Last reviewed: July 2026

Vitamin D: food, sun, and supplements, an honest guide

EFSA sets an adequate vitamin D intake at 15 micrograms (600 IU) a day for adults, yet a landmark European analysis found about 40 percent of Europeans sit below the 50 nmol/L blood threshold. Vitamin D is the exception to food-first advice, and honest guidance says so plainly: very few foods contain meaningful amounts, skin synthesis shuts down in northern winters, and for many people a cheap supplement is the evidence-based answer. Food still matters at the margins, and knowing which foods carry vitamin D helps you judge how big your personal gap is.

Why food alone rarely gets you there

Vitamin D occurs naturally in quantity in exactly one food group: fatty fish. A 100 g portion of salmon carries roughly 10 to 20 micrograms in composition references, and canned salmon or sardines sit in a similar league at a fraction of the price. After fish, contributions fall off a cliff: eggs provide about 2 micrograms per 100 g (nearly all in the yolk), and whole milk only matters where it is fortified, adding around 1 microgram per 100 ml in countries that do so. A typical European diet without fatty fish delivers 2 to 4 micrograms a day against a 15 microgram reference. Two fish meals a week narrows the gap; it does not close it in winter.

Vitamin D values are typical figures from food composition references (NIH Office of Dietary Supplements); links go to real Dietly product labels for the macros.

The sun does the heavy lifting, seasonally

Skin makes vitamin D from UVB light, and in summer that pathway dwarfs diet: short, regular spells of midday sun on bare arms can generate more than any normal meal. But UVB is unforgiving about conditions. Above roughly 50 degrees latitude, which includes the Netherlands, the UK and Scandinavia, the winter sun is too low for synthesis from about October to March, whatever the weather. Sunscreen, covering clothing, indoor work, older skin and darker skin at high latitude all reduce production further. This seasonality is why blood levels in Europe drift down through winter and why deficiency surveys look worst in early spring.

When a supplement is the honest answer

• Northern winters, almost everyone. A daily 10 to 25 microgram supplement from October to March is standard advice in much of northern Europe and costs a few euros a year.
• Year-round for higher-risk groups. The Dutch Health Council explicitly advises supplements for older adults, people with darker skin, people who cover their skin and those who rarely get outside.
• Not megadoses. More is not better: the EFSA upper limit is 100 micrograms a day, and trials of intermittent very high doses have shown harm signals, including increased falls in older adults. Daily moderate doses are the well-tested pattern.
• Test if in doubt. A 25-hydroxyvitamin D blood test settles arguments; below 50 nmol/L is the common sufficiency threshold in Europe.

What vitamin D will and will not do

The proven core is bone and muscle: vitamin D enables calcium absorption, and correcting deficiency protects against rickets, osteomalacia and, with calcium, fracture risk in older adults. It works as a team with dietary calcium, which is why the calcium explainer is the natural companion to this page. Beyond bone, large trials such as VITAL found that supplementing people who are not deficient does not prevent cardiovascular disease or cancer overall. Fixing a deficiency is valuable; stacking extra on top of sufficiency is not. If you are auditing your diet more broadly, run your staples through Dietly search and set your energy frame with the calorie calculator.

Bottom line

Aim for 10 to 15 micrograms a day. Eat fatty fish once or twice a week if you can, count eggs and fortified dairy as small change, and treat sunlight as your main supplier from spring to autumn. In a northern winter, take the cheap daily supplement instead of pretending food will cover it. That is the whole honest story, and it is covered in one blood test if you want certainty. For where supplements fit in general, see do you need supplements if you eat well.