February 15, 2024 | David F. Coppedge

Hummingbirds Thrive on Sugar

Why don’t hummingbirds get diabetes?
They didn’t evolve to live on sugar;
they were designed for it.

 

Those who have enjoyed Illustra Media’s beautiful videos about hummingbirds, or those who watch them at backyard feeders, certainly marvel at their aerobatics. But did you ever wonder how they live on sugar all day, and don’t get diabetes? Some scientists asked that question. They learned some data about hummingbird sugar consumption, but came to the standard illogical conclusion: “it evolved.”

Note: another animal has this sugar problem: fruit bats (see 11 Jan 2024).

Why Don’t Hummingbirds Get Diabetes? (The Scientist, 1 Feb 2024). This “Just Curious” article sets up the question about hummingbirds’ radical sugar diet.

It’s no secret that hummingbirds are sugar fiends. To fuel their energy-intensive hovering flight, a wild hummingbird consumes approximately 2 grams of sugar per day—the equivalent of a person consuming about 90 pounds of the stuff. In keeping with their sugar-rich diet, hummingbirds have exceptionally high blood glucose levels, up to 42 mM. In humans, levels over 10mM are cause for concern and can lead to diabetes-related cardiovascular disease, nerve damage, and even blindness. Yet hummingbirds appear to weather this hyperglycemic state without ill effects and, in fact, are quite long-lived considering their diminutive size.

The Scientist called on physiologist Kenneth Welch from the University of Toronto to answer the question of how these “speed demons” survive on “astronomical” amounts of sugar daily. But he doesn’t know. He thinks that their high level of aerobic exercise might account for part of it. Or maybe the birds don’t link their sugars to proteins as much as humans do, a process known as glycation, which is responsible for much of the damage in diabetics.

But Welch has to say something. So he calls on the standard answer to everything: Darwinian evolution. And with the just-so story, as usual, up goes the perhapsimaybecouldness index, futureware, and vaporware.

In the case of chickens (all birds are relatively hyperglycemic), one protein called albumin has evolved to have fewer exposed lysine residues, which may render it glycation resistant.

Welch said that it’s currently unclear whether hummingbird physiology research can prompt development of new therapies for metabolic disease in humans. However, he said, “Knowing more about how evolution can produce solutions to these functional problems in metabolic physiology can only help us formulate more creative solutions in the human biomedical context.”

For relief from the sappy answer “it evolved,” we turn your attention to one of Illustra Media’s films about hummingbirds.

See also “A Hummingbird’s Tongue” at The John 10:10 Project website where you can find these and many other short films in the “Awesome Wonders” category.

 

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