Walnuts slow growth of breast cancer tumors.
Article Type: Report
Subject: Tumors (Control)
Walnut (Health aspects)
Walnut (Research)
Breast cancer (Control)
Animal models in research (Usage)
Pub Date: 11/01/2008
Publication: Name: West Virginia Medical Journal Publisher: West Virginia State Medical Association Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2008 West Virginia State Medical Association ISSN: 0043-3284
Issue: Date: Nov-Dec, 2008 Source Volume: 104 Source Issue: 6
Topic: Event Code: 310 Science & research Canadian Subject Form: Tumours
Product: Product Code: 0173233 Walnuts NAICS Code: 111335 Tree Nut Farming SIC Code: 0173 Tree nuts
Geographic: Geographic Scope: West Virginia Geographic Code: 1U5WV West Virginia
Accession Number: 201087172
Full Text: Snack-sized quantities of walnuts slow cancer growth in mice, reports a Marshall pilot study published in the September issue of the peer-reviewed journal Nutrition and Cancer. The study is the first to investigate the effect of walnut consumption on cancer.

Primary investigator W. Elaine Hardman, Ph.D., said the study was designed to determine whether mice that got part of their calories by eating walnuts had slower breast cancer growth than a group eating a diet more typical of the American diet.

A group of 22 mice with human breast cancer tumors was divided into two groups. One group was fed ground walnuts daily in the amount equivalent to two ounces (28 walnut halves) for humans. The comparison group consumed a diet supplemented with corn oil, along with amounts of vitamins, minerals and fiber that were similar to the amounts occurring in the walnut diet.

After 35 days, the breast cancer tumors of the walnut-fed mice were only about half the size of the tumors in the mice that were not fed walnuts.

"What this study showed is that we had a significant suppression of cell proliferation in the walnut-fed group," said Hardman. "The time it took the tumor to double in size was 11.1 days for the corn oil fed mice compared to 23.3 days in the walnut fed group."

That such a small dose of walnuts could exert such influence intrigued investigators. "I was surprised by the results because, compared to most dietary studies, we were adding a very small amount to the diet and I didn't think this amount would be enough to suppresses the growth as much as it did," Hardman added.

"This is an intriguing finding that needs to be repeated, and ultimately confirmed in humans," said Karen Collins, M.S., R.D., nutrition advisor for the American Institute for Cancer Research. "But it fits with some of what we've seen from other studies. We know that walnuts have a lot to offer, such as omega-3 fat, vitamin E, and other antioxidants. Many of these substances have already shown anti-cancer potential individually."

Although the current study is the first to investigate the effects of whole walnuts on cancer, individual walnut components have displayed the ability to slow or prevent cancer in previous investigations.

One of those components, alphalinolenic acid (ALA), sets walnuts apart from other nuts, according to AICR's Collins. "Walnuts are one of the few plant foods that contain this kind of omega-3 fat, which protects against heart disease, inflammation and--potentially--cancer as well." Canola oil and flaxseed are also sources of ALA.

Studies suggest that omega-3 fats exert their influence by increasing the production of hormone-like, anti-inflammatory compounds. There is growing evidence that inflammation plays a role in the development of cancer.

Other much-studied cancer-protective substances within walnuts include gamma-tocopherol (a form of vitamin E), phytosterols and flavonoids. Lab studies funded by AICR and other organizations have shown that these compounds may slow cancer cell growth and fight inflammation.

"If it's not the omega-3 acting alone to prevent cell proliferation, it may be a synergy among some or all of the compounds," said Collins.

The mice in the current study were eating enough walnuts to account for 18 percent of total daily calories (an amount equivalent to 370 calories in a 2,000-calorie human diet).

Dr. Hardman co-authored the study with Gabriela Ion, Ph.D., also of the Marshall University School of Medicine.

The study was funded by grants from the American Institute for Cancer Research with a matching grant from the California Walnut Commission. Neither group had any input on the study design or findings.
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