In winter, calcium itself is just as easy to get as in summer, but vitamin D, the nutrient that helps you absorb it, is not. In Switzerland the sun is too low from roughly October to March for your skin to make meaningful amounts of vitamin D, and vitamin D contributes to the normal absorption and utilisation of calcium. A good winter routine for bones and muscles therefore combines calcium-rich meals (about 1,000 mg a day for adults) with an adequate vitamin D intake (15 µg a day according to Swiss recommendations, 20 µg from age 60) and regular movement.
Key facts: calcium and vitamin D in winter
- Calcium need (D-A-CH reference value): 1,000 mg a day for adults; the label NRV is 800 mg. Safe upper level (EFSA): 2,500 mg a day.
- Vitamin D recommendation in Switzerland (Federal Commission for Nutrition): 15 µg (600 IU) a day for adults up to 59, 20 µg (800 IU) from 60. The label NRV is 5 µg; the safe upper level is 100 µg a day.
- North of about 40° latitude, the skin makes little or no vitamin D in the winter months. Switzerland lies at 46 to 48° north.
- Calcium is a mineral and is not destroyed by cooking, but some of it passes into the cooking water.
- Calcium is needed for the maintenance of normal bones and contributes to normal muscle function; vitamin D contributes to the maintenance of normal bones and normal muscle function.
Why do calcium and vitamin D matter more in winter?
Your need for calcium does not change with the seasons. What changes is vitamin D. In summer, 15 to 30 minutes of midday sun on your face and arms lets the skin produce vitamin D. From about October to March, the ultraviolet B rays that start this process are too weak in Switzerland, so your vitamin D stores slowly run down and blood levels are typically lowest in late winter.
That matters for calcium because vitamin D contributes to the normal absorption and utilisation of calcium and to normal blood calcium levels. With little vitamin D, your gut takes up a smaller share of the calcium you eat. Winter habits add to this: less time outdoors, less walking and cycling, and for many people more time sitting. If you want a broader view of the season, read why winter requires a different kind of wellness.
Calcium and vitamin D for your bones and muscles
About 99% of the calcium in your body is stored in bones and teeth. Bone is living tissue that is broken down and rebuilt all the time, and calcium is needed for the maintenance of normal bones. Vitamin D contributes to the maintenance of normal bones as well, so the two nutrients work as a team.
Muscles depend on both too. Calcium contributes to normal muscle function: every contraction starts when calcium is released inside the muscle cell. Vitamin D contributes to the maintenance of normal muscle function. In icy conditions, muscle strength and balance help you stay steady on your feet, which is one more reason to keep moving through the winter.
Movement is the third pillar
Nutrients alone do not keep bones strong. Bone responds to load, so weight-bearing exercise such as brisk walking, hiking, stair climbing, dancing or strength training two or three times a week matters as much as your diet. Winter walks at midday also give you daylight, even if they produce little vitamin D. If you train regularly, our article on magnesium covers another mineral that muscles need. Bones, muscles and cartilage work together in every movement; our guide to joint care explains what keeps joints healthy.
Which foods contain calcium and vitamin D?
Calcium is found in many foods, including plant foods. Vitamin D is found in very few: oily fish such as salmon, herring and mackerel, egg yolks, mushrooms exposed to UV light and fortified foods such as some plant drinks and margarines. That is why vitamin D is the nutrient most people struggle to cover from food in winter.
The table shows plant-based calcium sources with approximate values. For the full list including dairy and mineral water, see our main guide on calcium: daily needs and the best food sources.
| Plant food | Calcium per 100 g (approx.) |
|---|---|
| Tofu set with calcium sulphate | 200 to 680 mg (check the label) |
| Chia seeds | 630 mg |
| Tahini (sesame paste) | 420 mg |
| Almonds | 270 mg |
| Dried figs | 160 mg |
| Calcium-fortified plant drink | 120 mg per 100 ml |
| Pak choi, cooked | 90 mg |
| White beans, cooked | 70 mg |
| Broccoli, cooked | 40 mg |
| Butternut squash, baked | 40 mg |
A plant-based winter day with about 1,100 mg calcium
This sample day shows that you can reach your calcium needs without dairy. Values are approximate and depend on the products you buy.
| Meal | What you eat | Calcium (approx.) |
|---|---|---|
| Breakfast | Warm oat porridge made with 200 ml calcium-fortified plant drink, 10 g chia seeds and two dried figs | 370 mg |
| Lunch | White bean and vegetable soup (150 g beans) with 150 g pak choi | 240 mg |
| Snack | A handful of almonds (30 g) | 80 mg |
| Dinner | Stir-fry with 100 g calcium-set tofu and 150 g broccoli, tahini dressing (15 g) | 425 mg |
| Total | about 1,115 mg |
A litre of calcium-rich mineral water (above 150 mg per litre) adds several hundred milligrams more. Warm soups and stews are an advantage in winter: the calcium that leaches from vegetables and beans into the liquid stays in your bowl.
