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How quercetin protects blood vessels against cholesterol
Foods that contain significant amounts of quercetin analogs or similar substances protect against cardiovascular disease. Thanks to fundamental research, carried out with mice and immune cells, we better understand why. Quercetin ensures that the body is better able to clean up a surplus of cholesterol.
The Chinese used mice that resemble people with a genetic predisposition to clogged blood vessels, heart attacks and strokes. The researchers also gave the animals food containing extra fat. The cardiovascular health of mice responds poorly to a high fat diet.
Some of the mice also received quercetin. If the animals had been adult humans, they would have received roughly 100 milligrams of quercetin per day. Mice in a control group received carboxymethyl cellulose sodium [CMCNa].
For decades, cardiologists have thought that reducing the amount of cholesterol in the body keeps blood vessels healthy, but that idea has proven too simple. We'll talk about that some other time.
The Chinese injected their mice with macrophages that had already absorbed a lot of cholesterol. The cholesterol was labeled so the researchers could track it.
The Chinese also found less malondialdehyde [MDA], a biomarker for the activity of free radicals, in the mice of the quercetin group. Quercetin apparently reduced free radical activity. This may also explain why the researchers found less oxidized phospholipids [bottom right] in the quercetin mice.
Phospholipids are essential components of HDL. The less oxidized phospholipids there are in HDL, the better HDL functions.
In test tubes, quercetin increased the production of transport proteins such as ABCA1 and ABCG1 in macrophages. Those proteins pump cholesterol out of the immune cell, after which the body can dispose of it.