The present study aimed to evaluate the quality of Internet information on the Mediterranean diet and to determine the relationship between the quality of information and the website source.

Website sources were categorized as institutional, pharmaceutical, non-pharmaceutical commercial, charitable, support and alternative medicine. Content quality was evaluated using the DISCERN rating instrument, the Health On the Net Foundation's (HON) code principles, and Journal of the American Medical Association (JAMA) benchmarks. Readability was graded by the Flesch Reading Ease score and Flesch–Kincaid Grade Level score.

The phrase ‘Mediterranean diet’ was entered as a search term into the six most commonly used English-language search engines.

The first thirty websites forthcoming by each engine were examined.

Of the 180 websites identified, thirty-two met our inclusion criteria. Distribution of the website sources was: institutional, n 8 (25 %); non-pharmaceutical commercial, n 12 (38 %); and support, n 12 (38 %). As evaluated by the DISCERN, thirty-one of the thirty-two websites were rated as fair to very poor. Non-pharmaceutical commercial sites scored significantly lower than institutional and support sites (P = 0·002). The mean Flesch Reading Ease score and mean Flesch–Kincaid Grade Level were 55·9 (fairly difficult) and 7·2, respectively. The Flesch–Kincaid Grade Level score determines the difficulty of material by measuring the length of words and sentences and converting the results into a grade level ranging from 0 to 12 (US grade level).

Due to the poor quality of website information on the Mediterranean diet, patients or consumers who are interested in the Mediterranean diet should get advice from physicians or dietitians.