It’s the age-old question: Can an individual lower their cancer risk through the foods they eat? Many studies have examined this topic and several organizations, such as the American Cancer Society, promote eating fruits and vegetables, whole grains and limiting processed and red meat to reduce risk.
Specifically, the role of diet in bladder cancer hasn’t been established. Therefore, researchers from around the world decided to examine the effect that the Mediterranean diet – which has already been shown to reduce heart disease and Alzheimer's disease risk, lower levels of “bad” cholesterol and decrease the incidence of cancer – has on this type of disease.
Using a pooled analysis of 13 studies included in the Bladder cancer Epidemiology and Nutritional Determinants (BLEND) study, they found that people who followed the Mediterranean diet had a decreased risk of bladder cancer.
The Mediterranean diet emphasizes eating primarily plant-based foods, such as fruits and vegetables, whole grains, legumes and nuts; replacing butter with healthy fats such as olive oil and canola oil; using herbs and spices instead of salt to flavor foods; limiting red meat to no more than a few times a month; eating fish and poultry at least twice a week; enjoying meals with family and friends; drinking red wine in moderation (optional); and getting plenty of exercise, according to Mayo Clinic
The researchers examined dietary data from more than 600,000 study participants, including 2,425 cases of bladder cancer — 945 had muscle-invasive disease and 1,480 were non-muscle-invasive. The studies comprised centers from Australia, Denmark, France, Germany, Greece, Italy, The Netherlands, Norway, Spain, Sweden, United Kingdom and United States.
In addition to diet information, data on participants also included age, gender, ethnicity, bladder cancer pathology — non-muscle invasive
and muscle-invasive — and smoking status.
“At present, the better-established risk factors associated with developing bladder cancer include smoking, age, male sex, occupation and to a lesser extent obesity and physical inactivity,” the researchers wrote. “Since most of the metabolites of ingested food come into direct contact with the bladder mucosa, diet might also play a role in the development of bladder cancer.”
A nine-point scale was used to measure patients’ adherence to the Mediterranean diet — zero (minimal adherence) to nine (maximal adherence). Scores between zero and three were classified as “low adherence”, scores of four and five were classified as “medium adherence” and scores of six or higher were classified as “high adherence.” Cereals, fruits and nuts, vegetables, legumes, fish, meat, dairy products, fats and alcohol/ethanol were the food items included in the studies.
Results showed cases of cancer were comparable between men and women. However, bladder cancer cases were more likely to be in men (74 percent) and in people who were current or former smokers (79 percent). Of all cases, 42 percent originated from countries in Western Europe, 22 percent from Scandinavian countries, 14 percent from Australia, 12 percent from Mediterranean regions and 10 percent from the U.S.
Researchers found that high and medium adherence to the Mediterranean diet was associated with a decrease in bladder cancer risk compared with people who had low adherence. “We could not isolate any particular subgroup of foods (i.e. fats, alcohol) from the Mediterranean diet score that provided a greater benefit over others,” the researchers wrote. “This may be because it describes the overall effect of the combined factors of the dietary pattern to be most protective.”