Perform simple searches, like the ones you use in Google. A single term for a condition and another for an intervention may suffice.
...vitamin C cold
There is no real need of using a taxonomy, or boolean terms, such as AND or OR (they work, but are rarely needed. If you are really fond of this kind of search strategies, you can use our advanced search).
You can search in your own language or in English. You can even combine terms from different languages.
Evaluation of the use of both marijuana and THC in cancer patients for the relief of nausea and vomiting associated with cancer chemotherapy after failure of conventional anti-emetic therapy: Efficacy and toxicity