Issue 10 — September 24, 2008

News Roundup:

  1. Chubby Mother Mice Make Chubbier Children
  2. Save that Muscle Mass: Exercise + Diet
  3. Green Tea May Help Fight Fat

W. Elaine HardmanOmega-3 Fats, In A Nutshell

Long before the nutrition community realized that all dietary fats are not the same, cell biologist W. Elaine Hardman was at the forefront of the field. An associate Professor at the Marshall University School of Medicine, Dr. Hardman’s research has shown that omega-3 fats may help prevent cancer and strengthen cancer therapy. Now, in the first study to investigate the walnut’s effect on cancer, Dr. Hardman has found that walnuts – rich in omega-3s – slow breast tumors in mice.

Fat Matters

Dr. Hardman’s research focuses on omega-3 fatty acids. Omega-3s belong to the family of unsaturated fats. Studies have shown that omega-3 protects against heart disease, inflammation, dementia and possibly cancer.

Foods are the key source of omega-3s, and dietary sources include oily fish (such as salmon, mackerel, albacore tuna) and certain plant and nut oils. Fish contains two types of omega-3 – DHA and EPA; walnuts and a few vegetable oils (canola, soybean and flaxseed) contain a third type, ALA (alpha-linolenic acid).

Dr. Hardman’s specialty in fatty acids began back in graduate school when she was analyzing data related to dietary fiber and cancer incidence. Unexpected results led her to notice that there were different levels of fat in the diet. “It turned out it was the dietary fat that was suppressing cancer incidence.” That led Dr. Hardman to omega-3s and “that’s where I’ve stayed; it’s turned out to be so interesting.”

Studies suggest that omega-3 fats increase the production of hormone-like, anti-inflammatory compounds. There is growing evidence that inflammation plays a role in the development of cancer. Consuming enough omega-3 fats may also decrease the amount of substances that lead to inflammation.

Slowing Tumor Growth

Hardman Walnut Graph
Nutrition and Cancer, v60, Issue 5, 2008

In Dr. Hardman’s new study, published this month in the journal Nutrition and Cancerexternal site, Dr. Hardman looked at the ability of walnuts to slow the growth of breast tumors using an amount comparable to what humans might eat.

The scientists divided a group of mice with human breast cancer tumors into two groups. One group was fed ground walnuts daily; an amount equivalent to two ounces (28 walnut halves) of walnuts per day for humans. The comparison group ate a diet supplemented with corn oil, along with vitamins, minerals and fiber similar to that of the walnut diet.

After 35 days, the tumors of the walnut fed mice were approximately half the size as the mice not fed walnuts. In the comparison group, tumor size doubled in about 11 days compared to 23 days for the walnut-eaters. An analysis showed that the walnuts may have slowed cell proliferation.

Given the relatively small amounts used, Dr. Hardman was happily surprised at the results. “Dietary studies usually start out using pretty high levels and then go down, where you see how low you can go and still get good effects,” said Hardman. “So 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 suppress the growth as much as did.”

Working Together

Along with omega-3s, walnuts include an array of compounds individually studied for their cancer-fighting properties, including gamma-tocopherol (a form of vitamin E), phytosterols and melatonin. Some of these compounds act as antioxidants in the body.

Support AICR ResearchThe study has led Dr. Hardman to investigate walnuts’ possible effect on cancer prevention. She is now completing a long-term animal study, which she expects results from within the year.

Drawing from her experience, Dr. Hardman hypothesizes that the nut’s omega-3s are not acting independently to reduce tumor growth. “It’s probably different components working together to provide the benefit,” said Dr. Hardman.

Earlier research by Dr. Hardman, some funded by AICR, has investigated whether omega-3 fats can augment chemotherapy and minimize side effects for breast cancer.

“We are finding out new things about fats every year,” said Dr. Hardman. The research can lead to a better understanding of the types of fats and how each may provide health benefits. But right now, what consistently shows up in diet-cancer studies are the benefits of healthful foods. “When we start trying to take the foods apart, we rarely see the kind of [cancer-preventative] effect we get from a whole food.”

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News Roundup

Chubby Mother Mice Make Chubbier Children

Overweight mothers with a genetic tendency for obesity may have children who become even heavier, suggests a new laboratory study – and changing the mother’s diet may break the cycle. Published in the International Journal of Obesityexternal site, the study looked at the effect of maternal obesity among three generations of genetically identical mice, all of which had an inclination to overeat. One group of mice ate a diet supplemented with methyl-rich nutrients that alter gene expression—a process known as epigenetics. Offspring of the mice fed a standard diet weighed more in each successive generation. But by the third generation in the methyl-supplemented dieters, there was a significant decrease in body weight relative to the unsupplemented group. The authors hypothesize that the methyl supplements may affect body weight by interfering with the area of the brain that regulates appetite.

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Save that Muscle Mass: Exercise + Diet

Fat Oxidation ChartOverweight, older adults can lose the fat and keep the muscle by getting active – regardless of weight loss – a new study suggests. Published in this month’s Journal of Applied Physiologyexternal site, the study highlights how activity may help older adults who tend to lose muscle as they age, which can lead to health problems. In the study, researchers divided 64 adults into one of three groups: exercise only; diet only; or exercise plus diet. All the participants were sedentary, and either overweight or obese. After 4 months, the diet and exercise plus diet group had lost a significant amount of weight, but it was the two exerciser groups who became more fit and burned more fat. The diet-only group’s weight loss resulted from a loss of both muscle and fat, whereas both exercise groups drew more of their energy source from fat. And results compared from the same fitness test at the beginning of the study showed the two exercise groups used fewer calories when compared to the diet-only group. Overweight adults who exercise could increase fat loss and use less energy for their daily activities, the authors conclude, which can help older people who have physical limitations.

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Green Tea May Help Fight Fat

glass of green tea

Past laboratory studies have linked green tea with health benefits, such as weight maintenance, fat loss, and cancer prevention. Now, a new laboratory studyexternal site has found that a compound in green tea – ECGC – may slow weight gain and decrease symptoms of the metabolic syndrome. The metabolic syndrome is a group of conditions related to obesity and insulin resistance, and linked to heart disease and diabetes. In one part of the study, published in this month’s Journal of Nutrition, the scientists found that mice on a 16-week high-fat diet supplemented with ECGC gained less weight than mice on the high-fat diet alone. The ECGC-diet fed mice also exhibited lower insulin resistance and had lower blood cholesterol than their high-fat counterparts. A second part of the study switched some high-fat fed mice to an ECGC-supplemented diet. At the end of four weeks, the ECGC diet had 22 percent lower blood glucose than those fed only a high-fat diet. Future studies need to determine how ECGC might reverse the effects of a high-fat diet and see if the effects also occur in people, conclude the authors.

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