In short:
- In Estonia (59th parallel), from October to March the sun’s angle is so low that the skin produces practically no vitamin D.
- According to EFSA, vitamin D supports the normal function of the immune system, bones and muscles.
- Vitamin D is fat-soluble and needs magnesium to be activated — it makes sense to take them together.
- To pin down your dose and any deficiency, ask your family doctor to run a blood test.
Vitamin D in winter is a chronic problem spot in Estonia. Because of the long, dark Nordic months, many people have low levels of this key vitamin exactly when the body needs it most to support immunity and energy. In this article we explain why the sun isn’t enough from October to March, how much vitamin D to take and why it needs magnesium as a partner.
Why does vitamin D run short in winter in Estonia?
Tallinn lies on the 59th parallel north. From October to March the angle of the sun’s rays is so low that the skin produces practically no vitamin D — no matter how much time you spend outdoors. That means that in winter we depend almost entirely on food and supplements. That is exactly why vitamin D in winter is a topic worth tracking deliberately, rather than counting on “spring sun”.
Vitamin D isn’t merely a “bone vitamin”. According to the conclusions of the European Food Safety Authority (EFSA), vitamin D contributes to the normal function of the immune system, the maintenance of normal bones and the normal function of muscles. You’ll find a more thorough overview of the role of vitamin D in the articles Vitamin D and vitamin D.
How much vitamin D should you take, and when?
Vitamin D is fat-soluble, so it is absorbed best together with food that contains fat — for example eggs, avocado, butter or nuts. Breakfast is the logical slot.
It’s hard to cover your vitamin D needs from food alone in winter. The best natural sources are fatty fish (salmon, herring, mackerel), egg yolk and vitamin D-fortified products, but the amounts are often small. It helps to know that morning daylight and vitamin D complement each other: bright light triggers the wake-up hormone cortisol and sets your circadian rhythm, while a vitamin D supplement covers what the skin can’t produce in winter. At the 59th parallel, a daylight lamp (about 10,000 lux) is a useful addition on winter mornings.
When it comes to dosage, a simple principle applies: the exact amount depends on your blood test. For people living in the Nordic countries, many specialists recommend higher daily doses in case of deficiency, while EFSA has set the tolerable upper intake level for adults at 100 µg (i.e. 4000 IU) per day. Higher doses shouldn’t be taken on your own for a long time — if you’re taking amounts close to the upper limit, have your doctor monitor your levels. A winter course usually makes sense from October to March, but make the final decision on dose and duration together with your doctor. In spring and summer, when the skin starts producing vitamin D again, the need for a supplement may decrease — this is also a good reason to have your levels rechecked from time to time, so that you take neither too little nor too much.
Why does vitamin D need magnesium?
One often-forgotten nuance: the body needs magnesium to activate vitamin D. Without magnesium, part of the vitamin D stays in an inactive form, which means you get only part of the benefit from the supplement. It’s no coincidence that magnesium and vitamin D deficiencies often go hand in hand — especially in Estonian conditions, where stress, depleted soils and dark winters drain magnesium reserves. The practical conclusion is simple: if you supplement vitamin D, also make sure you get enough magnesium — either from food (nuts, seeds, whole grains, leafy greens) or as a separate supplement. This is one reason why vitamin D in winter isn’t just one capsule, but part of broader support that includes light, good nutrition and other minerals.
How do you know if you’re vitamin D deficient?
The most reliable way is a blood test. If you feel persistent fatigue, frequent infections or a general lack of energy, ask your family doctor to check your vitamin D level (often together with magnesium, ferritin and a thyroid marker). Based on the results, the doctor can recommend a suitable dose.
Some people are at higher risk of deficiency. The higher-risk group includes older adults (whose skin produces less vitamin D), people with darker skin, those who cover most of their body from the sun, and people who spend most of their time indoors. Symptoms are often vague — persistent fatigue, frequent infections, bone and muscle aches or low mood — and overlap with many other conditions, so you can’t diagnose it “by eye”. That is exactly what makes vitamin D in winter a topic to check with a test rather than assume. If you’re interested in other vitamins that matter in winter, also see the article vitamin B. For persistent complaints, always consult a doctor — a supplement is no substitute for diagnosis.
References
- Energy and calm: a natural plan against stress, insomnia and fatigue (Fitness.ee e-guide, chapters 1 and 5).
- EFSA. Vitamin D health claims and tolerable upper intake level (100 µg/day for adults).
- Estonian Health Board. Vitamin D recommendations.
Frequently asked questions
Why can’t I get enough vitamin D from the sun in winter?
Estonia lies on the 59th parallel, and from October to March the angle of the sun’s rays is too low for the skin to synthesize vitamin D. Time spent outdoors during this period doesn’t change production significantly, so we remain dependent on food and supplements.
What time of day should I take vitamin D?
Because vitamin D is fat-soluble, it is absorbed better together with food that contains fat. It’s convenient to take it with breakfast, for example one that includes eggs, avocado, butter or nuts.
Should I take vitamin D and magnesium together?
Yes, it makes sense. The body needs magnesium to activate vitamin D, and without it part of the vitamin D stays in an inactive form. Getting enough magnesium helps vitamin D work better.
How much vitamin D is too much?
EFSA has set the tolerable upper intake level for adults at 100 µg (4000 IU) per day. Doses close to the upper limit shouldn’t be taken on your own for a long time — have your doctor monitor your blood vitamin D level and set the dose.
Come and work out! ArtGym
