Who needs carbohydrates?

Let me warn you: I've decided to pick a fight with the educated population and nutritionists who swallowed the nutritional pyramid that was literally shoved down consumers' throats, first by the cereal manufacturers' lobby, and then by the increasingly varied “processed foods.” I'll leave that part of the story for others to tell, or for the curious to investigate on their own. My part has to do with your brain.

The point is that scientists from various fields have become accustomed to thinking of glucose as the body's main source of energy—and carbohydrates as a source of glucose. Breaking down the carbohydrates in flour, potatoes, rice, and cereals into pieces of glucose and burning glucose as a source of vital energy is indeed trivial for the body.

But eating carbohydrates is completely unnecessary—and, according to a recent study, contributes to the progressive destabilization of brain function (I'll explain what that means in a moment).

Eating carbohydrates is unnecessary because the body's cells know how to make glucose when needed, and also how to build long carbohydrates using it as a building block. But there are nine amino acids that the human body does not produce, and at least two types of fat. These must come from food. Hence, a diet based on proteins and fats, with just a little bit of carbohydrates sprinkled on top – exactly the opposite of what the industry has been promoting – is what the body not only needs, but expects. When protein and fat are consumed first, all extra glucose is converted into fat, stored in tires and plaques throughout the body, waiting for better days.

Measuring the brain's glucose consumption is easy and has dominated studies in the field, but it is already known that the brain makes perfect use of ketones derived from dietary protein and fat. And much more: according to researchers at Stony Brook University in the US and Oxford University in the UK, after the age of 40, the brain's ability to stay “focused” on one type of activity while “doing nothing,” without switching between, for example, prioritizing vision or hearing or introspection, decreases.

But this is what happens with the “normal” diet, the carbohydrate-based food pyramid. When the study volunteers switched to a ketogenic diet, eating less than 50 grams of carbohydrates per day, their brain activity at rest immediately became more stable.

The researchers openly declare that they have a financial interest in their findings, as intelligent people do. If someone is going to profit from this (and someone obviously will), why not the authors of the research themselves?

Extracted from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in August 2020.