When there's oxygen around, nitric oxide breaks down slowly in tissues, which lets it travel farther from blood vessels than if it disappeared at a steady rate. Think of it like a scent that lingers longer so it can spread farther.

In liver cells from rats, nitric oxide lasts longer when there's less oxygen around because it doesn't get used up as quickly.

When your body's tissues are working harder and need more energy, a natural chemical called nitric oxide works with oxygen levels to make sure even the farthest cells from blood vessels still get enough oxygen to keep working properly.

Nitric oxide breaks down too fast in the body to be taken as a pill or swallowed—it has to be made inside the body using other substances because it disappears in less than two seconds.

As people get older, their bodies make less of a helpful molecule called nitric oxide, which makes it harder for blood vessels to work properly — and this can cause problems in the heart, brain, reproductive organs, and muscles.