By Sarah Best.
In response to our two recent articles regarding vegan diets, several of you wrote to ask us whether you need to be concerned about vitamin D. The short answer on this is very simple if you live in the UK or anywhere with a similar climate: you need to have a plan in place for getting enough vitamin D, and that plan will need to involve supplementation.
Why? Because you won’t be getting enough from sun exposure year round, and if you are vegan and don’t consume foods fortified with D (read: processed foods) your dietary intake will be either zero or close to zero, meaning you are at even higher risk of deficiency than your non-vegan friends and family members.
The Recommended Daily Amount (RDA) for vitamin D is 400 IU, but many experts believe that while this will stave off obvious diseases of deficiency (i.e. rickets) it is well below the amount needed for optimal health. Depending on who you listen to, that requires 1,000, 2,000, or even 5,000 IU or more a day.
Plant foods generally do not contain any vitamin D. The only exceptions are nettles and special mushrooms grown under ultraviolet light - other than that there is no vitamin D whatsoever in plant foods. The only other vegan foods that contain vitamin D are the fortified (i.e. cooked, processed) ones which list it on the ingredient label.
Ejaz wrote in to ask us whether three raw eggs a day would provide enough vitamin D. Although eggs do contain vitamin D, and they are often listed as a good source, one egg contains a mere 20 IU, so you would need to eat 20 eggs a day to reach even the widely-considered-to-be-inadequate RDA.
Milk isn't a great source of vitamin D either, providing just 40 IU per 100ml. Fish is much better - for example, a 100g serving of salmon packs 360 IU. So it is possible to meet the basic RDA if you are eating fish, but unless you're consuming vast quantities of it you won't be getting close to the higher intake levels many scientists consider necessary for optimal health.
So why is it so hard to get enough vitamin D from food - even if you're not vegan or vegetarian?
Because sunlight is the way nature intended us to get most if not all of our vitamin D.
As this article will show, that’s great if you live in Miami but not so great if you live in Manchester.
In the UK we don’t get enough of the kind of sunlight that causes our bodies to manufacture vitamin D under the skin. Only one kind of solar radiation does this: UV-B sunlight. While UV-A is present throughout the day, the amount of UV-B present has to do with the angle of the sun's rays and at higher latitudes it’s present only (a) on the hottest, brightest summer days and (b) during the middle of the day.
Latitude is a measure of distance from the equator, either north or south. Humans evolved in the low latitudes of the tropics, an area of year-round UV-B sunlight. Latitudes higher than 30 degrees (both north and south) do not have sufficient UV-B sunlight, according to leading vitamin D experts (more on this shortly).
So what latitude is the UK at? Well, here’s the really bad news. It ranges from 50 to 58 with London at 51 and Manchester at 53. The US mainland is located between 25 and 47, so health seekers (and especially vegans) living in many parts of the US should consider supplementation, too.
Here's a quick primer on latitudes and UV-B sunlight:
Latitudes with plentiful UV-B sunlight year round
Bali – 8
San Jose, Costa Rica – 9
Honolulu, Hawaii – 21
Miami – 25
Latitudes with insufficient UV-B sunlight 2+ months of the year
Cape Town – 33
Sydney – 33
Los Angeles – 34
Latitudes with insufficient UV-B sunlight 6+ months of the year
Madrid – 40
Rome – 41
New York City – 41
Paris – 48
London – 51
Manchester – 53
The effect of latitude on the skin's ability to synthesize vitamin D is rarely mentioned in raw vegan circles. Many raw vegans in the UK believe it’s no problemo to get enough vitamin D from the sun regardless of the season; it’s simply a question of spending time every day outside in it, wearing not very much.
First of all, this is tricky to do if you have a 9 to 5 job or if you prefer not to be near-naked in sub-zero temperatures – two conditions which leave few of us standing. But even if you are one of the few who can and does get outside (a) for a prolonged period (b) wearing very little (c) during the middle of the day (d) most days, evidence suggests this will have little if any effect on your vitamin D levels during the colder, darker months.
