GETTING enough vitamins and minerals is important for your health, and there’s a long list of essential ones. Vitamin D is one you may hear a lot about. It helps your body absorb calcium, a mineral your body needs to build strong bones.

Your heart, muscles, and nerves also need vitamin D. Even your immune system uses vitamin D to fight off germs. But just how much do you need?

Current guidelines recommend adults get 600 to 800 IUs (international units) of vitamin D each day. Those amounts are very important. Not getting enough can lead to serious health issues. Children’s bones can’t develop properly without enough vitamin D. In adults, a long-term deficiency can lead to fragile bones, or osteoporosis.

It’s important to make sure you get enough vitamin D. But scientists are finding that more isn’t always better.

The National Institutes for Health (NIH) said anyone can get vitamin D from the sun and from your diet. Your body makes vitamin D when your skin is exposed to the sun, which gives off UVB light.

But many people don’t go outside enough to get all the vitamin D they need this way. Other factors, such as clothing and sunscreen, can block how much vitamin D your skin makes when you’re in the sun.

How much melanin you have also plays a role. Melanin is a pigment that gives your skin color. Higher melanin levels cause darker skin complexions. The more melanin you have, the less vitamin D you can make from sunlight. This may put you at potential risk for vitamin D deficiency.

Sunlight exposure isn’t the only way to get vitamin D. Vitamin D is found naturally in some foods, like fatty fish. It’s also added to many dairy products and other fortified foods.

But getting enough vitamin D from foods can be difficult for some. These can include breastfed infants and people with certain gut problems that limit how nutrients are absorbed.

Older adults can be at risk of vitamin D deficiency, too. Their ability to make vitamin D in the skin declines. However, older adults may also be less likely to get outdoors as they’re at risk of heat stroke.

Although most people get enough vitamin D to avoid deficiencies, researchers have long wondered if adding extra vitamin D could be good for overall health. Many studies have linked higher levels of vitamin D in the blood with healthier outcomes.

Vitamin D expert Dr. JoAnn Manson, of Harvard University, and her team conducted a large clinical trial, called VITAL, to see whether vitamin D supplements could lower risk for some health problems. Participants were randomly assigned to two groups: half were given vitamin D supplements and half were given a placebo (an inactive pill that looked similar).

After five years, both groups had the same risk for most of the health problems studied. These problems included heart disease, cancer, depression, and bone fractures.

“So, the vast majority of healthy people did not benefit from vitamin D supplements,” Manson says. “But we didn’t find any risk from the 2000 IUs per day that we tested.”

“However, at higher doses you’re going to have to start to worry about risks,” Manson warned. The upper daily limit for vitamin D is 4,000 IUs daily. Consuming more can lead to side effects like kidney stones, nausea, vomiting, and muscle weakness.

Another research team, led by Dr. Sushil Jain at Louisiana State University, is investigating the connection between diabetes, vitamin D, and a molecule called glutathione. Glutathione helps the body use vitamin D efficiently.

For now, most people concerned about vitamin D would get the greatest benefit from living a healthy lifestyle, Manson explained. This includes getting outside, being physically active, not smoking, and eating a variety of healthy foods rich in vitamin D.

“A dietary supplement will never be a substitute for a healthy diet or a healthy lifestyle,” she added.