[Study of the health food information for cancer patients on Japanese websites].

The aim of this paper is to evaluate the reliability of websites providing health food information for cancer patients and, to assess the status to get this information online. We used four common Japanese search engines (Yahoo!, Google, goo, and MSN) to look up websites on Dec. 2, 2008. The search keywords were "health food" and "cancer". The websites for the first 100 hits generated by each search engine were screened and extracted by three conditions. We extracted 64 unique websites by the result of retrieval, of which 54 websites had information about health food factors. The two scales were used to evaluate the quality of the content on 54 websites. On the scale of reliability of information on the Web, the average score was 2.69+/-1.70 (maximum 6) and the median was 2.5. The other scale was matter need to check whether listed to use safely this information. On this scale, the average score was 0.72+/-1.22 (maximum 5) and the median was 0. Three engines showed poor correlation between the ranking and the latter score. But several websites on the top indicated 0 score. Fifty-four websites were extracted with one to four engines and the average number of search engines was 1.9. The two scales were positively correlated with the number of search engines, but these correlations were very poor. Ranking high and extraction by multiple search engines were of minor benefit to pick out more reliable information.