Vitamin D deficiency may increase the risk for a variety of chronic diseases, which has led to increased use of vitamin D supplements, often in high doses. However, taking a supplement "just in case" is not recommended to prevent chronic diseases until reliable knowledge about the efficacy or unwanted effects are available. This is the conclusion from a knowledge summary published in the British Medical Journal.
Vitamin D has received much attention in recent years. There is evidence that vitamin D deficiency may increase the risk for a variety of chronic diseases , such as cardiovascular disease, cancer, autoimmune diseases and type 2 diabetes. Is there sufficient evidence to recommend vitamin D supplementation to prevent these conditions?
Professor Haakon E. Meyer and researcher Kristin Holvik from the Norwegian Institute of Public Health, together with Professor Paul Lips from the VU Medical Centre in Amsterdam, Netherlands reviewed the existing published research. They concluded that combined supplementation of vitamin D and calcium can prevent fractures in the elderly. However, they agree that vitamin D supplements should not be recommended to prevent chronic diseases before reliable knowledge about the efficacy and any adverse effects are available.
Should vitamin D supplementation be used if you have vitamin D deficiency?
"Yes. Vitamin D should not be ignored. In the latest nutritional recommendations from the Norwegian Directorate of Health, 10 micrograms of vitamin D per day are recommended for adults and children and 20 micrograms per day for the elderly. A blood test is not needed to follow these recommendations. In the summer months, sufficient exposure to sunlight will help many to achieve these levels regardless of diet. In winter, many people need to take a supplement, such as cod liver oil. Otherwise, oily fish such as salmon, trout and mackerel are good natural sources of vitamin D, and butter, margarine and one type of skimmed milk (ekstra lett lettmelk) are fortified with vitamin D in Norway," says Meyer.
In the article, Meyer, Holvik and Lips systematically reviewed the available literature and described the possible benefits of taking vitamin D supplements and possible unwanted effects. They also described ongoing research and studies that may provide a clearer answer in the foreseeable future.
Has there been much research into vitamin D?
"Yes, there is a considerable research about vitamin D and the article refers to large randomized studies that are now underway to investigate whether supplementation with high doses of vitamin D can prevent various chronic diseases. The results will be available within five years" says Meyer.
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Meyer HE et al "Should vitamin D supplements be recommended to prevent chronic diseases?" BMJ 2015;350:h321