Our bodies can only make saturated or monounsaturated fatty acids from scratch.
Oils, especially “polyunsaturated” oils that have been thought to have been good because they decrease serum cholesterol levels, have actually been shown to increase cholesterol in tissues. The reason for this is that the polyunsaturated fatty acids are deposited into the membranes and the body needs to put more cholesterol into these membranes to stabilise them and maintain fluidity
Free radicals are derived from decomposition (oxidisation) of unsaturated fatty acids, especially polyunsaturated fatty acids.
Omega 3 & 6 are responsible for structural & signalling functions throughout the body and cannot be created by the human body. Research has shown that saturated fat is needed in the diet to adequately convert the essential Omega 3 fatty acid (a-linolenic acid) to the elongated Omega 3 FA EPA and DHA. These latter fatty acids are necessary for prostaglandin formation and visual function.
In addition to Omega 3 and 6, there is strong evidence that some of the medium-chained saturated fatty acids such as Lauric Acid (found in coconut oil) are essential since they are needed for maintaining the natural ability to fight potentially harmful microorganisms.
Tropical oils by gram have at least 2.56% fewer calories than replacement oils such as cottonseed, soybean and sunflower oils.
The Brain:
The brain can burn glucose and ketones as energy
The brain can't burn fat despite containing a lot of fatty acidsThe brain consumes 600 kcal per day despite only weighing 3 pounds. More than 10x the average energy used per pound around the body.
The brain has no reserve supply of glycogen and is reliant on a constant blood supply, containing both fuel and oxygen.
Even a small drop in blood sugar can cause an intense physiological response, such as increased heart rate, shaking, anxiety and intense hunger & cravings. Should blood sugar fall below half of the lower limit of normal, it would cause a coma. These reactions are due to a dramatic increase in adrenergic nervous system activity.
The Brain & low-fat vs. The brain & ketones
Low fat:
Low-fatt diets with a carb intake of 600kcal or less will not allow your liver to make ketones and will barely enough to feed your brain with the energy it requires. You may get the rest of your energy from protein converting into glucose via glycogenesis, but if you are active and like to exercise, then this can only last for so long before you either eat more or exercise less.
Ketones (low carb, high fat):
Supply of fuel to the brain from ketones improves cognition before and after exercise. Ketones also provide substrates (the substance on which an enzyme acts) to help repair damaged neurons, altering and improving membrane potential. The metabolic benefit of ketones has prompted research into low carbohydrate diets in the treatment of several neurological disorders, such as seizures and Alzheimers.
Cholesterol:
Cholesterol is an important part of a cell membrane and give the cells rigidity and help to keep its proper shape. Cholesterol is found in every cell of your body. It is especially abundant in the membranes of these cells, where it helps maintain the integrity of these membranes, and plays a role in facilitating cell signalling.
Without cholesterol, there would be no lipoproteins, which delivers fuel to your cells and no way to distribute fats and fat-soluble nutrients throughout the body.
Cholesterol is a high molecular weight alcohol glycerol that holds the fatty acid together in triglycerides. Cholesterol is the animal sterol, whilst plant sterol is called a “Phytosterol” and are both referred to as “fatty substances” because they are fat soluble, but are different from fatty acids and triglycerides.
Cholesterol is also a critical component of some of the cell receptors, which are protein molecules that bind specific chemicals to enhance their uptake into the cell. One such receptor is the glutamate receptor which are found in the brain (essential for memory formation) and nervous system.
The more unsaturated the fatty acids are the more cholesterol is needed to provide the membrane with the right amount of stiffness.
Cholesterol in the skin is used as a substrate for the production of Vitamin D (pro-vitamin D3) the cholesterol is in the form of dehydrocholesterol.
Cholesterol levels, if high are not necessarily a health problem if cholesterol is being produced when following a healthy diet with healthy oils and fats and reducing processed carbohydrate and sugar intake. The body needs cholesterol to repair damage and inflammation caused by free radicals, and carry essential enzymes around the body.
Further information:
A presentation by Peter Attia explains how cholesterol works in the body, and in the book Cholesterol Clarity you'll receive some advice on the questions you might want to ask your doctor or physician.
Peter Attia; The Straight dope on cholesterol
If you really want to delve further, Peter has his series of presentations on cholesterol that can be found at the following address: https://peterattiamd.com/category/cholesterol-2/
Cholesterol Clarity, written by Jimmy Moore & Eric C. Westman.
https://www.diaryofabiohacker.com/recommended-reading