The Mediterranean diet is associated with many health benefits, including protection against heart disease, Alzheimer's disease and even depression. Many wine drinkers are also fans because the diet includes moderate wine consumption. Now, a new report published in the European Journal of Nutrition suggests that the diet might also help reduce the risk of bladder cancer.
Bladder cancer is one of the most common forms of cancer, affecting approximately 70,000 adults in the United States each year. Conducted by a multinational team of researchers, the report analyzed data of 646,222 study participants—hailing from the U.S., Denmark, Australia, Spain, France, Greece, Germany, Italy, the Netherlands, Sweden, Norway and the United Kingdom—pulled from 13 cohort studies included in the Bladder Cancer Epidemiology and Nutritional Determinants (BLEND) study, to determine the association between Mediterranean diet and bladder cancer risk.
"Previous studies assessed the risk of developing bladder cancer for several single food items ([such as the] association between intake of vegetables and risk of bladder cancer) and showed promising results. However, we believed that dietary patterns may provide stronger evidence than individual dietary items," Willem Witlox, one of the study's researchers, told Wine Spectator. "The Mediterranean diet had been reported to effectively reduce risk of mortality, cardiovascular disease and several cancers. Altogether, this was our rationale to assess the association between this diet and the risk of developing bladder cancer."
Modeled after the eating patterns of people native to areas that border the Mediterranean Sea (such as Italy, Greece, southern France and Spain), the Mediterranean diet emphasizes many components, including fruits, vegetables, nuts, grains, legumes, seafood and moderate alcohol consumption (mostly wine), while limiting meat and dairy products.
Because the study didn't look at just one dietary component, the researchers used a points system to determine how much or how little individuals adhered to the Mediterranean diet, based on a prescribed, sex-specific median measurement of consumption levels for each of the nine categories it assessed.
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Participants scored either 0 points or 1 point for each component: For vegetables, legumes, fruits and nuts, cereals, and fish (the presumed beneficial components), participants earned 1 point for consuming as much as the median cutoff or more; they earned 0 points for consuming less than the median cutoff. For meat and dairy products (considered detrimental components), 1 point was assigned to those consuming less than the median cutoff, and 0 points were assigned to those consuming as much as the median cutoff or more.
For alcohol, 1 point was given to men consuming between 70 and 350 grams per week and to women consuming between 35 and 175 grams per week. (U.S. health authorities state that a typical glass of wine contains roughly 14 grams of alcohol, so the top figures represent approximately 25 and 12 glasses per week, depending on the wine). Anyone consuming alcohol at levels below or above those limits were given 0 points in that category.
After assigning the scores and adding them up, the researchers categorized participants into three groups: low diet adherence (0-3 points), medium adherence (4-5 points) and high adherence (6 points or more). Upon running a statistical analysis, the researchers found that participants in the "medium" and "high" groups were less likely to develop bladder cancer than those in the "low" group, thus revealing an inverse relationship between adherence to the diet and the risk of getting bladder cancer.
In the study's text, the researchers hypothesize possible explanations for why the Mediterranean diet, as a whole, might have a protective effect against bladder cancer. In addition to the consumption of fruits and vegetables, which has been previously shown to have an inverse association with bladder cancer risk, the researchers also highlight the consumption of both wine and olive oil as key components to the diet's potential benefits, due to their high polyphenol content.
"These dietary factors are well-known for their anti-oxidative and anti-inflammatory properties," the study's text reads. "In addition, polyphenols have been shown to have a beneficial effect on cellular function. Since processes such as deregulated cell proliferation and suppressed cell death often provide a basis for tumor progression, polyphenols … may help to protect the cells of the bladder membrane against further metastasis."
However, because the study looked at the diet as a whole, rather than breaking down its individual components, there's still no telling what, exactly, confers this potential protective benefit.
"We could not isolate any particular subgroup of foods from the [Mediterranean diet] that provided a greater benefit over others," the study's text read. "This may be because it describes the overall effect of the combined factors of the dietary pattern to be most protective."