The Mystery of Vitamin D

The Complicated Story of Vegans and Vitamin D
(and why you’re deficient despite your best efforts)

Vitamin D is no ordinary vitamin. It is actually a group of vitamins, the calciferols, and the one you need to know about is D3 (cholecalciferol). This is the one you can get from sunshine, but only if you meet certain conditions: You must have enough cholesterol in your body, because it doesn’t make Vitamin D3 from nothing – it converts cholesterol into D3, and sunshine is just a catalyst. If you have been vegan for long enough, and even if you’re dairy free and just have a high soy intake, you probably don’t have much, if any, cholesterol in your body. If this is the case, you can live out on a nudist beach but you still won’t get enough vitamin D. If this is you, you can either take a vitamin D supplement, or eat eggs or meat to get cholesterol that can be converted into vitamin D. Since cholesterol has been shown to be incredibly bad for you (although still not very well understood by scientists), the best option is probably a supplement. To confuse matters, all vegan supplements are vitamin D2, and this doesn’t convert to D3 at all or have the same benefits.

How Much Do I Need?

The daily value of vitamin D (also known as recommended daily allowance) is another complicated one. In the US, the DV is currently 15 micrograms, but they are in the process of changing the advice to make the DV 20 micrograms, because of the worldwide Vitamin D deficiency epidemic. In the UK, the RDA (DV) is currently 5 micrograms, possibly explaining why there are so many cases of Seasonal Affective Disorder since the UK gets a poor sunshine quantity anyway. In Australia and New Zealand, the Adequate Intake is 5 micrograms (age 0-50) and 10micrograms (age 51-70) and 15 micrograms (age 71 and above), and the Upper Intake is 25 micrograms (age up to 12 months) and 80 micrograms for everyone over one year of age. In the EU, although the recommended daily intake is 5 micrograms, the European Menopause and Andropause Society recommend 15 micrograms until age 70 and 20 micrograms over age 70. In Canada, they suggest that you get at least 10 micrograms until you are one year of age, then at least 15 micrograms to age 70, then at least 20 micrograms if you’re over 70, with upper limits at 25 micrograms until age 1, then the upper limit steadily increasing until 100 micrograms at age 9.
As you can see, it’s very difficult to know how much Vitamin D we need to get, when everyone seems to have different recommended amounts, with some places giving you a “between X and Y” answer and others giving you an absolute value, and some of those values being significantly lower than others.  On top of that, there’s no distinction between what type of vitamin D we need according to the Daily Values, despite the fact they do different jobs.

The benefits of Vitamin D:

These are also contentious – US labelling laws only allow Vitamin D supplements to say “may reduce the risk of osteoporosis” but EU laws state Vitamin D supplements can say that it helps “normal function of the immune system, normal inflammatory response, normal muscle function and reduced risk of falling.” Health Canada says supplements can claim “may help achieve strong bones in children and reduce the risk of osteoporosis in older adults.”
Vitamin D2 only helps bones.  The clinically observed benefits of Vitamin D3 are wider than this, though, and include: Promoting calcium absorption (for strong bones), improving white blood cell count (helping immune system), mineral absorption, and there are Vitamin D3 receptors in every major organ so it may have wider roles that we don’t know about. The direction of current Vitamin D research is firmly fixed on determining whether SAD (seasonal affective disorder) is caused by low Vitamin D3 levels, with early results indicating a link.

Vitamin D Deficiency:
Lack of Vitamin D3 can cause depression, low bone mineral density, hypocalcemia (not enough calcium absorption), osteomalacia (softening of the bones including bowing of the legs), chronic musculoskeletal pain (sometimes misdiagnosed as fibromyalgia or polymyalgia which are both descriptions of symptoms rather than diseases), cardiovascular problems and rickets. During pregnancy, gestational diabetes and pre-eclampsia are caused by inadequate Vitamin D intake. Deficiency can be diagnosed by a blood test.

Vitamin D Excess:

It’s difficult to overdose on vitamin D – you would have to take more than 1000 micrograms per day over several months to start getting signs of toxicity; if this happens to you, the symptoms are: firstly, increased urination and thirst, then anorexia (loss of appetite), nausea and vomiting, if you still have too much vitamin D, this will progress into weakness, nervousness, polyuria, polydispia, insomnia, and eventually renal failure.

