Two forms of vitamin D work for a vegetarian diet: D2 of fungal origin and D3 extracted from lichen. Both work, with one difference measured by meta-analysis: at the same daily dose, D3 raises total serum 25-hydroxyvitamin D by roughly 10.4 nmol/L more than D2, a gap of 40 % in D3’s favour according to a systematic review in Advances in Nutrition covering twenty comparative studies.

That gap is real and measurable, and it does not mean D2 is useless. What it implies, and what the large clinical trials have shown since, takes up the rest of this article. The short answer for anyone in a hurry: take whatever you can get in winter, at a sensible dose, and do not expect vitamin D to fix your mood or your winter infections.

Why the question arises in Switzerland

The Swiss dietary recommendations, in their long version updated in February 2026, are clear on one point: a diet following the food pyramid covers nutrient needs with two exceptions. Those exceptions are iodine and vitamin D, because both occur in food only in very small amounts. For iodine, the Swiss answer is iodised salt. For vitamin D, the text points to skin synthesis: a short but regular period outdoors, about ten minutes a day in summer.

That official wording rewards careful reading, because it already contains the whole problem. Ten minutes a day, in summer. Nothing is said about the months when solar intensity is not enough, and those are exactly the months when the supplement question comes up.

The mechanism is well understood: vitamin D3 forms in the skin from a cholesterol precursor under UVB. UVB intensity depends on the sun’s angle. At Swiss latitudes, as across northern and central Europe, that angle is too low for several winter months for the reaction to happen in useful quantity, no matter how long you stay outside. The UK NHS puts the same fact in calendar terms: from late March or early April to the end of September most people make all they need; from October to early March they do not.

The practical consequence is that the question is not “do vegetarians need a supplement” but “does anyone need one in winter”, which concerns the whole population. Vegetarianism does not create the need, it just narrows which forms are available to you.

That distinction is worth holding onto, because it separates vitamin D from the nutrients genuinely tied to the diet. Vitamin B12 is a shortfall specific to plant-based eating, iodine depends mostly on the salt you use, and long-chain omega-3s raise a question about where the source comes from. Vitamin D depends on latitude and the calendar.

What food actually delivers

The figures from the Swiss food composition database make the case quickly. Here is what the foods usually cited as vitamin D sources, and available to a vegetarian, contain per 100 g.

Food	Vitamin D (µg/100 g)
Raw egg yolk	5.6
Whole hard-boiled egg	2.9
Button mushroom, steamed	2.3
Button mushroom, raw	1.9
Salted butter	1.1
Oat drink fortified with calcium and vitamins	0.9
Tinned button mushroom	0

The reference point for reading that table is the NHS daily intake: 10 µg a day for children from age one and for adults, where 1 µg equals 40 international units, so 10 µg comes to 400 IU.

Reaching 10 µg from those foods means roughly two egg yolks a day, or more than a litre of fortified plant drink, or half a kilo of mushrooms. For a vegan, who rules out egg and butter, only fortified products and mushrooms remain. This is not a matter of willpower or planning: vitamin D simply is not present in ordinary food in sufficient quantity, and the federal document says as much itself.

Note the tinned mushroom line at zero. That is not a data-entry error but a useful reminder: mushroom vitamin D2 comes from ergosterol converted by UV, and a mushroom that has never seen light contains almost none. Our piece on boosting vitamin D when the sun is lacking covers the seasonal habits.

To spot fortified products, the nutrition declaration is the only reliable place to look: a fortified plant milk lists the vitamin D content and the percentage of the reference value, an unfortified one lists nothing. Our guide to reading a food label explains where to find that line.

D2 and D3: what the comparison really shows

This is the question that shapes the plant-supplement market, and it deserves better than a slogan.

D2, or ergocalciferol, comes from UV-exposed mushrooms and yeasts. D3, or cholecalciferol, has historically been extracted from lanolin, meaning sheep’s wool grease, which makes it non-vegan. For about fifteen years, producers have extracted D3 from lichens, giving a D3 with no animal material.

