Vitamin D is less a food than a weather report. Skin makes it from UVB, and above about 50 degrees north, which is all of Scandinavia, the whole of the British Isles and most of northern Europe, the sun sits too low from October to March for any to be made at all. Omnivores lean on oily fish, eggs and fortified dairy to bridge the dark months; a vegan plate has almost nothing to bridge with. Vegans in the largest European comparison sat lowest of every group in blood vitamin D. The fix is the cheapest on this site and the one with the most predictable blood test.
The signs vitamin D is low
- Bone and low-back ache, a deep tiredness in the thighs, tender shins when pressed.
- Muscle weakness and slower recovery; more colds than the rest of the household.
- Low mood through the dark months that lifts in May.
- Hair shedding; slow wound healing.
- In the longer run, bone density loss, which you will not feel until it matters.
The test, and what the number means
The test is 25-hydroxyvitamin D, 25(OH)D, a simple blood draw or finger prick.
| 25(OH)D | Meaning |
|---|---|
| below 30 nmol/L (12 ng/mL) | deficient; bones are affected |
| 30 to 50 nmol/L (12 to 20 ng/mL) | insufficient; most tired vegans in March are here |
| 50 nmol/L (20 ng/mL) and above | adequate by EFSA, the US Institute of Medicine and most authorities |
| 75 nmol/L (30 ng/mL) and above | the level many clinicians prefer for bone and muscle |
| above 250 nmol/L | too high; only reached by heavy supplementing |
Test in late winter, February or March, when the level is at its lowest. A good summer number tells you nothing about March.
How much you need
| Reference | Amount |
|---|---|
| EFSA adequate intake, adults | 15 µg a day (600 IU) |
| US RDA, adults to 70 | 15 µg a day (600 IU); 20 µg (800 IU) after 70 |
| Tolerable upper intake | 100 µg a day (4,000 IU) |
Those figures assume minimal sun. From a vegan plate without supplements, a typical intake is 1 to 3 µg a day. The arithmetic does the rest.
Vegan vitamin D foods, per serving
| Food | Serving | Vitamin D |
|---|---|---|
| UV-exposed mushrooms (label says “vitamin D” or “UV-treated”) | 100 g | 5 to 10 µg as D2, variable |
| Mushrooms you lay gill-side up in midday summer sun for an hour | 100 g | several µg; a real trick, not a plan |
| Fortified soy or oat milk | 250 ml | 1.9 to 3.8 µg (0.75 to 1.5 µg per 100 ml) |
| Fortified margarine | 10 g | 0.8 to 1 µg |
| Fortified breakfast cereal | 40 g | 1.5 to 4 µg |
| Fortified orange juice | 250 ml | about 2.5 µg where sold |
| Everything else on a plant-based plate | any | none |
Even a diligent day of fortified foods reaches perhaps 8 µg. Sun from April to September, 15 to 25 minutes of midday sun on forearms and face a few times a week, fills the rest in summer. In winter, nothing fills it but a supplement.
The supplement: vegan D3
- Form: D3 (cholecalciferol) from lichen is vegan and raises blood levels more reliably than D2 from mushrooms or yeast. Most “vegan D3” on the shelf is lichen-derived; the label will say.
- Maintenance: 25 µg (1,000 IU) a day from October to March; many clinicians now advise it year-round in the north, and there is no harm in that at this dose.
- If tested below 50 nmol/L: 50 µg (2,000 IU) a day for twelve weeks, then back to 25 µg, and retest.
- If tested below 30 nmol/L: 75 to 100 µg (3,000 to 4,000 IU) a day for eight to twelve weeks under a clinician’s eye, then maintenance.
- Take it with a meal containing fat; it is fat-soluble and absorbs poorly on an empty stomach. Morning or evening makes no difference.
- Pair it with enough calcium from food (fortified milk, tofu set with calcium, kale, tahini) and, if your plate is low in greens, a little vitamin K2 from natto or a supplement; both are what vitamin D sends calcium toward.
Do not take more than 100 µg a day for months without a test. Vitamin D is the one on this list where more is not better.
The one-week fix
- Buy vegan D3, 25 µg. Put it with the B12 by the kettle; same alarms.
- If it is between October and March and you have not had a test in a year, start at 50 µg for twelve weeks, then drop to 25.
- Switch to a milk fortified with vitamin D and calcium; the carton will say both.
- Book 25(OH)D for twelve weeks out. When it comes back over 50 nmol/L, you have your maintenance dose for life.
What the research says
- Crowe and colleagues, Public Health Nutrition, 2011, cross-section of 2,107 British adults aged 20 to 76 in EPIC-Oxford, 89 of them vegan, with season recorded: in this study mean plasma 25(OH)D was lowest in vegans at 55.8 nmol/L and highest in meat eaters at 77.0 nmol/L. The contrary finding: the gap narrowed with supplement use and in summer, and the vegan mean stayed above the 50 nmol/L level most authorities use for adequacy. doi.org/10.1017/S1368980010002454
The mean hides the March. Vegans who supplemented in that cohort looked like everyone else; the ones who did not carried the winter in their bones.
Questions women ask
Do I need vitamin D if I am outside every day? From April to September above 50°N, probably not. From October to March, yes, however much you are outside; the sun is too low.
D2 or D3? D3. It raises and holds blood levels better; lichen D3 is vegan.
How long before I feel it? Bone ache and mood often shift within four to six weeks at a correcting dose; the blood test takes twelve weeks to settle.