Vitamin D strengthens your body’s defences

  • Vitamin D activates your body’s innate and adaptive defence mechanisms
  • Low vitamin D content in the blood is linked to increased risk of contracting the common cold
  • Vitamin D supplement on its own cannot prevent the common cold from developing

Vitamin D deficiency (25-hydroxy vitamin D level in serum sample below 50 nmol/l) has historically been linked to skeletal diseases, because vitamin D deficiency causes rickets in children and osteomalacia, i.e. soft bones, in adults. Recent studies have shown that vitamin D affects the body’s defence mechanisms in many ways. It efficiently activates the body’s innate defence mechanisms by increasing, for example, the quantity of peptides known as cathelicidins, which prevent the growth of viruses and bacteria. Vitamin D also influences the body’s adaptive immunity by regulating the function of T cells. It strengthens the function of the respiratory tract’s epithelial cells. Surprisingly, vitamin D also have marked anti-inflammatory effects.

Several studies have shown that people with a low vitamin D content in their blood suffer more respiratory tract infections than those whose vitamin D content is considered sufficiently high. There is also proof that a significant amount of vitamin D supplement reduces respiratory infections in people who suffer from recurrent respiratory tract infections or whose defence mechanisms are impaired. Vitamin D has even be compared to antibiotics.

At the same time we must be aware that a vitamin D supplement on its own will not significantly reduce the number of common colds in healthy children or adults. This is probably due to the complexity of the body’s defence mechanisms.

Vitamin D is found in food (vitaminised milk and fat spreads, fish, egg, liver, mushrooms) and sunlight. In many countries, however, these are not sufficient to keep the body’s vitamin D content at a sufficient level. In Finland The National Institute for Health and Welfare recommends a 20 ug vitamin D supplement a day for elderly persons. It is possible that this dose is not immunologically sufficient for everyone, and the recommended blood level for aging persons is 75-100 nmol/l. The correct dose of vitamin D is a contentious issue. There is also controversy about whether an otherwise healthy person should have their blood vitamin D level tested. With the elderly, measuring it is supported by the fact that for example in Finland approximately a fifth of adults have been discovered to have a vitamin D content below the deficiency limit (50 nmol/l).

Vitamin D deficiency has been linked to numerous diseases, such as cancer, diseases of the blood-vascular system and diabetes, but there is no indisputable proof for this.