The Real Meaning Behind "You Are My Sunshine"

The Forgotten (science-based) Power of Sunlight

As we march deeper into the digital age, where we spend our lives behind screens and under bright LEDs remember: the sun is not your enemy. In fact, it is one of our oldest allies in living a vibrant, healthy, and emotionally rich life.

Get outside and let the sun touch your skin. Do it every day. Your body and mind were built for it.

Let me explain why.

Humans evolved under open skies, with hours of daily sunlight exposure. That light wasn’t just illumination; it was biological input. Today, we understand that sunlight affects us on multiple levels, including:

• Skin: Synthesises vitamin D 1, regulates immune and hormonal systems.

• Eyes: Calibrates our circadian rhythms and stimulates mood-related neurotransmitters like dopamine 2.

• Cells: Absorb near-infrared (NIR) light, which penetrates deep into tissue and stimulates mitochondrial ATP production 3.

Infrared Light: Sunlight That Powers Your Cells

Infrared light, particularly near-infrared (700–1400 nm), penetrates human tissue and reaches the mitochondria, where it stimulates cytochrome c oxidase. A key enzyme that drives ATP synthesis 3, 4.

This leads to:

• Improved energy metabolism

• Enhanced tissue healing

• Increased blood flow

• Reduced inflammation

These effects only occur if infrared light reaches your skin. Most clothing, glass, and artificial indoor lighting block these wavelengths 5. A pooled meta-analysis of 14 studies with over 11,300 women found that women wearing concealing clothing were 2.28x more likely to have vitamin D deficiency (serum 25(OH)D low) compared to women with less coverage. 18

So, yes. You need bare skin exposed to real sunlight to get the full benefit. If you aren't able to, consider taking a vitamin D supplement.

Sunlight and the Eyes: Circadian Gold

Your eyes contain intrinsically photosensitive retinal ganglion cells (ipRGCs), which detect blue and green light (~460–500 nm). This signal regulates:

• Melatonin suppression in the morning (signals your brain to wake up)

• Cortisol peak timing (gives you mental focus and wakes you up)

• Dopamine release in the retina (tied to mood and focus) 2, 6

A study in Proceedings of the National Academy of Sciences showed that morning sunlight exposure enhances sleep quality and mental health 7.

You don’t need to look directly at the sun (and actually please don't - you will screw your eyes). Just go outside and face the open sky without sunglasses or glass.

Sunscreen, Vitamin D, and the Fear of the Sun

Yes, excessive sun exposure and burns increase the risk of skin cancer. But as a populous, we’ve overcorrected.

• Sunscreen blocks UVB radiation, which is essential for vitamin D synthesis 1

• A single application of SPF 15 sunscreen can reduce vitamin D production by ~93% 8

• Many mineral sunscreens also reflect or absorb some infrared light, reducing the benefits 9

Worse, widespread sun avoidance has led to epidemic-level vitamin D deficiency, even in sun-rich nations like our gorgeous Australia 10. Your daycare teachers weren't impressed when I tried to explain why I didn't apply sunscreen to your "delicate young skin" when I dropped you off at 7am... I wasn't trying to be a hippy. I was literally following science.

Burning is harmful. But short, regular, unprotected sun exposure is essential.

Do Other Animals Benefit from Sunlight?

Because I knew you'd ask this. Your dog Louis has fur - so how is he possibly getting his dose of sun? I looked at this too - and Yes. Infrared and UV exposure benefits are shared across species:

• Reptiles rely on sunlight for vitamin D3 synthesis, immunity, and metabolic regulation 11

• Birds use preen oil activated by UV light to generate vitamin D 12

• Mammals, including dogs and horses, benefit from infrared photobiomodulation therapy—used in veterinary medicine to enhance healing and reduce inflammation 13

Even in fur-covered species, infrared light can partially penetrate. Animals instinctively expose their bellies, ears, and under-limbs to the sun’s rays.

Why Should You Care?

At the time of writing this entry we are living in a state of chronic sunlight starvation.

