Vitamin D in winter: a trendy hype or a real necessity?

Vitamin D has become a “star” of the media space over the past decade. It is credited with effects on bones, immunity, mood, cancer prevention, and even COVID-19.

Some of these claims are exaggerated, but the role of vitamin D in bone-muscle health and immunity is indeed well documented, especially in regions with low sunlight exposure.

This article examines who needs vitamin D diagnostics and correction in winter, and where it is just marketing.

Why vitamin D deficiency is so common

• Geography: latitudes with a short daylight period in autumn and winter.

• Indoor work, minimal sun exposure.

• Use of sunscreen in summer (which is also important).

• Limited number of foods naturally containing vitamin D.

According to European data, in many countries >50% of adults have insufficient or deficient 25(OH)D levels, especially in winter.

Table title: Vitamin D functions with clinically proven significance

Vitamin D and respiratory infections: what studies say

Meta-analyses of randomized studies have shown that preventive intake of vitamin D can reduce the risk of acute respiratory infections, especially in people with baseline deficiency. The effect is moderate but statistically significant.

At the same time:

• Vitamin D is not a fast-acting remedy for an already developed infection;

• There is no reason to increase doses above the recommended “just in case” level.

Table title: Who should primarily check 25(OH)D

Practical approaches to prescribing in winter

• For healthy adults in regions with low sunlight exposure, preventive doses in line with local recommendations are appropriate.

• For patients with osteoporosis, the elderly, and risk groups — it is advisable to monitor 25(OH)D levels and adjust doses individually.

• It is important to avoid self-administration of high “bolus” doses, especially in kidney disease.

In the articles “Digestive Enzymes: Why Even Healthy People Need Them in Winter” and “Folic Acid in Winter: Why Deficiency Is Not Just a Pregnancy Issue”, learn about the importance of other vitamins in winter for supporting immunity and health. You can conveniently order vitamins online at medizine.ua.

Questions and answers

Should everyone get a vitamin D test before supplementation?
For basic preventive doses in healthy adults, testing is not always mandatory. However, for long-term high-dose use or in risk groups (elderly, osteoporosis, kidney disease) it is advisable to know the baseline level.

Can excess vitamin D be harmful?
Yes. Vitamin D hypervitaminosis causes hypercalcemia, affecting the kidneys, heart, and vessels. Therefore, the “more is better” principle is dangerous here.

Does vitamin D really “protect against COVID-19”?
There is data linking low D levels with more severe courses, but this does not make vitamin D a specific preventive or therapeutic agent. It is part of the overall nutritional background.

Which form is better — drops, capsules, or tablets?
Clinically, it is more important to reach and maintain the target level than the form. Choice depends on convenience, compliance, and cost.

Conclusions

• Vitamin D is not a “magic pill for all diseases,” but it is a key nutrient for bones, muscles, and immunity.

• In winter, the risk of deficiency increases significantly, justifying preventive intake in moderate doses and more active screening in risk groups.

• It is the responsibility of doctors and pharmacists to maintain a balance between evidence-based recommendations and the trend of excessive intake.

References

1. Holick M.F. Vitamin D deficiency. N Engl J Med. 2007.

2. Martineau A.R. et al. Vitamin D supplementation to prevent acute respiratory infections. BMJ. 2017.

3. EFSA. Dietary reference values for vitamin D. 2016.

4. Pludowski P. et al. Vitamin D supplementation guidelines in Central Europe. 2018.