Diets high in flavonoid-rich cocoa powder and dark chocolate have a favourable effect on LDL ("bad" cholesterol) when compared with diets that limit or exclude other flavonoid sources such as tea, coffee, wine and onions, US researchers reveal this week.
Scientists at Penn State led by Dr. Penny Kris-Etherton , evaluated and compared LDL (low density lipoprotein) susceptibility to oxidation when the test subjects, 23 men and women, ate an average American diet purposely low in flavonoids and a diet that contained about one and a quarter oz (38 grams) of cocoa powder and dark chocolate which are rich flavonoid sources.
Oxidation of LDLs is thought to play an important role in the development of atherosclerosis or hardening of the arteries. Increasing LDL's resistance to oxidation is thought to possibly delay the progression of the disease. Flavonoids, which are present in a wide variety of plants, have long been known to inhibit LDL oxidation.
The study is detailed in a paper, "Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentration in humans" published in the November issue of the American Journal of Clinical Nutrition.
In the study, 10 men and 13 women, aged 21 to 62, ate one of two experimental diets, either an average American diet altered to be low in flavonoids or a diet containing about three quarters of an ounce (22 grams) of cocoa powder and a half ounce (16 grams of dark chocolate) for four weeks. After a two-week break in which the participants ate their habitual diet, they switched for another four weeks to the experimental diet they hadn't consumed during the first four-week period.
Both experimental diets contained the same amount of caffeine and theobromine, which are stimulants found in chocolate and cocoa. Cocoa butter was used in baked goods in the average American diet to match the amount of cocoa butter in the dark chocolate.
Subjects had blood drawn at the end of each diet period. The LDL was extracted from each blood sample and then subjected to oxidation in the laboratory. The researchers noted the amount of time it took for oxidation to begin, the rate at which oxidation proceeded and the amount of oxidized fatty acid produced.
When the subjects ate the cocoa and chocolate containing diet, oxidation occurred about 8 per cent slower compared to when they ate the experimental average American diet.
Analysis of their blood plasma also showed that total antioxidant capacity was four per cent greater after the cocoa and chocolate containing diet. HDL cholesterol (the "good" cholesterol) was four per cent higher after the chocolate diet than after the average American diet.
The paper notes, "The incorporation of dark chocolate and cocoa powder into the diet is one means of effectively increasing antioxidant intake. Furthermore, the inclusion of dark chocolate and cocoa powder in a diet that is rich in other food sources of antioxidants, such as fruit, vegetables, tea and wine, results in a high antioxidant intake and may consequently reduce the risk of cardiovascular disease."