The sun is our closest neighboring star. It is responsible for the light and heat that made it possible for early life to develop on Earth over 3.7 billion years ago. Today, sunlight is no less crucial to us humans than it was for those first single-celled organisms, and it should be a crucial component of your daily longevity routine.
Sunlight exposure has been linked to real, tangible benefits to health, from improved mood and sleep, to faster wound healing and increased pain tolerance, to higher levels of sex hormones and increased libido. It’s much more than just a source of Vitamin D, as many of us have been led to believe. While the sun can also be dangerous, getting controlled amounts of direct sunlights each day - especially in the morning - is one of the easiest and most effective ways you can improve your health and longevity.
In this blog we’ll look at the powerful and surprising ways sunlight can improve your health, and discuss what you can do to achieve those benefits for this month’s longevity challenge.
Components of sunlight - UVA and UVB
Sunlight is composed of different wavelengths of ultraviolet (UV) light. The two types that reach Earth and impact our health are UVA and UVB. Both types have health benefits, but they can also be harmful. UVA penetrates deeper into the skin and contributes to visible skin aging, but UVB is more dangerous as it causes sunburn and skin cancer. Sunscreen blocks both UVA and UVB rays, and it's crucial that you apply it if you are going to be out in the sun for long periods of time. Unfortunately, it also blocks the sun’s beneficial effects, so we recommend that you get natural sunlight when the sun is close to the horizon (i.e. around sunset or sunrise), when more of the harmful rays are absorbed by the ozone layer and it is safe to get exposure without sunscreen.
Wound healing and pain relief
One incredible impact of sunlight is its ability to augment the skin’s natural cellular repair processes. UV rays stimulate the growth of new cells, increasing blood flow to the surface and helping guard against infection.  There’s evidence that, by the same mechanism, sunlight can prevent scar formation too.  Sunlight also directly impacts your body’s response to pain,  with studies showing that exposure to light in the morning can significantly decrease pain, particularly in the lower back. [4, 5]
Sunlight and sex
Many of us can recall a previous summer romance, but it turns out there is a biological reason why a summer fling is so appealing. When UVB radiation hits the skin, signals are sent to the brain and the reproductive organs to increase the circulating levels of sex hormones - testosterone in males and oestradiol in females.  In this 2021 study, the equivalent of about 20-30 minutes of sunlight per day caused participants to seek out sexual encounters more and changed their perception of others, with increased perceived attractiveness of females and enhanced sexual desire in both females and males. Turns out getting your daily dose of sunshine could boost things in the bedroom!
Vitamin D production
The most well known impact of sunlight is Vitamin D production. Vitamin D is essential for healthy bones and muscles,  and your body can only make it when UVB radiation hits your skin. Of course there are harmful effects of sunlight too, but outside of the summer months the bigger risk is vitamin D deficiency, which is linked to an increased risk of respiratory illness, type 2 diabetes, and other chronic disease. [8, 9] Getting higher amounts of direct sunshine is also associated with better self-reported overall health .
Sleep and mood
The eyes are sometimes said to be an extension of the central nervous system. The retinas link directly to the brain via the optic nerve, so sunlight has a powerful and direct influence on the brain's activity. Exposure to the natural light-dark cycle throughout the day reinforces robust circadian rhythms which significantly improves the timing, duration and quality of your sleep.  Sunlight also has benefits for learning, memory and cognitive function, [12, 13] and studies have found that it can alleviate the effects of depression. [14, 15]
The power of morning sunlight
Viewing sunlight first thing in the morning is especially impactful. Just 10 minutes of direct sunlight upon waking (but ideally 30 minutes) will trigger immediate improvements in energy, mood and cognitive function that can last throughout the day and even improve your sleep in the evening. [16, 17] You can still get these benefits if it’s cloudy (although you should aim to spend a bit longer outside on gray days) but glass will block many of these benefits, so unfortunately sitting in the window is no good, you need to get outside!
For this month’s challenge, we want you to try just one simple trick to experience the amazing benefits of the sun:
Get at least 10 minutes of direct sunlight each morning, before 9am, for five consecutive days.
With the new Zest app you can track how much sunlight you are getting every day, as well as how much exercise and cold exposure you’re doing and what supplements you’re taking. You can also log your mood, allowing you to see what effect your different lifestyle interventions are having on your emotions.