How to absorb more calcium in winter
- Cover your vitamin D. Food alone rarely provides 15 µg a day, so many people in Switzerland need a supplement in winter. Ask your doctor or pharmacist which dose suits you, especially if you are over 60, spend little time outdoors or have darker skin.
- Spread calcium over the day. The gut absorbs calcium best in amounts of up to about 500 mg at a time.
- Choose well-absorbed plant sources. Calcium from pak choi, kale and broccoli is absorbed well. Spinach and rhubarb contain a lot of calcium but also oxalate, which binds most of it.
- Soak, sprout or ferment. Phytate in wholegrains and legumes reduces calcium absorption; soaking beans, sourdough bread and fermented foods lower it.
- Keep salt moderate. A high salt intake increases calcium losses in urine.
- Separate iron and calcium supplements. If you take an iron supplement, take it at a different time from calcium-rich meals.
Calcium, vitamin D and Sanbera
Daily Essential Women contains 120 mg of calcium (15% NRV) and 3.22 µg of vitamin D (64% NRV) per daily serving of three tablets; Daily Essential Men contains 120 mg of calcium (15% NRV) and 3 µg of vitamin D (60% NRV). Calcium is needed for the maintenance of normal bones, and vitamin D contributes to the normal absorption and utilisation of calcium and to the normal function of the immune system. The calcium amount is deliberately moderate: it complements a calcium-rich diet rather than replacing it. The vitamin D amount alone does not reach the 15 µg recommended in Switzerland, so check with your doctor or pharmacist whether you need additional vitamin D in winter. The Nightly Reload formulas contain neither calcium nor vitamin D.
For the full picture of vitamin D, including blood levels, read what vitamin D really does.
Frequently asked questions
What supplements should you take during cold weather?
In Switzerland the most important one is vitamin D, because the skin makes little of it from October to March; the recommendation is 15 µg a day for adults and 20 µg from age 60. Vitamin D contributes to the normal function of the immune system and to the maintenance of normal bones. Other nutrients, such as calcium, can usually come from a varied diet.
Is calcium heat-stable?
Yes. Calcium is a mineral element, so cooking, baking and boiling do not destroy it. Some calcium does pass from vegetables and legumes into the cooking water, which is why steaming, or using the liquid in soups and sauces, keeps more of it on your plate. Vitamin D is also fairly heat-stable, though some is lost with long frying or baking.
When should you take calcium and vitamin D?
Take them with a meal. Vitamin D is fat-soluble and is absorbed better with food that contains some fat, and calcium carbonate needs stomach acid, which is produced when you eat. Whether you take them in the morning or evening matters less than taking them regularly. Keep single calcium doses to about 500 mg or less.
Why shouldn't you take calcium and magnesium together?
In normal amounts, such as in a multivitamin, you can take them together. The advice to separate them applies to high-dose single supplements: large amounts of calcium and magnesium compete for absorption in the gut. If you take several hundred milligrams of each, taking them at different meals makes sense.
Which foods contain both calcium and vitamin D?
Few foods naturally contain both. Canned sardines and salmon eaten with their soft bones provide calcium and vitamin D together, and so do eggs, though in small amounts. For a plant-based diet, look for plant drinks and yoghurt alternatives fortified with both calcium and vitamin D; the label shows the amounts per portion.
Sources
- Federal Commission for Nutrition (EEK, 2012): Vitamin D deficiency: evidence, safety and recommendations for the Swiss population (report to the Federal Food Safety and Veterinary Office)
- German Nutrition Society (DGE): Reference values for calcium and vitamin D
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2015): Dietary Reference Values for calcium
- EFSA Panel on Nutrition (2023): Scientific opinion on the tolerable upper intake level for vitamin D
- National Institutes of Health, Office of Dietary Supplements: Calcium, Health Professional Fact Sheet
- U.S. Department of Agriculture: FoodData Central (food composition values)
This article is for general information and does not replace advice from a doctor or pharmacist. Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle.