The first separately printed treatise on diet, De particularibus diaetis, was written by the Egyptian-Jewish physician and philosopher Isaac Judaeus who lived from about 832 to 932 CE. He was also known as Isaac Israeli ben Solomon and Abu Ya'qub Ishaq Sulayman al-Israili. The Latin edition was a translation made from the Arabic, circa 1070, by Constantine the African (Constantinus Africanus,) and first printed in Padua by Matthaeus Cerdonis.
De particularibus diaetis was a portion of " 'Kitab al-Adwiyah al-Mufradah wa'l-Aghdhiyah,' a work in four sections on remedies and aliments. The first section, consisting of twenty chapters, was translated into Latin by Constantine [the African] under the title 'Diætæ Universales,' and into Hebrew by an anonymous translator under the title 'Ṭib'e ha-Mezonot.' The other three parts of the work are entitled in the Latin translation 'Diætæ Particulares'; and it seems that a Hebrew translation, entitled 'Sefer ha-Mis'adim' or 'Sefer ha-Ma'akalim,' was made from the Latin" (Wikipedia article on Isaac Israeli ben Solomon, accessed 06-08-2009).
A more complete printed edition of the text appeared in Basel in 1570. Digital facsimile of the 1570 edition from Google Books at this link.
Campbell, Arabic Medicine and its Influence on the Middle Ages I (1926) 73.