Writing in The Journal of Urology, the team behind the Spanish population study reported that men who followed a Mediterranean diet - rich in fish, boiled potatoes, whole fruits, vegetables, legumes, and olive oil, and low consumption of juices - had a lower risk of aggressive prostate cancer (PC) than those who followed other dietary patterns like Prudent or Western diets.
The research was part of the Multicase-Control Study on Common Tumours in Spain (MCC-Spain) population study conducted by numerous universities, hospitals and health institutes in Spain.
Individuals in the two highest intake groups in terms of adherence to the Mediterranean dietary pattern showed a reduced risk of aggressive prostate cancer of 32-34%, compared with those in the lowest intake group.
The likelihood of advanced stage cancer in the top intake group group was 51% lower than in the bottom group, said the Spanish authors - led by Dr Beatriz Perez-Gomez, from the Carlos III Institute of Health, Madrid.
"Our results show that a diet oriented towards the prevention of aggressive tumours in the prostate should probably include important elements of the Mediterranean diet such as fish, legumes, and olive oil, and suggest that a high intake of fruits, vegetables, and whole grains might not be enough," explained Perez-Gomes.
The researchers collected dietary information on 754 confirmed cases of prostate cancer and 1,277 controls aged 38 to 85 years old.
The scientists analysed adherence to the three dietary patterns of Mediterranean (described above), Western and Prudent. The Western pattern is characterised by dairy products, refined grains, processed meat, sodas, sweets, fast food, and sauces. The Prudent pattern consists of low-fat dairy products, whole grains, fruits, vegetables, and juices.
The degree of adherence to each pattern was assessed and divided into four quartiles from lower to higher adherence within each pattern. Adherence for each pattern was then correlated against PC risk according to tumour aggressiveness (Gleason score 6 vs greater than 6) and stage of disease progression.
Although there appeared to be a trend linking higher adherence to the Western diet with aggressive PC and advanced disease progression, the relationship was not statistically significant.
A perhaps surprising result was that men in the third quartile of adherence to the Prudent dietary pattern showed a 60% higher aggressive PC risk than those in quartile 1. The researchers hypothesised that this might be due to the dairy content of the Prudent diet.
Public health implications
Epidemiological data shows that PC is the most common type of cancer in men, and has the highest mortality rate after lung cancer. Previous studies linking PC to specific dietary exposures have been limited in number and shown inconsistent results.
However, these results indicate that the degree of adherence to a particular diet can significantly affect the risk for PC, suggested co-author Dr. Adela Castelló, also from the Carlos III Institute of Health.
"There is a striking contrast between the relevance of prostate cancer in terms of public health and the evidence regarding its primary prevention,” she explained.
“If other researchers confirm these results, the promotion of the Mediterranean dietary pattern might be an efficient way of reducing the risk of developing advanced PC, in addition to lowering the risk of other prevalent health problems in men such as cardiovascular disease. Dietary recommendations should take into account whole patterns instead of focusing on individual foods," Castelló concludes.
Source: The Journal of Urology
Volume 199, Issue 2, Pages 430–437, doi: 10.1016/j.juro.2017.08.087
Mediterranean Dietary Pattern is Associated with Low Risk of Aggressive Prostate Cancer: MCC-Spain Study
Authors: Adela Castelló, Beatriz Pérez-Gómez et al