The risk of developing polyps in the large intestine may increase calcium supplements, taken in combination with or without vitamin D, as reported by a major new American scientific research.
Scientists have spoken of an issue with potentially major consequences for public health, said further research should confirm their own and stressed that in any case the potential risks should be weighed against the benefits of calcium dietary supplements .
However, they underlined that, as millions of people worldwide get extra calcium for osteoporosis and for other reasons, new findings can have important implications for the diagnosis and prevention of colorectal cancer, a disease with more and more cases.
The researchers, led by Dr. Seth Crockett, of the University of North Carolina Medical School, who published the Gastroenterological Journal “Gut”, conducted a clinical trial of more than 2,000 patients aged 45 to 75 years old, who had a history of polyps and who were going to have a new colonoscopy in the years to come.
Patients were randomly assigned to four groups: the first one was given daily for three to five years of calcium supplements, the second daily vitamin D supplements, the third as much calcium supplements as D, and the fourth none of the two.
During the study, no correlation was found between dietary supplements and polyps. However, over a longer period of time six to ten years after the onset of supplementation, there was an increased likelihood of polyps occurring in those who received either extra calcium or vitamin D.
Taking plain vitamin D did not appear to be associated with an increased risk of polyps. Also, there does not seem to be a relationship between calcium taken with food (not with supplements) and polyps. Women and smokers also have a higher risk of polyps when they take calcium supplements than men and non-smokers.
Polyps develop in the lower part of the colon and are not malignant, but sometimes they may develop into cancer if not removed early through colonoscopy. There are many different shapes and sizes of polyps and the new study focused on mixed or toothed ones, which are less common than adenomatous but have the same risk of developing cancer.
Some categories, such as patients with a history of pre-cancerous polyps, especially women and smokers, appear to be at greater risk, and researchers have therefore recommended that they avoid calcium and vitamin D supplements until new studies clarify the issue.