A diet containing walnuts may lead to genetic changes that can slow growth of colorectal tumour, the third most common type of cancer worldwide, new animal study by Harvard Medical School has found.

The study examined whether walnut consumption can cause changes to micro-ribonucleic acids (miRNA), the nucleotides that are involved in altering gene expression.

"Our research demonstrates that a walnut diet causes significant changes in the expression profile of miRNAs in localised colorectal cancer tissue, and that a walnut diet incorporates protective fatty acids in the colonic tumour either through its direct effects or through additive or synergistic effects of multiple other compounds present in walnuts," said lead researcher Christos Mantzoros.

Walnuts are the only nut that contain a significant source of alpha-linolenic acid (ALA), an essential fatty acid critical to various body processes and is known to reduce inflammation.

Walnuts also contain a variety of antioxidants, and numerous vitamins and minerals.

The researchers conducted the randomised study with two groups of mice. One group was fed the equivalent of two servings (56 grams) per day of walnuts for humans, while the second group received a similar control diet with no walnuts.

After 25 days, researchers found that in walnut-fed mice, key miRNA that may affect cancer cell inflammation, blood supply and proliferation were positively engaged.

The study results found that a smaller tumour size was associated with walnut-containing diet, suggesting that ALA may provide a protective benefit.

Tumour growth rate was also significantly slower in the walnut group compared to the control group.

The study was published in the Journal of Nutritional Biochemistry.