Saturated fats(butter, coconut oil, hard fats) are very beneficial.
Unsaturated fats(fish oil, seed oil, liquid oils) have many harmful effects.
-Saturated fat protects against radiation induced intestinal damage, PUFA(polyunsaturated fatty acid) does not have this effect.(1)
-Alcohol liver disease is reversed when diet is composed of saturated fats(2); fish oils and unsaturated fats exacerbate the problem.(3)
-Cancers phospholipids contain less stearic acid(saturated fat) than the less malignant tumors.(4) Adding stearic acid to food delayed development of cancer in mice. (5,6)
-Saturated fatty acids are preferentially oxidized by many cells and albumin preferentially delivers saturated fat to actively metabolizing cells such as the heart. (7)
-In good health(children) the stress hormones are only produced in the amount needed because of negative feedback from the free saturated fatty acids which inhibit production of adrenalin and adrenal steroids. When fat stores are unsaturated the free fatty acids will contain PUFA mostly AA/LA these PUFA stimulate stress hormones, ACTH, cortisol, adrenaline, glucagon, and prolactin, which increase lipolysis producing more fatty acids in a vicious cycle. (8)
-PUFA alters structure of the protein alpha-synuclein; causing it to take the form seen in parkinsons and other brain conditions. Saturated fats have opposite effect on alpha-synuclein. (9)
-When the brain is injured AA and DHA(unsaturated fats) contribute to brain edema, weakening the blood brain barrier, increasing protein break down, inflammation and peroxidation. Stearic acid in the same amount caused no harm.(10)