Made & designed in Sweden.“Vitamin D” on a label can mean two different molecules: vitamin D2 or vitamin D3. They are close relatives, both are allowed in EU food supplements, and both are turned into the same compound in the body. But they come from different places — and the research suggests they don’t perform quite the same.
Two forms, two origins
| Vitamin D2 | Vitamin D3 | |
|---|---|---|
| Chemical name | Ergocalciferol | Cholecalciferol |
| Made by | Fungi and yeast exposed to UV light | Human skin in sunlight; animals |
| Found in food | UV-treated mushrooms, some fortified foods | Fatty fish, egg yolks, fortified foods |
| Supplement sources | UV-treated yeast | Lanolin (sheep’s wool), lichen or algae |
What happens in the body
Both D2 and D3 are converted in the liver to 25-hydroxyvitamin D, the form measured in blood tests, and then in the kidneys to the active hormone. The question is how efficiently each form raises and maintains 25-hydroxyvitamin D levels.
What the research says
A systematic review and meta-analysis of randomised trials found that vitamin D3 was more effective than D2 at raising blood levels of 25-hydroxyvitamin D. The difference was clearest when vitamin D was given in large, infrequent doses; with daily dosing the gap was smaller.
That is one reason D3 has become the default in most supplements. D2 still remains a recognised source of vitamin D, and it is common in plant-based fortified products.
Plant-based D3: from lichen and algae
For a long time, D3 for supplements came almost entirely from lanolin, the grease in sheep’s wool. People who avoid animal products therefore had to choose D2. That has changed: vitamin D3 can now also be produced from lichen and from microalgae, giving a non-animal source of D3.
Why vitamin D matters more in the north
The skin makes vitamin D3 from UVB light. In Sweden and the rest of the Nordics, the sun is too low from roughly October to March for the skin to produce any meaningful amount. That makes food and supplements the main sources for half the year.
The Swedish Food Agency recommends 10 µg of vitamin D per day for most adults and 20 µg for people aged 75 and over. EFSA has set the tolerable upper intake level for adults at 100 µg per day.
Reading µg and IU
Vitamin D is measured in micrograms (µg) on EU labels, but you will often see international units (IU) as well. The conversion is simple: 1 µg = 40 IU. So 10 µg is 400 IU, and 25 µg is 1000 IU.
What the EU allows anyone to say about vitamin D
- Contributes to normal absorption/utilisation of calcium and phosphorus
- Contributes to normal blood calcium levels
- Contributes to the maintenance of normal bones
- Contributes to the maintenance of normal muscle function
- Contributes to the maintenance of normal teeth
- Contributes to the normal function of the immune system
- Has a role in the process of cell division
Sources
- Tripkovic L et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012;95(6):1357–1364
- NIH Office of Dietary Supplements — Vitamin D fact sheet for health professionals
- Livsmedelsverket (Swedish Food Agency) — Vitamin D (in Swedish)
- EFSA NDA Panel. Update of the tolerable upper intake level for vitamin D. EFSA Journal 2023;21(8):8145
- European Commission — EU Register of nutrition and health claims
This article is general information about nutrition and is not medical advice. Food supplements should not be used as a substitute for a varied diet and a healthy lifestyle. If you have a medical condition, are pregnant or take medication, talk to your doctor before taking supplements.
