US researchers believe ellagic acid, a plant chemical found in fruit and vegetables, also slows the growth of fat cells – a "previously unappreciated function" of the compound.
They add the finding is significant because the chemical could help find a way to reduce harmful fat in the livers of overweight people (and therefore improve liver function), using a diet with common foods such as grapes.
Muscadine grapes are a dark-red variety native to the US’ south-east, commonly used to make wine and port.
These grapes have been touted as a health food for several years due to to significant amounts of resveratrol, another plant chemical which has previously been earmarked as an agent for lowering cholesterol and the risk of coronary heart disease. Both resveratrol and ellagic acid have also been linked to a role in preventing cancer.
A team from the University of Florida, University of Nebraska, and Oregon State University grew human liver and fat cells in the lab, and exposed them to four different natural chemicals from muscadine grapes. One of these was ellagic acid.
Researchers believe ellagic acid was responsible for dramatically slowing the growth of fat cells and delaying the growth of new ones. It also boosted the metabolism of fatty acids in liver cells.
Although they stress the compounds don’t improve body weight in themselves, they say they may boost fat burning, particularly in the liver.
Researchers also draw on results from a previous 10 week study, in which mice were fed a high fat diet. Some were also given grape extracts, scaled down to a mouse-sized portion, but otherwise equivalent to one and a half cups of grapes a day for a person. The portion size was chosen to make the study more applicable to a human diet.
Mice which consumed the grape extracts accumulated less fat in their livers than those who didn’t. They also had lower blood sugar.
‘Previously unappreciated’ attributes
“Numerous reports suggest that ellagic acid-containing fruits, vegetables and nuts are effective dietary sources to attenuate obesity,” said Soonkyu Chung, one of the study authors.
“To better understand the relationship between ellagic acid intake and adiposity [obesity], we evaluated results from the peer-reviewed literature. We observed that a daily intake of ellagic acid in the range of 5–88 mg/kg BW correlated with a >25% decrease of fat mass and improvement of glucose metabolism.
“The conclusion deduced from this review is consistent with our present data: that ellagic acid enriched muscadine grape phytochemical powder is associated with a reduction of fat mass, adipocyte hypertrophy [growth of fat cells] and hepatic lipid accumulation [gathering of fat in the liver]."
Ellagic acid: key ingredient
“Interestingly, the muscadine wine extract with almost identical phytochemical composition - except for a reduced ellagic acid content due to filtration - displayed reduced lipid lowering effects," Chung wrote. "This provides us with additional rationale to conclude ellagic acid is a key ingredient in muscadine grapes to reduce fat mass.
“It has been well documented that ellagic acid possesses anti-proliferative and anti-inflammatory characteristics in various transformed cell lines. Moreover, ellagic acid has shown to be effective in reducing atherosclerotic lesions [build up of plaque in arteries] and increasing cholesterol efflux in macrophages [white blood cells]," he added.
“In this study, we added the previously unappreciated function of ellagic acid as a lipid-lowering dietary compound.”
Chung believes the results are significant because they could help find a way for reducing fat accumulation by including common foods such as grapes in the diet.
“Ellagic acid may constitute a consumer-friendly dietary strategy that may be effective in reducing lipid accumulation, both in adipose tissue [body fat] and the liver.”
Researchers are now investigating whether the products of ellagic acid – urolithins - could be stronger than the chemical itself. They also suggest research is needed to find out whether ellagic acid works in isolation, or whether it works best in combination with other grape chemicals.
Title: ‘Ellagic acid modulates lipid accumulation in primary human adipocytes and human hepatoma Huh7 cells via discrete mechanisms’
Authors: Oklaa, M., Kanga, I. Kima, D.M. Gourinenia, V., Shayc, N., Gua, L., Chung, S.
Source: Journal of Nutritional Biochemistry 26 (2015) 82 – 90. DOI: http://dx.doi.org/10.1016/j.jnutbio.2014.09.010