Coffee is a beverage enjoyed globally, but its impact on cholesterol levels varies greatly depending on how it is prepared. The consumption of unfiltered coffee has been consistently linked to an increase in serum cholesterol. Unfiltered coffee refers to any brewing method where the water and ground coffee are not separated by a fine paper filter, allowing natural oily substances to pass through into the final cup. This difference in preparation method, rather than the coffee bean itself, determines whether your daily brew influences cardiovascular health.
Identifying Cafestol and Kahweol
The components responsible for the rise in cholesterol are two naturally occurring oily molecules found in coffee beans called diterpenes: cafestol and kahweol. These compounds are part of the lipid fraction of the coffee bean and are released when hot water interacts with the grounds. Cafestol is considered the more potent of the two, often described as one of the most effective cholesterol-elevating compounds known in the human diet.
The presence of these diterpenes is inherent to the coffee bean, existing in both regular and decaffeinated varieties. Their concentration is relatively high, especially in Arabica beans. When coffee is brewed, the oily diterpenes are physically trapped and absorbed by materials like paper filters.
Diterpene Levels in Different Brews
The concentration of diterpenes in a finished cup of coffee depends almost entirely on the brewing method used. Methods that bypass a paper filter allow these oily compounds to pass into the drink, resulting in high-diterpene coffee. Scandinavian boiled coffee and Turkish or Greek coffee, where the grounds are boiled with the water, contain the highest amounts. A single cup of these brews can contain several milligrams of cafestol.
The French press, or cafetière, is another popular method that leaves high diterpene levels because its mesh filter is not fine enough to trap the oily substances. Espresso, while unfiltered, contains intermediate amounts of diterpenes due to the smaller serving size and shorter contact time. In contrast, drip coffee or pour-over methods that use a paper filter contain negligible amounts of cafestol and kahweol, as the paper acts as a highly effective filter. Instant coffee is also low in diterpenes because it is filtered during its manufacturing process.
Biological Mechanism of Cholesterol Elevation
The increase in cholesterol is not caused by the diterpenes acting as cholesterol themselves, but by their interference with the body’s natural cholesterol regulation system in the liver. Cafestol and kahweol directly impact the metabolism of cholesterol, primarily by altering the expression of certain liver enzymes and genes. Specifically, cafestol has been shown to suppress the synthesis of bile acids by downregulating the enzyme cholesterol 7α-hydroxylase (CYP7A1).
Bile acids are compounds the liver produces from cholesterol, which are then used to aid digestion. When cafestol inhibits the production of bile acids, the liver senses a need for more cholesterol to maintain its supply. This signals the liver to produce more low-density lipoprotein (LDL) cholesterol, often called “bad” cholesterol, leading to higher concentrations in the bloodstream. This effect is significant; regular consumption of unfiltered coffee has been shown in studies to increase LDL cholesterol levels by 9 to 14%. The diterpenes also appear to affect the activity of LDL receptors, which are responsible for clearing cholesterol from the blood, further contributing to the buildup of LDL.
Recommendations for Moderation and Risk
The risk associated with unfiltered coffee is dose-dependent; the more you drink, the greater the effect on your cholesterol levels. Individuals dealing with high cholesterol, heart disease, or a genetic predisposition for high lipid levels should be the most cautious. For these individuals, a simple switch to paper-filtered coffee, such as a drip machine or pour-over, is the most effective mitigation strategy.
Studies suggest that consuming five to six cups of French press coffee daily can raise serum cholesterol substantially over time. While moderate consumption of espresso is less concerning due to its smaller volume, high daily intake of any unfiltered method should be reconsidered. By choosing a paper filter, you can still enjoy the flavor and other beneficial compounds of coffee while eliminating the vast majority of the cholesterol-raising diterpenes.