Remember: where UV-B sunlight is not present, your skin cannot synthesize vitamin D. So let’s look at what the scientists say. It is the opinion of Harvard Medical School that, “Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north or below 37 degrees south of the equator. People who live in these areas are at relatively greater risk for vitamin D deficiency.”
37! Remember, in the UK we’re at 50 to 58! Sultry Ibiza is at 38, sun-soaked Naples in southern Italy is at 40, and Cannes on France’s balmy Riviera is at 43. Yet Harvard Medical School is not the only credible authority saying that even these Mediterranean locations -much nearer the equator than us - don’t have the right kind of sunlight year round.
According to Krispin Sullivan, a certified nutritionist and vitamin D researcher: “In much of the US [...] six months or more during each year have insufficient UV-B sunlight to produce optimal D levels. In far northern or southern locations, latitudes 45 degrees and higher, even summer sun is too weak to provide optimum levels of vitamin D.”
Sullivan is among the vitamin D experts who say that 30 is the magic number when it comes to latitude and vitamin D production: if we are further from the equator than this, we won't be meeting our D needs year round from sunlight alone.
Only a very small percentage of the world’s population lives further than 50 degrees from the equator, so it really is no exaggeration to call the UK a "far northern location" when it comes to sunlight and vitamin D synthesis.
To assume that the scientists are wrong and that we can meet our D needs from sunlight all year round is a high-risk approach considering how essential this nutrient is to our health. Supplementing for at least six months of the year is a good deal more conservative. If we don’t do this and we are vegan, we risk a period of six months or more each year when our intake of vitamin D is zero or very close to zero.
But hold on… If we get out enough during the summer, including a stint of sun worship on the beach in Benidorm, Barbados or Bali, can we make and store enough vitamin D to get us through a London winter – or, for that matter, a Los Angeles one?
Again, opinions in the scientific community differ, but within a fairly tight range, with some experts saying we can rely on tissue stores of vitamin D for only two weeks while others say that as long as we have adequate stores at the start of the “zero UV-B period”, our tissue stores will stand us in good stead for two months. So if you live in a location like Los Angeles, which has adequate UV-B sunlight for around 10 months of the year, it’s not essential to supplement during the coldest, darkest 2 months as long as you got enough sun exposure during the other months of the year.
What constitutes “enough”? This varies greatly from person to person. If you have very fair skin, as little as 10 minutes a day could do it, assuming you are exposing most of your skin to the midday sun (i.e. wearing a bathing suit). You’ll need substantially longer if you’re only exposing hands, arms and face, or if you’re in the sun outside of the 10am to 2pm period. If you have very dark skin it may take up to two hours (and, as above, longer if you’re in the sun outside of these hours, or fully clothed). Your body is quite limited in how much D it can produce each day so once you have reached this threshold (at which point you’ll see a pinkish tinge on your skin) more exposure won’t lead to more D production.
The most important facts to bear in mind are these: If you are vegan and you live in the UK or anywhere with a similar climate, unless you are supplementing during the October to March period, you will be running your vitamin D levels down lower and lower as that period progresses.
You may not show any obvious signs of D deficiency, but come December your levels are more likely than not to be lower than needed for optimal health, and come March the situation will be worse still.
So we agree with the advice of John Jacob Cannell, M.D., executive director of the US-based Vitamin D Council: “It appears to us that the best thing to do is be conservative and maintain natural vitamin D blood levels year-round by receiving sunlight in the summer and supplementation in the winter." He adds, "In this case, 'natural' means levels similar to humans living in a natural relationship with the sun, such as farmers in Puerto Rico or lifeguards in the United States.”
How much vitamin D do you need to take to achieve this? According to the Vitamin D Council's Cannell, there is no easy answer, as it varies with “age, body weight, percent of body fat, latitude, skin colouration, season of the year, use of sunblock, individual variation in sun exposure, and – probably – how ill you are. As a general rule, old people need more than young people, big people need more that little people, heavier people need more than skinny people, northern people need more than southern people, dark-skinned people need more than fair-skinned people, winter people need more than summer people, sunblock lovers need more than sunblock haters, sun-phobes need more than sun worshipers, and ill people may need more than well people.”
Cannell adds: “Vitamin D is used by the body – metabolically cleared – both to maintain wellness and to treat disease. If you get an infection, how much vitamin D does your body use up fighting the infection? If you have cancer, how much vitamin D does your body use up fighting the cancer? Nobody knows the answer to these questions.”
Cannell gives the following supplementation guidelines for those who have little UV-B exposure: "Healthy children under the age of 1 should take 1,000 IU per day - over the age of 1, 1,000 IU per every 25 pounds of body weight per day. Well adults and adolescents should take 5,000 IU per day. Around 2–3 months later have a blood test."
While a dose of 5,000 IU a day is regarded by many to be safe, many practitioners recommend having your blood tested every few months if you are taking high doses like this as we all metabolize it differently and in rare cases an excess of it can build up and cause problems.
It is equally important to get your (and your children’s) vitamin D levels tested if you choose not to supplement. Especially your children’s, as their bodies - including their very D-dependent bones and teeth - are still growing.
Be sure to request the25 (OH)D test specifically (a much more reliable test than the 1.25-dihydroxy-vitamin D test some doctors will order).
And ask to see the test result as well as your practitioner's interpretation of it, as opinion differs as to what constitutes deficiency. "Most doctors who see a [level] of 30 ng/ml will tell you that level is fine when it is not," says The Vitamin D Council's Cannell, adding that:
“Levels should be above 50 ng/ml year-round, in both children and adults,” – this is the “minimum acceptable level.” Cannell quotes research (Heaney et al) which found that the body does not reliably begin storing vitamin D in fat and muscle tissue until 25(OH)D levels get above 50 ng/ml. “That is, at levels below 50 ng/ml, the body uses up vitamin D as fast as you can make it, or take it, indicating chronic substrate starvation—not a good thing. 25(OH)D levels should be between 50–80 ng/ml, year-round.”
Disturbingly, certified Nutritionist and vitamin D researcher Krispin Sullivan observes that, “In northern California 80% of clients tested during winter months have serum vitamin D deficiency (less than 20 ng/ml) or insufficiency (20-32 ng/ml).”
Note that these levels are substantially lower than the Vitamin D Council's recommended 50 ng/ml - and that Northern California is located between 37 and 42 degrees north, compared to the UK’s – forgive us for hammering this point home – 50 to 58.
Sullivan adds: “This problem increases dramatically in persons living at latitudes more distant from the equator and in persons living in all US latitudes with darker skins. In Texas there has been an increase in the number of children with African or Hispanic heritage suffering from rickets. Even in sunny southern California vitamin D deficiency or insufficiency is prevalent in part due to avoidance of midday sunlight and/or the use of sunscreens which block vitamin D production.”
Numerous studies around the world have identified high levels of vitamin D deficiency in the general population. In fact Vitamin D expert Michael Holick says that vitamin D deficiency is "the most common medical condition in the world”. Not spending enough time outside and use of sunscreen (which all but blocks vitamin D production in the skin) are the reasons for this in some parts of the planet.
But (a) the majority of the world’s population lives a lot nearer the equator than those of us in the UK do and (b) these populations are not vegan, so are at least consuming some vitamin D containing foods on a daily basis.
Throughout history, humans living as far north as the UK always consumed large amounts of fish and/or red meat and they met their vitamin D needs that way. In fact, evidence suggests that for most of history, humans living at 50+ degrees north, or anything close, got over 50% of their calories from meat and/or fish. With such high intake of animal flesh it would have been possible to obtain ample vitamin D, but eating that quantity of meat and/or fish is not a wise way to get our vitamin D today. Quite apart from any other consideration, we live on a polluted planet and pollution concentrates up the food chain.
Let us say it again: the best way to meet our vitamin D needs is through sun exposure!
This article was written for those who can't meet their vitamin D needs through sun exposure alone due to the latitude they live at, so who need to go to the next best solution. We'll end with a round-up of our advice for ensuring you get optimal levels of this nutrient that is - let us remember - absolutely essential for optimal health.
This advice is aimed specifically at people who live in the UK and similar climates, but worth considering for all living further than 30 degrees from the equator - and especially for those living further than 40 degrees. (If you live in the southern hemisphere, substitute any instance of "October to March" below with "April to September", and vice versa.)