Vitamin supplements have been heralded and hyped over the years, often only to ultimately fall from grace once research proves them to be little more than placebos in our quest for longer life or better health.

But at least one may have true merit — vitamin D.

Long considered just a supplement with calcium for bone health, this humble vitamin may have untapped potential in fighting or preventing disease, suggests an explosion of new research. Not only has it shown promise in reducing the risk of, among other things, diabetes, pancreatic cancer, breast cancer and cardiovascular disease, it also seems to improve infertility, weight control and memory.

The food industry is exploring ways to fortify more products. And Pub Med, an international database of medical literature, shows that 2,274 studies referencing the vitamin have been published just this year.

"Vitamin D is one hot topic," says Connie Weaver, a professor of foods and nutrition at Purdue University.

On Tuesday and Wednesday, hope and hype may collide. An Institute of Medicine committee will convene to discuss whether the recommended daily intake of vitamin D and calcium should be increased. Researchers overwhelmed by the vitamin's potential will square off against skeptics who say more study is needed before people are urged to take vitamin D supplements.

The last time guidelines were issued on the vitamin was in 1997, long before research suggested that people are getting too little. Currently, the recommended daily intake is 200 to 600 international units a day, with an upper limit of 2,000 IU per day.

Some researchers are advocating at least 600 IU per day, with an upper limit of 10,000 IU. Giving impetus to this push are the facts that many people seem to be deficient and that the nutrient appears to play a role in many other conditions.

Other scientists say it's too soon to urge everyone to take supplements. An influential report released in June by the Agency for Healthcare Research and Quality found little evidence it considered conclusive to support increasing the recommended amounts.

"I think there is a consensus that we might benefit from higher vitamin D levels," says James C. Fleet, a Purdue University professor who does research on the vitamin and prostate cancer. "But the committee is going to ask whether there is existing scientific evidence that is strong enough to make a change."

Vitamin D has long been known to be critical to bone and muscle health by improving calcium absorption in the intestines and the way calcium is regulated in bones. More recent research shows that receptors for it are found in almost every organ and tissue system in the body, suggesting that deficiencies may impact many types of cell functions.