Vitamin D: the best thing since sliced bread?
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Marks and Spencer recently announced it is to add vitamin D to all of its bread products. This is likely to have been fuelled by the public’s rising awareness and interest in vitamin D. It is currently a hot topic, (only last week I was asked to give my thoughts to a national journalist for a recently released article) and I’ve seen a huge surge in people coming to see me asking for their vitamin D levels to be tested. I always have a good chat about vitamin D with patients, so I thought it might be useful to share my views. To summarise:
Vitamin D supplements are really good for you!
Most people in the UK will need supplements, and need to take them indefinitely.
I’ll start by briefly summing up a bit of the science (biochemistry was never my specialist subject at medical school so I’ll keep it straightforward) - essentially vitamin D is key to ensuring your body maintains proper calcium levels, thereby enabling you to maintain healthy bones. The specific condition it helps to prevent is called osteomalacia, more commonly known as rickets, when children are affected.
A lot of bone diseases have similar names (generally all starting osteo-something!) but osteomalacia is basically a softening of the bone material. This can cause “bowed legs” in children as they grow, and generalised bone/body pain and tenderness in adults. There’s a huge amount of public awareness about osteoporosis - thinning of the bones - but this and osteomalacia are two very different conditions. Vitamin D is commonly used in conjunction with other osteoporosis treatments, but not on its own.
The benefits for bone health are well documented, but it’s the other emerging benefits that are proving so interesting. There have been a lot of studies to show that people with good levels of vitamin D suffer from fewer coughs, colds and other respiratory illnesses, and this is particularly so for young children and infants. The exact way this works is not clear, but it is thought that vitamin D plays a role in helping our immune system to function efficiently, thereby preventing the above infections. By a similar presumed mechanism, there is some evidence to show that such individuals also have a lower incidence of certain cancers.
In my own practice I’ve seen a lot of patients who have reported having vastly improved energy levels, and even feeling psychologically better after a course of vitamin D replacement. There’s no hard evidence for this, and there may be a placebo effect at play, but the fact that so many patients have said this makes it stick in my mind.
So: proven healthy bones, and potentially fewer coughs and colds, less cancer and more energy! Sounds pretty amazing doesn’t it, but I do think it needs to be taken with a pinch of salt, because as I said, not all of this is clinically proven yet. What I would say is that almost everyone in the UK could do with more vitamin D - I honestly don’t remember the last time I saw a ‘normal’ level in a person not on supplements.
So how does one get this miracle vitamin?
Sensible sun exposure is the natural way; vitamin D is made by your skin after it has been exposed to sunlight - more specifically, the UV-B spectrum of sunlight. However, your production of vitamin D will be affected by many different factors: sunscreen use is one, as it is rightly designed to block UVB. Obviously this is hugely important for skin cancer prevention long term, but the downside is it lowers vitamin D production. It’s important to find a balance and around 30 minutes of sun exposure twice weekly to the legs and arms can be enough.
Lighter skin tones are more efficient at producing vitamin D - if you think about this in terms of evolution, people with lighter skin originate from further away from the equator, where the sun (and UVB) is progressively less intense, meaning they need to be more efficient with what little UVB exposure they get. The UK being so northerly with much lower sun intensity puts many of us at higher risk of low vitamin D. Cloud cover, time of day, and season all contribute too - vitamin D levels are unsurprisingly always lower in winter. There aren’t many dietary sources of vitamin D, but they include: oily fish (mackerel, salmon etc.), fish liver oils and eggs.
Who especially needs supplementation?
As I’ve touched upon, those with darker skin are more at risk of deficiency given that sunlight is the biggest source of vitamin D and their bodies are naturally less efficient, as well as those at higher latitudes. But children are at risk too due to higher requirements during growth and development, and the same goes for pregnant women. Breast milk contains such little vitamin D that exclusively breastfed children should be on supplements (whereas formula contains it). Essentially my standard advice would be that pretty much everyone could do with taking some vitamin D supplementation, but these at-risk groups definitely should.
It is easy to get your vitamin D level measured with a blood test. Depending on the result, you may just need a small preventative dose of supplement, or a bigger treatment dose. The following are adult doses (link to kids’ doses at the bottom): prevention is often around 1000 units per day (which can be brought over the counter), whereas treatment usually consists of a 300,000 units course over 2 - 12 weeks, followed by the prevention dose. The rationale is that we boost the level up, and maintain it there. This brings me to one of the biggest stumbling points I come across: if you’re deficient, and you need a high-dose treatment course, you need to take the maintenance dose afterwards, every day, or your levels will simply fall again. A lot of people take the booster course, stop, see me again a few months later and unsurprisingly their level hasn’t changed much. I think the expectation is that you’ll just need a booster, but unless you’re spending your winters in Barbados, you’ll need vitamin D indefinitely in the UK.
So what are the downsides to this? No medicine or treatment is without side-effects or risk. If your vitamin D level is too high it can have the knock-on effect leading to a high calcium level, which is not particularly good for you to say the least. However, you’d have to take a very high dose of vitamin D for a very long time to build up such high levels. Otherwise, there are few other known side effects of vitamin D - ‘known’ being the key word here. Currently, there’s just no long term evidence available that suggests any harm. Could this be another potential scenario, à la HRT in the 90s, when it was freely prescribed without understanding the longer term risks? I’m not trying to scaremonger here, but just make the point that we simply don’t know the long term side effects, if any. The current opinion, and my own also, is that used sensibly there are likely no significant long term side effects.
So, as I said right at the start, vitamin D is seriously good for you and nearly all of us are lacking enough. Get tested, take it regularly and even if you don’t notice a difference you’ll be better off and healthier for it!
Final note: vitamin D3 (colecalciferol) dosing is often stated in terms of international units (iu) or micrograms (mcg or mg). To covert between them, 1mcg = 40iu.
For more information on vitamin D and specific dosing, click the following links:
