From October to March the sun in the Netherlands is too low to make vitamin D in your skin. You then live off the reserve you built up in summer. Anyone who did not build that reserve, or who belongs to a group that needs extra anyway, can run short in winter. Below you can read how to recognise a vitamin D deficiency, how much vitamin D you need per day, when to take a supplement and how long topping up takes.
How do you recognise a vitamin D deficiency?
With difficulty, because the signals are vague. Tiredness, muscle weakness, muscle pain or bone pain can be part of it, but those complaints have dozens of other causes. You often only notice a deficiency once it has existed for a long time. In young children a prolonged deficiency can cause rickets, with abnormalities of the skeleton. In adults and older people it can eventually lead to bone loss, osteoporosis and muscle weakness. Those facts come from the Netherlands Nutrition Centre.
The only thing that gives certainty is a blood test at your GP. It measures the value 25-hydroxyvitamin D. Your GP interprets the result; the lower limit differs per age and per laboratory, so a number on its own says little. If you recognise several complaints and belong to one of the groups below, that test is the logical first step. Not a jar of capsules.
Who is more likely to run short?
You only get a limited amount of vitamin D from food. Oily fish, eggs and margarine with added vitamin D are the sources, but the main source is sunlight. For people who get too little of it, the Dutch Health Council advises a supplement:
- Children aged 0 to 3: 10 micrograms a day
- Everyone aged 4 to 69 with darker skin: 10 micrograms
- Everyone aged 4 to 69 who spends little time outdoors during the day or covers their face: 10 micrograms
- Women aged 50 to 69: 10 micrograms
- Pregnant women: 10 micrograms
- Everyone aged 70 and over: 20 micrograms
If you are not in one of these groups and you spend fifteen to thirty minutes outdoors every day from March to October with your face and hands uncovered, you make enough. The advice is not black and white: outside those hours and with part of your skin exposed you still make vitamin D, just less.
How much vitamin D per day?
The recommended daily amount is 10 micrograms for everyone, and 20 micrograms from the age of 70. Labels often show IU (international units): 1 microgram is 40 IU, so 10 micrograms is 400 IU and 25 micrograms is 1,000 IU.
More is not better. Vitamin D is fat-soluble and is stored, so an excess builds up. The tolerable upper level is 100 micrograms a day from the age of 11, and in the Netherlands a supplement may contain at most 75 micrograms. How that works and which complaints belong to an excess is in too much vitamin D: symptoms and how much is too much. A supplement of 25 micrograms is well below those limits, but above the advice of 10 micrograms. Stick to the label, and consult your GP if you want to take more than it says.
When do you take vitamin D?
The time of day does not matter. What does matter: take it with a meal containing some fat. Vitamin D dissolves in fat, not in water. A cheese sandwich, an egg or a splash of oil on a salad is enough. On an empty stomach with a sip of water you absorb less. Choose a fixed moment, breakfast for instance, so you do not forget. A small daily dose works the same as a larger dose every few days, only daily is easier to keep up.
Vitamin D can be taken with almost anything: magnesium, B vitamins, omega 3, vitamin K2. Which combinations you do keep apart is in which vitamins can you take together.
Vitamin D in winter
Between October and March a supplement is already the year-round advice for the groups above, and for others the way to get through winter if the summer reserve falls short. That certainly applies if you were mostly indoors in summer, used a lot of sunscreen or wore covering clothes. Start in October and stop in April; that is the simplest rhythm.
How long does it take to top up a deficiency?
Weeks to months. Vitamin D is stored, so your blood value rises gradually. Your GP chooses the dose based on your blood value and checks again after a few months. With a proven deficiency they sometimes prescribe a temporarily higher dose than what you buy in a shop. Do not do that on your own.
Which supplement fits?
The vitamin D3 capsules by Together contain 25 micrograms (1,000 IU) per capsule, plant-based from lichen, with coconut oil in the capsule for absorption. One a day with a meal. Vitamin D contributes to normal absorption of calcium, to the maintenance of normal bones and of normal muscle function and to the normal function of the immune system.
If you want to combine vitamin D with vitamin K2, there is the D3 and K2 by Together with 75 micrograms of D3 per capsule. That is the legal maximum for a supplement and far more than the daily advice, so only for those who do that in consultation with their GP. For anyone who also wants to top up calcium, Bone Aid combines calcium from seaweed, 20 micrograms of D3 and K2 in two capsules a day.
A supplement does not replace sunlight or a varied diet. If complaints persist, see your GP.
Frequently asked questions about a vitamin D deficiency
What are the symptoms of a vitamin D deficiency?
Tiredness, muscle weakness, muscle pain and bone pain can be part of it, but they are not specific. With a prolonged deficiency, bone loss and muscle weakness can develop, in young children rickets. Only a blood test at your GP gives certainty.
How much vitamin D per day do you need?
10 micrograms (400 IU) a day for everyone, 20 micrograms from the age of 70. A supplement of 25 micrograms (1,000 IU) is above that, but well below the upper level of 100 micrograms.
When is it best to take vitamin D, morning or evening?
It does not matter. But do take it with a meal containing some fat, because vitamin D is fat-soluble. Choose a fixed moment so you keep it up.
How do I know if I have a vitamin D deficiency?
With a blood test through your GP. It measures 25-hydroxyvitamin D and your GP interprets the result according to your age and situation. A deficiency cannot be recognised from complaints alone.
How long does it take to top up a vitamin D deficiency?
Weeks to months, because vitamin D is stored and the blood value rises slowly. Your GP usually checks again after a few months.
Do I need a supplement in summer too?
If you belong to an advice group (young children, darker skin, little time outdoors, women from 50, pregnant women, everyone from 70), then all year round. Otherwise you make enough from March to October with fifteen to thirty minutes outdoors every day.