Where can I get vitamin D from?
It depends on what you can and can’t eat. Apparently, animal skin and milk are good sources of Vitamin D. Certain fungi contain vitamin D2, including portabella (0.3 micrograms Vitamin D per 100g of raw portabella mushroom); shiitake (3.9 per 100g of dried; 0.4 per 100g raw); alfalfa plant contains Vitamin D (4.8 micrograms Vitamin D2 per 100g). Another vegan source of Vitamin D is lichen, a naturally occuring moss-type plant, which contains 0.67-2.04 micrograms per 100g of lichen, due to production variance (it’s not exactly farmed), although it wasn’t stated which D-vitamin they produce. Since vitamin D3 is the important one, that’s the one you need to be looking to get.  One egg provides 5 micrograms of vitamin D3, so if you’re dairy free vegetarian (rather than vegan), this is an easy option for your vitamin D3 intake.

Are Vitamin D supplements vegan?

There are two ways Vitamin D is produced for supplements: either from lanolin (an oil found in sheep’s wool) or from fish organs. Both these sources contain 7-dehydrocholesterol, which is then exposed to UV light to cause Vitamin D3 production.
Obviously, the fish organs are not vegan. The lanolin is contentious – it comes from an animal, but the animal doesn’t have to die to get the ingredient, in fact, sheep grown for wool live out a natural length of life (the discussion of how they exist and what a “natural” life for a sheep is, is of course a whole ‘nother kettle of worms), so if you’re a honey-eating, urea-containing-creams wearing vegan, this might be an acceptable option for you. If not, then no, there are no Vitamin D3 supplements that are 100% incontrovertibly vegan. Also not vegan (by the same definition of vegan): cars buses or bicycles (look up where oil comes from), so each to their own.

My attitude is that as long as we are all doing everything we reasonably can, given our individual circumstances, to minimize dependency on (and therefore suffering of) animals, there’s no reason to cause harm to yourself because then you aren’t really encouraging other people to live like you. Whilst researching this article, I was quite shocked that a lot of pro-raw websites were saying there was no Vitamin D3 deficiency (or any nutrition deficiency) risk to vegans! This is completely untrue – you need to eat consciously, for nutrition, to succeed at a raw vegan lifestyle. The risks are there, for vegetarians and vegans, and even meat eaters, and we need more information on how to manage them and eliminate them through sensible eating and planning without giving in and going over to the Meat Eating Side, rather than denial of the problem. Denying the potential pitfalls just makes them look like they will bend the truth to get more converts, and if they’ve lied about that, people won’t trust their other information, which might be sound.

Vitamin D in plants:
If you’re scientifically literate, there’s an excellent peer-reviewed academic meta-analysis here about the state of research into Vitamin D in plants: which is the most informative and interesting article I found on the topic. The authors’ first languages are not English and so sometimes they make simple grammar mistakes (find someone who doesn’t), but their science is rigorous and I particularly liked reading about the chemical transformations that take place during conversion. If you’re not scientifically literate, or if you can’t be bothered with reading it, I’ll summarize it here along with one or two conclusions I’ve drawn from their work:
1. Most plant sources of vitamin D were found to be D2 not D3, which is less good.
2. For conversion from 7-dehydrocholesterol into vitamin D3, you need sunlight at a wavelength of 290-315nm (less than 290 would work but is totally filtered out by the O-Zone layer).
3. Only areas between 35 degrees above and below the equator gets this wavelength of sunlight all year round. The UK, Australia and Canada don’t get this wavelength of sunlight in winter, which underpins the theory that Vitamin D is linked to Seasonal Affective Disorder.
4. Vitamin D is only successfully converted if you are out in the sun for long enough (for 7-hydrocholesterol to convert to pre-vitamin D to degrade to Vitamin D3).
5. Vitamin D fortification takes place in some orange juices – so if there’s no “suitable for vegetarians” logo/statement on the packaging, it may have come from the fish sources I mentioned earlier.
6. If you put your portobella mushrooms out in direct sunlight for a while, the vitamin D3 will increase, making them theoretically a useful source of some of your vitamin D.
7. The reason most plants don’t have any Vitamin D3, is because it mostly comes from cholesterol (or, specifically, 7-hydrocholesterol), and most plants don’t contain cholesterol. So you need to get a plant that contains cholesterol (or lanoesterol) and expose the cholesterol to the right wavelength of sunlight for the right length of time to stimulate Vitamin D3 production.
8. Lanolin and mushrooms convert lanoesterol (another sterol) into Vitamin D3.
9. Theoretically, the researchers believe they have found a way to incite Vitamin D synthesis in plants, using arabidosis thaliana (a flower) as a model, through lanoesterol.
10. The production of Vitamin D in a plant that hasn’t evolved to do it naturally might affect the concentration of other vitamins – and toxins.
11. The source of high Vitamin D3 levels in fish are unknown, and particularly confuse scientists, because of the low levels of UVB light (necessary for D3 production) in their natural habitats; the researchers think the Vitamin D3 in fish might be due to microalgae, the beginning of the fishes’ food chain, and they point to two studies (Takeuchi et al, 1991) and (Sunita Rao and Raghuramulu, 1997) that measured high levels of vitamin D3 and pro-vitamin D in algae. Takeuchi also observed that the microalgae caught in August had higher levels of Vitamin D3 than that caught in October-December, supporting the idea that the sun is causing the Vitamin D3 in this plant. To further confuse matters, there are so many different types of algae that some seem to have the right sterols for Vitamin D3 production whilst others definitely don’t. However, with further study this could become a vegan Vitamin D3 source.
12. Sometimes, sterols turn to ‘soaps’ (saponification) before Vitamin D3 synthesis can be measured.

