How the sun can interfere with vitamin D absorption, a doctor tells us

The sun is the main source of vitamin D, which we get with tanning. But even frequent sunbathing does not always provide the necessary level of this substance in the body. This can happen in the presence of certain diseases. But there is another nuance that many people forget about – the duration of stay in the sun. So let’s talk about that.

certified clinical geneticist, nutritionist, expert of the Academy of Physicians UniProf

There is an opinion that prolonged sun exposure interferes with the absorption of vitamin D from ultraviolet light. Is this true?

What is the difference between vitamins D, D2 and D3?

We get vitamin D in an inactive form – in the form of vitamin D3, which comes from food and is also formed in the skin under the influence of ultraviolet light, and in the form of vitamin D2, which comes only with food. Which foods are rich in this substance, told in the article at the link below.

Both of these forms are equivalent to each other and together make up vitamin D (D2 + D3 = D). In fact, these forms of the vitamin are precursors to vitamin D itself. Therefore, before it can take effect, the vitamin must be activated, i.e. change its chemical structure. In the body, this happens in the liver and kidneys.

First, the inactive vitamin enters the liver, transforming into an intermediate form. Then it enters the kidneys, transforming into the active form. It is in this form that the substance begins its action in tissues and organs.

How the sun turns into vitamin D

The body synthesizes the chemical element, actually using only sunlight. Here’s how it happens.

• Sun. Ultraviolet rays penetrate the skin and react with a substance present in it from birth – 7-dehydrocholesterol, which is further transformed into vitamin D3.
• Liver. The vitamin enters the bloodstream and then the liver, where it is transformed into calcifediol.
• Kidneys. Calcifediol enters the kidneys, where it is converted into calcitriol (the active form of vitamin D), which is further distributed throughout the body via the bloodstream.

Does the sun interfere with the absorption of vitamin D

The main source of external vitamin D accumulation is the skin. The darker it is, the less vitamin D is formed in it. This is due to the higher content of melanin in dark skin – the pigment that determines its color.

Melanin reduces vitamin D production by limiting the amount of UV light reaching the skin. Therefore, the more we tan and the darker we become, the less active forms of vitamin D are produced in the body. So the body protects itself by preventing excessive formation of the biologically active substance during prolonged exposure to the sun.

Therefore, it is better to avoid active sunbathing, use sunscreen, wear panamas and clothing that protects from direct sunlight. What to wear in the heat to protect yourself from overheating, read in the material.

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