The importance of vitamin D intake when sunlight is scarce

Margreet Bierens
About the Author

Margreet Bierens is a psychologist and PhD candidate at the TRACE-project (the Netherlands). and works on emotion dysregulation in children and adolescents.

When exposed to UVB-radiation, the human body produces vitamin D out of cholesterol. Vitamin D is therefore also known as the “sunshine vitamin”. Healthy vitamin D levels in people are thought to play a role in preventing several health problems, such as cardiovascular diseases, osteoporosis, mood disorders, diabetes and other autoimmune diseases [1]. In most western countries, the beneficial effects of vitamin D are well-established. Pregnant women are even advised to add vitamin D supplementation to their diet to stimulate fetal growth [2].

People that live further from the equator, have fewer hours of UVB-radiation and are more prone to vitamin D insufficiency. For example, residents of northern Canada and Norway have very little UVB exposure from November through February. During those months, vitamin D intake is even more important.

Residents of the arctic circle, whose families have lived there for generations after generations, have diets that are traditionally relatively high in vitamin D. The diet contains among other things: liver, trout, Atlantic salmon, seals and whales. As younger generations gradually shift away from the traditional diet, vitamin D insufficiency becomes more common among northern residents [3]. It is yet unclear if the decline in traditional diets will be accompanied by a rise in vitamin D insufficiency-related health problems. However, it is well established that several of these health problems have been uncommon among northern residents in the past [4].

Research shows that in countries further away from the equator, vitamin D levels are steady with regular UVB-exposure: Going outdoors around noon, sunbed use (with caution) and sun-seeking holidays. And in the UVB-scarce months, regular vitamin D intake becomes in particular important to prevent low vitamin D levels and its possible consequences [5].