after alcohol ingestion. However, if aldehyde dehydrogenase is blocked by disulfiram (a medication used to help alcoholics maintain abstinence) then flushing is observed after ingestion of small quantities of alcohol. The acetaldehyde accumulation can lead to increased risk of upper gastrointestinal (GI) cancer, and cancer risk is greatly augmented by pharmacologic blockade of aldehyde dehydrogenase or natural genetic variation.58 As shown in Fig. 6, there are two common enzyme variants of ADH1B and ALDH2 that lead to alcohol-induced flushing, that are protective against alcoholism, and that play a role in the risk of upper GI cancer associated with alcohol consumption (Fig. 7).
