SUNLIGHT ON THE HEALTH SPECTRUM
Some of our most happy and memorable experiences are linked to being outdoors. Enjoying the beach on a hot summers day, a round of golf, a game of tennis, taking the dogs for an afternoon walk or even reading a book in a tranquil garden.
These experiences lift our mood and promote a sense of wellbeing that is unique. The common thread is sunlight.
Dangers of sun exposure
Of course, we are all well aware of the dangers of sunburn and cumulative sunlight exposure. Scientists have known for almost a century that overexposure to the ultraviolet component of sunlight leads to significant skin damage that includes DNA compromise, increased free radical formation, inflammation, as well as dramatically increasing the risk of developing various forms of skin cancer.
Skin cancers are a growing concern within the medical space due to their rising prevalence, especially the incidence of melanoma, which is a dangerous form of skin cancer that develops from the pigment-containing cells known as melanocytes.
Although the exact mechanism behind the development of melanomas is still unclear, Andrew Nelson and his team from Harvard University believe that genetic factors (in particular heritable alterations in the CDKN2A gene) have the greatest influence. This being said, the principal identified non-genetic risk factor is excessive ultraviolet radiation (UVR) exposure. An extensive meta-analysis of 57 studies by Italian researchers, found that frequent sunburns doubled the risk of developing melanoma.
Several other studies showed that sunburn is also a major protagonist in the development of other forms of skin cancer, including basal cell and squamous cell carcinomas.
A new perspective
Taking into account the associated risks, the message of complete sun avoidance is being reconsidered. Over the last 15 years, a wave of research has emerged, showing that without modest, regular, non-burning exposure to the sun, we may be susceptible to significant physical, emotional and cognitive compromise.
According to Dr Pelle Lindqvist, an epidemiologist from the world renowned, Karolinska Institute in Stockholm and author of one of the largest studies on sunlight exposure and health outcomes:
‘We know in our population, there are three big lifestyle factors that endanger health: smoking, being overweight, and inactivity. Now we know there is a fourth - avoiding sun exposure.’
Presumably, the key motivation behind research into the benefits of responsible sun exposure is linked to the growing prevalence of vitamin D insufficiency.
According to a meta-analysis performed by researchers from Harvard and several other US institutions, 69.5% of Americans and 86.4% of Europeans are currently vitamin D deficient.
To appreciate the significance of these findings one has to understand the impact that vitamin D has on our health. In a collaborative report involving 488 scientists from 50 countries, which aimed to better understand the root cause of chronic diseases, their patterns and global impact, it was discovered that of the 30 leading causes of premature mortality (including many cancers, neurological, cardiovascular and autoimmune diseases), 19 were linked to low vitamin D status!
The most effective means of elevating vitamin D status is not through supplementation or diet, but rather through sun exposure. When the sun strikes the body, the ultraviolet B portion of the sun’s spectrum enters the skin and is absorbed by a form of cholesterol (7-dehydrocholesterol), which is then converted to vitamin D3. This form of vitamin D requires further transformation to become biologically active, relying principally on the liver and kidneys. However, because vitamin D is so vital to human health, many tissues and cells in the body including immune, brain, breast, prostate, colon and skin, have the capacity to convert vitamin D into its biologically active form.
The benefits of vitamin D
Vitamin D acts as an enabler and must be present for many biological processes to occur. According to Dr Michael Horlick, an endocrinologist who has authored over 400 publications on vitamin D, this important molecule influences more than 80 different metabolic processes. Horlick attributes vitamin D to the control of almost 2000 genes, many of which control cell growth, immune function, blood sugar stabilization as well as proper heart and muscle function.
Although best known for promoting optimal skeletal development, one of the greatest influences of vitamin D is in the area of brain health. A recent study published in the journal Dementia and Geriatric Cognitive Disorders showed that vitamin D is important for memory, promotes structural integrity within the brain, has strong anti-inflammatory actions, facilities neurological detoxification well as offers strong defenses against the development of dementia and Alzheimer’s.
