The cocoa flavanols in dark chocolate have been credited with lowering blood pressure, increasing blood flow and improving mood and memory. Studies have suggested that they may reduce the risk of stroke and decrease insulin resistance. People respond so enthusiastically to good news about chocolate that researchers worry they may count on gobbling candy rather than eating a balanced and varied plant-based diet. With even more news this week, the experts will just need to keep on fretting.
Dark Chocolate Linked to Improvement in Vision:
Investigators now have evidence that consuming dark chocolate may improve vision within about two hours (Rabin et al, JAMA Ophthalmology, April 26, 2018). In the study, 30 healthy people participated in tests of visual acuity and contrast sensitivity starting about an hour and 45 minutes after consuming chocolate bars.
This was a randomized cross-over study, which means that half of the volunteers ate a dark chocolate bar in their first round, while the other half ate a milk chocolate bar. Then they switched.
What Chocolate Did the Volunteers Eat?
The investigators removed the wrappers from the chocolate bars (leaving the foil) and did not tell the participants which chocolate they were getting. (Wonder which chocolate the San Antonio-based scientists used? It was Trader Joe’s–72% Cacao Dark Chocolate and Crispy Rice Milk Chocolate.)
People did significantly better on their vision tests after eating the dark chocolate bar, although the improvement was not dramatic.
The investigators concluded:
“The findings reported suggest that a single dose of dark chocolate improves visibility of small, low-contrast targets within 2 hours compared with milk chocolate, but the duration of this difference and clinical relevance remains uncertain.”
Chocolate to Boost Brain Power:
Two more studies on chocolate made news this week. Both were conducted by scientists at Loma Linda University and presented at the Experimental Biology 2018 meetings.
In one study, the researchers recorded subjects’ EEG tracings (electroencephalograms) one-half hour and two hours after the volunteers consumed a 48 gram dark chocolate bar (70% organic cacao, Parliament Chocolate). They had initially recorded EEGs of the five subjects before they had eaten anything, after an overnight fast. The results showed that volunteers had a significant increase in gamma frequency electrical activity (yBA).
According to the investigators, this suggests that the chocolate:
“enhances neuroplasticity for behavioral and brain health benefits.”
Chocolate Affects the Immune System:
In the other study reported at the meetings, the Loma Linda scientists fed four volunteers a 48 gram dark chocolate bar every day for a week. They took blood at the beginning of the study, after two hours and at the end of the week and analyzed it for differentially expressed genes. Nothing much showed up in the first two hours after the first chocolate bar, but by the end of the week, 177 different genes had changed their activity. Thirty-seven had become less active, while 140 had been up-regulated. The genes with increased activity were related to immune system function, neural signaling and sensory perception.
While this research is fascinating, the scientists can’t tell us precisely what it means for immune function. The immune system is quite complicated, and the effects are not simple. Moreover, the study is small, with only four experimental subjects and one individual serving as a control (no chocolate for her!). We will have to watch for other investigations to explore this terrain more thoroughly.
You may wish to listen to our interview on the health benefits of chocolate. You might wonder, as one reader did in 2007, whether the health benefits of chocolate have been exaggerated.
Are the Health Benefits of Chocolate Being Exaggerated?
Q. A lot of press attention has been given recently to the benefits of dark chocolate for lowering blood pressure. A banner at the bottom of the television screen said that eating chocolate is as good as some blood pressure medicines.
However, in the studies from which this conclusion was drawn, the average systolic pressure was only lowered 5 points and the diastolic pressure by about 3 points.
While this is in the right direction, these numbers are hardly anything to get excited about. Why are people so enthusiastic about such limited results?
A. No one is suggesting that people eat chocolate instead of taking blood pressure medicine. You might be surprised to learn, however, that even standard blood pressure pills don’t lower blood pressure much more. A study in the Journal of the American Medical Association (Nov. 10, 2004) found the popular medications Norvasc (amlopidine) and Vasotec (enalapril) lowered systolic pressure by 5 points and diastolic by about 2.5 points.
A recent review of 35 trials confirmed that flavanol-rich chocolate and cocoa can lower blood pressure modestly (Ried et al, Cochrane Database of Systematic Reviews, April 25, 2017). The analysts point out that we need long-term trials to see whether cocoa flavanols in dark chocolate have an impact on the risk of cardiovascular events like heart attacks.