Vitamin D: What You Should Know About the ‘Sunshine Vitamin’ from Intermountain Health

Spring and summer in many areas means the start of period of time people here can absorb Vitamin D from the sun, which will help improve mood, immune function, and prevent the most common vitamin deficiency in the United States.

But Intermountain Health dietitians warn that sunscreen to prevent skin cancer can block the sunshine vitamin from being absorbed, and too much Vitamin D taken through supplements can lead to toxicity.

“Vitamin D deficiency is one of the most common nutrient deficiencies nationwide, and can lead to fatigue, bone pain or achiness, muscle weakness, depression, and getting sick more often,” said Carly Alba, registered dietitian nutritionist for Intermountain Health. “But people should be cautious before taking Vitamin D supplements more than 4,000 IU, which can cause Vitamin D toxicity in some people. The best thing to do if you’re experiencing these symptoms is to seek a consultation with a dietitian or your primary care provider.”

Vitamin D allows the body to absorb calcium. As many as 42 percent of Americans are vitamin D deficient, which affects their mood, immune systems, bone health, levels of inflammation in the body, cell growth, and neuromuscular and immune function.

The essential nutrient and fat-soluble vitamin is contained in very few foods, and mostly through animal sources, which can especially affect people who are vegan or vegetarian. Vitamin D is in fatty fish like salmon, mackerel, tuna and trout, and to a lesser extent, mushrooms, and fortified dairy products and breakfast cereals.

“There really aren’t very many natural food sources of vitamin D,” Alba said. “It’s also harder to get from the sun in Utah and similar northern latitudes, because it only can be absorbed by the skin from April to September,” Alba said.

Adults need at least 600-800 IU of Vitamin D per day, unless directed by a physician. To give perspective, a serving of milk might have 100 IU.

Supplements may be recommended to help prevent or correct a vitamin D deficiency. People who take a supplement should avoid exceeding the upper limit of 4,000 IU per day unless directed by a physician. Vitamin D toxicity, which means there’s too much calcium in the blood, can occur if the upper limit is exceeded over a long period of time and lead to nausea and vomiting, weakness, bone pain and kidney problems, Alba said.

So, what’s the best way to get enough, but not too much, vitamin D? Go outside and enjoy the sunshine. Even 10 minutes of sun exposure on the arms and legs can help the skin synthesize as much as 3,000 IU of vitamin D.

“While you can get a sunburn, you can never reach a toxic dose of the vitamin from the sun,” Alba said.

Here are some things affecting the amount of vitamin D that can be synthesized from the sun:

• Skin pigmentation. Darker skin with more melanin requires longer sun exposure.
• Time of day and season. UVB rays are strongest midday and during summer.
• Sunscreen. SPF above 8 blocks vitamin D synthesis in the skin, so consider spending 10-20 minutes in the sun before putting on sunscreen if it’s safe for you.
• Geographic latitude. Those living in northern latitudes, including Utah, cannot synthesize vitamin D from the sun between October and March.
• Weather conditions. Cloud cover and air pollution reduce vitamin D synthesis.
• Aging. Vitamin D synthesis decreases with age, and by up to 70 percent by age 70.

Clothing. Skin exposure is needed for vitamin D synthesis.

If you have questions about vitamin D deficiency, toxicity, or intake, contact your primary care provider or schedule an appointment with a dietitian at intermountainhealth.org.

About Intermountain Health

Headquartered in Utah with locations in six states and additional operations across the western U.S., Intermountain Health is a nonprofit system of 34 hospitals, 400 clinics, medical groups with some 4,600 employed physicians and advanced care providers, a health plans division called Select Health with more than one million members, and other health services. Helping people live the healthiest lives possible, Intermountain is committed to improving community health and is widely recognized as a leader in transforming healthcare by using evidence-based best practices to consistently deliver high-quality outcomes at sustainable costs. For more information or updates, see https://intermountainhealthcare.org/news.