title: Cancers of the Esophagus and Stomach: Potential Mechanisms Behind the Beneficial Influence of Physical Activity.
abstract: OBJECTIVE
  To compare findings from several recent meta-analyses showing a reduced risk of gastric and esophageal cancers in physically active individuals, to assess the magnitude of this benefit, and to seek information on potential underlying mechanisms.
  
  
  METHODS
  A comprehensive search of Ovid/Medline from 1996 to February 2016, using the terms physical activity or exercise or training and esophageal or gastric cancer, and supplementing the articles identified by material from references lists and personal files.
  
  
  RESULTS
  Moderate-to-vigorous physical activity is associated with a 20% to 30% reduction in the risk of gastroesophageal adenocarcinomas, with a significant dose/response relationship. Benefit is greater in women than in men, and greater for noncardia than for cardia or esophageal tumors. Mechanisms could include a reduction of visceral fat (with a lesser production of cancer promoting hormones and reduced gastroesophageal reflux) and/or a lesser likelihood of smoking and excessive alcohol consumption. Physical activity does not protect against Helicobacter pylori infections or gastric ulceration, but mechanisms related to the impact of exercise on immune function, antioxidant mechanisms, and gastroesophageal reflux remain to be explored.
  
  
  CONCLUSIONS
  Regular, moderate-to-vigorous physical activity is associated with a clinically significant reduction in the risk of gastroesophageal adenocarcinomas, but mechanisms are as yet unclear, and a causal relationship remains to be proven.
authors.affiliation: Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, Canada.
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Shephard
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology*; D004938:Esophageal Neoplasms / Q000453:epidemiology*; D015444:Exercise; D005260:Female; D005764:Gastroesophageal Reflux / Q000517:prevention & control; D016481:Helicobacter Infections / Q000453:epidemiology; D006801:Humans; D008297:Male; D015201:Meta-Analysis as Topic; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology*