Molybdenum is element #42, and it is a trace mineral in many foods. It is high in legumes and some whole grains, including barley and oats. It appears to help with nausea. My family and others have found that molybdenum gives them relief from “stomach bug” nausea/vomiting. Also, some women, myself included, have found it lessened “morning sickness.” (Here is a link to my published hypothesis about sulfite, molybdenum, and nausea and vomiting in pregnancy.)
How does it help? Molybdenum is used by five enzymes in our bodies, and the most relevant enzyme appears to be sulfite oxidase. Sulfite oxidase catalyzes the conversion of sulfite–which causes many symptoms including nausea–to less harmful sulfate. I think that a buildup of sulfite in the stomach (most likely from catabolism of hydrogen sulfide) irritates the lining of the stomach and upper small intestine and thus brings on nausea and vomiting. Syrup of ipecac brings on vomiting in the same way. By consuming enough molybdenum to support sulfite oxidase activity, we help our body break down sulfite more quickly and in that way decrease nausea and vomiting symptoms.
My preferred source of molybdenum is barley water or barley-containing soups and stews, preferably before vomiting has started, as vomiting negatively affects the ability to eat and absorb nutrients. I also utilize chelated molybdenum glycinate, preferably powdered. If considering taking a molybdenum supplement while pregnant, first clear it with your OB/GYN.