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Most carbon dioxide that travels from your muscles to your lungs for exhalation does so not as CO2 proper, but as part of bicarbonate: HCO₃—Bicarbonate's vital to maintaining your blood pH, and it also aids in digestion.
But it turns out bicarbonate also tweaks the activity of rod cells in your retina. In everyday vision, photons flood your rod cells, setting off a chemical cascade that eventually translates into an electrical message about what you saw. But in lab tests, higher than normal levels of bicarbonate allow the rods to recover from that photon response 30 percent faster. A 30 percent higher refresh rate, essentially—meaning your ability to detect movement would improve. The downside? This rapid reset of the rod cells means they're less sensitive to light.
"If you're sitting in darkness and you turned on a steady light, it might now take brighter light for you to say, 'I can see that.'" Study author Clint Makino, of the Massachusetts Eye and Ear Infirmary and Harvard Med School. "Or if the light's already on, it would take a larger increment in intensity for you to say, 'Ok, it looks brighter now.'" The results are in the Journal of Biological Chemistry. [Teresa Duda et al, Bicarbonate Modulates Photoreceptor Guanylate Cyclase (ROS-GC) Catalytic Activity]
Makino says heavy exercise—which causes a boost in CO2—might even alter the body's bicarbonate enough to trigger a measurable effect on the eye. "I don't think it's known whether your vision changes under conditions of vigorous exercise. So that'll be an interesting question for the experimental psychologists and the psychophysicists." And if you're eyeing your club soda as a shortcut to CO2? He says most of those bubbles never make it past the belch.
—Christopher Intagliata
[The above text is a transcript of this podcast.]
