Vitamin D
Vitamin D is the vitamin that lets the gut absorb calcium for bones. The skin makes it in sunlight, few foods contain much, and adults need 600 to 800 IU (15 to 20 mcg) a day, so supplements are a common source.
600-800 IUa day for adults, US RDA
200 IU on EU food labels (NRV), the figure behind label percentages
Upper limit · 4,000 IU (100 mcg) a day for adults, US and EFSA
- Most per 100 g 988IU Carp
- Most per portion 685IU 1 fillet salmon
- Main sources Sunlight and fatty fish then fortified milk, eggs and supplements
- Units 1 mcg = 40 IU divide IU by 40 to get mcg
Daily amount: the US RDA for adults aged 19 and over (NIH), 600 IU (15 mcg) up to age 70 and 800 IU (20 mcg) after; EFSA sets 15 mcg. Food figures per 100 g from USDA FoodData Central; fortified cereal and juice are left out of the ranking. The library's milk figure is for US milk with added vitamin D; unfortified milk has much less.
Foods High in Vitamin D
Ranked per 100 g, with what a usual portion gives, limited to 3 foods per category. Foods with a Caltide calorie page link to it.
C
Carp
2154 IU in 1 fillet
988IU / 100 g
E
Eel
1901 IU in 1 fillet
932IU / 100 g
T
Trout
713 IU in 1 small/regular fillet
792IU / 100 g
E
Egg yolk (pasteurized)
66 IU in 1 oz
231IU / 100 g
E
Egg yolk
37 IU in 1 egg
216IU / 100 g
P
Paneer
522 IU in 1 cup
212IU / 100 g
D
Duck fat
192IU / 100 g
L
Lard
192 IU in 1 cup
100IU / 100 g
E
Evaporated milk (2% fat)
202 IU in 1 cup
85.2IU / 100 g
E
Evaporated milk (skimmed)
202 IU in 1 cup
85.2IU / 100 g
E
Evaporated milk
202 IU in 1 cup
85.2IU / 100 g
D
Dry white cheese (queso seco)
22 IU in 1 piece
73.3IU / 100 g
Per 100 g vs. a Usual Portion
Why the food that ranks first per 100 g can give less in a real serving.
| Food | Usual portion | Per 100 g | Per portion |
|---|---|---|---|
| Salmon | 1 fillet (125 g) | 548IU | 685IU |
| Sardines | 1 can (92 g) | 192IU | 177IU |
| Cod | 1 fillet (180 g) | 48IU | 86IU |
| Tuna | 1 can (107 g) | 47IU | 50IU |
| Milk | 1 cup (236 g) | 45.4IU | 107IU |
| Egg | 1 egg (50 g) | 44.8IU | 22IU |
One salmon fillet gives 685 IU, more than the 600 IU most adults need. Few foods other than fatty fish come close, which is why diet alone rarely covers vitamin D for people who do not eat fish.
What Is Vitamin D?
Vitamin D works more like a hormone than most vitamins, and the body can make it. When UVB light hits the skin, a cholesterol-like compound turns into vitamin D3. The liver then converts it into 25-hydroxyvitamin D, the form a blood test measures, and the kidneys turn that into calcitriol, the active hormone.
What Vitamin D Does
Calcitriol tells the gut to absorb calcium and phosphate. Without enough vitamin D, the gut takes up only a small share of the calcium in food, and the body draws calcium out of bone to keep blood levels steady. In children this causes rickets, with soft, bent bones; in adults it causes osteomalacia, bone pain and muscle weakness. Vitamin D also plays a part in muscle function, the immune system and how cells grow.
Why Sunlight Is an Unreliable Source of Vitamin D
How much vitamin D skin makes changes with the angle of the sun. In winter, far from the equator, UVB rays are too weak and the skin makes little or none. Darker skin, older skin, clothing, glass, cloud and sunscreen all reduce it too. The US and EFSA set their daily amounts assuming minimal sun exposure, and UV exposure also raises skin cancer risk.
Vitamin D in a Day of Food Without Fish
One ordinary day built only from foods in the Caltide food library, in usual portions, with eggs and fortified milk but no fish. No supplements.
| Meal | Food | Amount | Vitamin D |
|---|---|---|---|
| Breakfast | Egg | 50g | 22IU |
| Breakfast | Milk | 236g | 107IU |
| Lunch | Ham | 60g | 17IU |
| Snack | Greek yogurt | 150g | 0IU |
| Dinner | Chicken breast | 135g | 0IU |
| Dinner | Potato | 200g | 0IU |
| Dinner | Butter | 14g | 2.2IU |
| Total | 148IU |
Against the 600 IU that the US and EFSA set for adults, this day reaches about 25%.