• We modern humans spend ~90% of our time indoors 14

• Children today play outdoors 50% less than they did 50 years ago 15

• Over 40% of adults in Australia are vitamin D deficient 10

• Excessive sun avoidance correlates with higher rates of depression, immune disorders, and all-cause mortality 16, 17

• A long-term Swedish cohort study found that women who actively avoided the sun had a 1.3–2x higher mortality rate than those with regular sun exposure even after adjusting for cancer risk 16.

  Now can you see why we kept dragging you out camping and into the street with your bikes and scooters? Remember how you use to eat breakfast on your little Paw Patrol table and chairs in the front garden? Keep doing it - there's a reason for it. (Maybe upgrade to some less wonky furniture).

Is the Sunlight Benefit Cumulative or Instant?

Both.

• One session of sunlight can improve mood, alertness, and energy. 2, 3

• Consistent daily exposure builds circadian resilience, supports hormonal cycles, and improves long-term immune and metabolic health.

• You don’t need a full 30-minute block. Multiple 5–10 minute sessions (especially morning) add up to the same or better effect. 7

So: Spend at least 30-minutes outside in the sun every day. Preferably making grass angels soon after waking, without being covered from head to toe.

1. Holick, M.F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281.

2. LeGates, T.A., Fernandez, D.C., & Hattar, S. (2014). Light as a central modulator of circadian rhythms, sleep and affect. Nature Reviews Neuroscience, 15(7), 443–454.

3. Hamblin, M.R. (2016). Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics, 3(3), 337–361.

4. Karu, T. (1999). Primary and secondary mechanisms of action of visible to near-IR radiation on cells. Journal of Photochemistry and Photobiology B: Biology, 49(1), 1–17.

5. Sayre, R.M., et al. (1997). Light transmission characteristics of window glass. Photochemistry and Photobiology, 66(3), 385–388.

6. Dkhissi-Benyahya, O. et al. (2013). Circadian regulation of dopamine: a role for the light–dark cycle. Frontiers in Cellular Neuroscience, 7, 112.

7. Byrne, M. et al. (2017). Light exposure and sleep outcomes: a systematic review. PNAS, 114(46), 12370–12375.

8. Matsuoka, L.Y., et al. (1987). Sunscreens suppress cutaneous vitamin D3 synthesis. Journal of Clinical Endocrinology & Metabolism, 64(6), 1165–1168.

9. Shaath, N.A. (2010). Ultraviolet filters. Photoprotection, 2, 13–22.

10. Daly, R.M. et al. (2012). Prevalence of vitamin D deficiency and its determinants in Australian adults. British Journal of Nutrition, 107(3), 397–404.

11. Ferguson, G.W. et al. (2003). Voluntary exposure of an herbivorous lizard to UV-B radiation and its effect on vitamin D3 synthesis. Physiological and Biochemical Zoology, 76(5), 576–583.

12. Bäckström, B. (1997). UV light and birds: The importance of preening oil. Journal of Ornithology, 138(1), 1–6.

13. Draper, W.E., et al. (2012). Red and near-infrared laser therapy on tendon healing. American Journal of Veterinary Research, 73(1), 94–100.

14. Klepeis, N.E., et al. (2001). The National Human Activity Pattern Survey (NHAPS). Lawrence Berkeley National Laboratory.

15. Gray, P. (2011). The decline of play and the rise of psychopathology in children and adolescents. American Journal of Play, 3(4), 443–463.

16. Lindqvist, P.G., et al. (2016). Avoidance of sun exposure is a risk factor for all-cause mortality. Journal of Internal Medicine, 280(4), 375–387.

17. Weller, R.B. (2020). Sunlight Has Cardiovascular Benefits Independently of Vitamin D. Blood Purification, 49(1-2), 163–168.

18. Mohamed, A. A., Al-Daghri, N. M., & Alokail, M. S. (2021). Clothing type and vitamin D status: A systematic review and meta-analysis. Endocrine Practice, 27(9), 915–929.