Written by
Dr.Sanjana.V.B. Bhms. Dbrm.Cdn

 Reviewed by SIAHMSR medical team

Health benefits of sun light

  Sun light is important for proper functioning of human body as it determines human behaviour, bone health and mental health.Sunlight is a part of the electromagnetic radiation emitted by the sun. It reaches earth after being scattered and filtered by earth’s atmosphere.

The sunlight has infrared, visible and ultraviolet [UV] rays. The UV rays have positive and negative effects on the health of humans  depending on the duration and time of exposure.

Sunlight affects your sleep wake cycle & mood

 Moderate exposure to sun for a short interval of time helps mental and physical health.You may feel liveliness or alertness.

Sunlight has crucial role in determining your mood, rhythm of brain with respect to sleep wake cycle and your alertness.You may feel depressed if you are not exposed to sunlight for long .

In long winters, people get too little exposure to sun and it affects their mood and behavior. They feel dull and depressed.

Depressive mood resulting from lack of exposure to sun is known as seasonal affective disorder.

 Sun exposure is linked with melatonin hormone production by brain and therefore the maintenance of normal circadian rhythm of human brain. What is meant by circadian rhythm?

Circadian rhythm is a natural mechanism of the body regulating sleep wake cycle and it is repeated every 24 hours .Pineal gland of brain secretes melatonin hormone which in turn regulates sleep wake cycle.

 The chemical melanin is produced in the skin by UV rays of sun which is  used for the production of melatonin hormone production. . Therefore sunlight plays a crucial role in melatonin hormone production by your brain .

   Light can advance or delay the circadian rhythm. The light and dark cycle of sun has great effect on circadian rhythm, sleep and alertness.

Your body’s circadian clock responds to light, as a signal to be awake, and alert. Darkness or dim light, works as a signal to fall asleep.

Increase your amount of light during the day to be more alert. Reduced or dim light at night helps in general well-being, inducing sleep especially in people having heart diseases.

Blue LED lighting at night suppresses melatonin hormone and regulate normal circadian rhythm compared to bright white light. So blue LED lights are recommended during night hours for better sleep.

What happens when sleep wake cycle is disordered?

 Shift work or chronic jet lag may disrupt the sleep wake cycle or circadian rhythm.Maintaining normal sleep and circadian rhythm is very important for brain health

Insufficient or disrupted sleep may lead to

1. metabolic syndrome

2. diabetes

3. hypertension [high blood pressure]

4. mental ill health [bipolar disorder]

5. sleep disorders [delayed sleep phase disorder]

Moreover , sleep is very important for maintaining your brain health as well as immunity. Therefore circadian rhythm or sleep wake cycle associated with light has crucial role in determining your overall health and behavior.

How does morning exercise in sunlight help your mood?

 Morning exercise in sunlight may help to reduce obesity shrinking fat cells beneath the skin. Sunlight also helps to keep your mood good boosting serotonin hormone .

                                  SIAHMSR                          

How does sunlight improve your bone health ?

     Moderate exposure to sun is essential for  your bone and muscle health as sunlight helps in vitamin D synthesis. Vitamin D is integral to bone and general health.90% of vitamin D  is that we get from sunlight . Vitamin D is formed from the 7 dehydroxycholesterol on the skin by U V rays of sun. Therefore sunlight is crucial in vitamin D production by your body.

Vitamin D is important for calcium absorption from gut and deposits it in bones .Thus vitamin D play a great role in preventing osteoporosis . Vitamin D deficiency may lead to osteoporotic fracture of bones particularly in post menopausal women.

Recent research studies points out that vitamin D deficiency may lead to thyroid dysfunctions and certain types of cancers.

How long should you get sunlight  exposure for good health?

Get sunlight exposure for 10-15 minutes a day on uncovered parts of your body between 11pm- 5pm everyday when UVB rays of sun can act on skin cholesterol and help vitamin D production.

However, excessive sun exposure is not recommended as it is associated with the risk of skin cancer and premature skin ageing.

