What Does It Mean To Have Nitrates And Protein In Urine?

I have a friend who is a diebetic and his Dr says he has too much protein and nitrate in his urine, his mother wants to know what foods have these compounds in. This friend has intellectral disability and doesn't understand and his mum wants to know what foods have them and what does it mean. There is too much on the computer and it is confusing please
Ta Heaps
Gwen