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Ayurveda, Sunlight, and Circadian Rhythms

Throughout the day, from sunrise to sunset, the solar energy from the sun changes. Like clockwork, with each passing hour, the atmosphere, in combination with the rotation of the earth around the sun, has created a daily solar symphony of electromagnetism that highlights certain rays while filtering others. The impact this has on our lives was mapped out in Ayurveda thousands of years ago.

These changes in the sun’s energy throughout the day are responsible for  nature’s circadian rhythms. The lifestyle you choose determines whether your biological clocks will turn on and off in sync with nature’s light-dark cycles.  

As the sun moves through the sky, its solar rays change. Specific solar rays turn our biological clocks on and off at the perfect times for us to get the most out of our exercise, meals, sleep, mental focus, immune system, and so much more.

Ayurveda, which is based on an in-depth study of nature, recognized the subtle differences in daylight at different times of day. While ancient Ayurvedic practitioners didn’t have names for visual light, infrared light, or ultraviolet light, they were very aware of the role these rays played in nature and more specifically how they affected the human body.

Kapha, Pitta, and Vata Times of Day

From this in-depth study, they knew that at sunrise, certain solar rays increase kapha (or earthy) qualities of nature until about mid-morning. Then as the sun rises to midday, solar heat  increases pitta (or fire) energy. Finally, as the sun sinks into the horizon, rays that support vata energy become more abundant.

The above kapha, pitta, and vata times of day are known as the Ayurvedic clock. It prompts Ayurvedic practitioners to prescribe more physical activity in the morning, bigger meals at noon, and activities that require mental clarity in the late afternoon.

Read on for more Ayurvedic and scientific detail about each of these times of day.

See also Shape your Day the Ayurvedic Circadian Way

Kapha Time: 6 a.m. to 10 a.m.

For about one hour before the sun rises, blue light from the visual light spectrum predominates. This is called the blue hour (which includes both blue and violet light). Blue light has a shorter wavelength and faster frequency than any of the other colors of the visual light spectrum. Before and during sunrise, the sun’s blue light is scattered across the sky by the atmosphere, turning the sky a deeper blue.

Studies on blue light suggest that it plays numerous roles in regulating the human body.

Recent research shows that blue light is an inhibitor of melatonin—the hormone that puts us and keeps us asleep at night. Blue light exposure during the blue hour begins to block melatonin in order to wake us up, both mentally and physically, and help us to transition from the early morning vata time of day to the daylit kapha time of day.  Research has also shown that blue light can balance anxiety and depression, while supporting cognitive function—which is much needed to start the day.

At sunrise, the sun’s rays appear to be in full force, yet most of the blue light is scattered, which turns the mid-sky blue and leaves orange and red light to shine on the horizon. Like blue light, ultraviolet light (both UVA and UVB) is scattered and diffused by the early morning atmosphere, making it a safe time for your skin to be directly exposed to the sun. During sunrise and sunset, when the sun is lower in the sky, the sun’s rays have to penetrate more of the Earth’s atmosphere. During these times, the longer frequencies of yellow, orange, and red light are more easily seen and shorter-wave blue and ultraviolet light are either scattered or blocked. At sunrise, more blue light is seen because wind generally dies down at night, allowing less atmospheric dust to block blue light  come sunrise.

Studies tell us that sunrise is nature’s “red light therapy” time of day.

Both red and near infrared light can activate energy production in our mitochondria. Red and infrared energy is powerfully kapha-balancing, helping to drive the mitochondrial energy needed to support physical labor before the midday heat. Kapha qualities are heavy, wet, and dull. Without this infusion of energy producing red and infrared light, kapha qualities would build, melatonin would persist, and we would likely sleep in and feel overwhelmingly groggy for much of the day.

Moreover, deeply penetrating infrared rays are healing and reparative for the soft tissues of the body. They prepare the skin to endure the onslaught of UV radiation that comes as the sun climbs into the midday sky. These infrared rays support muscular strength and recovery.

Kapha Time and Sunrise Summary

• One hour before sunrise is blue hour. Scattered blue light shuts off melatonin production while boosting mood and cognitive function.
• UV radiation is blocked while red and infrared light shine, boosting muscular strength, recovery, skin repair, and mitochondrial energy that balances kapha (heaviness) during the morning hours.

