Chronic inflammatory bowel diseases, such as Crohn’s disease, are very painful disorders that are still incurable today. Recent results suggest that an adequate intake of vitamin D could prevent the development of this disease.

Crohn’s disease is a chronic inflammation that can affect the entire digestive tract, from the mouth to the anus. It appears in early adulthood and is characterized by episodes of chronic diarrhea, severe abdominal pain (reminiscent of those associated with an attack of appendicitis), weight loss and chronic fatigue. .

This serious disease is caused by a dysfunction of the innate immune system, which reduces the effectiveness of the defense systems against various intestinal bacteria, resulting in a disproportionate inflammatory response and irritation of the intestinal lining.

The origin of this dysfunction is still unknown, but it probably involves a variety of factors. The risk of developing Crohn’s disease is 10 times higher for a first-degree relative of someone with the disease.

The environmental factor: more Crohn’s disease where there is less sun

In addition to hereditary factors, some observations suggest that environmental factors may also participate in the development of Crohn’s disease. This disease is indeed much more common in the countries of the northern hemisphere. The main characteristic of the northern regions is the low level of sunshine during the winter months. One consequence of this lack of sunlight is a dramatic drop in the production of vitamin D, this vitamin being formed in the skin as a result of the transformation of a molecule called 7-dehydrocholesterol by UVB rays from sunlight. .

Vitamin D suppresses the expression of the disease

To determine the potential role of vitamin D in Crohn’s disease, researchers examined the effect of this vitamin on the expression of genes involved in the defense against bacteria. They found that vitamin D dramatically increased levels of an antimicrobial peptide called beta-defensin as well as NOD2, a protein that alerts cells to the presence of microbes. These results are extremely interesting, because these two germ defense proteins are often defective in people affected by Crohn’s disease. By increasing their expression, vitamin D could therefore block one of the first steps that leads to inflammation of the intestinal mucosa.

Source

Wang et coll. Direct and indirect induction by 1,25-dihydroxyvitamin D3 of the NOD2/CARD15-defensin beta2 innate immune pathway defective in Crohn disease. J Biol Chem, 285:2227-31.

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