The US FDA says the following about olive oil "Limited and not conclusive scientific evidence suggests that eating about 2 tablespoons (23 grams) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil. To achieve this possible benefit, olive oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day is perhaps cautious. If you are in good health, 2 tablespoons per day will certainly do you good, in many ways.http://italianfood.about.com/b/2006/03/03/olive-oil-a-couple-of-tablespoons-a-day-will-keep-many-doctors-away-2.htm
That's the easy part to understand. Now it is going to get complicated.
The Monosaturated fats are unsaturated fats that are heart healthy..Saturated fats are bad for heart health.
Omega-3 fatty acids are also unsaturated fats not monosaturated like olive oil but rather are polyunsaturated. They are also heart healthy.
EPA and DHA are two Omega-3 fatty acids that are heart healthy. Fish and fish oil have large quantities of these two fats. Omega-3 fatty acids are also found in walnuts, winter squash, and beans like soy and kidney.
ALA is the third Omega-3 fatty acid. ALA needs to be converted by the body into EPA and DHA to be helpful. Flaxseed contains ALA and the body will need to convert it into DHA and EPA before any benefit can occur.
One of my many worries, as I get older, is developing prostate cancer. High ALA levels in the blood is associated with an increase risk for prostate cancer. It has not proven or disproven that flaxseed oil causes prostate cancer. I'll stick to fish oil until this debate is resolved. I take 3 1000mg fish oil capsules a day for my Omega-3 supplement..
This is what the Harvard Medical School has to say about flaxseed and prostate cancerhttp://hms.harvard.edu/public/disease/nutrition/page3.html