Sunlight: Friend or foe?

Summer has arrived, temperatures are rising, and so is UV exposure. As every year, the inevitable question comes sooner or later: "Should I spend time in the sun or not?"

According to the National Sun Report 2020, last year 90% of the Dutch experienced at least one sunburn, while 50% were even severely burned. This should come as no surprise, given that only 33% of Dutch men and 43% of women use sunscreen products when exposed to sunlight.

In addition, 60% of Dutch parents reported that their children had been sunburned at least once, 10% of them severely. Moreover, 25% of Dutch parents admit to not using sunscreen for their children when they are exposed to the sun.

The mantra of always applying sunscreen

Based on the National Sun Report 2020, the mantra is to always use sunscreen—a mantra we have been hearing in the media for years. The UV-protective clothing company that sponsored the report therefore advises using UV-protective clothing...

Nuance vs one-sided story

As with many health issues, the topic is complex and generally not well understood. The focus is often on specific details, leading to a simplified black-or-white viewpoint. Instead of simply advising to block UV light, shouldn't the advice rather be how to make sensible use of natural sun exposure and how to best build up solar callus? Or at least combine both pieces of advice so that people protect themselves while also being able to benefit from the health effects of sunlight in a natural and safe way.

No sun, no life

The sun has been with us since the beginning of time and shaped life on earth, nourishing the planet and all life forms. Are we now going to blame the sun for an ecological mismatch that we ourselves have created in the modern world? Covering all health aspects of sun exposure is too much for one blog. But below we highlight some interesting aspects to think about.

• Wearing glasses increases the chance of sunburn by creating a discrepancy between the environment and human physiology.
• Sunlight has a positive influence on the microbiome, as the body is actually a system of systems. There is such a thing as a skin-gut axis!
• Building up solar callus is possible through natural living and dietary factors that reduce the risk of sunburn.
• Just as plants use sunlight for photosynthesis, there is evidence that humans have similar capabilities via melanin.
• The benefits of sunlight include much more than just vitamin D; sunlight also increases many feelgood chemicals in the body, influences the immune system, blood pressure, and much more.

Experts in favor of balanced exposure

Taking these facts into account, there are some dermatologists who take a different, and seemingly more advanced and balanced, position on exposure to healthy sunlight. One of them is former professor of dermatology Carla Bruijnzeel. In a 2018 interview, she set out a very well-considered position on sun exposure. In short: for her personal skin type, she only uses sunscreen during spring. Through sun exposure, sun tolerance gradually increases because the outer layer of skin becomes thicker, which protects against sunburn. Thus, there is a risk-reward ratio in favor of sun exposure for health. Finally, Bruijnzeel expressed concern about the use of sunscreens in relation to toxicity.

Conscious sun vs indoor living

Another qualified voice that supports this narrative is that of UV expert Professor De Gruijl. He is not in favor of using sunscreen daily, as this prevents the skin from getting used to ambient UV, making the skin extra vulnerable in the event of "accidental" absence of sunscreen. He emphasized the importance of preventing sunburn, which everyone can agree on—but let biology do its work by gradually increasing daily sun exposure. This is exactly how nature has handled this for millions of years in more natural environments. This is in contrast to the current situation of spending most of the time indoors and then going all out on the first beautiful sunny day.

Practice makes perfect

By comparison: everyone knows that exercise is important and healthy, and that running a marathon without training is foolish and unhealthy. The body needs time to adapt and build tolerance to stress factors before it can handle major loads like a marathon—or a full day of high UV exposure from the sun.

Most dermatologists probably think that the advice of these experts is too complex for laypeople and prefer the simpler recommendation of always applying sunscreen. This is a "throwing out the baby with the bathwater" story. Should a general message be made so simple that a half-truth becomes the status quo? There we go again: blaming the sun for an unnatural situation that people have created themselves—living indoors 99% of the time.

Solar callus and the color spectrum of sunlight

Improving sun tolerance is known as "solar callus" and happens naturally when one lives more in harmony with nature. A perfect example is the fact that the early morning sun contains no UV light and more (infra-)red light than, for example, the midday sun: the color spectrum of the sun changes during sun hours. Furthermore, visible red light contributes in various cellular ways to protecting skin cells against UVB.

In a natural environment, people would be outdoors for most of the day from morning to evening, throughout all seasons, and without sunglasses, sunscreen, or UV-protective clothing.

Artificial light is no alternative to natural light

Furthermore, it is necessary to realize that the light we are exposed to indoors is not as balanced in colors as natural light. It is mainly in the blue light spectrum, which has been shown to be harmful to the skin in various ways. Artificial light may be a common optical replacement, but physiologically it is absolutely not equivalent to natural light. Again, it is better to examine the modern environment than to point the finger at the sun. Informing people with the full story seems to be the more ethical route to follow, because natural sun exposure is very important. English dermatologist and scientist Richard Weller even warns that avoiding sunlight is deadly, and in many more ways than people realize.

The world upside down

Sometimes it seems as if we live in an inverted world where the role and effects of natural phenomena such as sunlight, biologically healthy food, and natural therapeutics are demonized, while we promote artificial technological developments such as mobile phone radiation, biotech food, and medicines, and the possible side effects are barely addressed. There is always a gray area, and much depends on context, but when in doubt, try to look at things from an evolutionary perspective combined with the laws of nature. This brings clarity in the modern fuzz. We can fool ourselves with thoughts, assumptions, or feelings about what we think is healthy or normal, but we cannot fool our biology or nature.