Two "common sense" leaps of faith were taken as scripture, and generations of doctors and dietitians swallowed these "truths" hook, line, and sinker.
1) Cholesterol accumulates on the walls of our arteries, leading to atherosclerosis, heart disease, and heart attacks.
THEREFORE... The assumption made was that dietary cholesterol (cholesterol based foods we eat) was deposited RIGHT on our artery walls! Red meat, egg yolks, and butter were ticking time-bombs, heart-attacks-on-a-plate!
2) Eating saturated fat was shown to raise total cholesterol.
THEREFORE... not only dietary cholesterol was a "killer", but so was the saturated fat that came with it.
BUT... What we didn't know THEN was that dietary cholesterol (and saturated fats), like all the other fats, proteins, and carbs we eat... is broken down by our bodies into elemental glycerol molecules, fatty acids, and amino acids. These elemental parts are then reassembled, as needed, by the body... regardless of their source. We also failed to notice that VEGANS still got heart disease! Obese vegetarians were dying of heart attacks, strokes, and congestive heart failure too... despite virtually ZERO saturated fat or cholesterol intake!
Because our bodies turn ALL excess calories (even carbs and proteins) into fat to be stored... and the "vehicle" they use to deliver those fats to storage is Low Density Lipoproteins (LDL, bad cholesterol)... which it manufactures in the liver... LDL rises in the presence of EXCESS calories... NOT from consuming cholesterol foods or saturated fat foods. In fact, recent studies have shown that large intakes of carbs (remember... the GOOD stuff at the base of the food pyramid) drives insulin levels up... and has NOW been linked to you guessed it... bad cholesterol.
We've also discovered that consumption of saturated fat DOES increase cholesterol production...but mostly the GOOD cholesterol, HDL, and the lighter LDL molecules that "clean" plaques from your arteries, and deliver energy FROM your fat stores TO your liver to be burned.
So... Come to find out... The "evil" saturated fat, is GOOD for your heart, it's critical for testosterone production, and it's helpful in making us feel "satiated" (full feeling) after a meal.
OF COURSE... too much of a good thing is usually bad! OVER-consumption of saturated fat, or carbs, or proteins, will STILL make you fat, and still lead to heart disease! So don't over-do it! Keep your total calorie intake under control!!! But don't stress out over a really good steak, some butter on your toast, or amazing whole-egg omelettes!