Drinking red grape juice or red wine in moderation could improve the health of overweight people by helping them burn fat better, according to a new study coauthored by an Oregon State University (OSU) researcher.

The findings, published in the Journal of Nutritional Biochemistry in January 2015, suggest that consuming dark-colored grapes, whether eating them or drinking juice or wine, might help people better manage obesity and related metabolic disorders such as fatty liver.

Study method

Neil Shay, a biochemist and molecular biologist in OSU’s College of Agricultural Sciences, was part of a study team that exposed human liver and fat cells grown in the lab to extracts of four natural chemicals found in Muscadine grapes, a dark-red variety native to the southeastern United States.

One of the chemicals, ellagic acid, proved particularly potent: It dramatically slowed the growth of existing fat cells and formation of new ones, and it boosted metabolism of fatty acids in liver cells.

Improve liver function but not body weight, researchers

However Mr Shay cautioned that the plant chemicals were “not a weight-loss miracle”.

“We didn’t find, and we didn’t expect to, that these compounds would improve body weight,” Mr Shay said. “But by boosting the burning of fat, especially in the liver, they may improve liver function in overweight people,” he said.

“If we could develop a dietary strategy for reducing the harmful accumulation of fat in the liver, using common foods like grapes, that would be good news,” Mr Shay said.

Results complement mice studies

The study, which Mr Shay conducted with colleagues at the University of Florida and University of Nebraska, complements work with mice he leads at his OSU laboratory. In one 2013 trial, Mr Shay and his graduate students supplemented the diets of overweight mice with extracts from Pinot noir grapes harvested from Corvallis-area vineyards.

Some of the mice were fed a normal diet of “mouse chow,”containing 10 per cent fat. The rest were fed a diet of 60 per cent fat – the sort of unhealthy diet that would pile excess pounds on a human frame.

“Our mice like that high-fat diet, and they over-consume it,” Mr Shay said. “So they’re a good model for the sedentary person who eats too much snack food and doesn’t get enough exercise,” he said.

Equivalent portions would be ‘reasonable’ in human diet

The grape extracts, scaled down to a mouse’s nutritional needs, were about the equivalent of one and a half cups of grapes a day for a person.

“The portions are reasonable, which makes our results more applicable to the human diet,” Mr Shay said.

Mice fed extracts had less liver damage

Over a 10-week trial, the high-fat-fed mice developed fatty liver and diabetic symptoms, which Mr Shay said were “the same metabolic consequences we see in many overweight, sedentary people”.

But the chubby mice that got the extracts accumulated less fat in their livers, and they had lower blood sugar, than those that consumed the high-fat diet alone. Ellagic acid proved to be a powerhouse in this experiment, too, lowering the high-fat-fed mice’s blood sugar to nearly the levels of the lean, normally fed mice.

Higher levels of helpful metabolic proteins

When Mr Shay and his colleagues analysed the tissues of the fat mice that ate the supplements, they noted higher activity levels of PPAR-alpha and PPAR-gamma, two proteins that work within cells to metabolise fat and sugar.

Mr Shay hypothesised that the ellagic acid and other chemicals bind to these PPAR-alpha and PPAR-gamma nuclear hormone receptors, causing them to switch on the genes that trigger the metabolism of dietary fat and glucose. Commonly prescribed drugs for lowering blood sugar and triglycerides act in this way, Mr Shay said.

Mr Shay said the goal of this work was not to replace needed medications but to guide people in choosing common, widely available foods that have particular health benefits, including boosting metabolic function.

“We are trying to validate the specific contributions of certain foods for health benefits,” Mr Shay said. “If you’re out food shopping, and if you know a certain kind of fruit is good for a health condition you have, wouldn’t you want to buy that fruit?” he said.

The research was supported by the Institute of Food and Agricultural Science at the University of Florida and Florida Department of Agriculture and Consumer Services. The study appears in the January issue of the Journal of Nutritional Biochemistry.

Mr Shay’s research with mice was supported by the Blue Mountain Horticultural Society, the Erath Family Foundation, and the OSU College of Agricultural Sciences.