Sometimes called the “sunshine vitamin,” vitamin D is a fat-soluble vitamin that your skin produces when exposed to sunlight. It is available in some natural and fortified foods, as well as in supplement form.
What Does Vitamin D Do?
Vitamin D is a fat-soluble vitamin that is important for bone health and the proper functioning of the immune system. It is produced in the skin when it is exposed to ultraviolet B (UVB) radiation from the sun, and it can also be obtained from certain foods such as fatty fish, egg yolks, and fortified foods like milk and cereal.
Vitamin D’s main purpose is to regulate calcium and phosphate to keep your bones, teeth and muscles strong and healthy. A vitamin D deficiency can lead to rickets in children and osteomalacia—the softening of the bones—in adults. Meanwhile, preliminary research suggests getting enough vitamin D is associated with a lower risk of certain diseases, such as heart disease, type 2 diabetes and improved mental health.
Vitamin D plays a key role in calcium absorption and bone mineralization, the process in which bones are formed. When you have sufficient levels of vitamin D, you’re at a lower risk of developing stress fractures, Barbara Lewin, R.D.N., explains, because the vitamin optimizes your bone density.
Vitamin D: key facts
- Everyone is advised to take a vitamin D supplement containing at least 10 micrograms (400IU) a day during winter months, and those more at risk of deficiency should take it all year round.
- Don’t overdo it as vitamin D can build up in the body – 100mcg (4000IU) is the maximum safe daily dose for adults.
- Tablets are the cheapest option, particularly own-brand or generic versions.
- Gummies and chews are popular, but watch out for added sugar, and for high salt levels in soluble versions.
Vitamin D Health Benefits
Strong Bones and Muscles
Vitamin D helps regulate calcium and phosphate in the body, which are key to bone and muscle health. People who are deficient in it are at higher risk for developing osteoporosis, a condition in which bones become weak and brittle. Don’t forget your teeth are bones, too—so enough of the nutrient also means stronger teeth.
With that said, healthy midlife and older adults who aren’t deficient in vitamin D don’t necessarily benefit from supplementation, particularly in regards to minimizing bone fracture risk, according to a 2022 study in the New England Journal of Medicine.
Improved Immunity
There’s a lot of buzz around the role vitamin D may play in strengthening your immune system and preventing certain diseases like heart disease, type 2 diabetes and cancer. A large 2020 study by University of Chicago Medicine researchers even found a link between vitamin D deficiency and the likelihood of becoming infected with COVID-19.
But Dr. Marilyn Tan, an endocrinologist and clinical associate professor at Stanford Medicine who has studied vitamin D extensively, notes that the majority of the research around disease prevention (including COVID) is preliminary. “We think vitamin D plays some role in immunity, but it’s not a very clear and defined connection,” she says. “We know for sure that it has a role in preventing osteoporosis and bone loss, but that’s really it.”
Supported Mental Health
There is evidence to suggest that vitamin D may have a role in mental health. Low levels of vitamin D have been associated with an increased risk of depression, anxiety, and other mental health conditions.
Vitamin D plays a role in brain development and function. It may help regulate the production of neurotransmitters, such as serotonin, which play a role in mood. Vitamin D may also have an effect on inflammation in the body, which has been linked to mental health conditions.
However, it’s important to note that more research is needed to fully understand the relationship between vitamin D and mental health. While low levels of vitamin D may be a risk factor for mental health conditions, it is not a direct cause. If you are concerned about your mental health, it is important to speak with a healthcare provider.
Symptoms Of Vitamin D Deficiency
Vitamin D deficiency can cause a variety of symptoms, including:
- Fatigue and tiredness
- Bone and back pain
- Depression
- Impairment in physical performance
- Muscle weakness
- Hair loss
- Wounds that are slow to heal
- Bone loss
- An increased risk of infections
Foods With Lots Of Vitamin D
- Fatty fish: Salmon, mackerel, and sardines are all excellent sources of vitamin D.
- Cod liver oil: This oil is an extremely concentrated source of vitamin D.
- Egg yolks: The yolk of an egg contains small amounts of vitamin D.
- Cheese: Some types of cheese, such as Swiss and cheddar, contain small amounts of vitamin D.
- Mushrooms: Some varieties of mushrooms, such as maitake and shiitake, contain vitamin D.
- Fortified foods: Many foods are fortified with vitamin D, including milk, orange juice, and cereal.
