Just one meal of saturated fat can inflame the inner lining (endothelium) of blood vessels. This reduces the vessels' ability to expand and increase blood flow. Further, the inflammation can lead to lesions or cracks between the cells in the vessel lining, which are repaired by the body using cholesterol (oversimplification). When bad cholesterol (LDL) is used for the repair, plaque buildup and arteriosclerosis can result. When good cholesterol (HDL) is used for the repair, plaque buildup is less likely.
Just one meal of high saturated fats can reduce good cholesterol (HDL) levels. Conversely, one meal of unsaturated fats can increase good cholesterol (HDL) levels.
The researchers found that three hours after eating the saturated fat meal, the endothelium, or inner lining of blood vessels, in study participants showed reduced ability to expand and increase blood flow. Six hours after the meal high in saturated fat, the "good" HDL cholesterol's protective ability to prevent inflammation was also impaired, the researchers found. Inflammation has been linked to plaque buildup in the arteries.
In contrast, six hours after eating the meal high in polyunsaturated fats, HDL’s protective effects were enhanced. The researchers found fewer inflammatory agents in the participants' arteries than they did after the saturated fat meal.
"We have a situation where consumption of a single meal containing a high level of saturated fat is associated with … impairment of a normal protective property of HDL," says Nicholls. "In contrast, consumption of a meal high in polyunsaturated fat results in HDL that is more protective."
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