Adverse effects of excess  exposure to sun light:

   Excessive exposure to sun’s UV A rays & UV B rays cause damage to skin cells. Exposure to these rays can make the skin less elastic, thickened, leathery, wrinkled, or thinned and skin may look aged prematurely. This is known as photo-ageing.

Skin has repairing mechanism to resolve sun burn and damage inflicted on it, by constantly shedding the outer layer .But  as one get older, it becomes harder for the skin to repair itself and the signs of ageing become more prominent on the skin.

Over exposure to sun enhances the risk for skin cancers also .The UV rays of sun cause DNA [genetic material] damage and lead to skin cancer. The commonly affecting cancers of skin are melanomas .

Hence excessive physical activity in hot sun is not recommended for children too.

For the synthesis of vitamin D by skin regularly 15 minutes of exposure to sunlight is adequate. Therefore only moderate exposure to sunlight is recommended for the purpose of vitamin D synthesis by skin. Vitamin D may be obtained from foods of animal sources too but it is only considerably smaller amount.

How to protect yourself from UV RAYS of sun?

·       Sunscreens

Use of sunscreen lotions or creams are recommended for preventing the UV rays induced skin damage. Sunscreens come labeled with a sun protection factor (SPF), such as 15, 30, or 50,100 are available in the market.

 A sunscreen labeled SPF 30 may give you 93% protection from harmful rays of sun. Sun screens are available according to the skin types also. For dry skin, the best sun screen is that which hydrates the skin maintaining natural moisture barrier.

Sun screens are available with ingredients like glycerin, hyaluronic acid, ceramides, jojoba oil, aloe Vera etc. Most dermatologists recommend sunscreens with SPF30or higher as minimum recommended SPF  for better skin protection. SPF 50 provides98percent protection from UV rays.

Usage

 Apply sunscreens 30 minutes prior to going outside and reapply every two hours. If there is excessive sweating or chances of getting wet apply immediately. The amount of sunscreen you use and how often you use it is a crucial factor in your protection from the sun.

UV rays of sun can penetrate your skin even through windows on a bright sunny day or while you drive a car. Do apply sunscreen to prevent photo ageing of your skin.

 UVB rays are at peak on midday. SPF 50-100 is better than lower grades   but reapplication after 2hours is important .However no sunscreens can give 100 percent protection from skin damage. 

The effectiveness of sunscreens- Factors to check

   The quality and effectiveness of sunscreen is affected by several factors.

1.Expiry period

A sunscreen’s active ingredients can break down over time. Hence it is very important to check the expiry date on the container. Do not use sunscreens which have crossed the expiry date.

2. wet skin

Perspiration and swimming can also reduce the effectiveness of sunscreens. Re apply sunscreen immediately for getting better protection.

3. Spoiled sunscreen

If your sunscreen container smells bad, please take care to replace it quickly. The foul smell  of sunscreen is indicative of bacterial contamination. Do not reuse it ever.

Types of sunscreens

Physical [inorganic] and chemical [organic] sunscreens are available in the market. Physical sunscreens leave a white mark when applied. The ingredients are zinc oxide and titanium dioxide.

Chemical organic sunscreen gets absorbed easily into the skin and protects the skin through a chemical reaction that converts UV rays into heat. Sunscreen is advised to use over exposed skin areas every two hours when you are out of your home or exposed to sunlight somehow. 

A non-fragrant , non-irritating sunscreen is ideal for use.

Sun protective clothing

It is recommended to use sun protective clothing and hat along with a sunscreen having SPF 30- 50 ,if you go out in bright sun. Sun screen alone may not give you 100 % protection.

 written by dr sanjana vb[ copyright]

References

·https://www.cdc.gov/niosh/emres/longhourstraining/light.html#:~:text=The%20light%2Fdark%20cycle%20of,day%20to%20be%20more%20alert       

·  https://newsinhealth.nih.gov/2014/07/sun-skin