Scientists are beginning to discover the surprising roles sunshine plays in your wellbeing. From immune health to mood and sleep, learn how you can safely tap into the sun’s benefits for health.

The Sunshine Vitamin

Often referred to as the “sunshine vitamin,” vitamin D plays a critical role in our wellbeing. Vitamin D is an essential nutrient, but your body also has the ability produce its own vitamin D with the help of ultraviolet B (UVB) rays from the sun.

There are many factors that influence how effective this process is including how much time you spend outdoors, sunscreen use, the time of year, and where you live. Aside from fatty fish, egg yolks, and fortified milk, there aren’t many foods that provide a good source of vitamin D. For these reasons, upward of 50% of the U.S. population is deficient in vitamin D (1). This is concerning because vitamin D deficiency and decreased sun exposure are linked to negative health outcomes (1-4).

Vitamin D plays a vital role in bone health, but it is also critical for normal immune function. For example, vitamin D is necessary for cathelicidin production, an antimicrobial peptide that supports immunity. When vitamin D levels are insufficient, cathlicidin production decreases, leaving us with less immune defense (4, 5).

Circadian Rhythm for Mood and Sleep

Humans, like all other living organisms, have evolved with the daily rhythms of light and dark. As light enters our eyes, our retinas transmit a signal to a biological clock in the middle of our brain called the suprachiasmatic nucleus. This triggers thousands of physiological functions throughout the body including the release of hormones and stimulation of nerve activity as well as muscle, organ, and brain function. Light from the sun helps coordinate our body’s activities on a 24-hour cycle every single day (6, 7). This is referred to as a circadian rhythm.

Circadian rhythm is activated each morning when we are exposed to sunlight and our brains begin to release serotonin, a hormone that boosts our mood and creates a feeling of calm. Serotonin is converted to melatonin in darkness, allowing us to sleep more easily at night (8). Mood and circadian rhythm can be negatively impacted or enhanced depending on the duration of exposure and intensity of light. Late night artificial light exposure and not enough sunlight throughout the day are two common negative disruptors of the circadian rhythm.

While sunlight not only works to coordinate our bodies’ natural rhythms and lift our mood by regulating hormones, sunlight can also help support happiness and mental wellness. Ultraviolet light from the sun increases our body’s production of serum endorphins, a natural opiate responsible for feeling happy and good. A recent metanalysis of over 20 years of vitamin D research also found that vitamin D acts as a protective agent in our brains by providing neuroprotection and nervous and immune systems protection (9). These roles support mental health and promote normal brain function.

Too Much of a Good Thing? The Benefits of Balance

Although most of the vitamin D in our circulation is made with the help of ultraviolet light from the sun, UVB is the same solar radiation that burns our skin when overly exposed (10). That’s why it’s important to remember the old saying, “everything in moderation,” when it comes to sunlight.

Despite some of the remarkable health benefits we receive from sunlight, getting too much sun can also be detrimental by increasing our risk for sunburn, photoaging, and skin cancers. Studies show short bursts of sun exposure throughout the day provide optimal vitamin D production compared to prolonged exposure (1). Balancing our exposure with sunscreen when the UV Index is high and eating a diet rich in phytonutrient-dense fruits and vegetables also minimize the risk for harmful effects.

Improving your health doesn’t always have to be a chore, and in the case of vitamin D and your natural circadian rhythms, simply going outside and enjoying sunny weather is a step in the right direction!



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  2. Mead MN. Benefits of sunlight: a bright spot for human health [published correction appears in Environ Health Perspect. 2008 May;116(5):A197]. Environ Health Perspect. 2008;116(4):A160‐A167.
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  4. Davis CD, Dwyer JT. The “sunshine vitamin”: benefits beyond bone? J Natl Cancer Inst. 2007;99(21):1563‐1565.
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  6. Kościuczuk EM, Lisowski P, Jarczak J, et al. Cathelicidins: family of antimicrobial peptides. A review. Mol Biol Rep. 2012;39(12):10957‐10970.
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  8. Bollinger T, Bollinger A, Oster H, et al. Sleep, immunity, and circadian clocks: a mechanistic model. Gerontology. 2010;56(6): 574–80.
  9. Holick MF. A perspective on the benefitial effects of moderate exposure to sunlight: bone health, cancer prevention, mental health and well being. In: Giacomoni, PU, ed. Sun protection in men. Amsterdam, London, New York: Elsevier, 2001:11–37.
  10. Kalueff AV, Tuohimaa P. Neurosteroid hormone vitamin D and its utility in clinical nutrition. Curr Opin Clin Nutr Metab Care. 2007;10(1):12‐19.
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