EXCESS levels of vitamin D can increase the risk of heart disease or stroke, new research indicates.
The dangers of having too little vitamin D, also known as the sunshine vitamin because levels can be boosted by exposure to sunlight, are well known and have contributed to a rise in the number of people taking vitamin D supplements.
But a study by scientists at the University of Copenhagen, believed to be the biggest of its kind, has highlighted the connection between high levels of vitamin D and cardiovascular death.
Vitamin D is made by the skin in reaction to sunlight and can also be found in oily fish, eggs, fortified cereals and spreads or supplements. It helps to regulate the amount of calcium and phosphate in the body, keeping bones and teeth healthy.
A deficiency can lead to bone deformities such as rickets or bone pain and tenderness as a result of a condition called osteomalacia in adults.
But people who are taking too many vitamin D supplements over a long period of time can cause more calcium to be absorbed than can be excreted. The excess can be deposited in and damage the kidneys.
Excessive vitamin D can also lead to calcium being removed from bones, which can soften and weaken them.
The new study, published in the Journal of Endocrinology and Metabolism, also warned for the first time of the effect on heart health. It found that having too much vitamin D in the blood can be detrimental to health.
Professor of clinical medicine Peter Schwarz said: “We have studied the level of vitamin D in 247,574 Danes, and so far, it constitutes the world’s largest basis for this type of study. We have also analysed their mortality rate over a seven-year period after taking the initial blood sample, and in that time 16,645 patients had died.
“Furthermore, we have looked at the connection between their deaths and their levels of vitamin D.
“If your vitamin D level is below 50 or over 100 nanomol per litre, there is an greater connection to deaths.
“We have looked at what caused the death of patients, and when numbers are above 100, it appears that there is an increased risk of dying from a stroke or a coronary.
“In other words, levels of vitamin D should not be too low, but neither should they be too high.
“Levels should be somewhere in between 50 and 100 nanomol per litre, and our study indicates that 70 is the most preferable level.
“These are very important results, because there is such great focus on eating vitamin D.
“We should use this information to ask ourselves whether or not we should continue to eat vitamins and nutritional supplements as if they were sweets.
“You shouldn’t simply up the dose to feel better. We should only consume such vitamins in close co-ordination with your GP.”
In Scotland, suggestions of a link between vitamin D deficiency and multiple sclerosis (MS) prompted calls for all essential foods to be fortified with the vitamin.
George Ebers, professor of clinical neurology at Oxford University, published a study showing the link and said that rates of MS were so “dire” in Scotland that the Scottish Government could face legal action from people who go on to develop MS in the future, if ministers did not act on the evidence.
Scotland has the highest levels of MS in the world and the lowest levels of vitamin D, due to a lack of sunshine and a diet low in oily fish. MS is a disease affecting nerves in the brain and spinal cord, causing problems with muscle movement, balance and vision.
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