supplement –n. an additional amount of something (like vitamins or minerals)

literature –n. books and articles about a particular subject

empirical –adj. based on testing or experience

recommendation –n. a suggestion for someone to do something

habit –n. a usual way of behaving, something done in a repeated way

survey –n. an activity in which people are asked questions in order to gather information about what most people do or think

median –adj. the middle value in a series of numbers

recurrence –n. when something happens again or returns

caution –v. to warn or tell (someone) about a possible danger, problem, etc.