A mere six grams a day of dark chocolate can help reduce high blood pressure in older men and women. The thirty milligrams of polyphenols contained in this amount of chocolate helps lower their blood pressure, researchers at the university hospital in Cologne, Germany discovered.
The researchers gave forty test subjects six grams of dark chocolate daily for eighteen weeks. During the period the subjects’ systolic blood pressure decreased by three mm Hg. The diastolic blood pressure decreased by two mm Hg. The test subjects did not put on weight.
The researchers measured the concentration of polyphenols in the subjects’ blood after eating the chocolate. The results are shown below.
The researchers suspect that the polyphenols led to an increase in the production of nitric oxide [NO] in the blood vessels. This helps dilate the blood vessels and as a result blood pressure goes down. To test this theory they measured the amount of the enzyme S-nitrosoglutathione in the test subjects’ blood. This enzyme is a marker for the concentration of NO.
The graph below shows the effect of the chocolate on the enzyme level in the test subjects.
The graph below shows the effect on the levels of the same enzyme immediately after the chocolate was consumed.
This study is not just of interest to health maniacs. It is also of interest to weight trainers. NO is a factor in hypertrophy.
Anabolic supplements designed to increase NO production are already popular. Most of them contain the amino acid L-arginine or L-citrulline. Arginine supplements also reduce the loss of muscle mass during weight reduction. It may be that the polyphenols in cocoa strengthen the effect of these products.
Effects of Low Habitual Cocoa Intake on Blood Pressure and Bioactive Nitric Oxide
Context Regular intake of cocoa-containing foods is linked to lower cardiovascular mortality in observational studies. Short-term interventions of at most 2 weeks indicate that high doses of cocoa can improve endothelial function and reduce blood pressure (BP) due to the action of the cocoa polyphenols, but the clinical effect of low habitual cocoa intake on BP and the underlying BP-lowering mechanisms are unclear.
Objective To determine effects of low doses of polyphenol-rich dark chocolate on BP.
Design, Setting, and Participants Randomized, controlled, investigator-blinded, parallel-group trial involving 44 adults aged 56 through 73 years (24 women, 20 men) with untreated upper-range prehypertension or stage 1 hypertension without concomitant risk factors. The trial was conducted at a primary care clinic in Germany between January 2005 and December 2006.
Intervention Participants were randomly assigned to receive for 18 weeks either 6.3 g (30 kcal) per day of dark chocolate containing 30 mg of polyphenols or matching polyphenol-free white chocolate.
Main Outcome Measures Primary outcome measure was the change in BP after 18 weeks. Secondary outcome measures were changes in plasma markers of vasodilative nitric oxide (S-nitrosoglutathione) and oxidative stress (8-isoprostane), and bioavailability of cocoa polyphenols.
From baseline to 18 weeks, dark chocolate intake reduced mean (SD) systolic BP by ?2.9 (1.6) mm Hg (P < .001) and diastolic BP by ?1.9 (1.0) mm Hg (P < .001) without changes in body weight, plasma levels of lipids, glucose, and 8-isoprostane. Hypertension prevalence declined from 86% to 68%. The BP decrease was accompanied by a sustained increase of S-nitrosoglutathione by 0.23 (0.12) nmol/L (P < .001), and a dark chocolate dose resulted in the appearance of cocoa phenols in plasma. White chocolate intake caused no changes in BP or plasma biomarkers.
Data in this relatively small sample of otherwise healthy individuals with above-optimal BP indicate that inclusion of small amounts of polyphenol-rich dark chocolate as part of a usual diet efficiently reduced BP and improved formation of vasodilative nitric oxide.