How does diet affect brain development?

Early humans: smart through strength?

But not just meat: In contrast to the “Stone Age diet” without carbohydrates that is widespread today, our early ancestors in the Paleolithic were dependent on vegetable starch. Because only these carbohydrates from cooked food could meet the increased energy requirements of the growing brain, according to scientists. Accordingly, the sugar-dependent and specialized metabolic pathways still point to this today. This stands

How we humans were able to develop our large brain is still largely a mystery. Diet likely played a large role in this, especially how it has changed over the past three million years. Cooked food in particular had a decisive effect: food that was previously heated is easier to digest and the nutrients are more accessible. This also increases the energy that a person can get from one serving of food.

Strength as a source of energy

The consumption of meat has been discussed a lot in this context. It is widely believed that eating more meat gave early humans the bigger brain. The high meat consumption of our ancestors also inspired modern diets such as the low-carbohydrate Stone Age diet.

Scientists working with Karen Hardy from the Autonomous University of Barcelona argue differently: According to them, various archaeological, anthropological, genetic, physiological and anatomical details suggest that carbohydrates played a critical role in the rapid development of the human brain. In particular, starch as an energy source has long been neglected in research.

Our brain needs sugar

The main source of energy in our brain provides a first indication of how important carbohydrates are: It consumes a quarter of our daily energy requirements, but 60 percent of the glucose dissolved in the blood. Glucose requirements are also high during pregnancy and breastfeeding, and a deficiency affects the health of both mother and child. This sugar can also be synthesized in the body from other sources. However, the absorption of glucose with food is much more efficient.

According to the researchers, the best source of glucose is starch, which many plants store as a storage substance. It consists of long chains of linked glucose molecules. To our ancestors, it would have been readily available from various roots, seeds, and nuts. However, raw starch is not very easy to digest for humans. However, when heated, it loses its crystalline structure and can also be broken down in our digestive organs.

Only really smart through strength

This central importance of starch is also evident in our genes: the amylase enzyme, which is responsible for splitting the starch chains, is encoded six times on average in the human genome. Other primates only have two copies of this gene. When exactly the early humans received the additional copies of amylase is unclear. However, genetic studies indicate a period within the last one million years.

Hardy and colleagues believe that the cooking of food and the accumulation of amylase genes occurred in a kind of co-evolution. This, in turn, increased the amount of glucose available to the brain, especially during development in the womb. Around 800,000 years ago, this triggered a developmental surge in human intelligence: Eating meat could well have been the first trigger. But only cooked, starchy food together with the additional amylase genes really got us smart. (The Quarterly Review of Biology, 2015; doi: 10.1086 / 682587)

(University of Chicago Press Journals, 08/07/2015 - AKR)

August 7, 2015