycle—more during the evening and less during the morning, so we know it plays a role in sleep, according to the National Institute of Health’s National Center for Complementary and Integrative Health. Lots of light at night can prevent your brain from producing the hormone.

Do melatonin supplements work, though? Yes, for certain things! Melatonin is “remarkably effective” at preventing jet lag, according to a meta analysis. “It should be recommended to adult travelers flying across five or more time zones, particularly in an easterly direction, and especially if they have experienced jet lag on previous journeys,” the authors write, though if taken in the morning, it can cause grogginess during the day. Otherwise, it seems to help shift workers who need to sleep during the day, slightly improving their sleep length and quality, according to NIH reporting.

McGill reminded me that some foods, like tart cherry juice, also contain melatonin. That’s important because melatonin, like all of the supplements listed here, is not required to be approved by the FDA. Melatonin in pill form is basically an unregulated drug, and our diets don’t really contain (or need) that much melatonin. “Before the mad cow scare in the UK, [melatonin] was extracted from the pineal glands of cows,” said Saltzman. “Tell me how that is a dietary supplement. It’s a hormone being extracted from the brains of animals!”

Advertisement

And with supplements, you might not know whether the source is safe. “With the supplement industry there’s a lot of risk for contamination or selling you things with added ingredients,” said McGill. “I always recommend food first.”

Of course, this list doesn’t encompass everything—there are plenty of other supplements that folks with deficiencies might need, or that might prove to serve some medicinal benefit after repeated trials. Feel free to discuss supplements that interest you in the comments, or better yet, with your doctor.