Vitamin D: A Valuable Supplement for Autumn and Winter
In the Netherlands, we try to live in harmony with our four seasons as much as possible. In the spring and summer, we are outdoors as much as the weather allows, and we can rightfully call ourselves a nation of walkers and cyclists. In the autumn, we plan our days around the showers and perhaps prefer to pick up a good book rather than brave the weather. In short, for many, autumn and winter are times to turn inwards and spend more time at home with loved ones. Due to the lack of sunlight, we can become more susceptible to fatigue or the well-known Vitamin D winter dip. In this article, you will learn more about recent scientific studies on the absorption of Vitamin D in our bodies and why this is especially important in the autumn.
Why do we need Vitamin D?
Vitamin D is extremely important for our health; it contributes to a good immune system, strong bones, teeth, and muscles. We conveniently refer to it as Vitamin D to emphasise its indispensability in our bodies, but it is actually a pro-hormone formed from cholesterol. It doesn't provide a hormonal contribution in your body but is converted into the hormone calcitriol, which is 1000 times more active than Vitamin D itself.
Want to know more? Read all about Vitamin D here.
A recent analysis of the Food Consumption Survey shows that 92% of Dutch people do not get enough Vitamin D from their diet, precisely when we need it most.
We obtain about one-third of our daily Vitamin D requirement from foods such as oily fish, butter, dairy, or fatty meats, making sunlight and/or a supplement necessary to maintain our Vitamin D levels.
For vegetarians and vegans, it is fortunately now very easy to get enough Vitamin D with the well-absorbed plant-based D3 variant from lichen.
Can you build up a Vitamin D reserve?
You might think, I spent so much time outdoors last summer, surely I've built up a little extra buffer for this period? It's true that your body can store Vitamin D in fat cells and the liver, but the crucial question is, how much Vitamin D were you actually able to absorb during the summer months?
This depends on several factors such as diet, the strength of the sun or the UV index, which sunscreen you used, and also whether you work in an indoor shopping centre or an office. That's where the sun doesn't shine.
Even in a country like Australia where the sun is abundant, research shows that 30% of people have a Vitamin D deficiency at the end of summer, and even 40% at the end of winter. Fun fact: those who used sun protection still had a higher score, probably because they eventually spent more time in the sun.
Why is Vitamin D important in autumn and winter?
We now know that Vitamin D is important all year round to maintain our health. We need to make an effort to get enough Vitamin D through diet and sunlight, and since we obtain two-thirds of Vitamin D from sunlight, it quickly becomes clear that this absorption becomes difficult in autumn and winter, simply because the sun is too low to produce Vitamin D.
Sun protection: the culprit of your Vitamin D deficiency?
Using sun protection seemed for a long time to explain the global Vitamin D deficiency since Vitamin D is produced in the skin under the influence of UV radiation: the same radiation that sun protection blocks.
However, research in Rio de Janeiro has shown that normal use of sun protection does not affect the production of Vitamin D in the skin. It turned out that people who did not adhere (yes, you read that correctly) to the recommended 2 mg per cm2 but applied a thinner layer to their skin still produced Vitamin D. The British Journal of Dermatology recently came to the same conclusion, even when sunscreen was applied optimally.
Very interestingly, when using creams with a high UVA-PF, more Vitamin D production occurred in the skin than with a lower UVA-PF. The explanation for this is that more UV-B rays are allowed through, which is important for the production of Vitamin D. So choose your sun protection carefully if you want to absorb as much Vitamin D from sunlight as possible.
Can Vitamin D also protect the skin from sun radiation?
Nature wouldn't be nature if there wasn't a beautiful interplay between the sun, which indirectly provides us with Vitamin D, and the same Vitamin D protecting us from the harmful effects of the sun. A very high dose of Vitamin D can reduce redness, swelling, and damage in the skin after sunburn, as shown in a US study. In this study, a sunburn was simulated, and participants were given various high doses of Vitamin D, 50,000, 100,000, or even 200,000 IU (international units), an hour later. Those with the highest Vitamin D intake achieved the best results in terms of skin recovery. There was also higher activity of genes in the blood involved in skin repair.
More research is needed, but given the findings in Australia and sometimes wet summers in the Netherlands, it might be wise, now that we know how important Vitamin D is for us, to continue taking it in the summer to build up a reserve for the darker months.
Want to know more about Vitamin D? Read all about Vitamin D here.
