It may be less catchy than the playground rhyme, but an apple a day may prevent the hardening of arteries and lower bad cholesterol. The study was conducted by Robert A. DeSilvestro, Shi Zhao, and their colleagues at the Ohio State University. It found that eating an apple every day for just four weeks lowered blood levels of a substance that has been found to harden arteries by 40 percent.

The study examined 51 people who were between the ages of 40 and 60. The participants were all non-smokers, ate apples fewer than twice a month, and did not take supplements containing polyphenols or other plant-based pills. Of the group, 16 were given either a Red or Golden Delicious apple to eat, 17 were given pills with 194 milligrams of polyphenol (about the same amount that a person would get from eating an apple), and 18 took a placebo that did not contain polyphenol. The reason that polyphenol was chosen was that doctors think that the antioxidant effect of apples can be traced to that substance.

Researchers found that eating apples lowered the amount of LDL - low-density lipoprotein, or the "bad cholesterol." When LDL cholesterol becomes oxidized, it is more likely to cause inflammation and tissue damage.

The effect from apples was so strong that participants' arteries after apples versus the placebo resembled the difference between patients with normal coronary arteries and patients with coronary artery disease. While people received some benefit from the polyphenol pills, it was not as strong as the benefit received from eating apples.

"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," DeSilvestro said. He added that the pills could indeed be helpful though, either in high doses or for people who never eat apples.

DeSilvestro became interested in the link between apples and health when he read a Turkish article saying that apples increased a certain amount of an antioxidant enzyme in the study. The team could not recreate those findings, but were surprised at the effect that the fruit had on cholesterol. The study also found that eating apples affected antioxidants in saliva, which could have possible implications for dental health. DeSilvestro hopes to follow up that finding in a future study.

The apple study was published in the Journal of Functional Foods.