Not only are apples tasty, versatile, and economical at this time of the year, each bite offers a host of health benefits to runners and spectators alike. Yes, there’s science behind the adage that “an apple a day keeps the doctor away.” The widely consumed apple, rich in phytochemicals, such as flavonoids and antioxidants, has been linked to a reduction of the risk of some cancers, cardiovascular disease, asthma, and diabetes. But for those athletes who feel they are immune to these chronic diseases, the apple offers far more than stellar health benefits. Apples are rich in quercetin, a powerhouse of a natural flavonoid that exists in the skin of many fruits and vegetables, as well as in leafy vegetables, berries, black tea, and various fruit juices. Since it’s fairly widespread in the diet (at least for those folks who eat their veggies and the peels of the apples), you’re likely to have at least some quercetin in your diet. For those who feel like they just can’t get enough of the good stuff, there’s also quercetin supplements and food and drinks fortified with this flavonoid.
Like apples as a whole, quercetin offers a host of antioxidant, anticarcinogenic, anti-inflammatory, and heart-protecting effects, while also decreasing the risk of cancers and various chronic diseases. Another added bonus of quercetin is that it just might be thing you need to improve your running performance. Several studies have shown quercetin to affect the oxidation process in the muscles. Some animal studies (read: not necessarily human studies) have described the observed increased endurance performance and maximal oxygen consumption (VO2 max) that led to fitness gains following quercetin consumption.1 Other studies and some anecdotal reports by athletes have found no effects whatsoever. Yet others report that quercetin might reduce muscular damage and soreness, improve neuromuscular function, and even improve muscular strength as a result of long-term quercetin consumption. Still others looked not at quercetin’s effects on muscle soreness but on body composition changes (wouldn’t it be great it this little flavonoid could change fat mass into muscle mass?!), but alas, past studies did not find quercetin to have significant effects on these indices.
Another recent study looked at body composition changes, exercise performance, and select blood biomarkers in 60 male, athletic, students. The students were randomized to receive either a 500 mg supplemental quercetin capsule plus a 250 mg vitamin C pill, a 500 mg supplemental quercetin capsule plus a 250 mg placebo vitamin C pill, a 500 mg placebo quercetin capsule plus a 250 mg vitamin C pill, and a 500 mg placebo quercetin capsule plus a 250 mg placebo vitamin C pill, respectively, daily for eight weeks. (For reference, an average medium-size apple contains ~ 26 of quercetin glycosides.)
At the end of the eight-week trial, lean body mass, total body water, basal metabolic rate, and total energy expenditure increased significantly in the first group. VO2 max improved in the first and third groups but wasn’t found to be significant. This study is in line with a study by Utter and colleagues that compared the effects of 250 mg of daily quercetin for three weeks with placebo among marathon runners and cyclists. They did not report any significant difference in the ratings of perceived exertion between the two groups but also didn’t look at the possible synergistic effect of vitamin C. So at the end of the day, it may not be the quecertin alone that leads to performance benefits; the Vitamin C is a key player. Luckily, apples contain plenty of each.