There are three ways to get vitamin D: your skin makes it in sunlight, a short list of foods contain it, and supplements supply it. Each has limits, and which one matters most for you depends on where you live, the time of year, your skin and your diet.
Why does it matter where your vitamin D comes from?
Vitamin D helps you absorb calcium and keeps bones, muscles and the immune system working normally; our guide to what vitamin D does covers the details. Low levels are common. Using a cutoff of 20 ng/mL, an analysis of 2005-2006 national survey data found that about 42% of US adults fell short, and a later CDC analysis of 2011-2014 data found 5% of Americans at risk of deficiency and another 18% at risk of inadequacy.
How much vitamin D can you get from the sun?
When UVB light hits bare skin, your skin makes vitamin D3. How much depends on season, time of day, latitude, skin pigmentation, age and whether the light comes through glass, which blocks UVB entirely. Above roughly 33 degrees latitude, which takes in most of the continental US north of Atlanta or Los Angeles, the winter sun is too low for the skin to make much vitamin D at all.
- Skin tone. Melanin filters UVB, so darker skin needs considerably more sun to make the same amount of vitamin D.
- Age. Older skin has less of the vitamin D precursor, and aging can more than halve the skin's capacity to make it.
- Sunscreen. Sunscreen blocks UVB in the lab, but in real-life use studies have found little evidence that it lowers vitamin D levels. Keep wearing it.
Some experts suggest a few minutes of midday sun on the face, arms or legs is enough for many people, but the amount varies greatly from person to person, and more than a few minutes without sunscreen is not recommended because of skin cancer risk.
Which foods contain vitamin D?
Very few foods contain much vitamin D naturally. Fatty fish such as salmon, tuna and mackerel are the best sources; beef liver, cheese and egg yolks provide small amounts; and mushrooms provide some, more if they have been exposed to UV light. Most US milk is fortified with 400 IU per quart, and vitamin D is added to many breakfast cereals and some soy drinks, orange juice, yogurt and spreads, according to MedlinePlus.
Vegan food sources
If you eat no animal products, your food options are UV-exposed mushrooms and fortified foods such as plant milks and cereals. Mushrooms make vitamin D2, and fortified foods may use either D2 or D3, so check the label. The form can matter: in a 12-week winter trial at the University of Surrey, vitamin D3 raised blood levels more than the same daily amount of D2.
When does a vitamin D supplement make sense?
A supplement is the simplest option when sun and food fall short, such as in winter, for people who spend most of the day indoors, for older adults, for people with darker skin and for vegans. The 2024 Endocrine Society guideline suggests vitamin D supplements for children and teens, adults over 75, pregnant people and adults with high-risk prediabetes, and advises against routine blood testing for people without a medical reason for it.
Most adults need 600 IU (15 mcg) a day, or 800 IU (20 mcg) after age 70, and the upper limit for adults is 4,000 IU (100 mcg) a day. Our article on vitamin D deficiency symptoms explains when a test is worth asking your doctor about.
What to look for in a vitamin D supplement
- The form. Look for vitamin D3, which raises blood levels more reliably than D2.
- The dose. Count what you already get from food and other supplements, and know the reference points: the RDA above and the 4,000 IU adult upper limit.
- The source. Most D3 is made from lanolin, the oil in sheep's wool. If you avoid animal products, look for D3 from lichen; we explain the difference in why take vegan vitamin D.
- Testing. Look for a brand that publishes how its products are tested; here is how Ora tests its supplements.
Our Sol Food tablets give you 2,000 IU of vitamin D3 from lichen in one small organic, vegan tablet. Vitamin D is fat-soluble, so take it with a meal that contains some fat; when to take vitamin D covers timing. If you are pregnant, have kidney disease or take prescription medicines, check with your doctor first.