The conclusion states that:
“Traditionally, only animal products have been considered a source of vitamin D3, but today we know that vitamin D3 and its metabolites are formed in certain plants. Accordingly, fruits and vegetables have the potential to serve as a source of vitamin D. Especially, the Solanaceae family contains high amounts of vitamin D3, which is of special interest considering the importance of this family in human nutrition. The Solanaceae family includes important vegetables such as potato, tomato and pepper all of which have been found to contain vitamin D3. Our current knowledge is limited to the content in leaves, but future investigation will elucidate if also the edible portions contain vitamin D3. It would be valuable to screen a variety of crops and vegetables for vitamin D, but to carry out a larger screening development of less time-consuming and preferably more sensitive analytical methods are needed. A further challenge is to improve methods to study and quantify vitamin D conjugates in details.
Planktonic microalgae, inhabiting the sea, are another large group of photosynthetic organisms that contain vitamin D. Microalgae are, as part of the aquatic food chain, identified as a source of vitamin D for fish. Currently, the world’s wild fish stocks are being overexploited and there has been a growth in the aqua-culture industry. The current trend is to replace fish meals or fish oil partly by vegetable feed substitutes when feeding cultured fish will reduce the content of vitamin D compared to wild fish (Bell and Waagbø, 2008). Microalgae with a high natural amount of vitamin D may be used as a natural vegetable form for the bio-fortification of aqua-cultured fish.
Basic knowledge about the biosynthesis of vitamin D3 in photosynthetic organisms is still lacking and any increase in our knowledge will help us to manipulate the content to produce plants with a higher natural amount of vitamin D3. Vitamin D3 is only synthesized in minute amounts, which makes it challenging to study the pathways and enzymes involved. However, it also means that even small changes in vitamin D3 can have a significant impact on human health.”

“The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.”
(Japelt and Jakobsen, 2013, published in Frontiers, 13th May 2013: accessed 17/12/14).

I think the conclusion speaks for itself, and am looking forward to the results of the further study, in the hope that one day soon we can get all of our Vitamin D from tomatoes and potatoes, and algae. Wikipedia does state that algae is a vegan source of vitamin D but obviously if it’s not for sale in a supplement or in its original form, it doesn’t really count yet. When I looked on to find a supplement, there weren’t any vitamin D algae supplements. And if it’s not on, chances are it doesn’t exist.  Here’s a list of what they do have in the “vegan vitamin D” realm:
Vegan D3

“Vegan” vitamin D3 supplements:

There are some products (I’ve linked to one below) making very dubious health claims, and no proof that they really contain vitamin D3 (particularly when you consider “fatty acid esters” the ingredient that allegedly contains calcium and magnesium, but where you wouldn’t find them because they’re nothing to do with fatty acids, in the “vegan D3” probably contains the cholesterol needed for your body to convert into vitamin D3, rather than actual D3 itself, and that would account for the anecdotal evidence (from reviewers) that these supplements work.  See this article on fatty acids and notice it’s talking about cholesterol:
The volume of mushrooms needed to produce the amount of D3 allegedly in these products would be more expensive to produce than the products cost, so something odd is definitely going on here, I think they’re defining “vegan” differently to how most people define it due to it not being certified vegan by an independent body such as the Vegan Society (and how much they’re making of the fact it’s all “certified organic”): Questionable Vegan D3

