What can’t vitamin A do? Experts on the health benefits of the nutrient — and if you need to take a supplement.

Despite not being the buzziest nutrient out there, vitamin A plays an important role in your health, including your immune system function. The vitamin has recently gotten some attention as a possible way to treat certain infectious diseases like measles, but doctors stress that there’s a lot of misinformation surrounding this key nutrient. While you can get vitamin A from certain foods, it’s also available in supplement form. But dietitians and doctors warn against supplementing with vitamin A on your own since you can overdose on this nutrient. Here’s what you should know about vitamin A, including what it can — and can’t — do for your health.

What is vitamin A?

Vitamin A is the name for a group of retinoids, according to the National Institutes of Health (NIH). Like vitamins D, E and K, it’s a fat-soluble vitamin, which means it dissolves in fat and is stored in the body’s tissue and liver.

“Vitamin A plays many critical roles in our bodies, starting at the cellular level and should be consumed in a balanced way, as there are risks to consuming too little and too much,” Ashlee Bobrick, a dietitian nutritionist at the Ohio State University Wexner Medical Center, tells Yahoo Life.

Your body can’t make vitamin A on its own, so it needs to rely on the foods you eat to get it, Dr. Danbee Kim, an assistant professor at Rutgers New Jersey Medical School, tells Yahoo Life.

What does vitamin A do in the body?

“Think of vitamin A as the multitasking overachiever of the nutrient world — good for your eyes, skin, immune system and even cell growth,” Tony Yang, professor and associate dean for health policy and population science at the George Washington University School of Nursing, tells Yahoo Life. “But like any overachiever, too much can cause problems.”

Kim says these are the biggest roles vitamin A plays in the body:

• Supports vision health. “It helps maintain eyesight, especially in low light,” she says. “A deficiency can cause night blindness and increase the risk of vision loss.”

• Boosts immunity. Vitamin A strengthens your immune system by supporting white blood cells and protecting the body from infections, Kim explains.

• May lower cancer risk. “Some studies suggest vitamin A from plants may reduce cancer risk,” Kim says. But she also points out that high doses of the vitamin may be harmful, especially for smokers.

• Promotes healthy skin. “Vitamin A changes the way skin cells develop, from the inside out,” Dr. Ife Rodney, founding director of Eternal Dermatology + Aesthetics, tells Yahoo Life. “Some of our most popular skincare products change the way skin cells evolve, helping with acne, fine lines and some skin discoloration.”

• Supports reproductive health. The nutrient is “essential for fertility and healthy fetal development, but excessive intake during pregnancy can be harmful,” Kim says.

• Strengthens bones and teeth. Vitamin A helps with bone growth, but too much may increase the risk of fractures and osteoporosis, Kim says.

Overall, vitamin A has a role in “pretty essential stuff” in the body, Yang says.

What can’t vitamin A do?

Most of the confusion around vitamin A involves infectious diseases, in particular measles. While vitamin A is sometimes used to treat measles when someone is already infected, it can’t actually prevent people from getting sick like a vaccine can, Dr. Thomas Russo, professor and chief of infectious disease at the University at Buffalo in New York, tells Yahoo Life. But even using vitamin A as a treatment for measles is a bit complicated.

A 2010 scientific analysis found that there was “no significant reduction” in people dying from measles after taking vitamin A treatments across six randomized controlled trials. But, when the researchers broke things down by dose, they found that having at least two doses of vitamin A lowered the risk of dying from measles by 62%.

But here’s some important context: “The major studies that have been done about the benefits of the treatment of measles — particularly severe measles — have been done in the developing world where children are often malnourished and don’t have enough vitamin A to begin with,” Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Life. In those cases, certain doses of vitamin A, given as early as possible in infected children, may help lower the risk of measles complications like pneumonia and encephalitis (inflammation of the brain), Schaffner explains.

“But that’s in the developing world,” he says. Vitamin A deficiency in the U.S. is rare, according to the National Institutes of Health (NIH).

“Severe measles in children that have a vitamin A deficiency is very different than if you have adequate levels of vitamin A in your diet, which most Americans have,” Russo says. “It would be unusual for a child in America to have a vitamin A deficiency.”

Despite that, the American Academy of Pediatrics’ stance is that children with measles who are sick enough to be hospitalized should be given two doses of a vitamin A supplement to prevent eye damage and blindness. (Measles is most likely to cause blindness in people who are not vaccinated against the disease, according to the American Academy of Ophthalmology.) The World Health Organization (WHO) also recommends that children and adults with measles be given two doses of vitamin A by a health care provider 24 hours apart.

In American children, “the potential benefit is likely moderate,” Russo says. “Still, a couple of doses of vitamin A is unlikely to be detrimental,” he adds.

But Schaffner stresses that vitamin A will not keep people from getting measles in the first place. “Full stop: Vitamin A does not prevent measles,” he says. “It should not be considered a substitute for measles vaccination” — known as the MMR vaccine — “and there’s a lot of confusion around that.”

As for vitamin A’s role in cancer prevention, even the NIH notes online that data is mixed, writing, “Some clinical trial evidence suggests that supplemental vitamin A might reduce the risk of certain cancers but increase the risk of other forms of cancer, cardiovascular disease morbidity and mortality and all-cause mortality.” As a result, it’s not recommended that everyone takes vitamin A for cancer prevention.

How much vitamin A do you need?

The recommended daily allowance (RDA) for vitamin A is given as retinol activity equivalents (RAE) to account for the different types of vitamin A, which are converted by the body into retinol, according to the NIH.

The recommendations vary by age and sex, but it’s typically suggested that children under the age of 13 get between 300 and 600 mcg RAE, while people aged 14 and up should aim for 700 to 900 mcg RAE.

You can overdose on vitamin A

This is a big concern with vitamin A, and a major reason why experts don’t recommend taking a vitamin A supplement without consulting a health care provider first. “Unlike water-soluble vitamins that you just pee out if you take too much, excess vitamin A gets stored in your body, which can lead to toxicity over time,” Yang explains.

That toxicity can lead to a host of health complications, including liver issues and other organ damage, per the U.S. National Library of Medicine.

“Overdosing on vitamin A isn't pretty — it can lead to nausea, dizziness, headaches, liver damage and, in extreme cases, birth defects,” Yang says.

Best food sources of vitamin A

Vitamin A can be found in animal and plant products, Bobrick says. Worth noting: It’s unlikely that you’d overdose on vitamin A from food alone, notes Russo.

Bobrick says these are the biggest sources of vitamin A:

• Liver

• Sweet potatoes

• Eggs

• Milk

• Yogurt

• Butter

• Oily fish like salmon, cod liver and mackerel

• Dark, leafy greens like spinach and kale

• Carrots

• Butternut squash

• Red bell peppers

• Peaches

• Apricots

• Cantaloupe

• Mangos

• Fortified cereal

• Some plant-based milks

What to do if you’re considering a vitamin A supplement

Vitamin A shows up in some multivitamins, and Kim says those are fine to take. But adding an additional vitamin A supplement on top of that can be dangerous and put you at risk of toxicity.

“Definitely check with a health care provider first — more isn’t always better,” Yang says. “If your diet is balanced, you’re probably getting enough.”