• Posted October 18, 2024

Love Bread & Pasta? Humans' Hunger for Carbs Has Ancient Roots

Folks who struggle to reduce their carb intake might be able to blame ancient DNA still lurking in humans, a new study suggests.

Humans carry multiple copies of the salivary amylase gene (AMY1), which helps begin breaking down starch in the mouth -- the first step in digesting carb-laden foods like bread and pasta, researchers said.

The duplication of this gene might have occurred as far back as more than 800,000 years ago, long before the advent of farming, and it helped shape human adaptation to starchy foods, researchers argue.

Amylase is an enzyme that breaks down starch into glucose, and it also gives bread its distinctive taste, researchers said.

"The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest effectively,” said researcher Omer Gokcumen, a professor of biological sciences with the University of Buffalo.

For the study, researchers analyzed the genetics of 68 ancient human bodies, including a person who lived 45,000 years ago in Siberia.

They found that pre-agricultural hunter-gatherers carried an average of four to eight AMY1 copies in their genetic makeup, suggesting that people already had adapted to eating starchy foods long before they began growing foods like wheat and potatoes.

AMY1 gene duplications also were found in ancient human ancestors like Neanderthals and Denisovans, the researchers added.

“This suggests that the AMY1 gene may have first duplicated more than 800,000 years ago, well before humans split from Neanderthals and much further back than previously thought,” said researcher Kwondo Kim, a postdoctoral associate with the Jackson Laboratory for Genomic Medicine.

These initial duplications of the AMY1 gene “allow[ed] humans to adapt to shifting diets as starch consumption rose dramatically with the advent of new technologies and lifestyles,” Gokcumen said in a lab news release.

As humans spread around the world, the flexibility in the number of AMY1 copies allowed them to adapt to new diets, depending on the environment around them, researchers said.

Farming further altered human genetics. European farmers saw a surge in the average number of AMY1 copies over the past 4,000 years, likely driven by their starch-rich diets.

"Individuals with higher AMY1 copy numbers were likely digesting starch more efficiently and having more offspring,” Gokcumen said. “Their lineages ultimately fared better over a long evolutionary timeframe than those with lower copy numbers, propagating the number of the AMY1 copies."

The new study was published Oct. 17 in the journal Science.

This research could have practical, real-world consequences for modern humans suffering from obesity and type 2 diabetes, researchers said.

“Given the key role of AMY1 copy number variation in human evolution, this genetic variation presents an exciting opportunity to explore its impact on metabolic health and uncover the mechanisms involved in starch digestion and glucose metabolism,” said researcher Feyza Yilmaz, an associate computational scientist at the Jackson Laboratory. “Future research could reveal its precise effects and timing selection, providing critical insights into genetics, nutrition and health.”

More information

The National Institutes of Health has more on the digestive system.

SOURCE: Jackson Laboratory for Genomic Medicine, news release, Oct. 17, 2024