The human body can synthesise vitamin D in the skin under the influence of sunlight. Small amounts of this vitamin are also found in foods such as vegetable oils, oily fish, eggs and dairy products, but this is not enough to meet a person’s daily needs.

In the autumn and winter months, when sunlight is limited, vitamin D deficiency often occurs. It leads to a range of disruptions in how the body functions. The first signs are tiredness and reduced immunity, then bone disease, cardiovascular disorders and even depression may appear. To avoid these setbacks, vitamin D supplementation is necessary from September until the end of April. Older people and those diagnosed with a deficiency should take vitamin D all year round.