Fatty fish, fortified foods, and sunlight are the best sources of vitamin D, but most people don’t get enough from any single one. The recommended daily intake for adults up to age 70 is 600 IU (15 mcg), rising to 800 IU (20 mcg) after 70. Meeting that target usually takes a combination of food, sun exposure, and sometimes a supplement.
Fatty Fish and Other Whole Foods
Fatty fish are the richest natural food sources of vitamin D. A 3.5-ounce serving of sardines (about five small fish) delivers roughly 330 IU of vitamin D3, which covers more than half the daily target for most adults in a single portion. Salmon is another strong option, with wild-caught varieties generally providing more vitamin D than farmed. Mackerel, despite its reputation as a vitamin D powerhouse, actually comes in lower than you might expect: a 3.5-ounce serving contains about 82 IU, according to analysis from Boston University.
Beyond fish, the list of naturally vitamin D-rich foods is short. Egg yolks contain small amounts, typically 40 to 50 IU per yolk, with the exact number depending on what the hens were fed. Beef liver provides a modest amount as well. Certain mushrooms, especially those exposed to UV light during growing, contain vitamin D2 (a slightly less potent form than the D3 found in animal foods). Some grocery stores now sell UV-treated mushrooms labeled with their vitamin D content.
Vitamin D is fat-soluble, meaning your body absorbs it much better when you eat it alongside some dietary fat. This isn’t usually a concern with fatty fish or eggs, since they already contain fat. But if you’re taking a supplement or eating a fortified cereal, pairing it with a meal that includes some fat (avocado, nuts, olive oil, butter) will help you absorb more of it.
Fortified Foods
Because so few foods are naturally rich in vitamin D, fortification fills a major gap. In the United States, cow’s milk, many plant-based milks (soy, almond, oat), breakfast cereals, orange juice, and margarine are commonly fortified with vitamin D. A typical cup of fortified milk provides around 100 to 120 IU. Fortified cereals and orange juice usually fall in the same range per serving, though amounts vary by brand, so checking the nutrition label is worthwhile.
In the UK, fortification is voluntary rather than mandatory, so fewer products carry added vitamin D. Fat spreads and some breakfast cereals are the most common fortified options there. If you live somewhere without widespread fortification, you’ll need to rely more heavily on fish, sunlight, or supplements to hit your daily target.
Sunlight and Skin Production
Your skin manufactures vitamin D3 when ultraviolet B (UVB) rays hit it directly. For many people, this is actually the largest single source of vitamin D, at least during warmer months. Exposing your bare arms and legs to midday sun (between 10 a.m. and 3 p.m.) for 5 to 30 minutes, twice a week, can be enough to meet your vitamin D needs.
That wide range exists because skin pigmentation matters enormously. Melanin, the pigment that gives darker skin its color, acts as a natural sunscreen. People with dark skin may need up to ten times longer in the sun to produce the same amount of vitamin D as someone with fair skin. Season and latitude also play a role: if you live above about 37 degrees north (roughly the latitude of San Francisco or Athens), UVB rays are too weak during winter months to trigger meaningful vitamin D production, no matter how long you stay outside.
Sunscreen, clothing, window glass, and cloud cover all block UVB as well. This doesn’t mean you should skip sun protection. Rather, it helps explain why so many people end up with low vitamin D levels despite spending time outdoors.
How Much You Actually Need
The recommended daily allowance set by the NIH is straightforward for most of the population:
- Infants (0 to 12 months): 400 IU (10 mcg)
- Children and adults (1 to 70 years): 600 IU (15 mcg)
- Adults over 70: 800 IU (20 mcg)
- Pregnant and lactating women: 600 IU (15 mcg)
These numbers are set to maintain bone health and normal calcium metabolism. Some researchers and clinicians argue that optimal levels, especially for immune function and muscle strength, may require higher intake, but the official recommendations haven’t changed to reflect that position.
Checking Your Levels
A simple blood test measures your vitamin D status. The test looks at a form called 25-hydroxy vitamin D, which reflects both what you get from food and what your skin produces. Most experts consider a level between 20 and 40 ng/mL sufficient, though some recommend aiming for 30 to 50 ng/mL. Below 20 ng/mL is generally considered deficient, and below 12 ng/mL indicates severe deficiency that raises the risk of bone softening and weakness.
If you spend most of your time indoors, live at a northern latitude, have darker skin, or eat very little fish and fortified dairy, testing is a practical way to find out whether your current routine is working before committing to a supplement.
Supplements: D2 vs. D3
When food and sunlight aren’t enough, supplements are a reliable fallback. You’ll see two forms on store shelves: vitamin D2 (ergocalciferol, derived from plants or fungi) and vitamin D3 (cholecalciferol, the same form your skin makes). D3 raises blood levels more effectively and sustains them longer, so it’s the preferred choice for most people.
Supplements come in doses ranging from 400 IU to 5,000 IU or more per capsule. For adults, the tolerable upper intake level is 4,000 IU per day. Going significantly above that for extended periods can cause calcium to build up in the blood, leading to nausea, kidney problems, and other complications. Most people do well with a daily supplement of 1,000 to 2,000 IU during months when sun exposure is limited, but the right dose depends on your starting blood level and how much you’re getting from food.
Putting It Together
A realistic vitamin D strategy for most people looks something like this: eat fatty fish once or twice a week, choose fortified milk or plant milk with meals, and get moderate sun exposure when the season allows. During fall and winter (or year-round if you have limited sun exposure), a D3 supplement bridges the gap. Because the vitamin is fat-soluble, take it with your largest meal of the day for the best absorption.