Combining weight loss with vitamin D supplements may help reduce cancer risk, according to new research that suggests the combo targets inflammation linked to cancer and other chronic diseases.

The findings, by the Fred Hutchinson Cancer Research Center, are based on a randomized, controlled clinical trial involving more than 200 overweight, postmenopausal women who had insufficient levels of vitamin D.

"We know from our previous studies that by losing weight, people can reduce their overall levels of inflammation, and there is some evidence suggesting that taking vitamin D supplements can have a similar effect if one has insufficient levels of the nutrient," said lead researcher Catherine Duggan, Ph.D., a staff scientist in the Public Health Sciences Division at Fred Hutch.

But the new study is the first to show that combining the two — weight loss and vitamin D — would further boost this effect.

"Adding vitamin D augments the considerable effect of weight loss on inflammatory biomarkers," she said.

For the study — published online in Cancer Prevention Research, a journal of the American Association for Cancer Research — 218 women took part in a 12-month diet and exercise program (including 45 minutes of moderate-to-vigorous exercise five days a week).

Half of the study participants were randomly selected to receive 2,000 IU of vitamin D daily for the duration of the year-long trial, and the other half received an identical-appearing placebo, or dummy vitamin.

Biomarkers of inflammation were measured at the beginning and end of the study.

At the end of the study, all of the participants had reduced levels of inflammation, regardless of whether they took vitamin D, "which highlights the importance of weight loss in reducing inflammation," Duggan said.

But those who had the most significant decline in markers of inflammation were those who took vitamin D and lost 5-10 percent of their weight.

"We were quite surprised to see that vitamin D had an effect on an inflammation biomarker only among women who lost at least 5 percent of their baseline weight," Duggan said. "That suggests vitamin D can augment the effect of weight loss on inflammation."

Duggan encouraged women to speak to their health care providers about measuring their levels of vitamin D to determine the most appropriate dosage.