Phenols are a wide range of naturally-occurring molecules  found in many different natural plant-based foods. Within olive oil, the phenol content and type determine the health benefit of the oil.Multiple studies indicate that counts in the 200-400 range are required to improve health.  Most commercial EVOO is less than 50. The important thing is to get 5 mg of olive oil phenols per day in your diet.  More than this has not been shown to provide extra health benefits.Some brands have phenol counts of 1000-3000.  There is no evidence these higher levels provide more benefit.They often are far more expensive and have such a strong taste that some people do not enjoy the flavor.