Vitamin D in Autumn and Winter: When and How Much?

Summary

Men up to and including 69 years of age without a risk factor do not need to take vitamin D as a matter of course in winter. The winter sun is too low for sufficient production; your body partly draws on the reserve built up over summer. If you have a dark or tanned skin tone, or get little exposure to daylight, 10 micrograms per day is recommended; from the age of 70, the figure is 20 micrograms.

Table of Contents

In December it is already dark by half past four. During the week you drive to work and back in the dark, and the question arises naturally: should you start taking vitamin D? This article is for men who want to think that through clearly. By the end, you will know whether you belong to a group for which a supplement is recommended, what amount applies, and what sun through glass or a sunbed does and does not do.

Why your skin produces less vitamin D in autumn and winter

Your skin produces less vitamin D in autumn and winter because the sun in the Netherlands is too low at that time of year. Vitamin D production requires UVB radiation to reach your skin. In winter, the low sun delivers too little of it, meaning you cannot produce enough through sunlight alone.

Autumn is the period in which the sun sits progressively lower in the sky. As the sun's angle decreases, production falls, until in winter not enough remains. Vitamin D in autumn is therefore not tied to one fixed date when everything stops, but to a sun angle that yields less week after week.

Your body partly compensates for the dark months by drawing on a reserve. During the sunnier months you build up vitamin D, and in winter your body uses part of that stored supply. How much you build up depends on how much sun your skin has actually received during those months.

A low winter sun therefore does not automatically mean you need to start taking supplements. Whether a supplement recommendation applies to you depends on your age, your skin tone and how much daylight your skin receives during the day. The season raises the question; your situation determines the answer.

Sun, food and supplements as sources of vitamin D

Sunlight is the most important source of vitamin D; food provides a smaller amount. With vitamin D from the sun, strictly speaking there is no absorption involved. Your skin produces the vitamin itself under the influence of UVB. With food and supplements you do absorb vitamin D, from what you eat or take.

Food therefore supplements the winter, but cannot fully replace the production from sunlight that falls away. The balance shifts in the dark months: the largest source disappears, while the smaller source stays the same. A varied diet therefore remains the foundation, even if you also use a supplement alongside it.

A supplement is particularly relevant when your age, skin tone or limited exposure to daylight gives rise to an official recommendation. A supplement does not replace a varied diet and a healthy lifestyle. It fills in where sun and food together do not provide enough for your situation.

Vitamin D has a fixed role for your bones and muscles. Vitamin D contributes to normal absorption of calcium and phosphorus and to the maintenance of normal bones. In addition, vitamin D contributes to the maintenance of normal muscle function. That role does not change with the seasons; in winter only the source changes.

From our formulas

Vitamin D3 + K2 (SHIELD)

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Sun through glass, the sunbed and the choice between D2 and D3

Behind glass you produce hardly any vitamin D, the sunbed is not a recommended substitute, and there is no well-founded winner between vitamin D2 and D3. All three questions revolve around the same thing: where you get your vitamin D from when the sun lets you down.

Vitamin D and sun through glass

Sunlight through a window does not provide suitable exposure for vitamin D production. Glass largely blocks UVB radiation, and it is precisely UVB that is needed for production in your skin. The warmth you feel behind the window therefore says nothing about vitamin D. That applies to a south-facing office just as much as to the windscreen of your car.

Why the sunbed is not a source of vitamin D

The sunbed is not a recommended method for producing vitamin D. Artificial UV exposure carries risks for the skin, and for that reason the sunbed is not a winter substitute for the sun. If you are looking for a source in winter, look to food and, if a recommendation applies to you, to a supplement.

Vitamin D2 or D3: which form do you choose in winter?

Vitamin D is the collective name; vitamin D2 and vitamin D3 are two different forms. On an ingredient list, vitamin D3 appears as cholecalciferol. There is no well-founded general statement that D3 is always better, stronger or more effective than D2. In winter, something else carries more weight: whether you belong to a group for which a supplement is recommended, and whether you reach the recommended daily amount consistently.

When should you take vitamin D and how much per day?

You take vitamin D when you belong to a group for which the official Dutch recommendation mentions a supplement. That recommendation depends on your age, your skin tone and the amount of daylight your skin receives during the day. For men, the breakdown looks like this:

With a dark or tanned skin tone and up to and including 69 years of age: 10 micrograms per day.
Little time outdoors during the day, or your face usually covered, up to and including 69 years of age: likewise 10 micrograms per day.
From the age of 70: 20 micrograms per day.
Without any of these factors and up to and including 69 years of age, there is no general supplement recommendation, not even in autumn or winter.

There is no official threshold in hours or minutes for "spending little time outdoors". It refers to a lifestyle in which your skin rarely sees direct daylight during the day, for example because you work indoors from early to late. A short walk to the car does not turn an office week into an outdoor life.

