Abstract
Flavonoids have been suggested to play a chemopreventive role in carcinogenesis. However, the epidemiologic studies assessing dietary intake of flavonoids and esophageal cancer risk have yielded inconsistent results. This study was designed to examine the association between flavonoids, each flavonoid subclass, and the risk of esophageal cancer with a meta-analysis approach. We searched for all relevant studies with a prospective cohort or case-control study design published from January 1990 to April 2016, using PUBMED, EMBASE, and Web of Science. Pooled odds ratios (ORs) were calculated using fixed or random-effect models. In total, seven articles including 2629 cases and 481,193 non-cases were selected for the meta-analysis. Comparing the highest-intake patients with the lowest-intake patients for total flavonoids and for each flavonoid subclass, we found that anthocyanidins (OR = 0.60, 95% CI: 0.49–0.74), flavanones (OR = 0.65, 95% CI: 0.49–0.86), and flavones (OR = 0.78, 95% CI 0.64–0.95) were inversely associated with the risk of esophageal cancer. However, total flavonoids showed marginal association with esophageal cancer risk (OR = 0.78, 95% CI: 0.59–1.04). In conclusion, our study suggested that dietary intake of total flavonoids, anthocyanidins, flavanones, and flavones might reduce the risk of esophageal cancer.
Highlights
Esophageal cancer ranks as the 10th most common malignancy and the eighth most common cause of cancer-related mortality worldwide
A number of risk factors have been found to be strongly associated with esophageal cancer, including age, sex, cigarette smoking, alcohol drinking, body mass index (BMI), helicobacter pylori (H.p.) infection, low intake of fruits and vegetables, and poor nutritional status [3,4,5]
Two articles reported results for a duplicate population [41,42], one study reported urinary tea polyphenol in relation to gastric cancer and esophageal cancer [43], and another two articles reported the association between dietary flavonoid intake and Barrett’s esophagus [44,45]
Summary
Esophageal cancer ranks as the 10th most common malignancy and the eighth most common cause of cancer-related mortality worldwide. An estimated 455,800 newly diagnosed esophageal cancer cases and a related 400,200 deaths occurred worldwide in 2012 [1]. Dietary flavonoids occur ubiquitously in plant foods, such as fruits, vegetables, tea, soybean, grains, and their processed foodstuffs, and can be categorized into six major subclasses based on their structural complexity: flavonols, flavones, flavan-3-ols, flavanones, anthocyanins, and isoflavones [13]. In addition to their antioxidant properties [14], flavonoids have antiviral, antiallergic, antiinflammatory, and antitumor activities [15,16]
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