
Humans evolved in sunlight and have depended on sunlight forever. If the sun disappear, life would also disappear. Nothing is simpler to understand than this. And yet, in recent decades, negative publicity has been given to sunlight due to its association with an increased risk of skin cancer, ignoring the sun’s many benefits. I will try in this article to debunk this myth, with the help of the works of Dr. Michael Holick.
Dr. Michael Holick is a leading figure in the medical field. He has made numerous contributions to the biochemistry, physiology, metabolism and photobiology of vitamin D for human nutrition. Dr. Holick has established global recommendations regarding sunlight exposure as an integral source of vitamin D. He has helped raise awareness in the pediatric and medical communities of the vitamin D deficiency pandemic and its role in causing not only of metabolic bone diseases and osteoporosis in adults, but also increasing the risk of adults and children developing common deadly cancers, schizophrenia, infectious diseases including tuberculosis and influenza, autoimmune diseases, strokes and heart disease.
A little history
As the Industrial Revolution swept Northern Europe in the late 17th century, English doctors began to report that those children living in the inner cities of Glasgow and London were developing particularly prominent skeletal deformities of the legs, as well as stunted growth.
In the early 19th century an estimated 90 percent of children living in European industrial cities had this bone-deforming disease known as rickets. In 1822 a Polish doctor noticed that, compared to children in cities, those in rural areas are rarely affected by this disease, and notes: “strong and obvious is the influence of the sun on the cure of rickets and the frequent appearance of the disease in densely populated cities where the streets are narrow and poorly lit by the sun.”
This theory seemed inconceivable in the medical world at the time. Most scientists believed that the only effect of the sun’s rays was to generate heat, which is responsible for sunburn, causing swelling, blistering and pain on the skin. So the Polish doctor’s observation was ignored for almost 100 years. In 1889, an English doctor wrote to colleagues who lived in India and China, where children were extremely poor and lived in squalor, asking if they had seen children with rickets in those areas. They replied that it was a rare condition. The doctor argued that children living in London and Glasgow had better nutrition and better living conditions compared to those in India and China, and the only difference was that they were not exposed to sunlight. So he encouraged sun exposure as a method of treating and preventing rickets.
At the same time, Dr. Finsen was using sunlight to treat lupus vulgaris, a skin disease caused by tuberculosis infection. For his observations he received the Nobel Prize in 1903. And Dr. Windaus received the Nobel Prize in 1928 for his discovery, vitamin D3 and its relationship to sun exposure.
Fortification of food in European countries, especially milk, with synthetic vitamin D to prevent rickets in children soon began. In the late 1940s and early 1950s very high doses of vitamin D administered to infants led to the development of hypercalcemia. Babies began to be born with altered facial structure, heart problems and mental retardation. It was concluded that this was due to over-fortification of milk with vitamin D. As a result, Britain passed laws banning the fortification of any product, including food and even skin creams. It was then that the idea was born that vitamin D in high doses could cause birth defects and the spread of mental retardation throughout Europe and most of the world. As a result, most countries in the world today still do not allow fortification of even milk with vitamin D.
Nowadays, rickets is on the rise again. The reasons are no longer poverty and ignorance, but the fact that the children spend too little time outside, and when they do go out in the sun, parents are obsessed with protecting them with sunscreen all the time.
And some physics and physiology
Earth has been bathed in sunlight for more than 3 billion years. As life forms evolved in the ocean, they were exposed to sunlight. Energy from the sun was efficiently used by early phytoplankton to produce carbohydrates as an energy source. These organisms have developed ergosterol, a cholesterol-like compound in animal cells that, among other functions, uses the sun’s UVB radiation to convert it into vitamin D2. Thus, the connection between sunlight, vitamin D and calcium was born, allowing the emergence of vertebrates. Soon… man appeared.
The sun produces an enormous amount of energy: cosmic energy, gamma rays, X-rays, UVB and UVA radiation, visible radiation, and infrared radiation. All high-energy: cosmic, gamma, and X-rays are reflected or absorbed by the atmosphere surrounding our planet. Most UV radiation is effectively absorbed by the ozone layer. All UVC radiation is absorbed by the ozone layer and does not reach the earth’s surface at all. Most of the UVA and UVB radiation is also absorbed by the ozone layer. About 0.1% of UVB and 5% of UVA reaches the earth’s surface. A fraction of 39% of visible radiation and 56% of infrared radiation reach the earth’s surface.
