Metabolic Pathways of Proteins, Carbohydrates and Fats in Humans
The next time someone tells you that carbohydrates are essential for life, or that you’ll die if you don’t eat carbohydrates, point them to the metabolic pathways diagram and ask them to identify which metabolic needs go unmet without carbohydrate ingestion. Hard to do, right? That’s because there are none. Of course, understanding that “you don’t need to eat carbohydrates to support life” is not at all the same thing as thinking, “carbohydrates are not required to support life.” They are. Alice and Fred Ottoboni put it well, “Carbohydrate metabolism is, for all practical purposes, the metabolism of glucose (84)” and it is well understood that certain types of cells required to support life need glucose to survive.
The question is, of course, how much glucose is necessary to sustain life? Some estimates put it as low as 20g a day. Phinney and Volek indicate that the brain needs “less than 50 grams [of glucose] a day” (The Art and Science of Low Carbohydrate Living (44)). They also assert that your liver can produce up to 50 grams a day of glucose via gluconeogenesis.
So there you have it: you don’t need to eat carbohydrates in order to meet the minimal glucose demands of a limited number of cells that need glucose to survive. Anyone who tells you that you otherwise is propagating fear, uncertainty and doubt.