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[Energy metabolism of the brain in children (author's transl)]
Insights
The human brain uses 20% of resting energy metabolism (BMR), a proportion higher in infants (50%) than adults (20%). Brain size relative to body weight significantly impacts metabolic rates during growth.
Area of Science:
- Physiology
- Human Metabolism
- Neuroscience
Background:
- The human brain accounts for approximately 2% of body weight but consumes about 20% of resting energy metabolism (Basal Metabolic Rate - BMR).
- Mammalian brain oxygen consumption per unit weight is largely independent of body size, allowing for cross-species comparisons.
Purpose of the Study:
- To investigate the proportion of Basal Metabolic Rate (BMR) attributed to brain energy metabolism across different life stages.
- To analyze the influence of changing brain-to-body weight ratios on metabolic rate during growth.
- To explore potential links between brain weight, BMR, and nutritional status in children.
Main Methods:
- Calculations based on established data for brain oxygen consumption and body weight.
- Comparative analysis of brain weight proportion and BMR across different age groups (newborn, 12 years, adult).
- Examination of the relationship between relative brain weight and BMR changes during development.
Main Results:
- Brain energy metabolism constitutes approximately 50% of BMR in newborns, decreasing to about 30% by age 12.
- The decline in BMR per kilogram during infancy and childhood is significantly influenced by the decreasing proportion of brain weight to total body weight.
- Undernourished children exhibit a higher relative brain weight compared to eutrophic children, potentially explaining elevated BMR during nutritional rehabilitation.
Conclusions:
- Brain energy metabolism plays a crucial role in overall BMR, particularly in early life.
- Changes in relative brain size are a key factor driving metabolic rate shifts during growth.
- Relative brain weight differences may offer insights into the metabolic responses of malnourished children.
Abstract:
Oxygen consumption of the human brain is of the order of 3,5 ml./minute. Since the brain of a 70 Kg. man has a weight of 1,400 g., its total oxygen consumption is close to 50 ml./minute. Thus, whereas the brain weight accounts only for about 2 percent of the body weight its oxygen consumption accounts for some 20 percent of the resting energy metabolism (BMR) of the body. Measurements in animals of different size indicates that the oxygen consumption of the mammalian brain, per unit of weight, is practically independent of body size. Accordingly, the above figure can be used to make an estimate of the fraction of BMR accounted for by the energy metabolism of the brain, in different species. The proportion of brain weight to total body weight changes during the period of growth. The brain of a new-born baby represents some 10 to 11 percent of the total body weight. Therefore, in spite of the fact that the BMR/Kg. is higher in the infant, the fraction of BMR accounted for by the metabolism of the brain, is expected to be higher in the infant and child than in the adult. The calculations presented in this paper show that the energy metabolism of the brain may account for about 50 percent of the BMR in the new-born. As indicated by our calculations the proportion of BMR accounted for by the energy metabolism of the brain decreases with age, but it still accounts for about 30 percent of the BMR at age 12 years. Our calculations also show that much of the decrease of BMR/Kg. that takes place during infancy and childhood, is due to the decrease in the proportion of brain weight to total body weight. Undernourished children tend to have higher brain weight, relative to total body weight, than eutrophic children. It has been proposed, that this fact could explain the high BMR observed in malnourished children during nutritional rehabilitation.