Is dietary carbohydrate essential for human nutrition?

Although there is certainly no evidence from which to conclude that extreme restriction of dietary carbohydrate is harmless, I was surprised to find that there is similarly little evidence to conclude that extreme restriction of carbohydrate is harmful. In fact, the consequential breakdown of fat as a result of carbohydrate restriction may be beneficial in the treatment of obesity. Perhaps it is time to carefully examine the issue of whether carbohydrate is an essential component of human nutrition.

http://www.ajcn.org/content/75/5/951.2.long