Vitamin D from the Sun in Winter Months and How to Replace It
Vitamin D from the Sun
Vitamin D is a fundamental pillar of our health, yet a large portion of the population lacks it. It is responsible for the proper functioning of the immune system, bone and dental health, influences our psyche, and is even mentioned in connection with the prevention of lifestyle diseases. Unlike other vitamins, our body can produce it on its own—if we provide it enough sunlight.
And here's the first problem: how many of us spend enough time in the sun? And how many of us live in conditions where that's even possible? The Czech Republic is located at a latitude where sunlight during the winter months is absolutely insufficient for the production of vitamin D. Yet, we rely on the sun as the main source of this important vitamin. It's time to honestly admit that we cannot do without a conscious approach to this issue.
How Vitamin D is Formed and Why the Sun Matters More Than We Think
Vitamin D is produced in our body when the skin is exposed to UVB radiation from the sun. This process is very efficient—just 10 to 15 minutes of sun exposure several times a week can be enough to meet daily needs. But there's a catch. UVB radiation does not penetrate clouds, smog, or glass. Hence the common myth: sunlight through a window will not provide us with vitamin D.
Vitamin D from the sun does not form through glass, as UVB rays are blocked by the glass layer. So even if your office or living room is sunlit, your body will not gain any vitamin D from it. And the situation is similarly bleak during the winter months.
Vitamin D in Winter
From October to March, solar radiation in the Czech Republic is so weak and low on the horizon that the production of vitamin D from the sun is practically impossible. This is confirmed by data from the National Institute of Public Health, which indicates that up to 70% of the Central European population has a vitamin D deficiency in winter. This deficit affects not only seniors but also young healthy people, children, and pregnant women.
During winter, the question is not whether we have enough vitamin D, but rather how severe the deficiency is and what we are doing about it. The sun in winter in the Czech Republic is not sufficient. Additionally, there is the factor of outdoor activity. In winter, we naturally spend less time outside, and when we do, we are usually bundled up from head to toe. So, even when the sun shines, it hardly reaches our skin.
Our Lifestyle is Partly to Blame
Modern lifestyles give the sun little chance. We work in offices, commute by car or public transport, and when we finally get outside, we often protect ourselves with sunscreen. While these are important for preventing skin cancer, they also block UVB radiation, thus hindering vitamin D production. It's a bit of a vicious cycle.
To give you a concrete example—if you spent 15 minutes outside in June wearing a t-shirt and shorts (without sunscreen), your body could produce up to 10,000 IU of vitamin D. This is many times more than the daily recommended dose. However, if you do this activity behind a window or in December, the effect will be zero.
How to Supplement Vitamin D When the Sun Isn't Enough
In the summer months, the best solution is conscious sun exposure—but with caution and sense. Ideally, in the morning or late afternoon when the UV index is sufficient, but the risk of burning is minimal. Remember that exposing your face, hands, and forearms for about 10 to 20 minutes several times a week can allow your body to store vitamin D for several months ahead.
But as mentioned, in winter, you cannot rely on the sun in the Czech Republic. This is where diet and supplements come into play. Naturally, vitamin D is primarily found in fatty fish (salmon, mackerel, sardines), eggs, and liver. Unfortunately, even if you try, it's almost impossible to meet your daily needs through food alone. For example, you would have to eat over 200 grams of salmon daily to reach 2000 IU.
Therefore, most experts recommend supplementing vitamin D with quality dietary supplements, especially in winter. The Czech Endocrinology Society recommends doses between 1000 and 2000 IU daily for adults. Recommendations differ for children, pregnant women, and seniors, and it's advisable to consult a doctor about dosage.
The Importance of a Preventive Approach
Neglected vitamin D deficiency can manifest in various ways—from frequent colds, fatigue, and sleep disorders to worsened mood and tendencies toward depression. Some studies even show that low levels of vitamin D may be associated with a higher risk of autoimmune diseases and certain types of cancer.
According to a study published in The Lancet Diabetes & Endocrinology, there is evidence that regular vitamin D supplementation reduces the risk of respiratory diseases in people with severe deficiency by up to 70%. This is a strong argument, especially during flu and cold seasons when the immune system is extremely burdened.
As one famous medical wisdom states: "Prevention is always cheaper than treatment." And in the case of vitamin D, this is doubly true.
What About Children and Seniors?
Two groups deserve special attention—children and the elderly. In children, long-term vitamin D deficiency can lead to skeletal development disorders (rickets), while in seniors, it increases the risk of osteoporosis and fractures. Additionally, the skin's ability to produce vitamin D decreases with age, so even if an older person spends time in the sun, their body will produce less than a young person's body.
For these groups, it is therefore crucial to supplement vitamin D not only seasonally but often year-round—always under the supervision of a doctor or pediatrician.
How to Tell if You Lack Vitamin D?
Symptoms of deficiency are not always obvious, but the most common include:
- increased fatigue and sleepiness
- frequent colds and infections
- muscle and joint pain
- worsened mood, irritability
- hair loss
- slow wound healing
The only reliable way to verify vitamin D levels in the body is a blood test—specifically determining the level of 25(OH)D. It is typically conducted by a general practitioner or internist, and based on the results, supplement dosage can be adjusted.
In the Czech Republic, more and more people are taking an interest in the issue of vitamin D, but it is still a topic that is not sufficiently popularized. Yet, it is one of the simplest forms of prevention that we have literally "at our fingertips." All it takes is stepping out into the sun—or reaching for a quality supplement in time.
In conclusion, let's ask a simple question: How much time did you spend in direct sunlight today? If the answer is "little" or "none," maybe it's time to think about it.
