Vitamin A Is Good For You…Until It’s Not

In the world of nutrients, there are big names like vitamin C, iron, and calcium that hog all the attention. But vitamin A has been quietly hanging in the shadows, just waiting for its moment to shine. Apparently, that time is now.

The nutrient is being floated as a potential treatment for measles, and there are some unfortunate—and inaccurate—claims that it can help prevent measles. Given that measles continues to pop up around the country, it’s natural to at least wonder what vitamin A is about.

Just an early warning: Vitamin A is a slightly tricky nutrient. “There are risks to consuming too little and too much,” says Ashlee Bobrick, an RDN at The Ohio State University Wexner Medical Center. With that, it’s crucial to proceed with caution. So, what’s the link between vitamin A and measles? And what does vitamin A even do? We’re breaking it down.

What is vitamin A, exactly?

Vitamin A is the name for a group of retinoids, per the National Institutes of Health (NIH). This is a fat-soluble vitamin, so it dissolves in fat and is stored in your body’s tissues and liver.

“It exists in two forms: Preformed vitamin A (retinol) from animal sources and provitamin A carotenoids (such as beta-carotene) from plant sources, which the body converts into active vitamin A,” says Scott Keatley, RD, of Keatley Medical Nutrition Therapy.

Your body can’t make vitamin A. Instead, you have to get it from the foods you eat, Bobrick explains.

What does vitamin A do?

Vitamin A has a hand in a lot of different processes in the body. “Vitamin A helps promote healthy vision when consumed adequately, especially regarding how well our eyes adjust to darkness,” Bobrick says.

The nutrient can also help fight infections and potentially reduce the risk of cancer by acting as an antioxidant that fights off damaging molecules known as free radicals. (The NIH points out that data on cancer prevention is mixed, so it’s not currently recommended that everyone hop on a vitamin A supplement to prevent the disease.)

“Vitamin A assists with bone health, activating bone-forming cells,” Bobrick says. “As a bonus, vitamin A helps maintain healthy skin by promoting cell growth and repair, ultimately improving skin texture and reducing aging signs.”

But the relationship between measles and vitamin A is slightly complicated, which has allowed plenty of myths to circulate. Despite what you may have heard, “vitamin A will not prevent measles,” says Thomas Russo, MD, a professor and chief of infectious disease at the University at Buffalo in New York.

It may help treat measles, but even that is a little uncertain, Russo says. “We know from studies conducted abroad that if you are deficient in vitamin A, you’re at risk for more severe disease when you contract measles,” he says. “But it’s uncertain how much of an impact it has in the U.S., where vitamin A deficiency is rare.”

However, the World Health Organization (WHO)—which gives health recommendations for the developing and developed world—suggests that children and adults with measles be given two doses of vitamin A by a healthcare provider. The American Academy of Pediatrics also says that children who are hospitalized with measles should be given two doses of a vitamin A supplement to lower the risk of eye damage and blindness.

While Russo says that a few moderate doses of vitamin A are unlikely to be harmful, even if your current levels of vitamin A are fine, he also recommends talking to a doctor about dosing before putting yourself on a supplement.

Where to get vitamin A

Again, the body doesn’t make vitamin A on its own, so you need to get it from the foods you eat. The biggest food sources of vitamin A, per the NIH, include these:

• Beef liver
• Sweet potato
• Spinach
• Carrots
• Herring
• Cantaloupe
• Ricotta cheese
• Red peppers
• Eggs

Most Americans are doing just fine with vitamin A levels.

In fact, the NIH notes that vitamin A deficiency in the U.S. is rare.

“Most Americans get enough vitamin A, largely due to fortified foods and a diet that includes sources like dairy, eggs, and orange vegetables—carrots, sweet potatoes, and pumpkin,” Keatley says. However, some people with malabsorption disorders like Crohn’s disease, Celiac disease, or cystic fibrosis may be at risk for vitamin A deficiency, he says.

Bobrick stresses that vitamin A deficiency is not an issue most Americans face. “Vitamin A deficiencies are more common in less developed countries, where most individuals do not get enough vitamin A through food,” she says.

You can have too much of a good thing with vitamin A.

Because vitamin A is a fat-soluble vitamin, it can build up in your body when it’s taken in high amounts. (Conversely, you’ll usually just pee out excess amounts of water-soluble vitamins, like vitamin C.) With that, it’s possible to take too much vitamin A. That can lead to a condition called hypervitaminosis A, or vitamin A poisoning.

Acute vitamin A poisoning can happen quickly when an adult takes several hundred thousand international units (IU) of vitamin A, according to the U.S. National Library of Medicine. But you can also develop chronic vitamin A poisoning when you regularly take more than 25,000 IU a day. (While vitamin A shows up in many multivitamins, you will not achieve these high levels that can make you sick with those supplements, according to Keatley.)

“Acute toxicity can cause nausea, dizziness, headaches, and even increased intracranial pressure,” Keatley says. “Chronic toxicity can lead to liver damage and bone thinning.” Hair loss and dry, rough skin are other signs of vitamin A toxicity, Bobrick says.

How to know where your vitamin A levels stand

If you eat a healthy, varied diet, you’re likely doing just fine in the vitamin A department, Keatley says. But if you’re really concerned about your vitamin A levels or if you have one of the conditions we mentioned above, Bobrick says a healthcare provider may want to order a blood test to check your levels.

“If you are experiencing night blindness, which is often the result of a vitamin A deficiency, an eye examination may be required,” she adds.

Bobrick just underscores the importance of going through a healthcare provider if you’re interested in taking a vitamin A supplement due to the risk of poisoning. “If an individual is taking a multivitamin and follows a balanced diet, they likely consume enough vitamin A to prevent deficiency,” she says.