Do you have syphilis? Or snort cocaine, or smoke tobacco, or have a bacterial infection or periodontal disease that causes an overproduction of cholesterol to accumulate in your arteries? If you answered “no” to all of the above, the cause of chronic inflammation, and thus of atherosclerotic plaque in your arteries, is likely to be dietary.
The relationship between dietary fat and atherosclerosis, however, is contentious. The USDA’s current “MyPlate” and their Dietary Guidelines for Americans, promote a low-fat diet, based largely on belief that fat in the diet is atherogenic. The American Heart Association, the American Diabetes Association and the National Cholesterol Education Program make similar recommendations. Especially singled out are saturated fats, dietary cholesterol and trans fats. Trans fats are one of the few consensus points in nutrition as everyone thinks these are very bad for your health. But could all of these authorities be wrong about the role of saturated fats and dietary cholesterol?
In a word, “yes.” There is growing unanimity that monounsaturated fats, such as are found in olive oil and avocado, are healthy. But polyunsaturated fats, such as are manufactured by unnaturally processing seed crops (called euphemistically “vegetable” oils, are coming under increasing scrutiny. Soy bean oil and corn oil are the most widely used fats, accounting for over 90% of food oils used in the U.S. The latest (2015) Dietary Guidelines for Americans (DGA) still strongly and doggedly encourages their use and defends their safety.
Interestingly, though, the DGA’s recommended limits on dietary cholesterol of 300mg/dl, and 30% total fat of total calories, in place from inception (1980) up to 2015, has been lifted. The proscription on consuming saturated fat, however, remains. The government want Americans to “replace saturated fats with unsaturated fats.”
Polyunsaturated fats are particularly unstable. Referencing Wikipedia, they become damaged or oxidized very easily. In one study when oxidized or rancid fats were fed to lab rats, they developed atherosclerosis. In another, rabbits fed atherogenic diets containing various seed and grain oils showed the largest increase in “oxidative susceptibility of LDL.” In a study involving rabbits fed heated soybean oil, “grossly induced atherosclerosis and marked liver damage were histological and clinically demonstrated,” according to Wikipedia.
More from Wikipedia: Rancid fats and oils taste and smell very bad even in small amounts and people avoid eating them. But, in the United States, “vegetable” oils used in cooking are refined, bleached, deodorized and degummed. The resultant oils are colorless, odorless, tasteless, and have a longer shelf life than their unrefined counterparts. This extensive processing makes fully oxidized, rancid oils much more elusive to detection via human senses.
To properly protect polyunsaturated fats (all “vegetable” oils) from oxidation, it is best to keep them cool and in a dark, oxygen free environment. Keep them in the cupboard, not on the counter. And buy monounsaturated oils that are sold in dark glass bottles, not clear plastic ones. Finally, don’t overheat or use any of them repeatedly, such as in deep fat frying. And keep your Omega-3 fish oil capsules and Flax Oil (high in Omega-3s) in the refrigerator.
So, if atherosclerosis is defined by Wikipedia as “a chronic inflammatory response in the walls of arteries, promoted by LDL…without adequate removal of fats and cholesterol…by…HDL,” then we should be concerned about the quality and quantity of LDL in our arteries – lest it become oxidized LDL. Likewise, we should be concerned if our circulating HDL in not high enough to transport any oxidized-LDL back to the liver as it is supposed to do.
Why do the two bad conditions (high LDL and low HDL) co-exist in so many of us today? It’s our diet! To avoid oxidized LDL, we should eat far fewer polyunsaturated fats (PUFAs), especially ones that are partially hydrogenated or hydrogenated (as in margarine and many store-bought baked goods), oxidized, or heated (as in deep fat frying).
We can also take supplementary Omega-3s to help us regain a better Omega 6/Omega 3 balance (Retrospective #22. And, we can raise our HDL so they can do their job. For that, see Retrospective #34, “Foods that Raise HDL.”
The oxidized-LDL hypothesis as the cause heart disease, of inflammation and of atherosclerosis, posits that, “Once inside the vessel wall, LDL molecules become susceptible to oxidation by free radicals and become toxic to the cells.” Read Retrospective #48, “Inflammation and Atherosclerosis,” to refresh. Free radicals cause the oxidative stress that “triggers a cascade of immune responses which over time can produce the characteristic “atheroma” nodule in the artery wall that is the start of atherosclerosis.”
“Free Radicals and Oxidative Stress” is the subject of the next Retrospective, #50.