As old a remedy for nausea and motion sickness as ginger is, the exact mechanism of action is not known. It has been recommended for ages to alleviate the symptoms of motion sickness.
It has only been in the last few years that a number of good studies have shown clear benefit of ginger compared to placebo. These studies looked at a number of people before and during episodes of motion sickness at sea and on land. Nonetheless, the reason for a favorable outcome remains unclear.
For that matter, the exact mechanism of motion sickness itself is not understood. It is thought that the disparate signals to the brain of what feels like motion to the inner ear and what may or may not look like motion to the eye confuses and alarms a portion of the brain. Speculation about how this is sorted out has to do with which signal is stronger and how an individual can choose to ignore one signal over the other. For instance, trying to focus on the horizon or a fixed point to convince the brain there is stability, while ignoring the signal of motion, which is triggering the obligatory nausea, can alleviate the feeling.
Ginger has active compounds – speculation is that it promotes forward “gastrointestinal transport.” This means: it keeps things moving forward instead of coming back up. Anti-emetic drugs work in a similar manner. The drug increases the upper esophageal sphincter pressure to close off the lower esophagus at the top of the stomach, helping to prevent reflux, while enhancing forward movement through the stomach and gastric emptying in the correct direction. The mechanism of how the drug works may be how ginger creates a similar effect. Unfortunately, it’s all speculation about how ginger actually seems to help.
The benefit of ginger has not only stood the proverbial test of time but recent scientific studies as well. One common misconception is that ginger ale is helpful for nausea and vomiting. Unfortunately, the carbonation being mildly acidic and so gaseous actually makes the nausea worse. Moreover, there hasn’t been anything more than “ginger flavoring” in most of these beverages for more than 50 years. Your best bet is sucking on true candied ginger or powdered ginger in capsule form.
– Dr. Bruce Kaler