- Cocoa (Theobroma cacao)
- Blood Pressure
- itric Oxide Production
Re: Dark Chocolate Increases Nitric Oxide Levels and Decreases Blood Pressure in Prehypertensive Subjects
V, Sukmaniah S, Siregar P. Effect of dark chocolate on nitric oxide serum
levels and blood pressure in prehypertension subjects. Acta Med Indones. October 2011;43(4):224-228.
a risk factor for coronary heart disease and stroke, is defined as a systolic
blood pressure between 120 and 139 mm Hg or diastolic blood pressure between 80
and 89 mm Hg.1, 2 According to these authors from the University of
Indonesia, the mean blood pressure in Indonesians aged 25 to 34 years is
124.7/79.9 mm Hg. Risk factors for hypertension are obesity, age, high intake
of energy and sodium, a low level of physical activity, and alcohol intake.
Vascular disorders in prehypertensive patients are influenced by, among other
factors, a decrease in synthesis and bioavailability of nitric oxide (NO)
leading to endothelial dysfunction.3 Flavanols reportedly can
activate endothelial nitric oxide synthase, which increases synthesis and
bioavailability of NO and in turn restores endothelial function. Dark chocolate
(Theobroma cacao) is a major source
of flavanols. These authors conducted a parallel, randomized clinical trial to
investigate the effects of dark chocolate on NOx serum levels and blood
pressure in individuals with prehypertension. NOx serum levels are the sum of
nitrite and nitrate levels as the metabolite of NO. Investigators estimate NO
production by measuring NOx levels.
male and female employees of a dental faculty and a private company were
recruited and divided into 2 groups of 16 each. Exclusion criteria included those
with a history of hypertension; smokers; those who consumed red wine or alcohol;
pregnant or breast feeding women; menopausal women; those who used antihypertension
drugs; and those who took vitamin C, vitamin E, or other antioxidant
supplements. Data are reported on 30 of the subjects (14 in the treatment group
and 16 in the control group). The treatment group received 30 grams of dark
chocolate daily (containing 70% cocoa; no other data on the source given) and
dietary counseling. Those in the placebo group received 25 grams of white
chocolate daily (no data on the source given) and dietary counseling. The study
lasted 15 days.
subjects were aged 25 to 44 years, prehypertensive, and had a body mass index
(BMI) of 18.5 to 24.9 kg/m2. The characteristics of the members of
the 2 groups were similar, except that the treatment group was more physically
active than the placebo group.
intake data were obtained to determine energy, sodium, and polyphenol intake.
The subjects were asked to fast overnight for 10 to 12 hours before having
blood samples drawn to measure NOx serum levels.
baseline, on treatment day 8, and after treatment, blood pressure was measured for
all subjects. Mean intakes of energy and sodium were not significantly
different between the 2 groups. The polyphenol intake of the treatment group
during weeks 1 and 2 were significantly higher than those of the placebo group.
After 15 days, the NOx serum levels in the treatment group increased
significantly compared to baseline (P=0.001), while the same levels in the
placebo group decreased significantly compared to baseline (P=0.001). The intergroup difference was also
significant (P<0.001), with the treatment group being 4-fold higher than the
control after 15 days. After 15 days, the systolic blood pressure decreased by
an average of 8 mm Hg compared to baseline (significant, but P value not fully
reported). The difference in systolic blood pressure between the groups was significant
(P=0.001), while the difference in diastolic blood pressure was not
authors report a strong negative correlation between the changes in NOx serum
levels and the changes in systolic blood pressure, while there was a significantly
moderate negative correlation for the changes in diastolic blood pressure. The
authors cite a study4 confirming that increased NOx serum levels
increase vasodilation, which in turn decreases blood pressure.
to the authors, this study was limited by the difficulty in blinding between
the dark and white chocolate, although they claim that it was minimized by
placing the chocolates in boxes of the same shape and color.
authors conclude that in prehypertensive subjects, the consumption of 30 grams
of dark chocolate with 70% cocoa daily for 15 days increased NOx serum levels. Systolic
blood pressure was significantly decreased in those who consumed the dark
chocolate; however, the decrease in diastolic blood pressure was not significant.
There were a number of limitations to the study, including insufficient
blinding and use of a food database lacking in many of the locally eaten foods.
The reporting in this paper was also of poor quality with errors in data
interpretation, omissions of critical information about the study design, and
misreporting of statistics. The authors mention the importance of flavanols,
but yet no testing was done on the dark chocolate to evaluate the flavanol
level. The use of a list of polyphenol content is not enough.
1Chobanian AV, Bakris
GL, Black HR, et al. The seventh report of the Joint National Committee on
Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The
JNC 7 Report. JAMA. 2003;289(19):2560-2572.
2Lim S. Recent update
in the management of hypertension. Acta
Med Indones. 2007;39(4):186-191.
3Foëx P, Sear JW.
Hypertension: pathophysiology and treatment. Continuing Education in Anaesthesia, Critical Care & Pain.
4Hall WL, Formanuik
NL, Harnpanich D, et al. A meal enriched with soy isoflavones increases nitric
oxide-mediated vasodilation in healthy postmenopausal women. J Nutr. 2008;138(7):1288-1292.