Vitamin D and Dementia:

Another recent piece of research has shown a link between low vitamin D levels, and risk of developing Alzheimer’s or dementia. In the study (which was epidemiological), those whose vitamin D was a little low (<50nmol/l), risk of Alzheimers was increased by 69% and risk of dementia was increased by 53%. In patients with severe vitamin D deficiency (levels 25-50 nmol/l), there was a 122% higher risk of Alzheimer’s and 125% increase in risk of getting dementia. Since the study was epidemiological, it isn’t conclusive proof that vitamin D can prevent dementia, however, it is positive evidence that vitamin D is a piece of a bigger puzzle that could show us how to avoid dementia in the future. Read more about this study here:

Risks of Sun Exposure:
No discussion of the complexities of vitamin D would be complete without considering the risks of sun exposure. Sunscreen has been shown to be a confounding factor in vitamin D conversion – sunscreen with an SPF as low as SPF 8 reduces vitamin D synthesis by 95%! The key is to get enough unprotected sun exposure to stimulate vitamin D production without being out long enough to get sunburn, although the study which presented these statistics observed that there was no “safe exposure time” established yet, where vitamin D production would be optimal but cancer risk minimal, presumably because the research needed to produce such a time would be thoroughly unethical, because you would basically have to get participants to go out in the sun, measure their vitamin D levels until the point where they got cancer in order for it to be a fair test, and nobody’s going to carry out a study like that (I hope not, anyway). Additionally, the same study found that people living above the Arctic Circle in Finland got higher amounts of vitamin D than those living at lower latitudes (still above 35 degrees). It was also found that people in countries closer to the equator, but who culturally practised covering most of the body and eating a restricted diet, were more likely to be vitamin D deficient, although the authors definitely did not advocate the public practice of declothing for these groups, as this would be insensitive, rather the authors of the study thought these groups needed to be more aware of their vitamin D intake. The study can be found here: with the discussion of SPF fairly low down the page (do a “find on page” for “use of sunscreen”). One thing no study seems to have considered, is the role of UVB reflection which takes place in snowy environments (think of someone who has returned from a skiing holiday – they can sometimes look more tanned/burnt than if they’d gone on a beach holiday, due to sunlight reflection from the snow increasing the UVA and UVB exposure) – this would certainly have been a confounding factor in the Finnish study and could be the reason why vitamin D levels were higher in people who lived in the Arctic Circle (apart from the fact that the atmosphere is thinner up there so UVB penetration will be higher to start with). It certainly means there’s probably a band of latitude where UVB is sub standard, but further work needs to be done to establish exactly how far this band extends.

Vitamin D2 vs Vitamin D3:
Lastly, there are a lot of “vegan” vitamin D2 supplements on the market that do come from plants, but the problem with them is that D2 isn’t the D-vitamin that everyone’s getting deficient in, and it’s the vitamin D3 that doesn’t come from a plant source, but D2 will give your blood a false positive and it is only good for bone health. On top of that, a lot of packaging doesn’t actually specify which vitamin D it’s got in it, so sometimes you just don’t know what you’re buying. Vitamin D2 is of course also necessary for health, but studies have shown it is far less beneficial than vitamin D3, and has no effect on Alzheimer’s prevention ( Getting vitamin D2 is better than getting no vitamin D at all, while we all wait for a properly vegan vitamin D3 supplement.  As you can see, has plenty of vegan D2 for sale.

References: accessed 17/12/14).

What do you think about vitamin D3?  Are you excited that there will be 100% vegan (by every definition) supplements on the market very soon?


Author: MsAdventure

I am a twentysomething travel, photography and beauty blogger who occasionally writes about other topics. Within travel, I tend to write mostly about Europe because all the other travel bloggers seem to write about South East Asia. As a writer, I have written articles that are published in Offbeat Bride and on Buzzfeed, and as a photographer, I have taken photographs that are published in local and national news outlets in the UK. I have a blog at

1 thought on “The Mystery of Vitamin D”

Comments are closed.