Which cooking oil is best for colon health?

25 years ago I was recommended corn oil because research indicated omega 6 oils produced stronger artery walls from lab tests. Since then safflower oil is available and we use it in small amounts–and are ovo-lacto vegetarians for almost 40 years.

NOW I have been diagnosed with colon polyps, two pre-malignant. So, please reference an article that shows research in this area.