Vitamin D is often called the "sunshine vitamin" because your body can make it when your skin is exposed to sunlight. While it's best known for helping build strong bones, vitamin D plays other important roles in keeping you healthy. It affects several other systems in the body, from your immune system to your muscles and even your mood.
What does vitamin D do?
One of vitamin D's most important jobs is helping your body absorb calcium and phosphorus, minerals that are essential for strong bones and teeth. “Without enough vitamin D, your body can't properly use the calcium you get from food or supplements,” explains Jerome Rubbelke Jr., MD, Carilion Clinic Family Medicine.
But vitamin D does much more than affect bone health. It’s also involved in the body’s processes related to:
- Immune system
- Muscle function
- Mental health
- Nerve function
- Cell growth and repair
Are you getting enough?
Vitamin D deficiency is common. Some studies suggest that about 35% of adults in the U.S. have low vitamin D levels. You may be at higher risk for deficiency if you:
- Spend most of your time indoors
- Cover most of your skin when outside
- Have darker skin
- Are over age 65
- Have liver or kidney disease
- Are overweight or obese
- Are pregnant or breastfeeding
- Have certain digestive disorders like inflammatory bowel disease, Crohn's disease, ulcerative colitis, or celiac disease
- Take certain medications like steroids, antiseizure medicines, and antifungals
Signs of vitamin D deficiency
Many people with low vitamin D levels don't notice symptoms right away. When symptoms do occur, they can be subtle and easy to overlook. Possible signs of vitamin D deficiency include:
- Frequent illnesses or infections
- Fatigue or low energy
- Muscle weakness
- Bone pain or tenderness
- Back pain
- Mood changes, including feelings of depression
- Slow wound healing
“Because these symptoms can have many causes, a blood test is the only way to know for sure whether your vitamin D levels are low,” says Dr. Rubbelke.
Over time, vitamin D deficiency can lead to problems like osteoporosis, increased risk of falls and fractures, and softening of the bones.
Getting vitamin D from the sun
Your body can make vitamin D naturally when your skin is exposed to sunlight.
For many people, 10 – 15 minutes of sun exposure on unprotected skin several times per week can help maintain healthy vitamin D levels. But factors like season, cloud cover, and geographic location can affect how much vitamin D your body produces.
It's also important to balance sun exposure with skin protection. While sunlight helps the body make vitamin D, too much exposure increases the risk of skin damage and skin cancer.
Food sources of vitamin D
Few foods naturally contain vitamin D, but many are “fortified” with extra nutrients. Sources include:
- Fatty fish like salmon and tuna
- Egg yolks
- Fortified dairy products like milk and yogurt
- Fortified breakfast cereals
- Fortified juice
Should you take a supplement?
“Routine supplementation of vitamin D in adults is not recommended,” says Dr. Rubbelke. But for people with insufficient levels, supplements can help. “The Dietary Reference Intake for vitamin D is 600 IU per day for adults up to age 70 and 800 IU per day for adults over 70.”
It's best to talk with your care team before starting supplements. While rare, taking too much vitamin D can lead to a buildup of calcium in your blood and cause symptoms like frequent urination, nausea, vomiting, confusion, and kidney injury or failure.
If you have questions or symptoms of vitamin D deficiency, reach out to your primary care doctor.
