Vitamin D is one of the most commonly used supplements, popular among people with a deficiency or those who think they might have one. But what happens when you take vitamin D pills daily for a while? Here are three potential benefits—and one risk—to keep in mind.
If you’re not getting enough vitamin D through food or sun exposure, a daily vitamin D supplement may benefit your bones.
When you ingest vitamin D, your kidneys jump into action and transform it into calcitriol, the biologically active form of the vitamin. According to Stanford Medicine endocrinologist and internal medicine physician Marilyn Tan, MD, FACE, FACP, calcitriol then promotes calcium absorption from the intestines, which ultimately helps bones grow. Vitamin D also supports phosphorus absorption, which leads to bone mineral growth, she added.
If you aren’t deficient in vitamin D, however, taking extra vitamin D is unlikely to have a meaningful effect on bone health. A 2022 study found that healthy people who took vitamin D had no fewer fractures than those taking a placebo.
Another perk of taking vitamin D for those who don’t get enough: better oral health. Your teeth, like your bones, rely on calcium to grow, and vitamin D deficiencies have been linked to poorer oral health.
Wassim Diab, MD, FACP, MHA, an internist and the vice chair of the department of medicine at Northwell Health’s Staten Island University Hospital, said that vitamin D also helps maintain a healthy balance of minerals in the body, which promotes tooth mineralization.
Low levels of vitamin D can also throw you off balance. In addition to weakening bones, deficiencies are associated with “muscle pain and weakness, increasing the risk of falls and fractures,” Diab said.
Research suggests that increasing vitamin D levels can improve balance, strength, and gait in people with deficiencies.
While rare, there is such a thing as too much vitamin D. Ingesting excessive amounts can lead to hypercalcemia, a condition in which there is too much calcium in the blood. Symptoms include nausea, vomiting, abdominal pain, impaired cognition, and dehydration.
“Prolonged exposure can lead to serious complications, including kidney failure and potentially dangerous cardiac rhythm disturbances,” Diab said.
According to Tan, hypercalcemia is riskiest for people with chronic kidney disease, which can affect the kidneys’ ability to convert vitamin D to calcitriol, as well as those who have difficulty absorbing the vitamin. To promote absorption, she recommends taking the supplement, which is fat-soluble, with a fatty meal or snack.
For most people, however, especially those with a diagnosed deficiency, vitamin D is a low-risk supplement to take. “Moderate vitamin D supplementation under the guidance of a physician, including monitoring of kidney function, calcium levels, and vitamin D blood levels, is generally safe and beneficial,” Diab said.
A simple blood test can tell you if you’re deficient in vitamin D—something that’s surprisingly common. In the United States, about 41% of people don’t get enough of the essential vitamin.
For most people under 70, the recommended daily intake of vitamin D is 600 IU (15 mcg), which jumps to 800 IU (20 mcg) for older adults. It can be difficult to reach these goals because only a limited number of foods contain vitamin D or are fortified with it. Additionally, access to the sun’s rays, which trigger vitamin D production, isn’t always possible and comes with risks.
While vitamin D deficiencies are typically asymptomatic in adults, they may occasionally lead to fatigue, muscle pain or weakness, bone pain, and mood changes, Tan said. If you’re experiencing symptoms—or simply want to ensure your vitamin D needs are being met—talk to your doctor about getting tested.
