Covid-19 Part 10:
Vitamin D Part 2: Deficiency linked to obesity and diabetes

Just 20 minutes a day is all the sun you need

Vitamin D levels are thought to be a huge factor in determining Covid-19 severity, as I describe in my previous post. So how does it work? And how do we go about getting enough of it in our bodies to properly bolster our immune systems? 

With the help of a podcast interviewing Professor Susan Lanham-New from the University of Surrey, I summarise the most important points. 

How do we get Vitamin D?

Vitamin D is the only nutrient where the main source is from exposure to UVB rays, or sunlight. However, the body only creates it when exposed to certain wavelengths of sunlight. Therefore, countries that are in areas of northern latitude such as the UK, are only exposed to sunlight that can create Vitamin D in our bodies between March and the end of September. We make none during the winter. 

Not only is Vitamin D a nutrient, but a hormone too, making it very different to Vitamins B and C, both of which we get through our diet. 

Why do we need it? 

It is extremely important for our musculo-skeletal health; children with a deficiency will develop rickets, where the bone is not mineralised properly and becomes very soft. In adults, the effects are slightly different and can cause muscle aches, bone pain, lethargy and fatigue, in what’s known as osteomalasia. In extreme cases it can lead to the brittle bone disease, osteoperosis.

Vitamin D is also very important in diabetes, where the nutrient is an essential component of a properly functioning pancreas in producing insulin. 

Finally, it is crucial for immune system function. A link between it and seasonal upper respiratory tract infections has long been hypothesised. Vitamin D inhibits pulmonary inflammation responses, and in communities with high prevalence of rickets, there is a link with higher rates of upper respiratory tract infections. 

How long do we need to be outside to get enough?

Vitamin D toxicity can never be achieved from sitting in the sun too long, unlike supplementation through diet. After 20-30 minutes, the process of vitamin D creation in the body stops and a by-product is created. Exposing just 10% of your body to sunlight for twenty minutes a day is enough for healthy creation of the nutrient. It must be a direct effect of the sunlight on your body, without the interference of strong suncreams. 

Covid-19 link 

A study in Indonesia showed lower levels of the nutrient in more severe cases. People from Black and Ethnic Minority groups are much more likely to be deficient, due to many of them, especially those of African or Asian descent, having bodies genetically adapted to warmer climates. 

Obesity was also found to be a large risk factor in Vitamin D levels, where fat cells store it, rendering it metabolically inert, or unable to be used by the body. Those with higher BMI have lower levels of the nutrient. 


It is essential to increase Vitamin D levels for a wide range of health benefits for our body. This is why, from 2016, the UK recommended supplementation amount is 10mg per day. However, for most people who are going outside from April to September, it is ‘unlikely they will need a vitamin D supplement’. It seems senseless to buy supplements when you can get much more of it for free from the sun.

Our western lifestyles, full of examples where us humans try and play god and stop our bodies doing what they were naturally supposed to do, is causing us harm. We were meant to run, to be outside in nature, and to eat a balanced diet. The modern obsession with being scared of the sun is slowly killing us all, so get your bikinis and budgy smugglers on, have a jog, and soak up some of those rays before it’s too late! 

What do you think? Read the next installment in the Covid-19 Review here!

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2 Responses

  1. Spot on, and the groaning Guardian seem to have finally caught up with this:

    [Link deleted]

    Quite why the enquiry into Covid-19’s apparent greater lethality in BAME didn’t make vitamin-D levels in those communities a cornerstone of their investigation I really don’t know

    It’s well documented that the childhood ‘victorian’ disease of Rickets has increased (in UK) over the last 20 years or so:

    [Link deleted]

    As the article makes clear, the rise in BAME cases is significantly greater than in white people, which has nonetheless risen too; and I’d agree that lack of time outside and overuse of suncream when out is likely to be a significant contributory factor

    Can’t find much on rises in the adult equivalent of Osteomalacia, perhaps you’d like to research that

    Enjoyed your articles Kit, and largely agree with them. Look forward to reading any further instalments

    1. Thanks Patrick, glad you enjoyed it! I was sick of the mis-information in the media so I started these.

      That’s very interesting about Rickets – it gives the image of a disease which, as you say, was around long ago and should have died out by now! Very strange it has made a come back, and I assume partly due to our over-anxiety about the sun which is weirdly prevalent nowadays and for me just another symptom of our increased anxiety about the world. Interestingly worrying about skin cancer from the sun is often unfounded and over-egged in places like the UK, because our sun is so weak and doesn’t appear often. Studies have shown that you should be more worried about the chemicals in sunscreens (some of which are still known carcinogens) we are putting on our skin in huge amounts than the sun itself. Also another study found that quite apart from being outdoors in the sun being correlated to skin cancer, it was indoor living. The sun is so healthy for us in healthy amounts.

      I will have a look at that disease, I can imagine that will be increasing too!

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