Chocolate and Your Health
Can it be true? Chocolate lowers cholesterol, prevents heart attacks and improves blood pressure? Are these more “dietary supplement” claims or are they scientifically proven statements? Let’s take a closer look.
The Basis
The first indication that cocoa may have some health benefits was hinted at by the paucity of cardiovascular disease in the Kuna Indians, living on the islands off the coast of Panama. The Kuna ingest huge amounts of cocoa and have a cardiovascular mortality one ninth of native Panamanians. Even while flavoring their cocoa with salt, this holds true. When the Kuna move to the mainland and consume a western diet, however, their incidence of cardiovascular disease rises to that of the general population. This clearly points away from some genetic anomaly and straight to their cocoa-rich diet.
In addition, large population studies in both Wisconsin and Holland were trying to identify cardiovascular risk factors. Once multivariate analyses were completed, it became apparent that ingestion of cocoa or even dark chocolate was associated with a decrease in cardiovascular mortality.
Given this coarse epidemiological data, it was now time to try and isolate the active compounds derived from the fruit of the theobroma cocoa tree and put them to the test.
The Chemistry
It was thought that perhaps plant polyphenols, specifically “flavenoids” might be the compounds at work in cocoa. These chemicals are found in many fruits and vary in size and structure; the most studied being the group known as “flavanols”. While red wine contains these compounds, at a concentration of 80-300mg/l and blackberries at 130mg/kg, chocolate contains an amazing 460-610mg/kg.
When flavanols are ingested, they peak in the bloodstream after two to three hours, though there is considerable interpersonal variation in their absorption. Once in the body, there are several proposed mechanisms whereby they are thought to work. The most studied is the activation of Nitric Oxide (NO.) NO is found in tiny and fleeting concentrations in the blood vessels where its presence causes the blood vessel to relax. It inhibits white blood cell attachment and smooth muscle proliferation, both keys to the development of atherosclerotic plaques. In persons ingesting a diet rich in flavanols, urinary NO content is chronically elevated; again suggesting this may be the active role of these compounds.
Cocoa and Blood Pressure
Multiple well-designed scientific investigations have clearly shown the anti-hypertensive effects of cocoa. These studies have largely used chocolate as available in commercial preparations. While some papers used a 6g dose three times weekly for several weeks, other studies have shown an effect with one large 100g “dose.” The proposed mechanism for blood pressure reduction has usually been attributed the Nitric Oxide pathway. More recent studies have suggested another pathway may be at work as an ACE-inhibitor, one of the most prescribed classes of drugs for hypertension.
In addition to lowering blood pressure, cocoa has been seen to improve cerebral blood flow. In one study, ingestion of a cocoa based beverage was seen to increase blood flow to the gray matter for three hours as imaged by functional MRI scanning.
Cocoa and Platelets
Platelets are the tiny discs circulating in the bloodstream, which play a major role in blood clotting. Platelet activation and aggregation, while sometimes life saving, can also be life threatening. It’s the platelets clumping together that plug up the heart’s arteries causing ACS (Acute Coronary Syndrome) and heart attacks. Therapy, both acutely and chronically, is directed toward stopping the platelets from clumping together.
Experimentally, cocoa has been seen to stop platelet aggregation in young smokers. In addition, stearic acid, found in the fat of chocolate, also exerts an anti-platelet effect.
Cocoa and Blood Lipids
In the data analysis of many studies on chocolate, lipid-lowering effects have been seen. In one study, ingestion of 100g of dark chocolate daily for 14 days resulted in a 12% reduction in cholesterol levels. In another study 75g of dark chocolate daily increased HDL (good cholesterol) by 14%.
The lipid benefits of chocolate are thought to be due to the oleic and stearic acid fats present in cocoa. The authors of these studies go on to stress that chocolate processed with milk or saturated fat, like palm oil, may cancel any healthful effects.
Parting Thoughts
So there you have it: Chocolate as a Health Food. Several cautions are in order. Flavanols are very sensitive compounds. When subjected to heat, as in roasting, or alcohol, as in fermentation, their concentrations decrease dramatically. Industrial production of chocolate involves both of these processes so the flavanol content of commercial chocolate may be scant. High quality chocolate with less processing and roasting probably offers the healthiest choice with the “percent cocoa” left as a marketing tool. Future studies hope to look at specific commercial preparations and long term outcomes.
Myself? Well I’m going to design a study to see if dark chocolate, when ingested with red wine, results in a synergistic effect!
Nicholas G. Proia, M.D., F.C.C.P.
Professor of Clinical Internal Medicine
Northeast Ohio Universities College of Medicine
Founder, Brix Chocolate
Last Updated: May 27, 2010