There's more evidence that flavonol-rich chocolate or other cocoa products may contribute to better health, with the latest research from Australia suggesting that the confection slightly reduced blood pressure in people with hypertension as well as those with normal blood pressure.
The Australian researchers analyzed 20 studies over the past decade involving 856 mainly healthy adults, and found "a statistically significant blood pressure reducing effect of flavonol-rich cocoa products compared with control in short-term trials of two to 18 weeks duration."
"Although we don’t yet have evidence for any sustained decrease in blood pressure, the small reduction we saw over the short term might complement other treatment options and might contribute to reducing the risk of cardiovascular disease," said Karin Ried, lead researcher of the study from the National Institute of Integrative Medicine in Melbourne.
What is blood pressure and what's considered high?
- Blood pressure is a measure of the pressure or force of blood against the walls of your blood vessels (known as arteries). The top number represents the pressure when your heart contracts and pushes blood out (systolic) and the bottom number is the lowest pressure when the heart relaxes between beats (diastolic).
- Blood pressure that is consistently more than 140/90 mm Hg when measured in the doctor’s office or 135/85 mmHg when measured at home is considered high. If you have diabetes, 140/90 mm Hg is high.
- Normal blood pressure is between 120/80 mm Hg and 129/84 mm Hg.
- If your blood pressure is between 130/85 mm Hg and 139/89 mm Hg, you have "high-normal" blood pressure, which is more likely to develop into high blood pressure.
Source: Heart and Stroke Foundation of Canada
High blood pressure (a normal level is between 120/80 mm Hg and 129/84 mm Hg) is a prime risk factor for cardiovascular disease, attributing to about half of cardiovascular events worldwide and 37 per cent of cardiovascular-related deaths in the Western world. Canada's Heart and Stroke Foundation says high blood pressure is also the No. 1 risk factor for stroke.
For the Australian analysis, published Wednesday in The Cochrane Library, the researchers searched online databases to find randomized controlled trials, which are considered the gold standard of medical research. Those trials compared people eating cocoa products with high flavonol concentrations, to people eating low-flavonol cocoa powder or foods that contained none of the plant compounds.
The researchers found that study subjects who ate flavonol-rich cocoa products daily for a few weeks experienced a blood pressure drop of about two or three points — much less than the effects of blood pressure-lowering medication, but on par with the effects of changing one's diet or taking part in regular exercise.
One downfall of the study is the researchers couldn't verify that flavonols were directly responsible for lowering blood pressure in the study participants. However, the compounds, also found in foods such as green tea, berries and red wine, are linked to the body's production of nitric oxide — which helps relax blood vessels, resulting in the lowering of blood pressure.
"We were unable to identify any randomized, controlled trials that tested the effect of long-term daily ingestion of cocoa products on blood pressure and there were no trials that measured an effect on clinical outcomes related to high blood pressure such as heart attacks or strokes," the researchers report.
'You still have to exercise'
CBC's John Northcott reported that one downside of the study is that the researchers "looked at so many different studies, and each study used a different amount of cocoa, so they're not sure what the ideal amount is.
"They do think though that[having it] every day may be a factor, and the other caveat in all this is it's still no replacement for exercise. ... you can't sit by the pool and pop chocolates all day — you still have to get exercise."
The Australian researchers say more trials — comparing the intake of low-flavonol dosages with flavonol-free controls — are needed to test whether low dosages are effective in reducing blood pressure.
In addition, longer-term trials are needed to determine if regular consumption of flavonol-rich cocoa products help people maintain good blood pressure levels and cardiovascular health over the long term, and whether there are any adverse side-effects of ingesting cocoa products on a daily basis.
The Cochrane Library study was supported by The University of Adelaide in Australia and the Australian Government Primary Health Care Research Evaluation Development (PHCRED) Program.