Start here, and click through the links ('Symptoms', 'Causes', etc):
http://www.nhs.uk/con...ges/Introduction.aspx
Then click through the pages here:
http://www.corecharit...rticular-disease.html
('What should I eat?' is on Page 3)
Both of those links come from reputable bodies, in which I've no hesitation in pointing you towards. The following link is from an American site which appears to be OK to me but, as with any information on the web (where the source isn't an 'official' one), it should be treated with appropriate caution:
http://www.diet.com/g...rticular-disease-diet
This UK site, while 'unofficial', is generally well-respected and probably trustworthy:
http://www.patient.co...ealth/Diverticula.htm
Chris