A new study found that women's brains may convert sugar into energy at a higher rate than men's. Consequently, women's brains look younger than men's from a metabolic standpoint.
Glucose, a form of sugar, is the primary source of energy for cells in the human body. About half of all the sugar energy we ingest on a daily basis goes to the brain, the most energy-demanding organ in the body. Without glucose, critical brain functions such as thinking, memory, and learning would be disrupted. For instance, it's common for people with hypoglycemia (low blood sugar) to have poor attention and cognitive function.
The brain is most demanding for sugar when we are children, since it's a critical development period when new neurons grow and synaptic connections are established. The brain then tends to use less and less sugar as we progress from adolescence into adulthood and old age.
Intriguingly, researchers at Washington University found that adult women's brains appear to produce more energy than men, whether it's a young adult aged 20 or an elderly adult aged 80. The findings were made after researchers performed PET scans on 205 healthy individuals, which measured oxygen, glucose, and blood flow in the brain.
Male brain scans were fed into a machine-learning algorithm as input. When the machine was instructed to guess the metabolic activity of women's brains, it tagged them an average of 3.8 years younger than they actually were. When women's brain scans were used to train the machine, the algorithm predicted that men's brains were 2.4 years metabolically older than they actually were.
Does this mean that women's brains age slower than men's? Not necessarily: these differences held across all age groups. Instead, the researchers claim that men's brains always convert less sugar to energy from early adulthood. It's not clear yet what mechanism might be involved but one hunch is that estrogen may help the brain form more synapses at a young age, which would explain why women require more energy later on.
"It's not that men's brains age faster," said senior author Manu Goyal, assistant professor of radiology at Washington University School of Medicine, St. Louis. "They start adulthood about three years older than women, and that persists throughout life," said Goyal.
Although this was a small study, the findings may explain why women tend to live longer and stay more mentally sharp at old age than men.
It "could mean that the reason women don't experience as much cognitive decline in later years is because their brains are effectively younger," Goyal told AFP.
The findings appeared in the Proceedings of the National Academy of Sciences.