Why Do You Have To Fast Before Checking Cholesterol?
When you get your cholesterol checked, they instruct you to fast for 9 hours beforehand. The reason is, because it was much higher right after you ate and for a few hours afterwards. These postprandial cholesterol levels, lasting the majority of the day, are far more impactful on your health than the few hours at the end of your fast. So, the number they tell you is not fully representative of that day, though it is consistent over time.
If you didn’t fast, your numbers over months and years would vary wildly, depending on how many minutes it has been since you last ate and the food you ate before each test. Think of a sine wave. Your fasting cholesterol is the bottom of the wave, that is, the lowest level of the day. It is like, if you got stopped for driving erratically and the policeman wanted to check your blood alcohol level. Then, you said you wanted to wait for 9 hours before the test. Obviously, that test would not tell the story of your condition during the day!
Perhaps, in the ideal world, one would measure cholesterol continuously during every minute of the day and then average the 1440 results. That would give you an excellent value for overall level.
The fasting cholesterol doesn’t tell you the peaks or how high your cholesterol level was on average for the majority of the day. A person eating a high cholesterol (meaty) diet has a much higher level all during the day than the vegetarian eating no cholesterol. However, after a 9 hour fast, the cholesterol levels of these two people are relatively close. They have retreated back down to their baseline. Likely, their baselines are not too far apart, at least compared to the intraday peaks.
That means the meat eater’s arteries have been subjected to an unhealthy condition for many hours, but the fasting test doesn’t give any indication of the severity of the recent trauma. On the other hand, the vegetarian’s arteries were not subjected to such a trauma, but only a slight elevation.
What’s Wrong With a High Cholesterol Diet?
Dietary cholesterol increases the susceptibility of LDL to oxidize by 37%, vascular inflammation, oxidative stress, and postprandial hyperlipidemia and potentiates the harmful effects of saturated fat, impairs endothelial function, and increases cardiovascular events, meaning heart attacks. LDL oxidation is what triggers much of our arterial inflammation. Think about the many diseases aggravated by inflammation!