"Philippe Autier is willing to bet that taking vitamin D supplements will never be proved to do anything beyond helping to build strong bones  and certainly not to prevent heart disease cancer diabetes depression multiple sclerosis or the common cold as many claim. In fact the physician has wagered a few good bottles of champagne that none of three large randomized trials now underway will find proof of positive effects. To Autier a researcher at the Strathclyde Institute of Pharmacy and Biomedical Sciences in Glasgow Scotland the widespread faith in vitamin Ds benefits is like a religion. People want to have a simple story they can believe in he says. Cedric Garland meanwhile hews just as strongly to the opposite view  that vitamin D supplements confer a slew of benefits including warding off colon cancer breast cancer even Type  diabetes http The science is in my opinion unassailable says Garland an adjunct professor of epidemiology at the University of California at San Diego. Its just preposterous to say its not proven. In January  Autier published a statistical analysis http of results from hundreds of studies of vitamin D. He concluded Unfortunately there is probably no benefit to expect from vitamin D supplementation in normally healthy people. Garland on the other hand is the coauthor of dozens of studies http showing a strong inverse association between vitamin D levels and seemingly every disease under the sun. Indeed sun exposure is Garlands explanation for why rates of cancer Type  diabetes and other diseases tend to be higher the farther people live from the equator. Vitamin D after all is the sunshine vitamin synthesized from cholesterol in the skin in response to sunlight. Its a mathematical relationship he said in a telephone interview. The higher your latitude and the greater your areas average cloud cover the higher your rates of cancer. Since he and his late brother Frank Garland published the first study httpije.oxfordjournals.orgcontent.abstract in  revealing that relationship hundreds of other studies have explored the link between vitamin D including supplements and health  but none were large enough long enough or designed well enough to convince the skeptics. Now three nationally recognized researchers are leading landmark studies designed to settle at least some of the questions about vitamin D once and for all. The one thing the research leaders are certain of is that the publics faith in vitamin D as a modern panacea has far outpaced what the scientific evidence proves. Theres been a rush to judgment on vitamin D says JoAnn E. Manson chief of the division of preventive medicine at Brigham and Womens Hospital in Boston and a professor of medicine at Harvard Medical School. Everyone has gotten on the bandwagon. Unfortunately the lessons of history have shown repeatedly that many of these supplements that appeared to be very promising did not pan out in more rigorous testing. Manson should know. She has led or collaborated on more than a dozen large randomized placebocontrolled studies http dating back more than two decades which found none of the expected protection against cancer heart disease dementia or other diseases that scientists once attributed to beta carotene vitamin E or vitamin C supplements. She did find however that supplementation with folic acid vitamin B and vitamin B offered modest protection http against agerelated macular degeneration and for those with a diet low in B vitamins to begin with a hint of protection http against the loss of cognitive abilities. Now Manson is codirecting the Vitamin D and Omega Trial VITAL http testing whether compared with placebo a daily supplement of either  international units IU of vitamin D or one gram of fish oil another widely touted substance reduces the risk of stroke cancer heart disease and other health problems. The fiveyear study involving  men and women is scheduled to end in October . Another trial is testing whether a daily supplement of  IU of vitamin D will prevent Type  diabetes. The socalled Dd study which will run for four years is seeking to enroll  people older than  who are at high risk of developing diabetes due to weight or bloodsugar levels but who have not yet been diagnosed with the disease. I would call myself an optimistic skeptic says Anastasios Pittas principal investigator of the Dd study and a professor of medicine at Tufts School of Medicine in Boston. The indirect evidence is very strong. People with higher levels of vitamin D in their blood have been shown again and again to have a lower risk of developing diabetes in the future. These studies are as consistent as we have ever seen with any nutrient. But he adds those studies do not prove cause and effect. Before we make a blanket recommendation for the  million people in the United States who are at risk for Type  diabetes to go out and buy vitamin D supplements we need to know for sure if they help. A third trial designed to test whether  IU of vitamin D per day will slow the progression of multiple sclerosis in  patients is being led by Ellen Mowry an associate professor of neurology at the Johns Hopkins University School of Medicine. I do discuss vitamin D with my patients Mowry says. But I point out that we dont yet have randomized controlledtrials data to back it up. Thats why there are no official recommendations yet from any medical organizations. We have to be sure. So what are people to do in the meantime Four years ago Manson sat on a committee established by the Institute of Medicine to review how much vitamin D and calcium Americans need each day to maintain health and prevent disease. The report concluded that both are necessary for bone health but that as for preventing cancer heart disease diabetes and autoiummune disorders the evidence was inconsistent inconclusive as to causality and insufficient to inform nutritional requirements. Even so the committee recommended that children and adults up to age  get  IU of vitamin D daily  from food and if necessary supplements  and that adults age  and older get  IU.  Some studies have found no ill effects from taking far higher amounts and many of the prospective but not proven benefits against cancer and other diseases are believed to require doses ranging from  to  IU. Manson urges people to rely on the Institute of Medicine report which set a safe upper limit of  IU of vitamin D per day. Its fine to take that amount Manson said. But keep in mind there isnt yet evidence that taking those higher amounts will confer any benefits beyond the recommended daily allotment of  to  IU. Some studies she noted have even found evidence that very high levels of vitamin D circulating in the blood might be just as unhealthful as very low levels. A  study http for instance found that people with the highest levels of vitamin D in their blood more than  nanograms per milliliter were significantly more likely to die in the three months following a hospitalization as were people whose levels were between  and . ngmL. Such findings are why she Mowry and Pittas strongly advise people against taking more than the currently recommended upper daily limit of  IU even though doses as high as  IU are available online https and at many stores. Frustrated by the uncertainty Pittas takes it in stride. This is the beauty of medical research he says where you have some people convinced that vitamin D does nothing and others who believe its already proved to work. There is such controversy now that the only way to convince people who sit on those sides of the equation is to complete rigorous randomized trials. Well see what happens. I have a hypothesis that vitamin D will work but we have to test it. At the end of the studies one of us will be right. I just dont know which one. Hurley is a science journalist and author of Natural Causes Death Lies and Politics in Americas Vitamin and Herbal Supplement Industry http Broadway Books ."