Seasonwise, for instance, winter is typically a time to be more concerned about potentially low vitamin D levels, says Dr. Shapses. Yet it also depends on where you live—generally speaking, the farther you live from the equator, the less sun you get year-round, says Spence. In one study published in the Journal of the American Academy of Dermatology in 2010, for instance, a person with a medium skin tone could produce 400 international units (IU) of vitamin D by spending three to eight minutes in the sun at noon in Boston between April and October. They could make the same amount in three to six minutes in Miami no matter the month.
Another factor is skin color. Again, people with naturally darker skin tones produce less vitamin D thanks to the melanin in their skin that scatters UV rays. (That said, it’s not totally clear whether lower vitamin D levels, which are more common in Black people, negatively impact their health, the ODS explains. Either way, there aren’t different recommendations for sun exposure based on your skin color.)
Beyond that, we all know that sun exposure comes with a cost—it increases our risk of skin cancer, the most common cancer in the U.S. That’s why sunscreen is a must when you go outside. It shouldn’t interfere with the process: People typically don’t actually put enough sunscreen over all exposed areas to totally shield the skin from the vitamin D–producing rays in sunlight, according to the ODS. So by all means, enjoy your time in the sun and soak up that vitamin D—but stay safe, protect your skin, and keep on slathering on that SPF (minimum SPF 30). And instead of depending solely on the sun, look to your diet to help you hit your vitamin D levels.
While your body makes some vitamin D from sunlight, you need the nutrient in your diet too, Spence says. The recommended daily allowance (RDA) for vitamin D—which is calculated on the assumption that people are getting minimal sun exposure—is 600 IU of vitamin D per day for everyone from the ages of 1 to 70, according to the ODS. (We’ll give a few examples below to help you gauge what that amount actually looks like.)
The thing is, vitamin D doesn’t occur naturally in very many foods, according to the ODS; the best natural sources of vitamin are fatty fish, like trout, salmon, tuna, and mackerel. (Yet another reason to eat the two servings of fatty fish per week recommended for heart health, says Dr. Shapses.) For example, cooked pink salmon has 647 IU of vitamin D per half fillet, according to the USDA.
Some animal products, like cheese, egg yolks, and fatty meats, also have small amounts of vitamin D. For example, you can find 88 IU of vitamin D in a three-ounce serving of braised pork spareribs and 44 IU in a large hard-boiled egg, according to the USDA.
Another good source is some varieties of mushrooms, which are sometimes even treated with UV light to produce more vitamin D, according to the ODS. According to the USDA, morel, chanterelle, maitake, and UV-treated portabella mushrooms tend to contain the most vitamin D, although levels vary based on growing and storage conditions. For instance, chanterelle mushrooms have about 114 IU per cup, according to the USDA.
Most of the vitamin D in the American diet, though, comes from foods that are fortified with vitamin D. Almost all dairy milk sold in the U.S. is fortified with vitamin D, according to the ODS. (You can get 117 IU per cup of 1% milk with added vitamin D, for example.) Yogurt, plant-based milks (like soy, almond, or oat milk), cereal, and orange juice are also commonly fortified. For example, Cheerios have 60 IU of vitamin D in each 1.5-cup serving. Adding more of these foods that are naturally rich in vitamin D or fortified with it can help increase your vitamin D intake.
It’s possible to get enough vitamin D in your diet, but it’s not always easy. “If people aren’t eating a variety of foods, especially cereals, milks, yogurt, and fish, then a supplement might be needed,” says Spence.