In her second vitamin D instalment, dietician and Eat and Think founder Kelly McCabe, looks at the different factors that influence your vitamin D levels.
I suffer from eczema and recently asked my GP to check my vitamin D status. I was surprised to find that my vitamin D level was pretty low, despite a really healthy, varied diet and last year being one of the best summers on record – why?
The process by which the body makes vitamin D is complex. It starts when the skin absorbs rays in the invisible ultraviolet B (UVB) part of the light spectrum.
The liver and the kidneys play a key role in converting the vitamin into a form that the body can use. You can also get small amounts of the vitamin from foods such as eggs, oily fish and mushrooms which have been exposed to the sun.
There are many factors which influence the amount of vitamin D your skin can produce. Which ones apply to you?
Where do you live?
The further away from the Equator you live, the less vitamin D–producing UVB light reaches the earth’s surface during the winter months. In the UK for example most people get inadequate UVB exposure from September through to May.
Even in the summer months we only make vitamin D from sun exposure between the hours of 10am until 3pm. A good rule to remember is that you can make vitamin D in the summer only when your shadow is shorter than you.
How pale are you?
The darker your skin the harder you will find it to produce vitamin D from sun exposure. This is because your skin contains a greater proportion of the pigment melanin. Melanin competes with the substance in the skin that starts the body’s vitamin D production.
How sun safe are you?
With campaigns to help reduce melanoma risk by encouraging us to stay out of the sun, rates of vitamin D deficiency are increasing. Have 30 minutes of sun exposure regularly during the summer months. Even whilst wearing an organic sunscreen you will be exposed to some UVB radiation and produce good amounts of vitamin D.
But bear in mind, more than 30 minutes is unnecessary as our skin cleverly stops producing vitamin D after this length of time so as to avoid a toxic vitamin D overdose.
How much do you weigh?
Vitamin D is a fat-soluble vitamin and is stored in our adipose tissue, otherwise known as fat. This means that during periods of inadequate sun exposure we can use some of the vitamin D that has been stored away.
However, some studies have shown that overweight people find it hard to mobilise their vitamin D stores. This means that all of the vitamin D is hidden away in the fat stores but cannot be utilised for important bodily functions. If you are overweight you may require more vitamin D as it becomes less ‘bioavailable’.
How old are you?
As we age we find it harder to convert UVB rays into vitamin D in the skin, meaning we are more likely to require a dietary supplement.
As you can see vitamin D is a complicated nutrient to obtain. Although, we do not routinely recommend dietary supplements, unless a true deficiency is proven, vitamin D is likely to be required in supplement form by most people in the UK during the winter months (Sept-May).
This is even more important if you have minimal sun exposure during the summer, have dark skin or are over the age of 50. If you do decide to supplement try not to exceed 25ug (1000IU) of Vitamin D per day unless under medical supervision.”
Great advice, and something definitely worth bearing in mind if you fall under one of the above categories or suffer from a skin condition which can be helped by Vitamin D.
Do you take a Vitamin D supplement?