On comparative efficacy, two recent meta-analyses agree. The 2024 one in Advances in Nutrition cited above finds, across twelve daily-dosing comparisons analysed by liquid chromatography with tandem mass spectrometry, a weighted mean difference of 10.39 nmol/L, 95 % confidence interval -14.62 to -6.16, against D2. A review in Nutrients covering 1277 participants from 24 studies finds a difference of 15.69 nmol/L in D3’s favour, plus a better effect on parathyroid hormone.

Both add the same decisive nuance, and it is the one people forget to quote. D2 and D3 each raise their own corresponding hydroxylated form to a comparable degree: D2 raises 25(OH)D2, D3 raises 25(OH)D3. The difference shows up in the measured total, and it comes partly from D2’s shorter half-life in blood and from how clinical assays count the two forms. The Nutrients review also observes, by meta-regression, that the gap between the two narrows at lower doses.

Plainly put: lichen D3 is the more direct choice if you want to raise a measured level. D2 works too, especially taken daily and at a moderate dose, and the American Journal of Clinical Nutrition review that opened this debate in 2012 already reached the same ranking without ever concluding that D2 was ineffective.

The 2012 review adds a point the two recent papers indirectly confirm: D3’s advantage was clear when both forms were given as a spaced bolus dose, and it disappeared with daily supplementation. That is the opposite of the usual reading, which turns a gap seen mainly in bolus regimens into a permanent superiority of D3.

The 2024 meta-analysis flags one more factor rarely mentioned on packaging: body mass index. Its authors recommend taking it into account, alongside baseline level, when comparing the effect of D2 and D3, the information being available in only thirteen of the seventeen daily-dosing comparisons. Since vitamin D is fat-soluble and stored in adipose tissue, the same dose does not produce the same blood concentration in two people of different build.

One detail matters if you get your level tested: some laboratories measure total 25(OH)D, others only 25(OH)D3. If you take D2 and the laboratory measures only D3, your result will look artificially low. It is worth asking which method is used.

The doses, and where they come from

The reference figures differ between countries, which often confuses people. Here are the main ones, with their source.

The NHS recommends 10 µg, or 400 IU, a day for adults and children from age one, including during pregnancy and breastfeeding, and advises everyone to consider a supplement during autumn and winter. For babies up to one year the range is 8.5 to 10 µg a day. Children aged 1 to 4 fall under a separate rule: 10 µg a day all year, not only in the dark months. People at risk, including those who rarely go outside, live in an institution, cover up extensively or have dark skin, are advised to supplement year-round.

The upper limit is framed the same way, and it steps down with age. The NHS says not to exceed 100 µg, or 4000 IU, a day for adults including during pregnancy and breastfeeding, and for young people aged 11 to 17. For children aged 1 to 10 the ceiling drops to 50 µg, or 2000 IU. For infants under twelve months it is 25 µg, or 1000 IU. Those three thresholds are often lost on family supplement labels, which offer the same capsule to the whole household.

On the Swiss side, the federal ordinance on adding vitamins and minerals to foodstuffs sets a different but instructive frame. Its Annex 1 caps added vitamin D at 23 µg per daily ration in fortified foods. Its Annex 5 lists the permitted forms, and there are exactly two: vitamin D3 or cholecalciferol, and vitamin D2 or ergocalciferol. The two vegetarian-compatible forms discussed here therefore stand on equal legal footing in Switzerland.

That 23 µg ceiling does not apply to food supplements sold as such, which fall under a different regime, but it gives a sense of what the legislator considers a reasonable amount in an everyday food.

Between 10 µg as a baseline intake and 100 µg as an upper limit there is a lot of room, and that is where supplement marketing sets up shop. Products at 2000, 4000 and even 10 000 IU per capsule exist. Before picking a high dose it is worth knowing what those doses actually produce, and that is where the large clinical trials change the conversation.

What the large trials actually found

Until the 2020s, the vitamin D literature rested largely on observational studies: people with low levels fared worse on all sorts of measures. The weakness of that design is well known: a low level can be the consequence of poor health, less time outdoors or excess weight, rather than its cause. Three large randomised trials have since tested the hypothesis directly.

