Apples have long been associated with good health. The old saying, "an apple a day keeps the doctor away," came into being for a reason.
Now, a study funded in part by an apple industry group suggests the fruit can promote a particular kind of health - healthier arteries.
When people age they are at a higher risk of hardened arteries. The condition can be caused, in part, by a substance in the blood that interacts with LDL - the "bad" cholesterol - to harden the arteries.
In a study of healthy, middle-aged adults, consumption of just one apple a day for four weeks lowered levels of that substance by 40 percent. Taking capsules containing polyphenols, a type of antioxidant found in apples, had a similar, but not as large, effect.
Apples lowered cholesterol
The study found that apples lowered LDL levels. That's important because when LDL cholesterol interacts with free radicals to become oxidized, the cholesterol is more likely to promote inflammation and can cause tissue damage.
"When LDL becomes oxidized, it takes on a form that begins atherosclerosis, or hardening of the arteries," said lead researcher Robert DiSilvestro, professor of human nutrition at Ohio State University. "We got a tremendous effect against LDL being oxidized with just one apple a day for four weeks."
The difference was similar to that found between people with normal coronary arteries versus those with coronary artery disease, he said.
There are other antioxidants that can help but DiSilvestro described daily apple consumption as significantly more effective at lowering oxidized LDL than other antioxidants he has studied, including the spice-based compound curcumin, green tea and tomato extract.
Not all antioxidants equal
"Not all antioxidants are created equal when it comes to this particular effect," he said.
DiSilvestro said he stumbled across this finding while investigating another health food. A Turkish study led him to look at apple consumption as a way of increasing the amount of a specific antioxidant enzyme in the body. In the end, his team didn't find the same effect on the enzyme, but was surprised at the considerable influence the apples had on oxidized LDL.
For the study, half the group ate apples and the other half took a supplement containing polyphenols, a substance found in apples.
"We found the polyphenol extract did register a measurable effect, but not as strong as the straight apple," DiSilvestro said. "That could either be because there are other things in the apple that could contribute to the effect, or, in some cases, these bioactive compounds seem to get absorbed better when they're consumed in foods."
Still, DiSilvestro said polyphenol extracts could be useful in some situations, "perhaps in higher doses than we used in the study, or for people who just never eat apples."
The study also found eating apples had some effects on antioxidants in saliva, which DiSilvestro says could have important implications for dental health.