Is being a vegetarian healthy for your brain?
Eating meat drove the evolution of our big, powerful brain
By Rebecca Searles
If ancient hominids existed today, they might have a bone to pick
with their vegetarian descendants. Meat gave our distant ancestors the
brain power that makes higher-level decision-making—like, becoming a
vegetarian—possible, according to researchers speaking on Feb. 20 at the
2011 AAAS meeting in Washington, D.C.
The modern human brain is two to three times larger than that of our
closest relatives, chimpanzees. But to supply energy to such
metabolically demanding tissue, a distinct trade-off in energy
allocation had to evolve.
In 1992, researchers proposed that this gradual expansion of the
ancestral brain was made possible by switching from a vegetative diet to
a meat-rich, fat-rich diet. As meat became a dietary staple, the gut
shortened, and the brain no longer needed to rely on fuel from muscle
and fat stores in the body. A shorter gut requires a great deal less
energy than the lengthy gut of herbivores. Drawing on the extra energy
resources from a fatty diet, and a shorter gut, the brain could afford
Greg Wray, an evolutionary biologist at Duke University, studies the
genetic and molecular systems that co-evolved with this dietary shift to
produce a larger brain. At the meeting, Wray laid out the case for meat
and other protein-rich foods as evolutionary drivers of a bigger, more
complex human brain.
“For a long time now, anthropologists have known that [diet and
cognition] are connected at an organismal level,” Wray said. “But we now
see that there is a connection between these two at the genetic level.”
In order for brain growth to occur, brain cells need energy from
glucose, a basic sugar that fuels cellular activity. As diet changed
over time, the body’s way of converting food into energy may have needed
to evolve to keep up with these new, high-energy demands of the brain.
Wray’s research identified a gene that codes for a glucose transport
molecule—the only known molecule that allows glucose’s entry to the
brain. The human variation of this gene expresses two to three times the
amount of glucose transport molecules than its chimpanzee counterpart.
By examining clinical data, Wray determined this gene to be necessary
for proper human brain development.
“Severe [forms of the gene] can cause genetic microencephaly, [a
disease] in which no glucose can enter the brain, and it dies from
starvation,” Wray said. “So this boost in the brain, we can tell, is
critical for normal brain development.”
Wray’s work could have broad implications for evolutionary medicine,
an understanding of health and disease from the evolutionary
“Any time you take something as poised as a metabolic system and you
drag it off and make it do something different, there will be unintended
consequences,” Wray explained. “Something needs to compensate. So,
probably a lot of medical issues are a result of these unintended
As for vegetarians, Wray says they’ve had plenty to say to him about
his work. He has one piece of advice: Creatine is important. Creatine, a
natural acid gained from eating meat, plays a critical role in
cognition. Wray encourages vegans to consider taking a creatine
supplement, particularly if they’re pregnant.
Rebecca Searles is a biology and psychology student at the
University of North Carolina at Chapel Hill. She edits Carolina
Scientific, an undergraduate research publication, and she hopes to
pursue a career in science writing. She writes a blog, The Stone Age Mind, for Psychology Today. Reach her at firstname.lastname@example.org.
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