On fractures

The VITAL trial randomised 25,871 American adults, men aged 50 and over and women aged 55 and over, to 2000 IU of vitamin D3 daily or placebo, with a median follow-up of 5.3 years. On the fracture endpoint, published in the New England Journal of Medicine, 1991 fractures were confirmed in 1551 participants. Vitamin D had no significant effect: hazard ratio 0.98 for total fractures, 0.97 for non-vertebral fractures and 1.01 for hip fractures. No modification of the effect appeared by age, sex, body mass index or baseline 25-hydroxyvitamin D.

The crucial point sits in the recruitment criteria: participants were not selected for deficiency, low bone mass or osteoporosis. The result therefore says something precise and nothing more: adding vitamin D to generally well-supplied adults does not reduce their fractures. It does not say that a genuinely deficient person gains nothing from correcting that deficiency.

On mood

The VITAL-DEP arm, published in JAMA, followed 18,353 participants aged 50 and over for a median treatment duration of 5.3 years. The result is unambiguous: 609 depression events in the vitamin D group against 625 on placebo, hazard ratio 0.97. Change in the PHQ-8 mood score did not differ either, with a mean difference of 0.01 points against a clinically meaningful threshold set in advance at 0.5 points. The authors conclude that these findings do not support using vitamin D3 in adults to prevent depression.

This is the most important correction to the usual talk about vitamin D and mood. The association between low levels and low mood exists in observational data. The randomised trial that tests it directly finds no effect.

On respiratory infections

Here the picture has shifted most interestingly, because the answer changed recently. A 2021 meta-analysis of 37 randomised trials found a statistically significant protective effect, odds ratio 0.92 with a confidence interval of 0.86 to 0.99. An update published in 2025 in The Lancet Diabetes & Endocrinology added six new trials, one of them with 15,804 participants, reaching 40 studies and 61,589 participants.

The new result is an odds ratio of 0.94, confidence interval 0.88 to 1.00, with p at 0.057. The authors say it plainly: the point estimate is close to the previous one, but the confidence interval now includes 1.00, meaning there is no longer statistically significant protection. Pre-specified subgroup analyses found no effect modification by age, baseline vitamin D status, dosing frequency or dose size. The analysis also revealed funnel plot asymmetry, which points to publication bias in the earlier literature.

Three lessons come out of these three trials. First, taking vitamin D in winter remains reasonable at Swiss latitudes, for the simple reason that skin synthesis stops. Second, pushing the dose above official reference figures has no support in these data: the dose-size analyses show no gradient. Third, none of the three reported a worrying safety signal at the doses tested, with the 2025 meta-analysis finding no difference in the proportion of participants with at least one serious adverse event, odds ratio 0.96.

How to read a supplement label

Here is what to check on a bottle, in order of importance.

The origin of the molecule. If the label says “vitamin D3” with no further detail, the industry default source is still lanolin. A plant D3 is labelled as coming from lichen, often with the genus name Cladonia, and the producer highlights it because it is a selling point. When in doubt, the absence of a mention is a bad sign. D2 comes by construction from mushroom or yeast and does not raise the question.

The shell. This is the most commonly missed detail. A conventional softgel is made of gelatin, so animal-derived, including when it contains lichen D3. The alternatives are hydroxypropyl methylcellulose capsules, tablets, drops and sprays. A product can be entirely plant-based in its active molecule and animal-derived in its shell.

The fat carrier. Vitamin D is fat-soluble. Drops are suspended in an oil, often sunflower, coconut or olive, which is an advantage: the fat is already there. For a dry tablet, the usual advice is to take it with a meal containing fat.

The dose per unit. Check whether the label states micrograms or international units, and convert, since 1 µg equals 40 IU. A 1000 IU capsule is 25 µg, two and a half times the NHS daily intake. That is not dangerous, but it is worth knowing before taking two a day.

The other ingredients. Formulas pairing vitamin D with vitamin K2 are everywhere. The argument is that K2 directs calcium towards bone rather than arteries. The hypothesis is mechanistically plausible, and it is not established by clinical trials in people eating normally. If you pick a combined formula, do it knowing you are paying for a mechanism rather than a demonstrated outcome. Our piece on calcium and magnesium without dairy takes up the same question from the food side.

