Whole grains, a rich source of phytochemicals, bran, fibre, minerals and vitamins, have been gaining increasing attention from researchers, with studies reporting reduced risks of metabolic syndrome, diabetes, and colorectal cancer. The latter causes 492,000 deaths each year worldwide.
The link between colorectal cancer and whole grains has been put down to the fibre content, although this remains an area of intense debate.
The new study, published in the journal Nutrition Research, supplemented the diet of Min mice, a model strain that has a 100 per cent chance of developing intestinal cancer, with ground wheat.
Five cultivars of wheat were used in the study, and the mice randomly assigned to one of eleven diet groups. Each wheat cultivars was provided as either wheat bran or whole wheat, and a control group ate a casein-based diet with no wheat added.
After the 10-week feeding period, the researchers examined the number and size of the intestinal tumours were measured.
"There was a strong correlation between the antioxidant content of the wheat samples and their tumour suppression activity in the intestine of Min mice," wrote lead author John Carter from Wichita State University.
Two of the cultivars, Ike and Madison, reduced the number of tumours in the small intestinal tract by about 60 per cent.
"These cultivars contained the highest amounts of dietary antioxidants," said Carter.
It was also noted that wheat bran diets were more effective than the whole wheat diets for inhibiting the growth of the tumours.
The researchers reported that the main phytochemicals in the wheat were orthophenolics, including diferulic, ferulic, caffeic and chlorogenic acids.
The potency of these phytochemicals in the suppression of cancer is said to be enhanced by the presence of dietary fibre.
"The bioavailability may be aided by their ester linkage to the plant cellulose wall components, thus protecting them from degradation until they are released by endogenous glut flora," proposed Carter.
More study is planned by the scientists, still using the Min models. The two main unanswered questions are the specific phytochemical or phytochemicals that protect against cancer, and the minimum dietary concentrations needed.
This study adds to a number of observational studies linking whole grains to lower risks of the diseases - news that has already been grasped by cereal makers as the number of wholegrain products look set to rise.
Sales of whole grains products in the US have increased following recommendations of the health benefits in the USDA's new Dietary Guidelines for Americans.
In Europe, the € 16 million Healthgrain Integrated Project was recently launched to the effects of bioactive compounds in wheat and rye, identify new sources of nutritionally enhanced grain, as well as to develop methods to make cereal products more appealing to consumers.