Is There a Link Between Diet and Esophageal Cancer?

Silvano Gallus; Carlo La Vecchia

Disclosures

Nat Clin Pract Gastroenterol Hepatol. 2006;4(1):2-3. 

Esophageal cancer is the sixth leading cause of cancer-related death worldwide. The overall incidence and associated mortality of esophageal cancer in the US has increased by 15−20% over the past 3 decades.[1,2] By contrast, in the European Union, esophageal cancer mortality reached a plateau and has subsequently been declining in men since the late 1980s.3 The main esophageal cancer subtypes are squamous-cell carcinoma and adenocarcinoma.[2] Over the last 30 years, the incidence of squamous-cell carcinoma has decreased in several areas of the world, but adenocarcinoma has risen by over fourfold in the US as well as in Australia and several areas of Europe; its incidence has particularly increased in men.[1,2,3] In the US, the squamous-cell carcinoma to adenocarcinoma incidence ratio has decreased from 3:1 in 1975 to 2:1 in 1988, and to 1.2:1 in 1994. Currently, there are more new cases of adenocarcinoma than of squamous-cell carcinoma.[2]

The widespread unfavorable trends for the development of esophageal adenocarcinoma have been related to a number of risk factors, which are (at least in part) different from those of esophageal squamous-cell carcinoma.[2] Tobacco use and alcohol consumption are the dominant risk factors for squamous-cell carcinoma,[1] while the dominant risk factors for adenocarcinoma are mainly related to tobacco smoking and gastroesophageal reflux, but unrelated to alcohol drinking.[1,2] BMI seems to be inversely associated with the risk of squamous-cell carcinoma,[2] whereas overweight and obesity have been directly linked to adenocarcinoma.[1,2]

Several studies have examined vegetable and fruit consumption in relation to esophageal cancer. The World Cancer Research Fund[4] reviewed data from one cohort and 22 case−control studies, and reported that "the evidence that diets high in vegetables and fruits decrease the risk of esophageal cancer is convincing"; subsequent studies have confirmed this view for both esophageal squamous-cell carcinoma and adenocarcinoma.[1,2,5,6] In a population-based, case−control study from various areas in the US, the percent population-attributable risk (PAR) (i.e. the amount of cancer in the study population that would be reduced if a given risk factor was removed) was calculated for selected risk factors.[1] As a cancer can be attributed to more than one factor, the PAR for several factors can add up to more than 100%. The study revealed that the PAR of ever smoking was 57% for squamous-cell carcinoma and 40% for adenocarcinoma.[1] The PAR of low fruit and vegetable consumption was 29% for squamous-cell carcinoma and 15% for adenocarcinoma. The PAR of ever having consumed alcohol was 72% for squamous-cell carcinoma, and the PAR of BMI above the lowest quartile and history of gastroesophageal reflux were 41% and 30% for adenocarcinoma, respectively.[1]

Diets rich in fiber, carotenoids, folate and vitamin C have been associated with a decreased risk of esophageal cancer,[4] whereas diets high in saturated fat and cholesterol have been associated with an increased risk. Among added lipids, olive oil intake has been related to an appreciable reduction in esophageal cancer risk, while butter consumption has been associated with an increased risk.[5,7] Diets high in refined cereals have also been associated with an increased risk of esophageal cancer, possibly because they are deficient in a number of protective micronutrients,[4] although the role of a high glycemic index and load, and consequently of insulin-related growth factors is also possible. Conversely, whole-grain foods have been associated with a decreased esophageal cancer risk.[7] Red and processed meat intake have been associated with an increased risk of both esophageal squamous-cell carcinoma and adenocarcinoma.[4,6] Conversely, fish and white meat consumption have been inversely associated with risk of esophageal squamous-cell carcinoma in case−control studies from Italy, Switzerland, and Uruguay.[5,6]

No consistent association has been found with reference to consumption of milk and other dairy products, or tea and coffee.[4] Very hot drinks and foods, however, which include burning hot coffee, tea and soups, but mainly hot maté drinks in South America, have been associated with an increased risk of esophageal squamous-cell carcinoma.[4,5,6]

Among the food items that have been recently investigated, fried foods have been associated with an increased risk of esophageal cancer.[8] Carbonated soft drinks (CSD) have been associated with gastroesophageal reflux, and the trend for an increased incidence of esophageal adenocarcinoma has paralleled average CSD consumption. CSD intake, therefore, might be related to the development of esophageal adenocarcinoma. Epidemiologic data from 2006, however, indicated that CSD consumption did not increase the risk of esophageal cancer, and that a moderate inverse association between CSD intake and risk of both esophageal squamous-cell carcinoma and adenocarcinoma might exist.[9]

The epidemiologic evidence suggests, therefore, that a low-risk diet for both esophageal squamous-cell carcinoma and adenocarcinomas would include increased vegetable and fruit intake, reduced meat intake, but also substitution of refined carbohydrate with whole-grain foods, and substitution of saturated fats with olive oil or other unsaturated fats. Several of these characteristics are included in the 'Mediterranean diet'. The relation between a simple and intuitive score, which summarizes eight of the major characteristics of the Mediterranean diet (i.e. high monounsaturated to saturated fat ratio, moderate alcohol intake, high consumption of cereals, legumes, fruit, vegetables, and low consumption of meat and milk or dairy products) and the risk of squamous-cell esophageal cancer has been evaluated using data from a case−control study conducted in Italy.[7] A significantly reduced risk for esophageal cancer was found to correlate with increased numbers of characteristics of this previously defined nutritional pattern: subjects with ≥ 6 Mediterranean dietary characteristics, compared with those with <3 characteristics, decreased their risk of developing esophageal cancer by fourfold.[7]

Dietary factors have an important role in the risk of esophageal carcinogenesis. The preventable fraction of esophageal cancers that are attributable to diet (excluding alcohol drinking) might comprise 20%−40% of the total.[1] Moreover, the dramatic increase in the incidence of esophageal adenocarcinoma found in the US and in several Western countries[1,2] is caused, at least in part, by upward trends in obesity as well as changes in dietary lifestyle. Lifestyle habits (such as the use of belts or chronic sitting posture), which might increase gastroesophageal reflux[10] have been speculated to underlie the trends for increased esophageal adenocarcinoma incidence in Western countries.


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