If you were out in the sunshine today you got a boost of vitamin d. But with shorter days and less sunshine during the fall and winter, you could develop a vitamin D deficient.
However, not everyone agrees on how much vitamin D you should be getting naturally and how much should come from supplements.
"It's harder than you would think to define what is enough vitamin D," says Dr. Ian De Boer, an epidemiologist with UW Medicine.
De Boer says doctors know vitamin D levels dip during the winter, but there's no evidence suggesting we need to prevent that dip.
Adding, the Institute of Medicine does not recommend routine vitamin D supplementation unless you have certain diseases. As a guide, he says everyone should get at least 600 units a day, either from food or sunshine.
You can get vitamin D from fish, egg yolks, milk and some fortified grains.
Vitamin D is essential for strong bones and teeth. It also helps with our immune system, mood and preventing osteoporosis, diabetes and kidney disease.
People with a vitamin D deficiency may be tired, have bone or muscle pain, or memory problems.
If you think you have a vitamin D deficiency, talk to your doctor.