Patients who had high levels of vitamin D and had surgery in sunny months were more than twice as likely to be alive five years after surgery compared to patients with low levels of vitamin D who had surgery in the winter, the researchers said.

Exposure to sunshine is a significant source of vitamin D, which also comes from food and dietary supplements.

Researchers at Harvard Medical School and Harvard School of Public Health studied the survival data of 456 patients with early stage lung cancer treated between 1992 and 2000.

"The survival advantage at five years is pretty dramatic," lead researcher, Dr. David Christiani said in a telephone interview. "It's 72 percent versus 29 percent when you compare the highest level of intake (of vitamin D) versus the lowest level of intake."

If the research is validated it may mean that taking vitamin D or fortified nutritional supplements soon after a diagnosis and before surgery could provide "a survival advantage," Christiani said.

The link between vitamin D and surgery outcome is not known but other studies have hinted that it may work to inhibit a variety of cancers, the researchers said.

"It looks like vitamin D is anti-proliferative, so it inhibits proliferation of abnormal cells," Christiani said, adding that there was also evidence to suggest vitamin D inhibits the spread of tumors.

While ultraviolet rays from the run trigger the production of vitamin D in the skin, the researchers said they are not suggesting that people make season or location factors in scheduling their cancer surgeries.

"There's certainly no implication that anyone should ever postpone their surgery or move to L.A. or Florida," Christiani said.

 "The only reason season comes into play is that in certain parts of the country, like the northeast, during winter we make virtually no activated vitamin D, so the entire population is pretty deficient in it."