How can daylight affect our gut health?

December 21st marks the winter solstice in the Northern Hemisphere, when the sun provides the least light in a 24-hour period and we experience the shortest day and the longest night. This is the point in the year that the Northern Hemisphere is tilted furthest away from the sun.

This year, the winter solstice, also known as the ‘hibernal solstice’ or the moment when the sun reaches its southernmost point in the sky, takes place on 21st December at 10.02 UK time. In London, the sun will set at approximately 15:53, giving just eight hours of daylight. 

Festivals and rituals are held on this day to celebrate the sun’s return, the start of longer sunlight hours and to protect from evil spirits. Some communities also celebrate hopes and dreams and the coming increase in energy in the year to come.

Circadian rhythm

Many of us are aware of a natural rhythm that allows us to wake in the morning and to feel sleepy at night. Called our circadian rhythm, it is linked directly to the amount of daylight (or sunshine) we are exposed to in a 24-hour period.

Every system, organ and tissue in our body has its own clock and optimum function of all organs and tissues and synergy between them is dependent on synchronising these clocks together and tying them to the day/night cycle.  When they become de-synchronised, this is referred to as circadian disruption.

A lack of daylight (as experienced around the winter solstice in the Northern Hemisphere) can result in circadian disruption and is thought to contribute to seasonal affective disorder.

Circadian rhythm and the gut

Our circadian rhythm also links to our gut health, translating environmental light cues to intestinal cells, shaping intestinal health and metabolism, and regulating when our body can best digest food, when we produce hormones and when it repairs cells and fights infections. 

In fact, we now understand that all of the following digestive processes are under direct circadian control:

• Stomach acid production and secretion
• Bile production and secretion, responsible for fat digestion
• Pancreatic enzyme production and secretion, responsible for protein digestion
• The ‘migrating motor complex’ (MMC), which is essential for the complete digestion of food
• The microbiome, which changes and interacts with the cells in your gut 
• The ‘tight junctions’ in the cells in the gut wall that manage fluid and nutrients entering the bloodstream
• Sensitivity to inflammation
• Colonic muscle movement – allowing waste products to exit the body

What about vitamin D?

Our circadian rhythm is also linked to our microbiome via sunlight and vitamin D. A skin-gut axis has been discovered that links exposure to sunlight directly to changes in our gut microbiome. It is currently unclear whether this link is dependent on or independent of vitamin D, although vitamin D is certainly important for gut health and IBS sufferers have been shown to suffer from low vitamin D levels.

Supporting circadian rhythm (and gut health) during the shorter days:

• Some of us are lucky enough to have some time off during the festive period, which means we have the perfect opportunity to wrap up warm and embrace the outdoors and the limited daylight available. Spending time outside between 11am-3pm can help to maximise exposure to UV light.
• For those of us working from home or the office, get outside in your lunch break – 30 minutes in the daylight can help to boost us both physically and mentally.
• Eat a healthy ‘sun-filled’ vegetable-rich diet – as plants grow in the light, they help link us to the outdoors, as well as providing prebiotic-fibre, vitamins, minerals and other health-supporting nutrients that can’t be found in other foods.
• Eat fermented foods containing live bacteria like natural yoghurt and sauerkraut.
• Add in supplements if you feel you need some additional support through the darker days.

Other related articles regarding the relationship between daylight and gut health:

• Does sunlight change our gut microbiome? – Medical News Today
• Exposure to Sunlight Boosts Good Gut Microbiome Bacteria, and Vitamin D Levels – Geneng News

Want to know more?
ProVen Probiotics aim to provide the best support for both you and your health. If you wish to know more about gut health please do not hesitate to call us on 01639 825107 or alternatively, learn more via our blogs or in-depth ProVen research.

ProVen Probiotics, Unit 2 Christchurch Road, Baglan Industrial Park, Port Talbot, SA12 7DJ. Tel: 01639 825107