Diabetes: Question on food choices

I am supposed-to- be vegan most Wednesdays and Fridays, during Christmas Lent, Great Lent, Apostles' Fast, and Dormition Fast - all added together, about half the year. Although I have my priest's blessing to use fish and eggs during the longer fasts, I try to do it completely vegan the shorter fasts and individual days. My son-in-law, who is also diabetic, is ovo/lacto/once- in-a-while- fish/vegetarian.