Why we need vitamin D — and sun exposure isn't the only way to get it

Vitamin D is a real multitasker. It “helps your body absorb calcium, which is essential for strong bones and teeth and helps prevent rickets in children and osteoporosis in adults,” Nicholas Rush, a registered dietitian at Fay, tells Yahoo Life. “Vitamin D also plays a role in supporting a healthy immune system and glucose metabolism and reducing inflammation.”

But 35% of Americans aren’t getting enough of it.

There are several reasons why — the main factors being lack of sun exposure (the body produces vitamin D when exposed to the sun’s ultraviolet light), location, age and skin color, explains Vanessa Rissetto, registered dietitian and chief executive officer of Culina Health. “The darker the skin tone, the harder it is to synthesize vitamin D from the sun,” she explains. According to the National Library of Medicine, the most at-risk populations for vitamin D deficiency are the elderly, obese people, nursing home residents and hospitalized patients.

But before you run out to pick up a bottle of supplements or start walking around without any sunscreen, here’s what experts want you to know about vitamin D.

Bone health isn’t its only superpower

Strong bones and osteoporosis prevention might be vitamin D’s claims to fame, but they’re not its only specialty. According to the National Institutes of Health, the nutrient helps your immune system fight off viruses and bacteria, which is especially timely for cold and flu season. Vitamin D also assists in regulating blood sugar and helps your brain manage mood. For example, some studies have found links between low blood levels of vitamin D and an increased risk of depression.

The sun isn’t the only way to get more vitamin D

Before stocking up on capsules from the vitamin aisle, evaluate your diet for vitamin D gaps. That’s right: The sun isn’t the only way to get this important nutrient. “Fatty fish like salmon, tuna and sardines are packed with vitamin D and egg yolks, beef liver and cheese contain smaller amounts,” says Rush. Many foods are also fortified or enriched with vitamin D, he adds, including milk, plant-based milk alternatives, cereal, orange juice and yogurt. “Checking the nutrition facts label is the easiest way to see if a food contains vitamin D,” he says.

More isn’t better when it comes to vitamin D

There is such a thing as vitamin D toxicity that can pose serious health risks. “Overdoing it on vitamin D, usually from high-dose supplements, can lead to elevated calcium levels in the blood known as hypercalcemia,” explains Rush. “This can trigger a range of symptoms, including nausea, vomiting, muscle weakness, confusion and even kidney stones. In severe cases, vitamin D toxicity can cause kidney failure, heart problems and in rare instances, death.”

The recommended daily allowance of vitamin D is 600 international units (IU) for people ages 1 to 70 and 800 IU for adults over 70. “However, your doctor may recommend a higher dose if you have a deficiency,” Rush says.

The supplement shouldn’t be taken alone

“Vitamin D is a fat-soluble vitamin, meaning it's absorbed best when consumed with fat,” says Rush. “Having a snack with some healthy fats, like avocado, nuts or seeds, can help your body absorb the vitamin D supplement more effectively.”

It’s also a good idea to make sure you’re getting enough vitamin K — another nutrient found in leafy greens — or if your doctor recommends it, taking a supplement with both vitamins (such as D3 and K2). That’s because vitamin K and D work together, with vitamin K helping to distribute the calcium produced by vitamin D.

It’s not an excuse to get more sun exposure

Low vitamin D doesn’t give you a free pass to a day of sun tanning. “Some research suggests that five to 30 minutes of midday sun exposure several times per week could be enough for most people to produce sufficient vitamin D,” says Rush. The proper amount of time varies depending on your skin tone, the amount of skin exposed to the sun, the time of day, the season and where you live, he adds.

Whether you spend five or 30 minutes getting your vitamin D fix, it shouldn’t be without sunscreen. According to The Skin Cancer Foundation, “Clinical studies have never found that everyday sunscreen use leads to vitamin D insufficiency. In fact, the prevailing studies show that people who use sunscreen daily can maintain their vitamin D levels.” That’s because no sunscreen offers 100% protection from the sun’s UV rays so even with sunscreen, some of those rays will still reach your skin. “It’s important to protect your skin from sun damage to reduce the risk of skin cancer,” Rush says.