Most people in northern hemispheres are depleted in the vitamin because of the weakness of sunlight, the short summers and an over-zealous 'safe sun' campaign—and almost every rheumatoid arthritis sufferer has low levels, and probably that's true for people with other inflammatory diseases too.
For people who don't get enough sunshine, supplementing is important, and foods that are rich in the vitamin include eggs, and oily fish such as sardines and salmon.
Researchers from the University of Birmingham in the UK are the latest to discover the importance of the vitamin. In a series of tests on rheumatoid arthritis patients, they discovered that healthy cells responded well to vitamin D, but those already affected by the arthritis weren't helped. This is because arthritis leads to vitamin D insensitivity, which means that cells no longer respond.
Vitamin D therapy could still work on patients if they are given very high doses, the researchers suggest.
One of the authors, Prof Martin Hewison, said that "almost everyone in the UK has vitamin D deficiency"—which is true, but at odds with the official view from the Department of Health that most of us get all the vitamin D we need from food and sunshine.