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by Sonya Collins
Updated May 4, 2023
Vitamin D is probably best known for its role in bone health. You need it to keep your bones strong. That’s because vitamin D helps your body absorb calcium — the foundation of strong, healthy bones. Vitamin D has a lot of other pretty important jobs. Muscles can’t move without it, and nerves need it to relay messages from the brain to the rest of the body and back. Your immune system can’t function without it, either. The powerful vitamin helps ward off harmful viruses and bacteria when they invade.
You can get vitamin D from some foods, including fatty fish such as salmon, tuna and mackerel. In smaller quantities, you’ll get it from beef liver, cheese and eggs. But these aren’t enough to give adults the 600-800 international units (IU) of vitamin D they need every day. That’s why food manufacturers add it to most cow’s milk, many cereals and some orange juice, yogurt and nondairy milks, such as soy and almond.
Your skin makes vitamin D when you expose it to direct sunlight — that is, without sunscreen and not through a window. You’ve got to be outdoors on a sunny day with uncovered skin. Given concerns about skin cancer, Americans don’t get a lot of direct sun exposure. But many doctors recommend that people over 50 get 15 minutes three times a week on uncovered arms and legs. For those who live in places with long, dark winters, following this recommendation can be difficult.
Though supplements will help your body meet its daily vitamin D needs, there’s not enough evidence that they would have an impact on your brain health. That was the conclusion of a 2019 report from the Global Council on Brain Health, "The Real Deal on Brain Health Supplements."
Some studies, though not all of them, suggest a possible connection between low levels of vitamin D and memory problems or dementia. A recent study of 12,388 older adults compared those who took vitamin D supplements with those who did not over 10 years. The supplement group had 40 percent fewer dementia diagnoses, as reported in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring. Before doctors recommend any new habit however, such as taking a vitamin pill, they must see repeated studies that include large groups of people and get the same results again and again. Researchers haven’t produced that level of support for taking vitamin D to help the brain.
Doctors often recommend vitamin D supplements to prevent osteoporosis in postmenopausal women, who have an inherent increased risk for brittle bones. Health care providers may also recommend supplements to people who have a diagnosed vitamin D deficiency. The only way to know for sure if you lack healthy levels of the vitamin is through a blood test. Older people, those with dark skin, people who are obese and people who don’t get sun exposure are at increased risk.