The difference between 10 and 20 micrograms is an age threshold: from the age of seventy, the recommended amount is twice as high. Both recommendations concern a daily intake. If a recommendation applies to you, you take that amount every day, not only on days when it is grey outside.

Why SHIELD contains 25 micrograms of D3 in olive oil

SHIELD delivers 25 micrograms of vitamin D3 per softgel, dissolved in extra virgin olive oil: one daily dose in a carrier that suits a fat-soluble vitamin. Behind those numbers are a few choices that also help you read other packaging.

On a supplement you encounter three numbers that each mean something different. The general recommended daily amount of vitamin D is 10 micrograms; from the age of 70 the recommendation is 20 micrograms. The reference intake (RI) on labels is 5 micrograms, which means 25 micrograms appears there as 500% RI. The upper limit for adults is 100 micrograms per day.

We chose 25 micrograms of vitamin D3 as cholecalciferol per softgel. That amount is above the recommended values of 10 and 20 micrograms and at a quarter of the upper limit for adults. Because D3 is fat-soluble, the vitamin is carried in olive oil rather than a dry powder.

In addition to D3, the softgel contains vitamin K2 as menaquinone-7 (MK-7), the long-chain form. Both vitamins are fat-soluble and therefore fit in the same oil. The softgel itself is made from bovine gelatine, so it is not suitable if you eat vegetarian or vegan.

We take SHIELD in the morning, at breakfast. A daily supplement stands or falls by the place it gets in your day, and that is why we believe in a fixed morning ritual: the same moment, at the same table.

SHIELD: per softgel 25 µg vitamin D3 (cholecalciferol, 500% RI) and 37.5 µg vitamin K2 (menaquinone-7, 50% RI) in extra virgin olive oil. One softgel per day with a glass of water, preferably during a meal containing some fat. Each pack contains 30 softgels, a full month.

When winter on its own is not a reason to take vitamin D

For men up to and including 69 years of age without a risk factor, winter on its own is not a reason to take vitamin D. No general recommendation applies to that group, not even in the dark months. Food and the reserve built up during the sunnier months do their job in many cases.

That also applies to our own range. We see a vitamin D supplement as something for those who have a recommendation, not as a standard step for every man the moment the clocks go back. A supplement is also not a diagnosis: whether your vitamin D level is low is not something you can read off from the season, but something you establish with a measurement.

Consult your GP if any of the following situations apply to you:

A low vitamin D level has been established in you.
You have osteoporosis or are being treated for it.
You are unsure whether you belong to one of the risk groups.
You use multiple products containing vitamin D and are not sure how they add up together.
You use anticoagulant medication such as acenocoumarol or phenprocoumon and are considering a supplement containing vitamin K, because vitamin K can affect how those medications work.

Vitamin D in your winter routine: does a supplement suit you?

Start with your situation, not the calendar. If you belong to a group for which a supplement is recommended and you want vitamin D3 and K2 in one softgel, SHIELD fits into your morning at breakfast. That way vitamin D becomes a fixed part of your morning ritual, rather than something you only think of in January. If you do not belong to such a group, winter alone is not a reason to start.

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Magnesium Glycinate + Taurine (DUSK)

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Frequently asked questions about vitamin D in winter

How long do you need to be in the sun for vitamin D in winter?

In the Dutch winter, there is no amount of time outdoors that guarantees sufficient vitamin D production. The well-known recommendation is to spend 15 to 30 minutes outside daily, between 11:00 and 15:00, with your face and hands uncovered. That recommendation applies to the months in which the sun is high enough for production. Being outdoors remains part of a healthy lifestyle, but in winter it does not replace a supplement recommendation if you belong to a risk group.

At what time of day do you take vitamin D?

The recommendation for vitamin D concerns an amount per day, not a fixed time. Because vitamin D is fat-soluble, taking it with a meal containing some fat makes sense. Whether that is breakfast, lunch or dinner makes no difference to the recommendation.

How much vitamin D do you get if you use two supplements?

Add up the vitamin D from all products, as it is your total daily dose that matters. An example from our own range: SHIELD and DUSK each contain 25 micrograms of vitamin D3 per daily serving, together 50 micrograms per day. That is half the upper limit of 100 micrograms for adults. If you use both, keep track of any other products containing vitamin D that you take alongside them.

Do you stop taking vitamin D when spring arrives?

The supplement recommendation depends primarily on your situation, not on the calendar alone. If you belong to a group for which a supplement is recommended, such as men from the age of 70 or men with a dark or tanned skin tone, the recommended daily amount applies for as long as that situation exists. Someone who works indoors during the day also spends little time outside in summer. For men without a risk factor, spring changes nothing: they already had no general recommendation in winter.