We hear regularly from health organization and experts that we should eat less sugar. As we know that fruit is also valuable source of sugar. So, consumption of more fruit is harmful for human health ?
I think not. At least, not in practice. The difference is how quickly the body has to process these types of sugar, and how the excess is stored.
It is difficult to take in sucrose, fructose, and glucose from fruit fast enough to do any harm. Fruit is very filling, so you tend to not overeat, and besides, you would probably have gastrointestinal problems first, if you ate so much fruit that you were overdosing on these sugars.
Table sugar is sucrose, and the sweetest of fruits also contain sucrose mostly. Less sweet fruits may contain no sucrose. Turns out that glucose is absorbed through the intestine, and either used right away, or stored as glycogen. Glucose is the simplest sugar. And glycogen, a carbohydrate, is used preferentially by the body, when energy is required, because it can be processed more quickly than fat.
Fructose is also absorbed through the intestine, but it has to be converted into glucose by the liver. Any excess fructose is stored as fat. So if you overdo it, fructose can be harmful.
Sucrose has to be broken down into fructose and glucose first, through digestion, and then the fructose broken down by the liver. Again, what fructose is not needed, is stored as fat, and what glucose is not needed is stored as glycogen. Sucrose is the refined, added sugar we know, and the easiest to be over-ingested too quickly. Although processed fructose also has this risk.