Research has found evidence that a daily consumption of walnuts, the equivalent to two servings a day in humans, reduces the growth of breast cancer tumors in mice.
In the study, the researchers looked at the ability of walnuts to slow the growth of breast cancer tumors using an amount comparable to what humans might consume.
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.
“This is an intriguing finding that needs to be repeated, and ultimately confirmed in humans,” said Karen Collins, Nutrition Advisor for 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.”
“What this study showed is that we had a significant suppression of cell proliferation in the walnut-fed group,” said W. Elaine Hardman, lead researcher. “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.”
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, a type of omega-3 fatty acid called alpha-linolenic acid (ALA), sets walnuts apart from other nuts. 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 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, each one of these substances might be present in too small an amount on its own, but when they all come at the tumor from different directions, they may have an effect.
Walnuts also contain fiber, which studies have shown can help with weight control. One caution is that walnuts pack a lot of calories into a relatively small portion.
Calories still count, even in a healthy food that has plenty of nutrients, it’s not a matter of adding extra handfuls of walnuts to your normal diet, it’s about substituting walnuts for other foods so you don’t increase your calorie consumption. Once you start gaining weight, you start to cross out a lot of the health benefits.