Methylating is like acetylating. It's kind of a go-to thing to try in medicinal chemistry.
May I ask why?
Depending on the compound, skipping this step may cause the compound to be relatively inert. This is why, for example, calcium carbonate is a poor source of calcium as a nutritional supplement, but calcium citrate is readily absorbed- the citrate itself is an organic compound, so the body more readily takes it up out of the digestive system and the calcium can be used.
Calcium carbonate will react with stomach acid to form calcium chloride (along with CO2 and water). When given intravenously, calcium chloride is perfectly bioavailable. However, within the small intestines, it has very poor uptake, both through the intestines' active and passive mechanisms. Any remaining calcium carbonate has no uptake at all.