The skin contains a variety of macromolecules, including RNA, DNA, and proteins, that efficiently absorb UVB photons, and therefore almost all UVB photons are absorbed by macromolecules in the epidermis. These macromolecules are less efficient in absorbing UVA radiation and as a result UVA radiation penetrates through the epidermis into the dermis. Very little visible and infrared radiation is absorbed by the epidermis or dermis and thus can penetrate deep into the body to the internal organs.
In response to exposure to sunlight, the skin increases the amount of the top dead layer, the stratum corneum, which acts as mirrors and reflects and refracts UVA and UVB radiation, and in addition produces melanin, which acts as an umbrella to absorb UVB and UVA for not to enter the cells. Their absorption into cells could cause the formation of free radicals that can damage proteins, DNA and RNA. In short: we have internal mechanisms by which we can protect ourselves from the unpleasant effects of UV radiation.
Why are we afraid of the sun?
In the late 1970s, Jonathan Shanklin, a meteorologist at the British Antarctic Survey, noticed that something was happening to the ozone layer that “shrouds” the Earth, and retains, as we have seen, most of the sun’s ultraviolet rays. He followed this phenomenon for several years, and in 1985, together with 2 other colleagues, published a paper in which they presented their findings, suggesting a link to a man-made compound called chlorofluorocarbons (CFCs), used in aerosols and devices. cooling (refrigerators and air conditioners). Their discovery, the thinning of the ozone layer over Antarctica, came to be known as the “ozone hole”.
This work sparked a general mobilization that has never been equaled before. Although the industries tried to combat the scientific papers showing that CFCs were destroying the ozone layer at a rapid rate, the evidence was overwhelming. In 1987, the Montreal Protocol was adopted to protect the ozone layer by phasing out chemicals that deplete it. In the 1990s and early 2000s, the production and consumption of CFCs was stopped. Since its adoption, the Montreal Protocol has been signed by every country on Earth and is, by now, the only treaty that has been universally ratified.
Today, the ozone hole still exists, smaller and smaller, but only for a few short months a year in the spring, and only over Antarctica. It closes during the summer as stratospheric air from lower latitudes is mixed, until the following spring when the cycle resumes. But there is evidence that this hole is starting to disappear and recover more or less as expected. Based on scientific assessments, it is believed that by mid-century the ozone layer will return to pre-1980 levels. Healing is slow because of the long lifetimes of molecules that deplete the ozone layer. Some persist in the atmosphere for 50 to 150 years before degrading.
How good the sun can do to us
The dangers of not exposing to the sun are greater than we think. Studies have been done that prove that if you avoid the sun all the time you are exposed to a danger similar to smoking, obesity and sedentary lifestyle, the habits of the modern world. Moderate but constant sun exposure has more benefits than disadvantages.
Vitamin D
Technically, the optimal level of vitamin D, as measured by the 25OHD assay, should be greater than 30 nmol/L. Recent studies have shown that optimal health is ensured by a level higher than 48 nmol/L. in the general population there is a worrying deficit, somewhere between 40% in adults and up to 70% in young children. This calculated with the minimum level of 30 nmol/L, not with the optimal level of 48 nmol/L.
The most effective way to ensure your vitamin D intake is exposure to the sun. Few foods contain vitamin D in a proportion that ensures the daily requirement, and supplements should only be used if we cannot stay in the sun: in the case of diseases that induce photosensitivity, in winter or if you live in extreme northern or southern areas.
The benefits of vitamin D are multiple: bone health (it is vital in the calcium and phosphorus mechanism), teeth, skin, colon health, supports the immune system in the fight against infections and alleviates autoimmune diseases, reduces the growth of cancer cells and many others.
A good mood
Sunlight increases the release of serotonin and endorphins, hormones associated with well-being and enjoyment of life. Soothes depressive and anxious states. Exposure to the sun instantly triggers a state of general calm. “You will immediately notice that you simply feel better. This is your entire system responding to the sun,” says Michael Holick.
A better sleep
Sun exposure also helps the secretion of melatonin, the sleep hormone. When you stay in the sun during the day and in the dark at night, the body knows how to distinguish between day and night. It improves the circadian rhythm, the rhythm that tells our body when to sleep, when to wake up and when to be active. Lack of sunlight and artificial light disrupt this rhythm.
Lowers blood pressure
When the sun hits the skin, it releases nitrogen oxide (nitric oxide). This, once released into the blood vessels, lowers blood pressure, thus reducing the risk of heart attack and stroke.
A low risk for certain cancers
As we have seen, the sun can increase the risk of certain skin cancers. But a number of studies have shown associations between sun exposure and lower risks of colorectal, prostate and breast cancer, as well as non-Hodgkin’s lymphoma.
