A bar of dark chocolate may be more than just a tasty indulgence. According to a review of studies, eating certain types of cocoa products, including dark chocolate, can lead to a small but potentially meaningful drop in blood pressure.
High blood pressure is a leading cause of heart and circulation problems, accounting for more than 1 in 3 deaths from heart disease in the UK and other Western countries.
If you have high blood pressure, medicines can help lower it, as can lifestyle changes such as losing weight, exercising, and eating less salt. Researchers have suggested that regularly consuming chocolate with high amounts of flavanols - a type of plant chemical - might also make a difference.
Flavanols are thought to help lower blood pressure by boosting the amount of nitric oxide in the body. Nitric oxide helps relax and widen the blood vessel walls, which lowers the pressure on them. The amount of flavanols in cocoa products varies widely but, in general, dark chocolate contains higher amounts than milk chocolate.
Several small studies have looked at a possible link between flavanol-rich chocolate and blood pressure. Researchers have now pooled the results of the best studies to see what conclusions they might draw.
In total, they looked at 20 studies with 856 mostly healthy people. The participants in each study were randomly assigned to consume either a flavanol-rich cocoa product (such as dark chocolate, or cocoa powder mixed with milk or water), or a ‘dummy’ treatment (a placebo). The placebos used in the studies included chocolate that contained only low levels of flavanols, and milk or water without cocoa powder. Most of the studies lasted between two and eight weeks.
People in the flavanol group had a small but significant drop in their blood pressure. On average, their blood pressure readings were 2 to 3 mm Hg lower than those in the placebo group (mm Hg is short for millimetres of mercury, the measurement doctors use to measure units of pressure).
The difference was greater when researchers excluded the low-flavanol participants from the placebo group, as even low amounts of flavanols might have an effect on blood pressure. In this comparison, the average blood pressure readings in the flavanol treatment group were 3 to 4 mm Hg lower than in the placebo group.
The drop in blood pressure was also greater when the flavanol products contained only low amounts of sugar. This was particularly true for overweight and obese participants. The researchers also found a larger drop in blood pressure for younger participants than for participants aged 50 and older.
How reliable is the research?
This was a well-conducted review that included only randomised controlled trials, which are the best type of study for finding out the effects of a treatment. However, we still need more research to confirm these findings and explore several questions, such as who might benefit most from flavanol-rich cocoa products, how much flavanols people should ideally consume in a day, and whether long-term use of these products might lower the risk of heart disease. We also don’t know if the potential benefits might be outweighed by the risk of weight gain.
What does this mean for me?
Although the average drop in blood pressure in the flavanol group was small, even slight improvements have the potential to make a difference in the risk of heart disease. However, it’s too soon to recommend eating chocolate as a way to lower your blood pressure. But these findings might give you reason to savour your next dark chocolate bar a bit more.
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