Walnuts Slow Growth Of Breast Cancer Cells

A study, published in the peer reviewed medical journal Nutrition and Cancer, has found that walnuts can dramatically cut the growth rate of breast tumors in mice.

The study, conducted by researchers at the Department of Biochemistry and Microbiology at the Marshall University School of Medicine in West Virginia, USA, involved the implantation of human breast cancer cells in a group of 22 mice. The tumors were allowed to grow to between 3mm and 5mm in size at which point the mice were divided into two groups. The first group received a walnut rich diet where walnuts constituted 18.5% of the daily caloric intake of the mice, the equivalent of 56 grams of walnuts a day in humans. The second group were fed a corn oil based diet that contained identical proportions of vitamins, minerals, and fiber to the walnut based diet.

The researchers found a significant reduction in the rate of tumor growth in the walnut fed group. The tumors in the walnut group grew at a rate of 2.9mm per day compared to 14.6mm per day in the control group.

The researchers noted that cell proliferation, or the rate that cells divide, was much lower in the walnut fed mice however the rate of cell apoptosis (programmed cell death) was similar in both groups.

The researchers believe that a particular omega-3 acid in walnuts known as alpha-linolenic acid (ALA) may be responsible for their cancer fighting effects. Walnuts, along with flaxseed, kiwifruit, soy beans, and canola oil are some of the few plant based sources of ALA. Omega-3 fatty acids are potent anti-inflammatory compounds. Chronic inflammation is thought to increase an individuals susceptibility to cancer and might create conditions in the body where cancerous cells can thrive.

Walnuts are also rich sources of vitamin E, polyphenols, and carotenoids, which are all powerful antioxidants. Melatonin, a naturally occurring hormone, is also found in walnuts. Melatonin can enhance the function of the immune system and has been shown to inhibit cancerous cell growth in some studies.