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09.12.2008

Cup of coffee good for cholesterol levels

Large amounts of coffee are not good for the heart and blood vessels, but drinking just a couple of cups a day reduces the risk of cardiovascular disease. Epidemiologists have known this for a few years. But how moderate coffee intake protects the heart was not known. Until now.

Study
The relationship between coffee and cardiovascular disease is represented by a J-curve. The graph below is from a Finnish study published in 2004. [J Nutr. 2004 Sep;134(9):2381-6.] It shows the relationship between coffee consumption and the number of cases of heart attacks in middle-aged men.

The researchers monitored two thousand men for five years.

Results
As the graph shows, a coffee intake of six hundred millilitres per day has a protective effect. How this works is explained in a Swiss study published recently in the American Journal of Clinical Nutrition. In that study the researchers gave ten test subjects a cup of coffee early in the morning and then took blood samples. The Finns then exposed the 'bad cholesterol' LDL in the samples to copper ions. These oxidize LDL. Oxidized LDL is pretty bad for the blood vessels.

The researchers observed that, after drinking coffee, the LDL in the test subjects was protected against oxidation. At least, it took longer for the LDL to be oxidized.

Immediately after drinking the coffee nothing happens - but the LDL in a sample taken half an hour after drinking coffee oxidizes more slowly. And the LDL in a sample taken an hour after intake oxidizes even more slowly.

Mechanism
When the researchers analyzed the LDL they saw why. After drinking the coffee, phenols in the coffee like ferulic acid and the related chlorogenic acid embedded themselves in the LDL. These compounds prevent the LDL from being oxidized.

And it's not only the phenols in coffee that are incorporated into LDL. "Incorporation into LDL was already shown for only a few other phenolic compounds", the researchers write. They are referring to "quercetin and catechin, daidzein and genistein, rutin and quercetin, and tyrosol." These substances are found in green tea, soya and olive oil.

Sponsor
By the way, the research was financed – you guessed it – by the food industry. In this case by institutes with scientific sounding names funded by the sector, such as the Institute for Scientific Information on Coffee and the Physiological Effects of Coffee Committee.

Sources:
Am J Clin Nutr. 2007 Sep;86(3):604-9.