Sugar converts to glucose easily and makes your digestive system lazy. Over a period of time, more than half of what you eat is thrown away, without being broken down.
I am not asking you to give up sweet taste though. Replace refined sugar with alternatives like honey or jaggery. Dates and raisins are good sources of sweetness. Also sugars that are available in fruits are healthy.
An estimate says that our kidney takes 3 days to flush out a spoon of refined sugar from the body and cleanse it.