Combine all of your concepts and synonyms in one search by using round brackets to separate the ORs from the ANDs. This is similar to algebra. In the example below I have also applied truncation and phrase searching where appropriate.
For example, the search strategy (diet* OR nutrition OR "food intake") AND (migraine OR "vascular headache") AND (teen* OR adolescen*) will retrieve results that include at least one of the terms from each category. Brackets have been placed strategically to separate the ANDs from the ORs (a bit like algebra).