Even if you remove most air from olive oil, some healthy compounds still break down—but if air gets in occasionally, they break down even more.

When olive oil is stored for a long time with air or light, its natural healthy compounds break down into different chemicals, some of which are less beneficial.

Frying olive oil too long breaks down its natural compounds and creates new ones—but adding olive extract slows this breakdown and even boosts total antioxidants for the first few hours.

When olive oil sits too long, its natural compounds break down into simpler molecules like tyrosol and 3-hydroxytyrosol, which are also found in other foods.

Storing olive oil in dark glass or a metal can helps keep its healthy compounds intact better than clear plastic bottles—metal cans produce the fewest bad breakdown products.