You’ve likely heard that carbohydrates are necessary for the body to use as energy. You might have even heard that your brain needs 130 grams of carbohydrates a day to function. When you eat carbs, your body breaks them down into glucose and your cells use glucose for energy. But what if you’re following a low carb or keto diet and are eating less than 130 grams of carbs a day?
Note that glucose is the easiest fuel for the body to use. It is the quickest source of energy. The body will always revert to burning glucose for fuel when it’s available. When you’re regularly consuming carbohydrates, the body relies on carbs and glucose for energy.
The body also stores glucose in the form of glycogen. Your liver stores 100-120 grams of glycogen and can release glucose for the brain to use as energy and to keep blood sugars stable. Your muscles store 400-500 grams of glycogen, but the body cannot break down muscle glycogen for glucose for the brain. Muscle glycogen is for muscles.
When you are following a low carb or ketogenic diet, the body adapts to burning fat for fuel. The fat the body burns for fuel is called ketones and a person is in ketosis when they are able to use fat for fuel instead of glucose for fuel.
But does your brain need carbs and glucose for fuel? The brain is the only carbohydrate-dependent organ, but it too can adapt to using ketones (fat) for fuel. Ketones can account for about 80% of the brains energy needs. If you’re following a keto diet, the liver will convert amino acids (protein) into glucose for the remainder of the brain’s energy needs. This process is called gluconeogenesis (1).
In conclusion, your brain does need glucose for fuel, but you don’t have to eat 130 grams of carbs a day to supply the brain with glucose. There are no essential carbohydrates. There is no such thing as a carbohydrate-deficiency syndrome. But there are essential amino acids and essential fatty acids (2).