You’ve heard about ultra-processed food. But did you realize that ultra-processed light, i.e., LED and indoor lighting that generally only contains visible (mostly blue/green) light, could be even worse for your metabolic (and overall) health?

Natural sunlight, like natural food, contains a rich variety of light “nutrients” we have evolved under and need for optimal health.

Natural light and its essential “nutrients”

Starting from high energy (short wavelength) to lowest energy (long wavelength):

1. UVB: UVB is essential for vitamin D production. Vitamin D is a hormone made from a cholesterol precursor in the skin. When irradiated by 280-315nm UVB is made into the hormone known as “vitamin D”. Almost every cell in the body has a vitamin D receptor. Vitamin D controls gene expression, immune function and metabolic health. Low solar exposure and low vitamin D is linked to a multitude of chronic health conditions from increase in diabetes and cancer to asthma and autoimmunity.

2. UVA: UVA is responsible for the erythema response (aka getting pink in the sun), and melanin production. Melanin has important properties that allow increased energy production and cell function (through splitting water in free hydrogen, oxygen, and electrons), as well as acting as an important metal chelator, helping us to rid ourselves of heavy metals (heavy metal load is also linked to diabetes [1]). Melanin can be internalized to support neuromelanin, sensory, and brain function. Your dermatologist is wrong, if he says “there is no such thing as a healthy tan”.

UVA promotes nitric oxide release in the body, an essential component in protecting the cardiovascular system, lowering blood pressure and increasing blood flow to tissues. Dr Weller, author of the huge UK biobank study on sunlight and melanoma, says we have a 100X greater risk of dying of a cardiovascular event due to insufficient sunlight than we do of melanoma from too much [2].

3. Visible light: The ratios of blue, red, violet, etc., visible light spectra present in natural sunlight are constantly changing from sunrise to sunset. This powerfully triggers circadian biology, cortisol, melatonin, and sex hormone release, digestive function, and neurotransmitter synthesis. Steady-state indoor junk light is one of the biggest drivers of poor hormone function and mental health.

4. Near Infrared: NIR light is low energy long wavelength and can penetrate deeply into the body (even through the skull) to nourish our mitochondria and increase energy production. Near-infrared light is one of the most important drivers of intracellular melatonin production, which represents about 70% of our total melatonin levels [3]. This type of melatonin is not released in a circadian fashion into the bloodstream like pineal melatonin (which is sensitive to the changing levels of blue light). Melatonin promotes autophagy and mitophagy (cell recycling), is one of the body’s most important endogenous antioxidants, and has been shown to regulate inflammation and provide antiviral benefits, among many other essential functions [4, 5]. Check out the learn section of the Circadian app for a deep dive into melatonin.

Light & metabolic health

Did you know similarly to processed food, artificial light can increase blood sugar and insulin levels (without even having a snack) [6, 7, 8, 9]?

Lack of full-spectrum sunlight is associated with an increased risk of cancers, cardiovascular, autoimmune, metabolic diseases, and more [10].

Red/infrared light lowers blood glucose by 27% [11]. By the way, you don’t need a red light panel, you just need to spend more time outside. Natural sunlight is 50% red & infrared light.

Light at night, like eating junk food, increases blood sugar and diabetes [12].

Artificial light at night will ruin your metabolism, make you gain weight and increase your risk for obesity [13, 14, 15].

Further, ultra-processed light from LEDs and indoor lighting stimulate dopamine release (that’s why your phone and laptop are so addictive), which over time will deplete your reserves, zapping your willpower and leading you to want to overeat the ultra-processed foods.

Indoor lighting is also linked to an increased risk of myopia, whereas sunlight does the opposite [x]. Artificial light likely increases the risk of neurodegenerative diseases like Parkinson’s [16]. Sun exposure, on the other hand, is linked to lower rates of cancer, cardiovascular, neurodegenerative, metabolic, and autoimmune diseases [17].

Circadian disruption resulting from insufficient bright natural sunlight during the day and exposure to junk light at night is a well known driver of many pathologic conditions, including sleep disorders, cardiovascular disease, metabolic dysfunction, infertility, poor physical performance, as well as cancer [18].

So while we need to avoid ultra processed food, we need to realise that ultra processed light could be as problematic.

If you take the care to eat a natural, unprocessed diet but don’t expose yourself to natural light during the day and stay up after dark on your laptop or phone (without protection), you are also ruining your metabolic health, so you may as well just eat all that Easter chocolate.

Mind your rhythm, mind your light, and spend more time outside ☀️