Olive-Oil-Enriched Dark Chocolate May Improve Endothelial Function

Marlene Busko

September 07, 2017

BARCELONA, SPAIN — Eating a small bar of dark chocolate containing olive oil every day may improve endothelial function, a small, randomized crossover study suggests[1].

Results showed that when 26 middle-aged adults with at least three cardiovascular risk factors ate a 40-g bar of dark chocolate enriched with extra virgin olive oil every day for a month, their levels of endothelial progenitor cells—important for vascular repair and reduced in people with cardiovascular risk factors—improved.  

"These results, in our opinion, can motivate people to be more indulgent in a small piece of dark chocolate daily, which has at least 70% cocoa, and which may help longevity," Dr Rossella Di Stefano (University of Pisa, Italy) told a press conference here at the European Society of Cardiology (ESC) 2017 Congress.

The same beneficial effects were not seen when the study participants ate dark chocolate that had been enriched with red apple, although the authors speculate this may have been because the concentration of added apple was insufficient.

A paper published in the New England Journal of Medicine[2] has shown that endothelial progenitor cells "can repair endothelium and are lowered by cardiovascular risk factors," Di Stefano told theheart.org | Medscape Cardiology. "We can improve this with statins, for example, but we can also improve this with chocolate."

The study participants found that the olive-oil–enriched chocolate tasted good, and there are some versions that are commercially available.

"The idea is very interesting," but this is a preliminary study, session co–chair Dr Joep Perk (Linnaeus University, Kalmar, Sweden), who was not involved with this research, told theheart.org | Medscape Cardiology.

"This is the first step," he cautioned. "We'll need a much longer observation period and much larger groups of patients" before widely recommending this. "But it is a door opener, and I hope people will go through that door."

Cocoa, Olive Oil, Dried Apple, and Endothelial Cells

Several Dutch and Swedish cohort studies and epidemiologic studies such as those in Kuna Indians—who consume a lot of cocoa and don't have hypertension or cardiovascular disease—have linked cocoa with cardiovascular protection related to its polyphenol content, said Di Stefano.

A small piece of dark chocolate contains as much polyphenol as two glasses of red wine or one cup of green tea, she noted, and olive oil and apples also contain polyphenols.

For this analysis, then, the researchers aimed to examine the effects of eating dark chocolate enriched with olive oil or dried apples on endothelial progenitor cells and metabolites related to cardiovascular risk.

They investigated this in 14 men and 12 women living in Tuscany who had a mean age of 51, a mean body mass index of 29 kg/m2, and at least three cardiovascular risk factors.

Most study participants were overweight (20 patients) or had a family history of CAD (19), followed by dyslipidemia (15), hypertension (14), and active smoking (nine).

After a 2-week washout, the participants were randomized to eat a 40-g bar of dark chocolate that contained either 10% extra virgin olive oil or 2.5% dried apples, every day for 4 weeks.

After another 2-week washout, the participants ate the other type of supplemented chocolate bar, every day for another 4 weeks.

At the end of the month where they ate the olive-oil–enriched dark chocolate, the participants had no significant changes in glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, or diastolic or systolic blood pressure.

However, flow cytometry showed that their levels of circulating CD133+/KDR+/CD34+ antigens, a surrogate for endothelial progenitor cells, increased.

In addition, proton nuclear magnetic resonance (1H-NMR) assays of urine samples showed improvement in levels of two of four metabolites that are increased in people with cardiovascular risk factors.

That is, mean levels of carnitine and 2-hydroxyhyppurate decreased by 14.5% and 22%, respectively, although mean levels of L-tyrosine and phenylalanine did not decrease.

In contrast, after a month of eating dark chocolate enriched with dried apples, the participants' mean LDL cholesterol levels increased from 132 to 142 mg/dL (P=0.03), and there were no significant changes in endothelial progenitor cells or biochemical markers.

The improved endothelial function seen with the olive-oil–enriched dark chocolate is probably due to the additive effect of the polyphenols in olive oil and cocoa, the researchers suggest.

This Toscolata trial was supported by the Tuscany Region. The authors have no relevant financial relationships.

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