The price per microgram. This is the calculation nobody makes and the one that separates two comparable products fastest. Divide the price of the bottle by the total number of micrograms it contains, not by the number of capsules. The spread between a generic D2 and a lichen D3 sold as premium is considerable, without the molecule changing. The same method applies to algae-based omega-3 supplements and to zinc supplements.

Blood testing: when it helps and when it does not

A serum 25-hydroxyvitamin D test measures your reserve. It makes sense in a few specific situations: suggestive symptoms such as bone pain or muscle weakness, stacked risk factors, a condition affecting fat absorption, or a treatment whose effect you want to verify.

It makes far less sense as a routine check in a healthy adult already taking 10 µg a day in winter. The reason is pragmatic: the result will probably not change what you do, and the test is not free.

Two traps are worth knowing. The first is seasonal: a test in September and a test in March do not measure the same thing, and comparing two results from different seasons is meaningless. The second is the assay question already mentioned: if you take D2, check that the laboratory measures total 25(OH)D. Our guide to the annual nutritional deficiency check places vitamin D among the other parameters worth monitoring.

As for cut-off values, they vary between authorities and learned societies, which is why the same result can be called insufficient by one laboratory and normal by another. Interpreting it belongs to a health professional who knows your situation, and this article cannot stand in for that.

UV mushrooms, a real option with a limit

Getting your vitamin D from mushrooms is an appealing idea, and it rests on a correct biological fact: mushroom ergosterol converts to vitamin D2 under UV, exactly as the cholesterol precursor converts to D3 in skin.

The laboratory numbers are impressive. EFSA assessed a UV-treated button mushroom powder in 2021 containing 580 to 595 µg of vitamin D2 per gram, and in 2022 a comparable product at 125 to 375 µg per gram. In both cases the panel concluded the ingredient was safe under the proposed conditions of use.

Two limits stop this being a standalone strategy. First, those concentrations describe an industrial powder treated under controlled conditions, not the mushrooms in your basket, which the Swiss database puts at 1.9 µg per 100 g raw. Second, the use envisaged in those dossiers is incorporation into fortified foods and supplements, not eating mushrooms as such. The requested use levels in the 2022 dossier make that plain: 1.125 or 2.25 µg of D2 per 100 g or 100 ml of food as consumed, and at most 15 µg a day in a supplement for people over one year old.

The same opinion carries a caveat worth reading if you stack fortified products. The panel notes uncertainty about the general population’s combined exposure to vitamin D, because the range of fortified foods has widened over the years while high-dose supplements are marketed alongside them. At the scale of a weekly shop, the risk does not come from one product but from their quiet addition.

In other words, UV mushrooms are an interesting D2 source as an ingredient and a modest top-up as a food. If you buy them, the UV treatment has to be stated on the packaging: without it, you are buying an ordinary mushroom. Our guide to edible mushrooms covers the rest of their nutritional value, which does not stop at this vitamin.

Five common mistakes

Believing winter sun is enough if you go outside. It is not a question of duration but of angle. From October to early March, UVB intensity at our latitudes no longer allows useful synthesis, even on a clear day.

Taking a high dose to make up for months without. Vitamin D is stored in fatty tissue, but the dose-size analyses in the recent trials show no gradient of benefit. Regular moderate intake is better documented than a catch-up dose.

Confusing plant origin with the complete absence of animal material. Lichen D3 in a gelatin capsule remains an animal-derived product by virtue of its shell.

Expecting an effect on mood. VITAL-DEP, covering 18,353 people followed for more than five years, found no effect on depression incidence or on mood scores.

Comparing two blood tests taken in different seasons. Levels fall naturally by late winter and rise by late summer. Without a matching season, the comparison says nothing.

Adapting to your situation

For someone who rarely goes outside, works indoors or covers up extensively, supplementation makes sense year-round rather than in winter only, which is exactly what the NHS states for people at risk.

For dark skin, melanin absorbs some of the UVB and lengthens the exposure needed for the same synthesis. The NHS puts this profile among those advised to supplement year-round.

For older adults, skin synthesis capacity declines with age, and national recommendations generally raise the advised intake past 60. This is a decision to make with a doctor, all the more so because concurrent medications are common in that age group.

For pregnancy or breastfeeding, the NHS keeps 10 µg a day and the same 100 µg limit. This is not a place to improvise: raise it at your antenatal appointments.

