by Craig Weatherby
The conventional “lipid hypothesis” of cardiovascular disease blames that killer condition on excess consumption of cholesterol and saturated fat.
We’ve reported on deep flaws in this theory, which drives the sales of cholesterol-lowering statin drugs like Lipitor (Search our newsletter archive for “cholesterol”).
But the “lipid hypothesis” of cardiovascular disease retains considerable evidentiary support, and cannot be dismissed entirely.
So it comes as good news that the antioxidants in colorful plant foods may help enhance people’s cholesterol profiles… that is, they may reduce levels of “bad” (LDL) cholesterol and raise levels of “good” (HDL) cholesterol.
While there is a good deal of epidemiologic evidence linking higher fruit and vegetable consumption to reduced risk of cardiovascular disease and cancer, less is known about which food factors are most responsible for this apparent protective effect.
Among all the antioxidants in plants, the pigments known as anthocyanins appear to have some of the strongest beneficial impacts. (Like vitamin E and the flavanols in tea, anthocynanins belong the the beneficial polyphenol family of phytochemicals.)
Anthocynanins abound in berries, grapes, cherries, cranberries, raw cocoa (or dark chocolate made with it), and red cabbage - among other colorful fruits and vegetables - and impart blue-red-purple hues.
New findings from a small clinical trial suggest that anthocyanins exert effects that may protect heart muscle from the damage caused by free radicals
However, our story begins with the striking results of two heart studies in animals.
Animal studies sets stage for clinical trial
In 2007, Turkish researchers reported that the food-borne antioxidant called quercetin protected rats’ hearts from a loss of blood flow like that seen in cardiovascular disease (Ikizler M et al. 2007).
And last year, researchers divided rats into two groups for an eight-week study led by renowned French heart researcher Michel de Lorgeril (Toufektsian MC et al. 2008).
One group in the study was fed a corn-based diet rich in anthocyanins; the other was fed an anthocyanin-free diet that was otherwise similar in every respect.
The rodents that received an anthocyanin-rich diet had about 30 percent less damage to cardiac tissue following an artificially induced cut in blood flow… possibly because their diet produced higher levels of the internally produced antioxidant called glutathione in heart tissue.
As de Lorgeril’s team wrote, “Our findings suggest important potential health benefits of foods rich in anthocyanins... clinical intervention trials are warranted to determine if anthocyanin consumption in humans also has cardio-protective effects.”
The results of the first such clinical trial were published earlier this month… and they’re quite encouraging.
Clinical trial links food-borne antioxidants to better cholesterol profiles
Scientists from China’s Sun Yat-Sen University randomly assigned 120 middle-aged people with unhealthful blood lipid profiles to one of two groups for a 12 week trial.
In the introduction to their report, the Chinese researchers explained why they conducted it: “Anthocyanins have been shown to exert benefits on the lipid [cholesterol] profile in many animal models. Whether these molecules have similar beneficial effects in humans is currently unknown.”
During this double-blind trial, 60 participants received a daily dose of 320 mg of berry-derived anthocyanins (160mg taken twice a day), and the other 60 people got placebo pills.
After 12 weeks, HDL (“good”) cholesterol levels increased by almost 14 percent in the anthocyanin group, compared to a rise of only 2.8 percent in the placebo group.
And LDL (“bad”) cholesterol levels decreased by 13.6 percent in the anthocyanin group, compared with an increase of 0.6 percent in the placebo group.
In addition, removal of excess cholesterol from cells increased by 20 percent in the anthocyanin group, compared to only 0.2 percent in the placebo group.
How the berry antioxidants worked their wonders
Looking for an explanation for the beneficial effects of the anthocyanins, the Chinese team examined the activity of a protein called plasma cholesteryl ester transfer protein (CETP).
CETP collects triglycerides (fats) from LDL cholesterol and exchanges them for cholesteryl esters from HDL, and vice versa.
Greater CETP activity is linked to lower levels of beneficial HDL cholesterol, and is perceived as a risk factor for cardiovascular disease and target for drugs or foods that can reduce CETP activity (Ansell B, Hobbs FD 2006; Hunt JA, Lu Z 2009).
In the people taking the anthocyanin supplements, the activity of CETP fell by 6.3 percent, while CETP activity fell by only 1.1 percent in the placebo group.
Not only did this small pilot trial document clinically significant benefits in the participants, it also demonstrated that anthocyanins suppress a recognized risk factor related to cholesterol management.
Not bad for simple berries!
- Ansell B, Hobbs FD. The potential for CETP inhibition to reduce cardiovascular disease risk. Curr Med Res Opin. 2006 Dec;22(12):2467-78. Review.
- Hunt JA, Lu Z. Cholesteryl ester transfer protein (CETP) inhibitors. Curr Top Med Chem. 2009;9(5):419-27. Review.
- Ikizler M, Erkasap N, Dernek S, Kural T, Kaygisiz Z. Dietary polyphenol quercetin protects rat hearts during reperfusion: enhanced antioxidant capacity with chronic treatment. Anadolu Kardiyol Derg. 2007 Dec;7(4):404-10.
- Qin Y, Xia M, Ma J, Hao Y, Liu J, Mou H, Cao L, Ling W. Anthocyanin supplementation improves serum LDL- and HDL-cholesterol concentrations associated with the inhibition of cholesteryl ester transfer protein in dyslipidemic subjects. Am J Clin Nutr. 2009 Sep;90(3):485-92. Epub 2009 Jul 29.
- Toufektsian MC, de Lorgeril M, Nagy N, Salen P, Donati MB, Giordano L, Mock HP, Peterek S, Matros A, Petroni K, Pilu R, Rotilio D, Tonelli C, de Leiris J, Boucher F, Martin C. Chronic dietary intake of plant-derived anthocyanins protects the rat heart against ischemia-reperfusion injury. J Nutr. 2008 Apr;138(4):747-52.