What effect do trans fatty acids have on cholesterol levels?

Trans fatty acids are known to have a significant negative impact on cholesterol levels by decreasing high-density lipoprotein (HDL, often referred to as "good" cholesterol) while increasing low-density lipoprotein (LDL, known as "bad" cholesterol). This combination can elevate the risk of cardiovascular diseases.

When trans fats are consumed, they are metabolized by the body in a way that disrupts the normal balance of lipoproteins that carry cholesterol. Increased levels of LDL can lead to the buildup of cholesterol in the walls of arteries, contributing to atherosclerosis, which is the hardening and narrowing of the arteries. At the same time, reducing HDL diminishes the body's ability to clear excess cholesterol from the bloodstream, further compounding the risk.

Thus, the answer that states trans fatty acids decrease HDL and increase LDL accurately reflects the adverse effects these fats have on cholesterol levels and overall heart health.