Regarding Food, there is something called Glycemic Index(GI). It measures how quickly blood sugar rises after the consumption of food ( ideally after 2 hours of consumption). Accordingly, the food is categorized into

• Low GI food (<55 )
• Medium GI food (56 to 69 )
• High GI food (> 70)
  A GI of 100 is considered standard.
  A food with high GI ( white bread ,corn flakes etc) raises the blood sugar quickly. So, they are not advised to the diabetes patient with high blood sugar. But they are considered useful in case of the hypoglycemic patient.

Low GI food are: peaches, strawberries, mangos,mushrooms, beans ,wheat, millet, oat, rye etc. They are considered comparatevely good for diabetes patient.
Further reading:-

• https://en.wikipedia.org/wiki/Glycemic_index
• https://www.betterhealth.vic.gov.au/health/healthyliving/carbohydrates-and-the-glycaemic-index
• http://www.glycemicindex.com

nice article @justtryme90