Is the Sun our best friend or our deadliest enemy? We take a closer look at how ultraviolet radiation causes cancer, why redheads are most at risk, and whether you should take vitamin D

The sun is both the source of life on Earth and a serious threat to our health. It helps our bodies produce vitamin D and fight depression, but at the same time, it causes skin cancer, cataracts, and premature aging. Together with biologist Alexander Panchin, we explore how to strike a balance in our relationship with the Sun, which myths about sunscreen we need to debunk, and why an inevitable end awaits us all in five billion years.

Why Does the Sun Make Us Age (and What Do Long-Haul Truck Drivers Have to Do With It)?

There are two types of skin aging: natural (chronological aging) and photoaging. The latter is caused specifically by ultraviolet radiation, which damages proteins and DNA in cells.

The most striking example of photoaging was a viral photo of a long-haul truck driver with 30 years of experience: the side of his face that was closest to the window (on the driver's side) looked significantly older due to constant exposure to the sun.

В научных кругах часто звучит цифра, что 80% старения кожи вызвано именно ультрафиолетом. Хотя этот факт часто цитируется некритично, исследование компании L’OREAL на группе из 298 женщин подтвердило, что у «светолюбок» (любительниц загара) действительно значительно больше морщин и пигментных пятен, а «светофобки» выглядят в среднем на пару лет моложе своего возраста.

How do rays A, B, and C differ?

Ultraviolet radiation is classified into three types based on wavelength:

• Ultraviolet C (100–280 nm): It is the most dangerous, but fortunately, it is completely absorbed by the Earth's ozone layer.
• Ultraviolet B (280–320 nm): It affects the outermost layer of the skin (the epidermis), causing burns and redness. It is precisely these photons that are directly absorbed by DNA, causing mutations that lead to skin cancer. Ordinary window glass provides protection against this type of radiation.
• Ultraviolet A (320–400 nm): Составляет более 95% всего УФ-излучения, достигающего нас. Он проникает глубже, разрушает коллаген и эластин, а также повреждает ДНК косвенно, через образование активных форм кислорода. Regular glass doesn't protect against it.

It is important to understand that there is no such thing as “safe” ultraviolet radiation. In 2009, the WHO classified all tanning devices as Group 1 carcinogens.

The Sun as a Cause of Cancer: Melanoma and Beyond

Skin cancer is one of the main dangers posed by the sun. Although melanoma is mentioned most often, it is 20 times less common than non-melanoma skin cancers, such as basal cell carcinoma. However, melanoma is extremely dangerous: it grows rapidly and metastasizes to the brain, lungs, and liver. In stage I, the survival rate is close to 100%, but in later stages, the prognosis is significantly worse.

Risk factors include:

• Genetics: Mutations in certain genes can increase the risk of melanoma sixfold.
• Appearance type: Рыжие люди и обладатели светлой кожи наиболее уязвимы. У 80% рыжих людей «поломан» ген рецептора меланокортина-1, из-за чего их кожа плохо вырабатывает защитный меланин.
• Moles and freckles: A large number of moles indicates that the body has frequently “stopped” cells from beginning to divide uncontrollably. Freckles, on the other hand, can be either genetic or acquired as a result of sun damage (lentigo).

Sun Allergy: When "Vampirism" Becomes a Reality

There is a real diagnosis— sun urticaria. This is a rare condition (3 cases per 100,000 people) in which the skin develops blisters even after brief exposure to sunlight or even the light from halogen lamps. It is likely that UV rays alter the structure of proteins in the skin, causing the immune system to attack its own altered tissues.

Certain plants (such as Sosnovsky's hogweed) or even grapefruits can cause a similar effect, as they contain photosensitizing substances that make the skin extremely sensitive to light.

Vitamin D: Take a Supplement or Get Some Sun?

The link between sunlight and bone health was first observed as early as the 19th century, when children in sunny rural areas were less likely to develop rickets than city dwellers. When exposed to UVB rays, the skin synthesizes vitamin D3, which regulates calcium metabolism.

However, modern medicine is skeptical of the idea of “synthesizing” vitamin D from sunlight for several reasons:

1. Geography and Age: People living north of the 35th parallel (including all of Russia) produce virtually no vitamin D from November through March due to the angle at which the sun's rays strike the Earth. As people age, the skin's ability to produce vitamin D decreases by a factor of three.
2. Risks: The sun is a confirmed carcinogen. Trying to make up for a vitamin deficiency by sunbathing increases your risk of skin cancer.
3. Dosing accuracy: Doctors recommend using prescription forms of vitamin D instead of dietary supplements, as they provide more precise dosing. The preventive dose for at-risk groups (children, pregnant women, and the elderly) is usually between 600 and 3,500 IU, depending on the recommendations.

How to Protect Yourself Properly: A Guide to SPF

Sunscreen works either by reflecting rays (physical filters: zinc oxide, titanium dioxide) or by absorbing them (chemical filters: avobenzone, etc.).

What You Need to Know About SPF:

• SPF 30 means it will take 30 times longer for you to get sunburned than it would without sunscreen.
• These creams have been proven to protect against photoaging.
• There is the Peltzman effect: People who use sunscreen feel invulnerable and spend too much time in the sun, ultimately doing themselves more harm than good.
• The ideal sunscreen should protect against both Type A and Type B rays, have an SPF of 30+, and be water-resistant.

An important point to note: some ingredients in sunscreen (such as oxybenzone) are banned in certain regions (such as Hawaii) because they damage coral reefs.

Not Just Harm: Disinfection and Mood

The sun isn't just a threat. Ultraviolet radiation (especially type C) effectively kills microorganisms by damaging their DNA, a process used in hospitals for disinfection.

In addition, light is critically important for mental health. Seasonal Affective Disorder (SAD) or seasonal affective disorder is directly linked to shorter daylight hours and disruptions in circadian rhythms. In such cases, light therapy—the use of special lamps that mimic sunlight—can help.

Scientists are exploring ways to achieve a “safe tan” using pills or injections of hormone analogs (melanotan), but so far these have not been approved by regulatory agencies due to the risk of side effects and the potential to cause cancer.

Ultimately, the sun is the foundation of life: without it, there would be no photosynthesis or oxygen. But in 5 billion years, it will expand, evaporate all the water on Earth, and engulf the planet. Until that moment arrives, the best advice is to use sunscreen, wear a hat, and seek out the shade.