Before you venture olive oil, a few useful tips from a semi expert (humble-me):
~Buy Extra-virgin olive oil only. ~Production date should not exceed 12 months (my deadline is 6 months at most) ~The less acidity, the better. No more than 0.8%, my preference is 0.4%-0.5%, but 0.8% is quite ok too.
Follow above guidelines, the rest will take good care of itself.
Studies have shown that people who consumed 25 milliliters (mL) - about 2 tablespoons - of virgin olive oil daily for 1 week showed less oxidation of LDL cholesterol and higher levels of antioxidant compounds, particularly phenols, in the blood.(4)