Vitamin D supplements may help people with diseased hearts, a study suggests. A trial on 163 heart failure patients found supplements of the vitamin, which is made in the skin when exposed to sunlight, improved their hearts' ability to pump blood around the body. The Leeds Teaching Hospitals team, who presented at a meeting of the American College of Cardiology, described the results as stunning". Vitamin D is vital for healthy bones and teeth and may have important health benefits throughout the body but many people are deficient. "The skin's ability to manufacture vitamin D also gets less effective (with age) and we don't really understand why that is," said consultant cardiologist Dr Klaus Witte. Patients were given either a 100 microgram vitamin D tablet or a sugar pill placebo each day for a year. Dr Witte told the BBC News website: "It's as cheap as chips, has no side effects and [leads to] a stunning improvement on people already on optimal medical therapy." The study also showed the patients' hearts became smaller - a suggestion they are becoming more powerful and efficient. Dr Witte ... told the BBC: "Data have shown improvements in heart function, they may show improvements in symptoms and we now need a large study." It is thought every cell in the body responds to the vitamin. Most vitamin D comes from sunlight, although it is also found in oily fish, eggs and is added to some foods such as breakfast cereals.