A recent study is building hope that a miracle substance can prevent most cancers.
It's not a drug, it's vitamin D.
Studies have shown that the supplemental vitamin D can cut the risk of several types of cancer by 60 percent overall for older women in the most rigorous study yet.
The body makes vitamin D in the skin -- but most people are probably deficient, according to studies.
Some specialists say the new research strengthens the case that vitamin D is a powerful cancer preventive. Experts remain split, though, on how much to take.
In the study, participants took 1,100 international units a day for four years. That's almost three times the government recommendation.
Some critics say it was too small a study to be that significant. Others note that the study was of women only. Still others point out the study was designed to look at bone health, not cancer.
But physicians like Don Colbert were already convinced about vitamin D even before the study came out.
"Vitamin D actually helps to put the brakes on cancer cell growth or on cell growth, in particular," Colbert said. "So we're finding now that vitamin D helps to prevent prostate cancer, breast cancer and even colon cancer."
The research comes at a time when more and more benefits of vitamin D are being researched. Those potential vitamin D advantages include boosting circulation, the immune system, and even mental health.
But cancer is a major killer, and if the benefits are even half what the researchers found, the research is a breakthrough for medicine and public health.
The research has so impressed the Canadian Cancer Society that it's recommending most adults take 1,000 international units every day in fall and winter. In those months, people don't get enough sun to make much, if any, vitamin D in the skin.
In fact, there is nothing else known -- no drug, no lifestyle change, no nutrient -- that can prevent cancer like this vitamin D study seems to show.