UV radiation linked to nitric oxide liberation
In a surprising twist, researchers have uncovered another mechanism by which sunlight exposure influences our functionality. This may explain some of the limitations experienced with vitamin D supplementation.
In a recent study published in the Journal of Investigative Dermatology, a team of researchers from Edinburgh and Southampton Universities showed that when the skin is exposed to UV radiation, an enormous amount of nitric oxide gas is liberated into circulation (from nitrite and nitrate reserves found in the skin). The result: a dilation of our blood vessels; the lowering of blood pressure and dramatically enhanced functionality of the cardiovascular system.
According to a 2016 review published in Cancer Research Frontiers, nitric oxide mobilization through UV exposure is also associated with better weight control, improved glucose tolerance, lowered insulin resistance, and lowered cholesterol – all key factors in healthspan and longevity. This may explain why researchers from the Karolinska Institute, have (perhaps controversially) concluded that complete avoidance of the sun is as bad for one as smoking. This statement comes off the back of a 20-year study following the sunbathing habits of nearly 30 000 Swedish women. The study that was published in the Journal of Internal Medicine showed that avid sunbathers had a significantly lower risk of death from cardiovascular disease and other conditions that were not related to cancer. The study also showed that as those who experienced modest sun exposure had a 40% lower risk of all-cause mortality than those who avoided the sun completely.
Sunlight improves functioning of our immune system and deactivates certain viruses
Another important discovery as to why sunlight exposure lowers the occurrence of certain illnesses including various autoimmune disorders and cancers emanates from Professor Gerald Ahern from Department of Pharmacology and Physiology at Georgetown University. Dr Ahearn and his team found that low levels of blue light (found in morning sun rays), energize specialized immune cells (T-cells) creating robust movement and enhanced activity. Incredibly, although immune activity increases on the surface of the body, the inverse pattern occurs internally. A 2015 study published in the journal Archives of Biochemistry and Biophysics showed that UV radiation was able to control immune and various inflammatory processes within the body.
Not only does sunlight improve functioning of our immune system, but according to virologist, Dr Phil Rice, it also deactivates many highly infectious viruses.
Morning sunlight boosts metabolic rate and lowers body-fat
Three years ago, researchers at from the Department of Neurology at Northwestern University, published a study showing a direct relationship between metabolic rate and body composition with respect to the intensity and timing of sunlight exposure. In the same vain, two earlier studies by Russian and Canadian scientists found that exposure to 45 minutes of bright early morning light (between 6-9am) ramped up metabolic rate, lowered body fat and even controlled appetite.
Sunlight activates more than 5000 genes responsible for health
Incredibly, sunlight exposure also appears to enhance the functionality of our genetic material (DNA). In a 2015 study published in the Journal Nature Communications, researchers evaluated blood and tissue samples from 16 000 people living in various regions of the world. The study, headed up by a research team from Cambridge University aimed to identify the seasonal differences in human health profiles (i.e. higher prevalence of autoimmune, psychiatric and cardiovascular diseases during the winter months). The scientists discovered that direct sunlight exposure activates over 5000 genes (20% of our gene pool), many of which have been shown to have a key influence in the promotion of health by means of lowering inflammation.
Sunlight exposure increases levels of ‘feel good’ beta-endorphins
In 2014, Harvard researchers published a study in the journal Cell, showing that our skin produces a neurohormone called beta-endorphin in response to UVB exposure. This neurochemical promotes a feeling of wellbeing, super charges our immune system, relieves pain, promotes relaxation, speeds up wound healing, and even facilitates the specialization of cells. This molecule may be the driving force behind our desire to expose ourselves to sunlight.
Proceed with caution
Although a recent landmark study in the Journal Dermato-Endocrinology has world-renowned researchers calling ‘insufficient sun exposure an emerging health problem’, it is important to be mindful that sun exposure can be extremely dangerous, especially in excess. The weight of the scientific literature still leans towards the risks and as such, warnings on the dangers of sun exposure should be heeded.
For a balanced perspective, speak to your dermatologist and/or doctor, as sun exposure guidance should be tailored to the individual. Factors such as age, skin type, history of skin and other cancers, and concurrent medical conditions should always influence health practices.