New Research Shows How Your Skin, Brain And Guts Are All Linked By Sunlight

The news that scientists have found a link between sunlight exposure and the health of your gut microbiome means that you’ve got another good reason to look out for your Vitamin-D levels as shorter, darker days herald the approach of winter.

Around five per cent of the US population live with seasonal affective disorder (SAD), or seasonal depression, which has symptoms so similar to depression that it can be hard to tell them apart.

Due to our genetic profiles, some of us are more SAD resistant than others, but we all benefit from well regulated serotonin levels. Now, scientists have found another way that sunlight regulates our mental health – through our gut microbiome.

RSNG investigated to answer the most common questions about sunshine and mental health…

I know that levels of daylight can affect my mood in the winter, but how does this work?
It’s been known for a while now that sunlight is effectively a natural antidepressant, which like many anti-depression drugs, stops the ‘happy-hormone’ serotonin from being removed from the brain by serotonin transporters.

People more resistant to the effects of SAD are able to downregulate their levels of brain serotonin transporter in the winter, to make up for the reduced hours of sunlight, and skin exposure to UVB light.

How does vitamin D come into this?
Vitamin D is the only vitamin that is also a hormone, and every tissue in the human body has Vitamin D receptors, making it vital for the normal functioning of the body. One of these functions is to activate genes that release neurotransmitters including dopamine and serotonin, which regulate our moods.

OK, so where can I get my Vit D?
Vitamin D is made when your skin is exposed to the UV radiation found in sunlight – it’s also present in certain foods such as eggs, red meat and oily fish. A 2008 Dutch study found that low levels of Vitamin D in the blood corresponded with episodes of minor and major depression.

‘In some latitudes, sunlight from October onwards doesn’t contain enough UVB radiation to make vitamin D’

I’m outdoors a fair bit in the winter – won’t this be enough?
That depends on where you live. In the UK, for instance, the sunlight from October to late March doesn’t contain enough UVB radiation to make vitamin D – you could be sunbathing naked and all you’d achieve would be hypothermia.

What’s this about sunlight levels affecting my gut – how does that work?
A brand new study published in Frontiers In Microbiology has discovered that skin exposure to UVB light alters the gut microbiome in humans, and vitamin D mediates this change.

This goes some way to explaining the protective effect of UVB light in inflammatory diseases such as IBD and MS. Inflammation occurs in the body as an acute and necessary response to injury, reducing as you heal. But an unhealthy lifestyle and other factors can cause chronic, low-grade inflammation throughout the body, which can contribute to the development of diseases.

It seems that skin exposure to UVB – in people not taking Vit D supplements – gave them a more balanced, diverse and healthier gut biome.

That’s interesting, but what does inflammation have to do with my mood?
Well, inflammation in the body has been linked with depression. Writing in the Psychiatric Times, Dr Andrew Miller says that inflammation increases the activity of serotonin and dopamine transporters, removing those neurotransmitters from the brain, while interfering in the synthesis of new neurotransmitters.

This double-whammy can have a big impact on how you feel in winter, and on the mental energy that’s available to you to perform day-to-day tasks.

‘Vitamin D is a fat-soluble vitamin so supplements are best eaten with fatty foods’

OK, so what’s the fix if I live somewhere where I’m not going to get Vit D from sunlight in the winter?
Eating more vitamin D-rich foods is the go-to solution, but some people struggle to do this, especially if they are vegan.

Vitamin D supplementation is the other route, but it’s had some bad press recently, with studies casting doubt on their effectiveness in helping bone health and preventing cancer and heart disease. One issue is that vitamin D from foods and supplements is absorbed in the area of the gut immediately downstream from the stomach, so any gut health issues can interfere with this – and it’s a fat-soluble vitamin so is best eaten with fatty foods.

What isn’t in doubt is the body needs Vitamin D, and around 42% of adults in the US are vitamin D deficient. RSNG has spoken to healthcare professionals who unofficially recommend Vitamin D sprays, which you apply under the tongue, because gut absorption issues are less likely to be a factor – just watch the dosage because too much can create toxic effects by sending your calcium levels through the roof.

Whatever you do to get your Vitamin D, make sure you add it to your ‘body winterisation’ to-do list!

WHAT NEXT? If you want to find out more about how different foods can affect your mood, then read this RSNG article

Comments are for information only and should not replace medical care or recommendations. Please check with your Doctor before embarking on exercise or nutrition regimes for the first time.

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