In the last blog post, I discussed where cholesterol comes from and its vital functions in the body. Now, you’ll learn where it comes from and how our bodies use it.
Cholesterol can be made in our body, or it can come from foods.
Our cells manufacture the cholesterol they need for their membrane requirements in response to demand. For instance, when we drink alcohol, it dissolves in and fluidizes our membranes. In response, cells build more cholesterol into the membrane, and thereby bring the membrane back to a normal (less fluid) state. As the alcohol wears off, the membrane hardens, and some membrane cholesterol is removed to reestablish normal (greater) membrane fluidity. The extra cholesterol is hooked up (esterified)2 to an essential fatty acid (EFA) and shipped via our bloodstream to our liver to be changed into bile acids, as long as the vitamins and minerals necessary for this change are present. Our liver dumps bile acids into our intestine to help with fat digestion, and then removes them from our body with solid wastes, as long as our foods contain sufficient fiber and bowel action is regular enough to prevent bile acids in our intestine from being reabsorbed and recycled.
Besides our cells’ production of cholesterol, our liver, intestine, adrenal glands, and sex glands all make cholesterol for the other functions in which cholesterol is involved. During pregnancy, the placenta also makes cholesterol, from which it manufactures progesterone, which keeps pregnancy from being terminated.
Making homemade cholesterol
Our body makes cholesterol by hooking 15 two-carbon acetates (vinegars) end to end to make a 30-carbon chain. Through many steps involving different enzyme catalysts, this chain is cyclized, and finally 3 carbons are clipped off to produce the 27-carbon cholesterol molecule. The process is complex and interesting for biochemists, but the important nutritional question is to find the source of the 2-carbon acetates.
When our cells break down fatty acids, sugars, starches, or amino acids in our energy-producing mitochondria, they clip off 2-carbon acetates at each step. Alcohol also provides acetates for cholesterol production.
Proteins and EFAs
Our body conserves proteins as much as possible for building structures and enzymes, so proteins are burned for energy only in extreme circumstances: fasting, some disease states, and after consumption of excessive amounts of protein.
Our body also conserves EFAs for non-fuel functions. Since EFAs are conserved by the body for other vital functions, saturated and monounsaturated fatty acids are the main sources of acetate fragments from fats.
Foods rich in refined carbohydrates also produce an excess of acetates in our body, which ‘push’ increased cholesterol production. High cholesterol levels in people living in ‘processed foods nations’ often involve excessive calorie intake.
Stress also increases homemade cholesterol production.
Cholesterol from food sources
Only foods from animal sources contain cholesterol – plant foods are cholesterol-free. Cholesterol is found in eggs, meat, dairy products, fish, and shellfish. One egg, 1/4 pound of liver, and 1/4 pound of butter each contain about 250 mg of cholesterol; fish and shellfish contain somewhat less.
The average North American adult consumes about 800 mg of cholesterol daily, of which about 45% comes from eggs, 35% from meat, and 20% from dairy. About half of the dietary cholesterol is actually absorbed. The rest passes through unused.
For 70% of the affluent populations of the world, increased cholesterol consumption decreases cholesterol production within their body by means of a regulating feedback system that protects them. The other 30% of the population may not have adequate feedback, and are wise to limit their cholesterol consumption. What is not clear is to what extent drugs (some of which are known to increase our body’s cholesterol production) and other toxic molecules from foods, water, air, and the environment play a role in making the feedback system ineffective. A good topic for research!
Body Content of Cholesterol
The average person’s body ‘owns’ about one-third of a pound (150 grams, or 150,000 mg [5 ounces]) of cholesterol. Most of this is found in membranes, and about 7 grams is carried in our blood. The daily turnover of cholesterol is about 1100 mg, or just over 1 gram. These figures vary depending on diet, state of health, and body size. The daily cholesterol turnover on a strict vegetarian diet (who does not eat meat, eggs, or dairy products) is less than 1 gram; bodies of meat eaters turn over more cholesterol as cholesterol consumption increases, but less as fiber consumption decreases.
Removal of Cholesterol
Cholesterol is unique in that our body can make it but, once made, cannot break it down. By contrast sugars, fatty acids, amino acids, and nucleic acids can all be taken apart and turned into carbon dioxide, water, and ammonia. As a result of this peculiarity, cholesterol must (and can only) be removed from our body through our stool (in the form of bile acid and cholesterol molecules).
The removal of cholesterol is increased by dietary fiber. If fiber is absent, up to 94% of the cholesterol and bile acids are reabsorbed and recycled. This is one of the reasons why low-fiber diets increase blood cholesterol levels.
About two-thirds of the North American, European, and affluent populations world-wide suffer from atherosclerotic deposits to some degree. These deposits, made of proteins, fats, cholesterol, and minerals, narrow arteries and slow down blood flow. In addition, cholesterol and saturated or denatured fatty acids make our platelets sticky, increasing the risk of a clot forming.
The combination of atherosclerosis and clots may completely block an artery, cutting off oxygen and nutrients to the cells of the part of our body supplied by that artery. These cells then die.
If an artery to our brain is blocked, a stroke occurs and, depending on the size and location of the blocked artery, the stroke may be minimal or fatal. Narrowed arteries to our heart produce chest pains (angina pectoris) on exertion or after a meal high in fats that makes blood thicker and less capable of supplying oxygen. Blockage of an artery supplying our heart results in a heart attack (coronary occlusion).3 If a clot blocks an artery in our lungs, pulmonary embolism occurs. A blocked artery to our legs results in impaired circulation that can lead to gangrene.
Blindness and deafness can occur when arteries supplying sense organs are blocked.
Atherosclerotic deposits also ‘harden’ our arteries, resulting in raised blood pressure because the arteries’ resilience, which normally takes up the pressure generated by each heartbeat (contraction), is lost. This results in a heavier load on our heart and kidneys which, when prolonged, leads to water retention (edema) and heart and kidney failure.
Cholesterol has suffered under some extreme controversy. But there’s much, much more to the story — including how it benefits our overall health. Read my next post or order my book Fats That Heal, Fats That Kill to learn how to help cholesterol work for you.