Media Releases

Hummingbird metabolism unique in burning glucose and fructose equally

December 5, 2013

TORONTO, ON - Hum­ming­bird metab­o­lism is a mar­vel of evo­lu­tion­ary engi­neer­ing. These tiny birds can pow­er all of their ener­getic hov­er­ing flight by burn­ing the sug­ar con­tained in the flo­ral nec­tar of their diet.

Now new research from the Uni­ver­si­ty of Toron­to Scar­bor­ough shows they are equal­ly adept at burn­ing both glu­cose and fruc­tose, which are the indi­vid­ual com­po­nents of sug­ar; a unique trait oth­er ver­te­brates can­not achieve.

“Hum­ming­birds have an opti­mal fuel-use strat­e­gy that pow­ers their high-ener­gy lifestyle, max­i­mizes fat stor­age, and min­i­mizes unnec­es­sary weight gain all at the same time,” says Ken­neth Welch, assis­tant pro­fes­sor of bio­log­i­cal sci­ences at UTSC and an expert on hum­ming­birds.

Welch and his grad­u­ate stu­dent Chris Chen, who is co-author on the research, fed hum­ming­birds sep­a­rate enriched solu­tions of glu­cose and fruc­tose while col­lect­ing exhaled breath sam­ples. They found the birds were able to switch from burn­ing glu­cose to fruc­tose equal­ly as well.

“What’s very sur­pris­ing is that unlike mam­mals such as humans, who can’t rely on fruc­tose to pow­er much of their exer­cise metab­o­lism, hum­ming­birds use it very well. In fact, they are very hap­py using it and can use it just as well as glu­cose,” says Welch.

Hum­ming­birds require an incred­i­ble amount of ener­gy to flap their wings 50 times or more per sec­ond in order to main­tain hov­er­ing flight. In fact, if a hum­ming­bird were the size of a human, it would con­sume ener­gy at a rate more than 10 times that of an Olympic marathon run­ner. They are able to accom­plish this by burn­ing only the most recent­ly ingest­ed sug­ar in their mus­cles while avoid­ing the ener­getic tax of first con­vert­ing sug­ar into fat.

From an evo­lu­tion­ary per­spec­tive the find­ings make per­fect sense, says Welch. Where­as humans evolved over time on a com­plex diet, hum­ming­birds evolved on a diet rich in sug­ar.

“Hum­ming­birds are able to move sug­ar from their blood to their mus­cles at very fast rates, but we don’t yet ful­ly under­stand how they are able to do this,” he says.

Humans are not good at burn­ing fruc­tose because once ingest­ed much of it gets tak­en into the liv­er where it’s turned into fat. The preva­lence of high fruc­tose corn syrup found in prod­ucts like soda pop is also strong­ly linked to a rise in obe­si­ty rates.

On the oth­er hand because hum­ming­birds burn sug­ar so fast that if they were the size of an aver­age per­son they would need to drink more than one can of soda every minute even though it’s most­ly made of high-fruc­tose corn syrup.

“If we can gain insights on how hum­ming­birds cope with an extreme diet then maybe it can shed some light on what goes wrong in us when we have too much fruc­tose in our diet,” says Welch.

The research will appear in the upcom­ing edi­tion of the jour­nal Func­tion­al Ecol­o­gy and is cur­rent­ly avail­able online.

Watch the com­pan­ion video on YouTube.


Media Con­tact:

Don Camp­bell
Media & Rela­tions Offi­cer
Uni­ver­si­ty of Toron­to Scar­bor­ough
Phone: 416–208-2938