Vitamin D has been hailed in the media as some sort of super vitamin that can help with everything from relieving symptoms of arthritis, to curing autism to preventing COVID-19. Unfortunately, as with many things in life (and particularly with nutrition), when something sounds too good to be true, it usually is.
It might not be a superhero, but you definitely still want it on your side.
Vitamin D is important for our health and has many roles in our body's, but many of us don't get anywhere near the amount we need. Sunshine is our main source of vitamin D (see the problem?) so even if you eat a healthy, well-balanced diet, you are still likely to not have enough. In the summer months, you make vitamin D under your skin when you are exposed to UVB light; between 10am-3pm only 20 minutes of daily sun exposure of your face, arms and legs is enough to top up your vitamin D stores. But in the autumn and winter, no amount of sun exposure, even on a bright and sunny day, will provide you with any vitamin D at all.
It sounds simple enough, 20 minutes of sun exposure per day in the summer. Right now though, it's summer and as I look out my window it is grey, overcast and raining.
When it is bright and sunny, many of us spend those core hours of 10am-3pm working indoors, will cover our legs or arms to prevent sunburn or wear sunscreen; all of these will weaken or stop the UVB rays from reaching our skin. Skin colour also plays an important role, a person with black skin will need to spend longer in the sun than a person with white skin to create the same amount of vitamin D.
For many people, particularly those who have been cocooning and spent a lot of their time indoors over recent months, this could be a real challenge and we are likely to be very low in vitamin D at a time when we should be nearing our peak levels.
You might be asking yourself why this is a problem if vitamin D isn't the superhero that it is reported to be. Well, it still plays some really important roles;
1. Helping your body absorb calcium, which is needed for healthy teeth and bones as well as muscle contraction.
2. Regulating cell growth, neuromuscular and immune function, and the reduction of inflammation (this is probably where the link with curing or preventing COVID-19 comes from).
3. Many genes that regulate the life-cycle of a cell are affected in some way by vitamin D.
4. Many of our cells have vitamin D receptors, but we are still trying to understand the specific role that it plays.
We measure vitamin D levels through a blood sample, the Institute of Medicine state that someone with <50nmol/L is insufficient and someone with <30nmol/L is deficient. If your vitamin D levels are deficient then you are at a high risk of developing osteomalacia (or rickets in children) as well as other health concerns such as respiratory illnesses and reduced immune function. Two recent studies showed that potentially one in eight adults in Ireland (Cashman et al, 2016) are deficient, with 18-50 year olds at an increased risk when compared to those over 50 years (Laird et al, 2016). This is a worrying trend, especially when we now consider that many of the over 50 years age group could also fall into the deficient category due to the recent restrictions.
Fortunately, there is something you can do - vitamin D is also present in some foods and comes in supplement form.
Foods high in vitamin D include the following:
1. Oily fish such as salmon, sardines, pilchards, trout, herring, kippers and eel
2. Cod liver oil (but don’t take this if you are pregnant).
3. Egg yolk, meat, offal and milk contain small amounts, but this varies during the seasons.
4. Margarine, some breakfast cereals, orange juice, infant formula and yoghurts are fortified with added vitamin D.
As you look through the list above there are probably a few of the items that you would eat regularly, but not in large amounts. You aren't alone in this, dietary surveys show 90% of Irish adults commonly consume <10 micrograms per day, with 18-35yr olds consuming the least (IUNA, 2011). Although any credible nutritionist would recommend a "Food First" approach, there is the odd occasion where we need to stray from this rule a little. The risks of being deficient in vitamin D and the health concerns that this could lead to outweigh the risk of taking a vitamin D supplement (so long as the supplement is from a credible supplier, such as your local pharmacy, and not a dodgy website).
In the UK the recommendation is for all adults to take a supplement of 10 micrograms of vitamin D per day between October and March but there isn't the same blanket recommendation for adults in Ireland yet. Although high levels of vitamin D can cause health problems, these are seen when supplements of 1000 micrograms or more are taken daily over a few months.
So again, if we think about the risk of not taking a supplement vs the benefits gained from taking one, it's no wonder that the shelves were empty the last time I went to stock up on my vitamin D.
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