Many people have probably heard that ``Sunbathing is good for the body.'' However, many people do not know exactly what effects they have or why they affect health. The reason why sunbathing is good for you is related to the functions of hormones and vitamins in your body.

In this article, we will introduce in detail the health benefits of sunbathing. We also explain precautions to take when sunbathing, so please refer to it.

Why sunbathing is recommended for health

There are four main reasons why sunbathing is recommended for your health. Let's take a look at them one by one.


● serotonin is secreted

Serotonin is a brain substance that stabilizes the mind and is sometimes called the "happy hormone." Along with noradrenaline, which excites the nervous system, and dopamine, which brings about a feeling of pleasure, it is one of the three major nerve substances that have a major impact on the human mind.

Serotonin is also secreted during rhythmic exercise and when interacting with others. A lack of serotonin can cause symptoms such as irritability, fatigue, and depression.

The main cause of seasonal affective disorder (winter depression), a type of depression, is a decrease in serotonin secretion. It is thought that this is due to a decrease in serotonin secretion due to shorter daylight hours.


● Melatonin secretion is promoted

Melatonin is a hormone also known as the "sleep hormone." It has the function of regulating sleep and wakefulness rhythms. When the rhythm of sleep and wakefulness is adjusted, the body clock is kept normal and the quality of sleep improves.

Exposure to sunlight in the morning suppresses melatonin, which increases again 15 hours after waking up. The amount of melatonin secreted at night is tens of times higher than during the day, making you naturally sleepy. This effect allows humans to switch between wakefulness and sleep.

To maintain health, it is important not to disturb the rhythm of melatonin secretion. Exposure to strong light from computers and smartphones during the night suppresses the secretion of melatonin, making it easier for the body's rhythm to become disrupted.


● vitamin D is produced

Vitamin D is one of the nutrients essential for maintaining health. However, due to changes in dietary habits, many Japanese people tend to be deficient in vitamin D.


According to a 2023 study by the Jikei University School of Medicine, a survey of 5,518 people who underwent health checkups in Tokyo found that 98% were vitamin D deficient.

【source】
"98% of Japanese people are 'vitamin D deficient'; first standard value in Japan announced; almost no plant-derived vitamin D detected" (Tokyo Jikei University School of Medicine)
https://www.jikei.ac.jp/news/press_release_20230605.html


● Adjust your body clock

The biological clock is a rhythm that humans are born with. The earth rotates on a 24-hour cycle, but the human body clock is said to be one hour longer than the 25-hour cycle.

Sunlight is needed to compensate for this one-hour difference. Sunlight has the ability to advance the body clock and align it with the 24-hour cycle.

When your body clock is disrupted, you are at increased risk of feeling fatigued and losing your appetite. Also, be careful as it can cause lifestyle-related diseases such as high blood pressure and diabetes.

Points to remember when sunbathing for health

There are several points to keep in mind when sunbathing. To get the full benefit of sunbathing, be sure to observe the following points:


● Understand the approximate amount of time you should be exposed to sunlight

The recommended amount of time for sun exposure is about 15 minutes a day in spring and summer, and about 30 minutes a day in autumn and winter. The best time to sunbathe is in the morning. Melatonin production is suppressed, making you feel refreshed and awake.

It's also a good idea to wake up at a certain time every day to keep your body clock moving normally. Even if you went to bed later the night before, it's important to wake up at the same time. Depending on your body clock, you will become sleepy approximately 15 hours after exposure to morning light, so try to keep your wake-up time as consistent as possible.


● Continue sunbathing

It is important to make sunbathing a habit as much as possible. It's a good idea to adopt a method that suits your lifestyle and is easy to maintain.

To make sunbathing a habit, we recommend taking a walk or walking. Walking after eating breakfast is said to help keep blood sugar levels in check. It also promotes blood circulation, allowing you to start your day feeling refreshed. You can also expect the effect of increasing the efficiency of work and housework.

Doing yoga or stretching outside is also a good way to get into the habit of sunbathing. Some places also offer yoga classes in parks and beaches. You can feel relaxed as you can move your body while listening to the sounds of nature. If you do yoga or stretching outside, please be careful not to disturb other users.


● Do not use sunscreen when sunbathing

Sunscreen can inhibit vitamin D production. The wavelength of ultraviolet light involved in the production of vitamin D is almost the same as the wavelength of ultraviolet light that causes sunburn. It has been shown that using SPF 30 sunscreen reduces vitamin D production by less than 5%.

However, UV rays can also cause age spots and sagging, so some people may want to apply sunscreen. If you're concerned about the effects on your skin, it's a good idea to apply sunscreen only to your face and expose your hands and feet to direct sunlight.

You can also stimulate the production of vitamin D in your palms and soles of your feet. The palms and soles of the feet don't have much melanin, so they don't get sunburned as often. There is no problem with the production of vitamin D, so those who want to reduce the effects of sunburn should expose their palms and soles to sunlight.

[Source] “Ultraviolet Environmental Health Manual 2020” (Environment Agency)
https://www.env.go.jp/content/900410650.pdf

Points to note when exposed to sunlight for health reasons

Although sunbathing has positive effects on your health, there are some precautions. Here we will explain the precautions to take when sunbathing.


● Avoid prolonged sunbathing

Prolonged exposure to sunlight can cause redness and pigmentation. Redness caused by sunburn is a phenomenon called "sunburn." It occurs when cells are damaged and blood flow increases in the skin.

In addition, "suntan" is pigmentation caused by sunburn. This occurs when the skin secretes melanin pigment to prevent UV rays from entering.

Excessive tanning can therefore have negative health effects. If you spend long periods outdoors, it's important to protect your skin with clothing and sunscreen.

[Source] “Ultraviolet Environmental Health Manual 2020” (Environment Agency)
https://www.env.go.jp/content/900410650.pdf


● Get sunlight outdoors as much as possible

There are two types of ultraviolet rays, and the ultraviolet rays involved in the production of vitamin D cannot pass through glass. Therefore, when sunbathing, it is a good idea to go out on the balcony or open the window.

Also, for vitamin D production to occur efficiently, exposed skin needs to be exposed to sunlight. Vitamin D is produced more easily when you sunbathe in short sleeves than in long sleeves.

Stay healthy by soaking up the sun

In this article, we explained the health benefits of sunbathing and the reasons behind them. Sunbathing can have a variety of health benefits, including relieving stress and improving sleep quality. Especially if you spend a lot of time indoors, it would be a good idea to actively incorporate it.

Also, when sunbathing, it is important to expose the light directly to your skin. Be careful when using sunscreen, as it will reduce its effectiveness. Please refer to this article and incorporate sunbathing into your daily habits to help maintain your health.

Article supervision

Director Yu Hasegawa
You's clinic Aoyama

After graduating from Juntendo University School of Medicine and Graduate School, he joined the Department of Plastic Surgery and Radiology at Juntendo Hospital.
After working at a beauty clinic in Tokyo, she became the director of multiple clinics.
You's clinic Aoyama opened in March 2021.
She deals with beauty and health every day while working closely with patients in a private space.

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