For an infant, the rule differs from the adult one: 8.5 to 10 µg a day up to one year, unless the baby is having more than 500 ml of infant formula a day, which is already fortified.

For anyone on long-term medication or living with kidney disease, liver disease or a fat malabsorption disorder, supplementation should be discussed medically. Vitamin D metabolism runs through the liver and the kidney, and those situations change the arithmetic.

What this evidence does not say

The VITAL trials cover American adults aged 50 and over, mostly well supplied with vitamin D at baseline, and test a single dose of 2000 IU a day. They do not support conclusions about genuinely deficient people, about younger populations, or about other dosing schedules.

The 2025 respiratory infection meta-analysis concerns the risk of catching at least one infection. It does not separately address the severity or duration of episodes.

The D2 versus D3 comparisons measure a blood concentration, not a clinical outcome. Neither meta-analysis cited here compares the two forms on fractures or infections, which would be the more useful information.

The EFSA assessments of mushroom powder cover the safety of a novel ingredient, not its effectiveness at correcting a deficiency.

Finally, the Swiss database values are category averages. A mushroom’s vitamin D content depends on its light exposure, and a plant drink’s depends on the manufacturer’s fortification decision, which can differ from one product line to the next.

Frequently asked questions

Is D2 enough if I would rather not use lichen D3? Yes for maintaining intake, with one caveat: at the same dose, D2 raises total 25-hydroxyvitamin D less than D3, by roughly 10 to 16 nmol/L depending on the meta-analysis. Taken daily and at a moderate dose, the gap narrows.

Should vitamin D be taken with a meal? Preferably for dry tablets, since vitamin D is fat-soluble. Drops are already in an oil, which makes the constraint weaker.

Daily or weekly? The subgroup analyses in the 2025 meta-analysis found no effect modification by dosing frequency. Daily remains the easiest to keep up and the best documented for ordinary use.

Can I build up summer reserves for winter? Partly. Vitamin D is stored in fat tissue and blood levels decline gradually after summer. That reserve does not cover the whole winter for most people, which is the reason behind the NHS seasonal advice.

Can a supplement replace the sun? For vitamin D, yes, that is exactly its function. Sun exposure has other effects, notably on circadian rhythm, that a tablet does not reproduce.

What are the signs of too much? Excess vitamin D causes hypercalcaemia, which can show up as nausea, fatigue, heavy thirst or kidney problems. The NHS sets the limit not to exceed at 100 µg, or 4000 IU, a day for adults. These situations almost always come from very high doses taken for a long time, not from recommended intakes.

Does vitamin D protect against colds? The evidence has moved. The updated 2025 meta-analysis, across 40 studies and 61,589 participants, arrives at an odds ratio of 0.94 whose confidence interval includes 1.00: there is no longer a statistically significant protective effect.

Should vitamin D be paired with K2? The pairing is common commercially and rests on coherent mechanistic reasoning, without solid clinical demonstration in people eating normally. It is not harmful, it is simply not established.

Sources

• Federal Food Safety and Veterinary Office, Swiss dietary recommendations for adults and the long version, February 2026
• Federal ordinance on adding vitamins, minerals and certain other substances to foodstuffs, Annexes 1 and 5
• NHS, vitamin D fact sheet
• Swiss Food Composition Database, FSVO
• Jolliffe D.A. et al., vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis, The Lancet Diabetes & Endocrinology, 2025
• LeBoff M.S. et al., supplemental vitamin D and incident fractures in midlife and older adults, New England Journal of Medicine, 2022
• Okereke O.I. et al., effect of long-term vitamin D3 supplementation on risk of depression, JAMA, 2020
• Comparison of daily vitamin D2 and vitamin D3 supplementation on serum 25-hydroxyvitamin D, Advances in Nutrition, 2024
• Relative efficacy of vitamin D2 and vitamin D3 in improving vitamin D status, Nutrients, 2021
• Tripkovic L. et al., comparison of vitamin D2 and vitamin D3 in raising serum 25-hydroxyvitamin D status, American Journal of Clinical Nutrition, 2012
• European Food Safety Authority, safety of vitamin D2 mushroom powder as a novel food, 2021 and the 2022 assessment