The study – published in the Journal of Functional Foods – revealed that consumption of one apple per day for four weeks lowered levels of artery hardening low-density lipoprotein (LDL) cholesterol in blood by 40%.
Led by Robert DiSilvestro from Ohio State University, USA, the researchers revealed that whilst consumption of supplement capsules containing polyphenols had a similar but not as great effect.
"We got a tremendous effect against LDL being oxidized with just one apple a day for four weeks,” said DiSilvestro.
“Since both the apples and polyphenols extract gave an effect, the apple effect seemed to be due, at least in part, to the polyphenols present,” added the researchers. “However, the apple effect was greater than the capsule effect.”
DiSilvestro said that daily consumption of an apple seems to be significantly more effective at lowering oxidized LDL than other antioxidants he has studied – including curcumin, green tea and tomato extract.
"Not all antioxidants are created equal when it comes to this particular effect," he said.
The study was funded by industry group the US Apple Association and Futureceuticals Inc – who also supplied the polyphenol apple extract.
As part of the study 16 healthy adults ate a large Red or Golden Delicious apple daily for four weeks; while 17 took capsules containing 194 milligrams of mixed apple polyphenols and 18 took a placebo containing no polyphenols.
The researchers found significantly lower levels of oxidised LDL in both those consuming apples and those taking the polyphenol supplements, while no effect was observed in those taking placebo.
"We think the polyphenols account for a lot of the effect from apples, but we did try to isolate just the polyphenols, using about what you'd get from an apple a day," said DiSilvestro.
"We found the polyphenol extract did register a measurable effect, but not as strong as the straight apple,” he added – with the researchers noting that ‘one or more’ of three possible explanations could explain why the supplements did not perform as well:
- The apple effect derived from factors besides polyphenols;
- Whole apples give better absorption of the polyphenols than extracts;
- The disparity resulted from the differences in polyphenol composition differences between the extract, which came from a number of apple varieties, and the whole apples, which were just two varieties.
However the lead researcher said polyphenol extracts may still be useful in some situations, "perhaps in higher doses than we used in the study, or for people who just never eat apples."
DiSilvestro said he initially became interested in studying the health effects of eating an apple a day after reading a previous study that suggested the dietary regimen may increase the amount of a specific antioxidant enzyme in the body.
Despite his research not finding the same as this previous finding, DiSilvestro said he was ‘surprised’ by the considerable influence the apples had on oxidized LDL.
The study also found eating apples had some effects on antioxidants in saliva, which has implications for dental health, DiSilvestro said. He hopes to follow up on that finding in a future study.
Source: Journal of Functional Foods
Published online ahead of print, doi : 10.1016/j.jff.2012.08.010
“Intakes of apples or apple polyphenols decease plasma values for oxidized low-density lipoprotein/beta2-glycoprotein I complex”
Authors: Shi Zhao, Joshua Bomser, Elizabeth L. Joseph, Robert A. DiSilvestro