If you're having trouble thinking of search terms or aren't getting the results you expect, & you do find an article that is exactly (or close to) what you want, look at how that article is indexed. On the Abstract page, click on the MeSH Terms link in the menu on the right of the page or scroll down the page. You'll find MeSH terms that you can add to your search to improve your results. The words that follow the forward slash are subheadings. Using them can focus your search too much, so focus on the first portion of the entry, for example, Calcium, Dietary is the MeSH term (you may want to use this term) and Administration & dosage is the subheading (you should ignore this term).
In other databases, you'll see indexing terms such as Emtree (in Embase) and Subject or Subject Headings (CINAHL, Global Health) below the article title on the main search page.