Vitamin D supplements could spare more than three million people from colds or flu in the U.K. each year, researchers claim. The sunshine vitamin is vital for healthy bones, but also has a role in the immune system. The immune system uses vitamin D to make antimicrobial weapons that puncture holes in bacteria and viruses. But as vitamin D is made in the skin while out in the sun, many people have low levels during winter. Supplements can help. According to the study, one person would be spared infection for every 33 taking vitamin D supplements. That is more effective than flu vaccination, which needs to treat 40 to prevent one case.