See also The Biological Benefits of Being Outside at Sunrise

Pitta Time: 10 a.m. to 2 p.m.

As it turns to midday, ultraviolet radiation is finally able to penetrate the atmosphere in full force. UVB radiation activates vitamin D production in the skin, which amps up pitta energy production and offers protection from damaging UVA rays. Both UVA and UVB can be pitta-aggravating and in excess can cause skin cancer, but it is all a matter of exposure.

In smaller dosages, studies  have found that UV radiation can be pitta-pacifying and treat skin diseases such as psoriasis and dermatitis. In addition to prompting the production of vitamin D, UV radiation is antimicrobial. It also boosts nitric oxide, which lowers blood pressure and reduces cardiovascular risk. UV radiation also acts as a neurotransmitter to boost mood and cognitive function.

One 2019 study found that exposure to UVB light can boost metabolism, which supports the circadian science that links digestive strength to eating your main meal midday. This study also found that UVB light exposure, independent of its production of vitamin D, can limit diet-related obesity, metabolic syndrome (high blood sugar, high blood pressure, high cholesterol, triglycerides, and visceral fat), and arterial plaque.

During the daytime, the remaining rays of the sun are very pitta-balancing and help to mitigate heat. The blue light that makes the sky blue is scattered by the atmosphere, acting as a cooling blanket for the sun’s excess pitta, or heat. White light is made up of red, blue, and green light, which, when combined, cancel each other out and become invisible white light. This invisible white light illuminates the earth and boosts alertness and mood.   

Pitta Time and Midday Summary

• UV radiation, in combination with infrared light, reaches its peak at midday, boosting pitta and metabolism. Morning red and infrared exposure without UV penetration is nature’s sunscreen.

• Blue light at midday is scattered, turning the sky bright blue and cooling pitta. This can energize the body and stimulate cognitive function.

• Red, blue, and green light during midday combine to make invisible white light that balances pitta while boosting mood and alertness.

See also Circadian Rhythm: Learn to Balance Your 5 Internal Clocks

Vata Time: 2 p.m. to 6 p.m.

The white light that illumes the earth in the afternoon increases vata, which is why Ayurveda suggest that late afternoon is the best time for mental activity.

Also, after a full day’s exposure to infrared light, the cellular mitochondria have been stimulated to boost enormous amounts of energy, increasing vata qualities.

Nature always offers the antidote or a balancing agent. At this time of day, as the sun begins its afternoon push to the horizon, UV light is steadily blocked by the atmosphere, which reduces vata. Without the UV light competing with the infrared and red light, warm deeply penetrating and vata-balancing red and infrared light begin to predominate.

The final vata-balancing affect that switches our biological clocks from day mode to night mode is the surge of vata-balancing orange, red, and infrared light at sunset. This light balances both vata (2-6 p.m.) and the initial stages of kapha (starting at 6 p.m.).

As heat rises during the day from the sun, winds pick up and create significantly more dust in the atmosphere at sunset than there is at sunrise. The windblown dust in the atmosphere at sunset blocks blue light and enhances longer-frequency yellow, orange, and red light.

In the presence of greater levels of red and infrared light and less blue light, sunset acts as a circadian zeitgeber that tells the body to start producing melatonin. Melatonin while a hormone to help us sleep, is perhaps more importantly, the trigger that stimulates nighttime rebuilding, repair and rejuvenation.

Vata Time and Sunset Summary

• Daytime exposure to white, blue, UV, and infrared light all build energy that increases vata. In particular, a full day’s exposure to red and infrared light boost mitochondria, which powerfully stimulates vata and mental energy.
• As the sun descends toward the horizon, UV light is filtered by the atmosphere, calming vata.
• Without UV penetration at sunset, infrared and red light provide deep tissue repair and calm the nervous system.
• At sunset, most of the melatonin inhibiting blue light is blocked or scattered by atmospheric dust, which dramatically enhances lingering yellow, orange, and red light.

See also 5 Ways the Sun Can Help You Sleep