The USZ News puts it succinctly and clearly in a nutshell: people with a vitamin D deficiency are more tired. Those who then take vitamin D are less tired. It sounds banal, but this is the first time in the world that this has been proven in a randomized double-blind placebo-controlled study. We asked Dr. Albina Nowak, head of the study and senior physician at the Clinic and Polyclinic for Internal Medicine at the USZ, what consequences this has for the population.
Dr. Nowak, what does “randomized double-blind placebo-controlled study” actually mean?
Neither the test subjects nor we knew which person was receiving the placebo and which the vitamin D. The study was therefore double-blind and the risk of influencing the results was largely excluded. The study involved 120 healthy people of different ages and both sexes who complained of fatigue with low vitamin D levels. The random selection is called randomized. By administering a substance with no effect (placebo) to half of the test subjects, the effect of vitamin D could be effectively demonstrated in comparison. Medical and psychiatric causes for the fatigue were also ruled out by the study team.
Their study now shows that taking vitamin D reduces fatigue in vitamin D deficiency. Can winter fatigue often be explained by vitamin D deficiency and how common is this?
Yes, that is indeed the case. We were able to show the causal relationship between vitamin D deficiency and fatigue. Of course, there are also other factors for winter fatigue: people move less, daylight hours are short, etc. However, the study clearly showed that fatigue is reduced by taking vitamin D in the event of a vitamin D deficiency.
Almost everyone in our latitudes is affected by a vitamin D deficiency in the period from around mid-January to spring. If you don’t spend weeks in the sun, you can’t produce vitamin D in your skin. The measurements have shown that the values are up to 50 percent below the European guideline values in some cases. Certain population groups are particularly hard hit. For example, dark-skinned people in our latitudes usually have lower levels, as they can produce less vitamin D themselves when there is little daylight. Overweight, elderly and chronically ill people also tend to have lower vitamin D levels. Gender, on the other hand, plays no role; men and women are affected in roughly equal measure.
Is the conclusion that you recommend taking additional vitamin D in winter?
In principle, chronic fatigue should be considered a vitamin D deficiency. The study clearly showed that although the placebo group also reported being slightly less tired, the group taking vitamin D was significantly less tired, almost five times less tired. It therefore makes sense to take a daily dose of 800 units of vitamin D in winter to prevent a deficiency. The vitamin does not work immediately, so it makes sense to take it from November onwards.
In what form should you take vitamin D?
The best way to take it is in drop form. Vitamin D is fat-soluble and should ideally be taken before meals. We do not recommend taking a mega dose of vitamin D “in stock” at the beginning of winter; continuous intake works better in the long term.
Are there any risks when taking vitamin D?
The risk of an overdose is low, but very large quantities would have to be taken at once. In the case of an overdose, we know that the side effect is an excessively high calcium level. In older people, the intake of megadoses of vitamin D led to frequent falls.
Now that the sun is shining again, has the danger of vitamin D deficiency been averted?
The low values often extend into spring, and as long as the temperatures are still low, we show little skin, through which we produce vitamin D through sunlight. Even taking it during the summer months is certainly not harmful, especially if you don’t go out in the sun much or during long periods of bad weather. In summer, for example, people who work night shifts or otherwise spend little time outdoors during the day are also at risk.
