People used to eat waaaay more sugar. 3000-4500 cal / day was normal in France a hundred years ago. A lot of that was refined sugar.
What their food didn't have was:
- the extra, hidden starches that high fructose corn syrup, for example, has and on which gut bacteria go bonkers, giving you a truckload of endotoxins to deal with
- the phyto-estrogens in everything
- the unsatured fats at insane ratios
- BPA's and a bunch of other nearly untraceable toxic byproducts of current manufacturing tech
- being irradiated with a spectrum of new/strong emf's that interact with it at a cellular level
Some of the most healthy tribes have been living high-starch, high-collagen lives.
Dextrose is a sugar that doesn't even make it to your gut bacteria because it is directly absorbed. It has been used a healing agent for that reason. Very clean way to gain energy.
Clean sugar isn't a problem ,unless you lack the cofactors needed for its combustion. But that list of cofactors is waaay shorter than anything else you'd choose to consume for energy anyway.