Sugar is not literally a poison. Anything ingested to excess is bad for you, even water.
Water can be a poison if it wants to be too, however, sugar is orders of magnitude more poisonous than water.
Sugar is not a substance like water in which "hey if you drink enough water, more than most people can even if they were trying to, you can die." It's more like, the body is constantly struggling to keep blood sugar levels at a level that won't kill it, and there are great many metabolic disorders in which it fails to do this, and dies.
Also, there are diets which can simply overwhelm the body's ability to regulate blood sugar levels, some which lead to the body dying, see: type 2 diabetes.
If you count up the premature deaths(looking at human-life-years lost is probably most informative) associated with type 2 diabetes and heart disease related to sugar-induced metabolic disorders, one might be surprised that the poison we call sugar may have one of the highest kill counts of all known poisons. And to top it off, it happens to be a poison that we are, by an unfortunate evolutionary happenstance, generally addicted to. Oh yeah, it's also supported and pushed by multiple billion dollar industries with significant lobbying power.
Sugar has been implicated as a cause of type II diabetes by many people [1]. Whether they are right or not is up for debate.
Even my great grandmother, born in 1915, used to warn that too much sugar would cause diabetes. According to her this was conventional wisdom when she was young.
[1] http://www.npr.org/blogs/thesalt/2013/02/28/173170149/sugars...
The GP said he or she had never seen sugar implicated as a cause, like that was something he'd never heard of--when in fact it was and is a common belief. Whether that belief is true isn't something I'm arguing.
Are you aware that just like the body regulates sugar, it also regulates water? The body tries to maintain the right level of water, and it's easy to show: drink a lot. In short order, you'll be pissing a lot, to get rid of the excess water. People that have their ability to regulate water inhibited also show a lot of illnesses as a result - in terms of demographics, this can be seen in cultures where women aren't allowed to go to the toilet during the day. Sugar doesn't get magical, unique treatment in biology - water even has its own organ system that is primarily devoted to managing water content. And if you want to get socio-political about it (unsure why this means it's a poison...), we're also addicted to water and nations go to war over fresh water supplies... something that is pretty rare for corn or cane fields.
The point is that labeling sugar as a poison is being simplistic, and the picture is far more complex than that when discussing diet.
Besides, sugar is the primary fuel for your brain; without sugar, we don't exist. It's a funny sort of poison that is necessary for our existence.
> Besides, sugar is the primary fuel for your brain; without sugar, we don't exist. It's a funny sort of poison that is necessary for our existence.
Arsenic, along with several other low-dose poisons, is also necessary for our existence[0]. Do you disagree it's a poison?