Walnuts found to improve metabolism in obese mice: study

A new study suggested that consumption of walnuts, a known health-boosting food rich in omega-3 fatty acids, had a particular ability to improve the metabolisms of obese mice that were fed an unhealthy, high fat, high-sugar diet.

Adding other healthy whole foods from plants, like raspberries, cherries or green tea, made the effects even more significant.

In the study published in the Journal of Nutrition, a group of mice was given the equivalent of the cheeseburger-fries-and-soda diet, which is often consumed by millions of Americans and is contributing to rising obesity among humans. Another group of mice received a regular low-fat diet as a control.

Neil Shay, in the College of Agricultural Sciences at Oregon State University, and his team reported that mice eating walnuts, at a reasonable level of consumption equivalent of humans having about one and a half servings a day, had more of the "good" inflammation-reducing fatty acids in their blood at the end of the nine-week study, and much less fat in their livers, than mice that ate the high-fat diet alone.

The walnut-fed mice didn't lose weight, as they ate just as many calories as their non-walnut-eating counterparts.

"Walnuts alone had a good effect when they were part of the high-fat diet," Shay said. "But adding some of the other foods produced additional benefits," such as boosting the levels of anti-inflammatory compounds in the mice's blood by as much as 50 percent, and reducing levels of pro-inflammatory compounds.

Walnuts are a good source of alpha-linolenic acid, or ALA, an omega-3 fatty acid that the body needs for normal growth and development.

The other foods tested in the study were raspberries, apples, cranberries, tart cherries, broccoli, olive oil, soy protein and green tea that contain other plant chemicals known to benefit human health. The researchers fed each of these, in powdered form, to one of eight subgroups of the walnut-fed mice.

The walnut-fed group, as a whole, had better scores on key indicators of metabolic health, including better glucose tolerance, a measure of how efficiently the body uses sugar; significantly higher blood levels of high-density lipoproteins, or HDLs, the so-called good fats; and generally lower levels of the "bad" low-density lipoproteins, or LDLs.

The mice that got walnuts and also raspberries, apples or green tea had the best glucose-tolerance scores. Poor glucose tolerance is a precursor to Type 2 diabetes.

In addition, the walnut-fed mice had half the liver fat as the mice on the high-fat diet alone; and the mice that ate walnuts plus broccoli or green tea had even less fat in their livers.

They also had higher levels of heart-healthy polyunsaturated fatty acids in their livers, and lower levels of the fatty acids that trigger inflammation.

And the fat globules in their livers were smaller than in the livers of the high-fat-fed mice. Bigger fat globules signal a condition called steatosis, in which fat accumulates within liver cells, distorting their structure and impairing their function.

"Even though we did this study in mice and not in humans," said Shay, acknowledging that further study is needed. "I think it's safe to say that if you include a serving of walnuts and one or more of these other foods in your daily diet, it would do no harm and might have beneficial effects." Endit