The old proverb, “An apple a day keeps the doctor away,” rings true when you consider the healthy attributes of the apple. Apples are rich in antioxidants—nutrients that protect against the harmful effects of oxidative stress—especially when you include the peel. Also, the high fiber content of apples gives this fruit its digestive and heart health benefits.

A recent study published in the Journal of Functional Foods found that consumption of an apple a day for four weeks was associated with a decrease of oxidized LDL cholesterol in healthy, middle-aged adults. You probably already know about LDL cholesterol, the “bad” type of cholesterol associated with the development of atherosclerosis, or buildup of plaque in the arteries.

Interestingly, the state in which LDL is found is what determines its ability to trigger plaque buildup. When LDL becomes oxidized due to the interaction of free radicals with LDL cholesterol it is more likely to promote inflammation and damage the artery lining, leading to heart disease. Bottom line, you don’t want your LDL oxidized.

The study also examined the effect of an apple polyphenol extract on oxidized LDL levels. “We found the polyphenol extract did register a measurable effect, but not as strong as the straight apple,” stated Robert DiSilvestro, professor of human nutrition at Ohio State University and lead researchers.

I would like to caution against consumption of apples in people concerned about blood sugar or insulin resistance. In general, the sugar content of apples tends to be high, which can have its own undesirable effects. But in the context of a low-sugar, low-processed and refined carbohydrate diet, an apple a day is OK for many people. If you already have risk factors for heart disease, stick to berries and perhaps an apple polyphenol extract for the best overall heart health advantage.

My new PBS show and book, both by the name of Heart of Perfect Health, delve deeply into the topic of heart health and its underlying causes. And of course, I talk about how your digestive system ties into the picture. Watch for my PBS show in November and December for some eye-opening information about the true causes of heart disease and what you can do to stop it.