A pharmacist's perspective on health and metabolic disease
Cherries and Apricots in the supermarket, and the pohutukawa trees are looking marvelous with their red blossom. All signs that we are near to Christmas*. But when you live in the part of the world that is blessed with little pollution, but also has less ozone, the signs of summer also herald sunburn season.
I’m English, which means my skin has two main shades – pale white and lobster red (often with a reasonable amount of peeling in between). Going without sunscreen in the height of summer can mean losing two layers of skin…..not fun.
So it has been hard balance to get sufficient UV light for Vitamin D without getting scorched. But since going low-carb, high-fat a few years ago, I have found myself getting less sunburn and even obtaining a slight tan. (Which is handy since I have also discovered that I am allergic to many sunscreens!)
What is the mechanism for this?
I still don’t really know, but there may be effects from reduced inflammation, but this mouse study from Cell Reports “Time-Restricted Feeding Shifts the Skin Circadian Clock and Alters UVB-Induced DNA Damage” may have part of the answer.
It appears that skin has a circadian rhythm which changes our sensitivity to UV damage. This rhythm can be disrupted when we eat at different times of the day. In this study, mice that ate during the normal feeding times, had less UV damage when exposed to UV light during the day compared to the amount of UV-induced skin damage when exposed to the UV light overnight. This has been extrapolated to suggest that humans who snack overnight are more at risk of sunburn.
I think this study has to be taken with a bit of caution as it is a mouse based study, and the results don’t always translate to humans. In this case, mice normally feed at night, so they had the most UV damage when exposed to UV light after feeding. Does this mean that humans are are at increased risk of UV after eating, or are our circadian rhythms set up so that if we eat during the day – our normal eating time – we will have better protection from UV light.
The main risk of UV skin damage from excessive sun exposure is the increased risk of the potentially fatal melanoma skin cancers. (Hyperinsulinaemia is also associated with melanomas.) But a lack of vitamin D is also associated with increased risk of cancer, osteoporosis, and dementia. To be able to increase vitamin D exposure and reduce sun damage means that LCHF and restricted eating times is a win-win.
*To better understand the Southern hemisphere Christmas, try this Ronan Keating video