““Carbohydrates are not required in a healthy human diet. Another way to say this (as proponents of carbohydrate restriction have) is that there is no such thing as an essential carbohydrate. Nutritionists will say that 120 to 130 grams of carbohydrates are required in a healthy diet, but this is because they confuse what the brain and central nervous system will burn for fuel when diets are carbohydrate rich—120 to 130 grams daily—with what we actually have to eat. If there are no carbohydrates in the diet, the brain and central nervous system will run on molecules called “ketones.” These are synthesized in the liver from the fat we eat and from fatty acids, mobilized from the fat tissue because we’re not eating carbohydrates and insulin levels are low, and even from some amino acids. With no carbohydrates in the diet, ketones will provide roughly three-quarters of the energy that our brains use. And this is why severely carbohydrate-restricted diets are known as “ketogenic” diets. The rest of the energy required will come from glycerol, which is also being released from the fat tissue when the triglycerides are broken down into their component parts, and from glucose synthesized in the liver from the amino acids in protein. Because a diet that doesn’t include fattening carbohydrates will still include plenty of fat and protein, there will be no shortage of fuel for the brain.””
