Electromagnetic radiation given off by the sun is called sunlight. Sunlight is filtered through the atmosphere on Earth. When its direct radiation is not blocked by clouds, we experience it as sunshine, a combination of heat and light. If you’re near the Poles, sunlight occurs even at night.
While sun exposure is definitely necessary for the absorption of Vitamin D, modern-day dermatologists focus on the skin’s harmful rays and the preventive measures one ought to take when out in the sun. Skin cancers are a real danger today when the atmosphere’s ozone layer is being constantly depleted.
 The truth about UV, UB and UC radiation
Ultra-violet radiation is divided into categories based on the wavelength. UVC radiation is absorbed by the atmosphere and does not cause skin damage. UVB radiation affects the epidermis and is the primary agent responsible for sunburns. UVA radiation penetrates deeper into the skin and its intensity is more constant than UVB without the variations during the day and throughout the year. Both UVA and UVB radiation cause wrinkles by breaking down collagen, creating free radicals and inhibiting the natural repair mechanisms of the skin.
The sun’s nuclear energy source was discovered by Hans Bethe.
 Sunscreen: Your first line of defense
Sunlight accounts for 90% of the symptoms of skin damage. Most skin experts agree that a good-quality sunscreen with SPF 15 or higher is the first and best line of defense against the sun, arguably the skin’s worst enemy. Here are some facts about its application for best results.
- The most common mistake people make has to do with application. Using inadequate amounts of sunscreen is of no use. Most people only use 25-50% of the recommended amount. Truth is, it ought to be applied liberally on all sun-exposed areas of the skin.
- It takes 20-30 minutes for sunscreen to be absorbed, so be sure to apply it a half hour before stepping outdoors.
- It should be reapplied after swimming, excessive sweating or towelling the body dry. Also, reapply after 2 - 4 hours in the sun.
- Even when out of a swimming pool, or in the outdoors, apply sunscreen even when in the shade. Concrete, sand and water all reflect harmful rays.
- Sunscreen should also be the last product applied on facial skin as some sunscreens can break down in the presence of water contained in water-based foundations and moisturizers.
 Seasonal Affective Disorder
Lack of sun exposure causes its own set of problems. In countries where sunlight is seasonal, people suffer from Seasonal Affective Disorder (SAD) or ‘sunlight deficiency’ in simpler terms. Such people suffer symptoms of depression during seasons that have shorter days and consequently less sunlight. Our biological internal clocks or circadian rhythms are tuned to symptoms include craving for sugary foods and refined carbohydrates.
A circadian rhythm is the body’s natural cycle that controls appetite, energy, mood, sleep and libido. When our body is out of sync with nature, the rhythms are upset and cause mood swings, sleep disruption or anxiety disorders. Sadness, anxiety, irritability, withdrawal from usual activities, lack of energy, fatigue, increased need for sleep, increased appetite and weight gain are the common symptoms of SAD. Three-quarters of the sufferers are women in their 20’s to 40’s. The illness is more commonly seen in people who live at high latitudes i.e. geographic locations father north or south of the equator where seasonal changes are more extreme.
Levels of serotonin and melanin are imbalanced in the body owing to the diminished hours of sunlight. Lack of sunlight on the skin results in a host of health effects like depression, osteoporosis, breast cancer and even schizophrenia. That is because our bodies were designed to be exposed to the sun on a frequent basis.
 Our body’s natural rhythm
Like most of nature’s cycles, our body also functions by its own set of rhythms. These rhythms include the four seasons and the 24-hour rotation of the earth. The body takes its cues from nature’s rhythms. That is why we wake up when the sun rises, our energy levels peak and we tend to feel a dip in energy towards the end of the day. The morning light of a new day cues the body to produce hormones and neurotransmitters that bring a person awake, cause blood pressure to increase and body temperature to rise. At sunset, our body responds to dusk and starts to secrete melatonin so body temperature drops and we start to feel sleepy. As our bodies depend on sunlight to keep these rhythms in sync, a seasonal change where we do not see enough sunlight is enough to upset the cycle.
 Circadian rhythm disorders
We have tampered with nature’s cues with the lifestyle changes we have adopted. A modern day neither starts at the crack of dawn nor does it end at 8 pm. We use an alarm clock to wake us up, work in offices that are flooded with artificial lighting and spend our time outdoors when there is no sunlight. These man-made cues affect the circadian or natural rhythms, thereby causing an imbalance.
 Vitamin D: The Sunlight Vitamin
Vitamin D is what your body makes when your skin comes into contact with the sun. It is produced by our skin in response to the ultraviolet radiation from natural sunlight. Your diet cannot provide for the body’s requirement of this vitamin. Therefore sun exposure is the only reliable way to generate vitamin D in the body.
- The further you live from the equator, like the UK, Canada and many American states, the more sun exposure you need to generate adequate levels of vitamin D in your body.
- People with dark skin may need 20-30 times more the exposure to sunlight as their light-skinned counterparts to generate the same amount of the vitamin.
- Vitamin D is activated in your body by your liver and kidneys before it can be used.
- Vitamin D is absolutely crucial for the absorption of calcium in your intestines.
- Vitamin D is one of the most powerful healing chemicals in your body and your body makes it absolutely free.
- Our bodies have ‘internal sunscreens’ to ensure you can stay under the sun for long periods without burning.
- Our body has the capability to self-generate and regulate just how much it needs.
 Useful Websites
- Vitamin D and Your Health
- Apollo Health