Most of it comes from the milk, which in the US has vitamin D added.
Who Is Most Likely to Be Low in Vitamin D
- Breastfed babiesbreast milk has little vitamin D, so the American Academy of Pediatrics advises 400 IU a day for them
- Older adults and people indoorsaging skin makes less, and people who are housebound get little sun
- People with darker skinmore melanin means less vitamin D made from the same sun
- Fat malabsorption or obesityCrohn's, celiac disease and gastric bypass cut absorption; body fat holds vitamin D away from the blood
Vitamin D Deficiency: Signs and Testing
What a long shortage does to bones, and how a blood test shows whether you have enough.
| nmol/L | ng/mL | What it means |
|---|---|---|
| Below 30 | Below 12 | At risk of deficiency |
| 30 to 49 | 12 to 19 | At risk of too little for some people |
| 50 or more | 20 or more | Adequate for bone and overall health in most people |
| Above 125 | Above 50 | Linked to possible harm, especially above 150 nmol/L (60 ng/mL) |
The test measures 25(OH)D, the form the liver makes from vitamin D, so it reflects what comes from food, supplements and sunlight together. To turn nmol/L into ng/mL, multiply by 0.4. Labs and expert groups do not all use the same cut-offs.
Vitamin D Supplements: Forms and IU to mcg
Supplements are also a source of vitamin D, and for many people the main one in winter. Labels give the dose in IU, mcg or both.
| IU | mcg | Against 600 IU a day |
|---|---|---|
| 400 | 10mcg | 67% |
| 1,000 | 25mcg | 167% |
| 2,000 | 50mcg | 333% |
| 4,000 | 100mcg | 667% |
Vitamin D in Caltide
- Logged automaticallyCaltide adds up the vitamin D in every food you log from the food library and shows it against the amount for your age and sex in the Nutrition tab.
- Supplements count tooAdd your vitamin D once with its dose as an ingredient. Each day you tick it off, it counts toward your total. Sunlight is not counted, because no app can measure what your skin makes.
Vitamin D Sources and References
The figures and claims on this page are checked against these sources. Food amounts come from USDA FoodData Central.
Questions About Vitamin D
Adults need 600 to 800 IU (15 to 20 mcg) a day: the US RDA is 600 IU up to age 70 and 800 IU after. EFSA sets 15 mcg (600 IU) for adults. EU food labels use a lower reference, 200 IU (5 mcg).
Divide by 40. 1 mcg of vitamin D is 40 IU, so 1,000 IU is 25 mcg and 4,000 IU, the adult upper limit, is 100 mcg.
Fatty fish. In the Caltide food library, carp has 988 IU per 100 g, then Eel (932 IU) and Trout (792 IU). A boiled egg has 44.8 IU, mostly in the yolk.
Sometimes. Skin makes vitamin D from the sun's UVB rays, but how much depends on season, latitude, time of day, cloud, skin color, age and sunscreen. In winter at high latitudes, the skin makes little or none, and experts have not agreed on an amount of sun that raises vitamin D without adding to skin cancer risk.
Both raise blood levels and both treat deficiency. Several studies found that D3 (cholecalciferol) raises blood levels more and keeps them up longer than the same dose of D2 (ergocalciferol), which is the form in UV-treated mushrooms and many vegan supplements.
Yes, from supplements. The adult upper limit is 4,000 IU (100 mcg) a day, set by both the US and EFSA. Far higher doses over time raise blood calcium, causing nausea, vomiting, muscle weakness, confusion and kidney stones. Sunlight cannot cause it, because the skin limits how much it makes.
The test measures 25-hydroxyvitamin D. The US National Academies consider 50 nmol/L (20 ng/mL) enough for bone health in most people, and below 30 nmol/L (12 ng/mL) a deficiency. Labs and experts do not all use the same cut-offs.
Only when they have been exposed to UV light. Ordinary mushrooms grown in the dark have very little, which is why the Caltide food library lists 0 IU for raw mushrooms. UV-treated ones, labeled as such, can have a lot of vitamin D2.
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