Strong bones
We need strong bones at any age. But the most important is in childhood, when the bones support the body’s growth, and in the old age, when marked deterioration begins and cell regeneration decreases. Then the bones start to weaken, demineralize. As we saw above, vitamin D deficiency in the general population is high, and constant and moderate sun exposure could provide the necessary and vital supply.
Reduces pain in autoimmune diseases
If you have an autoimmune disease that involves photosensitivity, you can’t stay in the sun too much. It depends on the level of photosensitivity and whether you have a flare or not. But if you can sit in the sun take advantage. A few minutes of daily exposure to the sun, without sunscreen, relaxes muscles, reduces joint pain and gives a feeling of well-being. You will notice the effects immediately. If you have an autoimmune disease, your vitamin D level is most likely low, and exposure to the sun can only help.
How bad the sun can do us
When the internal protection mechanisms do not do their job well, when we intervene on the skin or when we spend too much time in the sun without prior gradual exposure, mutations occur in the attacked or unprotected cells.
Wrinkles
They are unpleasant, but not dangerous. UVA that penetrates the skin can cause damage to the collagen-elastin network, resulting in damage and “wrinkling” of the skin.
Melanoma
It is the most dangerous type of skin cancer and is caused by a genetic mutation of melanocytes. Melanoma is often found on the areas least exposed to the sun (soles, between the toes, private area, on the scalp or under the nails). Risk factors for melanoma are the number of sunburn experiences in childhood and young adulthood, genetic predisposition, red hair color, and the large number of moles on the body.
It has been shown that people who work indoors, and therefore spend little time outside in the sunlight, are more likely to develop skin cancer compared to those who work outdoors. By contrast, constant exposure to the sun throughout life is associated with a lower risk of malignant melanoma, as long as this exposure is moderate and the skin is not damaged by sunburn.
Photosensitivity
It can be induced by certain drugs (antibiotics, anti-inflammatory, antipsychotics, hypoglycemics, diuretics or renoids) or by prolonged exposure to the sun without gradual prior preparation (as most people who go “to the sea” do). These types of photosensitivity heal on their own when the allergen has been removed.
People with photosensitivity caused by certain autoimmune or genetic diseases have a special situation: systemic lupus erythematosus, vitiligo, albinism or xeroderma pigmentosum, a rare genetic disease characterized by increased sensitivity to UV radiation.
How much time to expose to the sun
How much vitamin D we can synthesize by sitting in the sun without exposing ourselves to the danger of burning our skin depends on several factors:
Time of day
The skin produces more vitamin D when we are in the sun in the middle of the day, when the sun is at its highest point in the sky. When our shadow is smaller than us. That is the best way to stay in the sun for optimal vitamin D levels.
The amount of skin exposed
The more skin a person exposes, the more vitamin D the body will produce. Exposing the back, for example, allows the body to produce more vitamin D than just the hands and face. We should aim for sun exposure of at least 25% of the skin.
Skin color
Lighter skin produces vitamin D faster than darker skin because the latter has more melanin.
Current advice is for people to stay in the sun for half the time it takes for their skin type to burn, i.e. before covering up and retreating to the shade. This should give them all the vitamin D they need without increasing their risk of skin cancer. That means somewhere between 15 minutes for the whitest skin and 2 hours for the darkest.
Positioning on the globe
The closer a person is to the Equator, the greater the amount of vitamin D synthesized by their skin. For example, in winter, in temperate areas the sun is too low, and vitamin D cannot be synthesized, even if there is sun.
What can prevent us from getting vitamin D from the sun
- Sunscreen or other creams applied to the skin immediately after exposure to the sun.
- A closed window, even if we feel the heat, prevents UV rays from entering.
- Dark-skinned people have a harder time synthesizing vitamin D.
- Older people have skin less able to synthesize vitamin D.
- People with certain kidney or liver diseases.
- People with certain autoimmune diseases, whose gut is affected: those with Crohn’s disease or celiac disease, for example.
Conclusions
We are not vampires. Sunlight has always been part of our lives. Moderate but constant sun exposure has more benefits than disadvantages. We should aim to get at least a few minutes of sun a day during the spring, summer and autumn months. Just that and it would be enough to prevent a lot of diseases.
Repeated sunburns can be a health hazard. Let’s know our skin type to know how long we can stay in the sun without burning. Dr. Michael Holick says that exposure to the sun for a few minutes a day, but constant, is preferable to prolonged, but sporadic, as happens when we go on vacation in the summer. We do not need to tan to produce vitamin D, on the contrary, tanned skin prevents the accumulation of vitamin D.