Why the sun is not enough in winter
Vitamin D is unusual in that we make it ourselves — in the skin, when it is hit by UV-B radiation from the sun. During the summer half-year, short spells outdoors are enough to cover much of the need, and what we make is stored in the body. The problem at northern latitudes is the angle of the sun: during the winter half-year the sun sits so low that UV-B radiation does not reach down through the atmosphere in sufficient amounts. In practice that means the skin cannot make any vitamin D at all from roughly October to March, no matter how much time you spend outside. That leaves two sources: what the body stored over summer and what we get through food. Foods such as oily fish, eggs, and fortified products (some milk varieties, spreads, and plant drinks) contribute, but for many people it is not enough during the dark part of the year. This is why the Swedish Food Agency highlights vitamin D supplementation during the winter half-year, especially for those who are outdoors little. How large the need is varies from person to person, however — depending on skin tone, age, diet, how much sun you got over summer, and more. This article describes the general picture; your individual situation is worth checking with a healthcare professional if you are unsure.
What the research says
At northern latitudes the angle of the sun during the winter half-year is too low for UV-B radiation to make vitamin D in the skin. From roughly October to March, then, we get no vitamin D from the sun — no matter how much time we spend outdoors.
The Swedish Food Agency states a recommended daily intake of 10 micrograms of vitamin D for most adults, and highlights supplementation during the winter half-year especially for those who are outdoors little. For some groups — for example older people and those who are covered up, dark-skinned, or rarely outside — 20 micrograms per day is recommended.
Vitamin D is needed for the body to absorb calcium and matters for the skeleton, muscles, and immune system. That is why the Swedish Food Agency sees supplementation during the dark months as relevant precisely for those who would otherwise risk getting too little.
Build the habit in 3 steps
A supplement only works if you remember to take it. This plan makes vitamin D an obvious part of your day during the dark part of the year — without fuss.
Vitamin D supplements come as drops, tablets, and capsules. Use the Swedish Food Agency's recommendation as a benchmark, but let your situation guide you: if you are unsure about dose or need, ask at the pharmacy or with a healthcare professional. If you take other medication or have a medical condition, a checked answer is especially worthwhile.
Vitamin D is fat-soluble and is often absorbed best together with food containing some fat. Link the supplement to a meal you eat anyway — breakfast or lunch — so it becomes part of a routine you already have. Keep the bottle visible.
The habit is mainly needed during the winter half-year, when the sun does not contribute. Many take a break during the bright summer months if they spend time in the sun, but taking a supplement year-round is also fine. Set a reminder in October so you start in good time.
Worth keeping in mind — and common questions
Vitamin D is stored in the body, and very high doses over a long time can be harmful. Stick to recommended levels and do not stack several supplements that all contain vitamin D without tracking the total. When in doubt — ask a healthcare professional.
Skin tone, age, diet, medication, and how much sun you have had all affect the need. This article gives the general picture, not personal advice. If you are unsure, pregnant, breastfeeding, or have a medical condition — check the dose and need with a healthcare professional. Cipoli does not replace medical advice.
Oily fish such as salmon, herring, and mackerel, eggs, and fortified products (some milk varieties, spreads, and plant drinks) contribute vitamin D. The supplement is a complement during the dark months, not a substitute for a varied diet.
Cipoli-analys
What does the data show about vitamin D in winter?Here we will show a group comparison between Cipoli users who take a vitamin D supplement during the dark months and those who do not — and how it relates to perceived energy and well-being during the winter half-year.
- ›Comparison of perceived energy during winter
- ›Relationship between supplementation, outdoor time, and mood
- ›Correlations with sleep quality and seasonal variation
We need more responses to create meaningful analyses. The more people who map their health, the better and more reliable the analyses become.
Your personal connection
Current index → potential with the habitSummary
- At northern latitudes the sun sits too low from roughly October to March for the skin to make vitamin D — during that time the sun does not contribute at all.
- The Swedish Food Agency states 10 micrograms per day as a benchmark for most adults and highlights supplementation during the winter half-year, especially for those who are outdoors little (20 micrograms for some groups).
- Make the supplement a daily routine tied to a meal; many pause during sunny summer months.
- Needs and dosage vary between people — more is not better, and when unsure you should check with a healthcare professional. Cipoli does not replace medical advice.