Index
This delicious food is made with roasted cocoa beans without the addition of milk.
Dark chocolate is chocolate without the addition of milk solids. Dark or dark chocolate has a more pronounced chocolate flavor than milk chocolate, as it contains no milk solids to compete with the taste of chocolate.
However, the lack of dairy additives also means that dark chocolate is more prone to a dry, chalky texture and a bitter taste.
While the flavanol content in cocoa can improve certain health markers, such as blood flow, it is still too early to say what effects it might have on visual performance.
A new study in healthy young adults reports significant improvements in short-term visual performance eating dark chocolate compared to milk chocolate.
These results are ploy for tabloid headlines, so we’ve carefully studied the subject to give you a quick, ad-free analysis.
How does the study was realized?
This was a randomized, single-mask crossover study of 30 healthy young adults (age ≈26) who had 20/20 vision in each eye and no history of eye disease.
All participants were tested with milk and dark chocolate, but the sessions were separated by a minimum of 72 hours.
On the test days, the subjects consumed 47 g of 72% dark chocolate (316 mg of flavanols) or 40 g of a serving of milk chocolate (12.4 mg of flavanols) followed by a round of visual acuity tests in 2 hours eating the chocolate.
Visual performance was assessed using three tests specified below:
- High contrast visual acuity.
- Small print contrast sensitivity.
- Contrast sensitivity of large letters.
What were the results of this study?
All 30 participants completed all the test rounds. Significant improvements were only seen in small print contrast sensitivity. Neither high contrast visual acuity nor large print contrast sensitivity improved significantly.
The authors speculated that the observed improvements could be due to cocoa flavanols increasing the “retina, visual pathway and / or cerebral blood flow, improving the bioavailability of oxygen and nutrients to metabolically active sites.”
The implications of the study
While it is well documented that cocoa flavanols can improve blood flow, only one other trial has evaluated their effects on visual performance in healthy subjects.
In that trial, subjects who consumed an acute dose of cocoa flavanol of 720 mg showed improvement in some visual test measures 2 hours after ingestion.
However, flavonoids have shown promise for improving vision function in those with glaucoma or ocular hypertension.
There are some limitations to note in this study. Mainly, the flavanol content of the chocolates used was not directly measured. The 72% flavanol content of dark chocolate was assumed based on a previous analysis.
It is not clear how the flavanol content of milk chocolate was obtained.
Quantifying the flavanol content is very important because not all chocolate is processed in a way that preserves flavonoids. Alkali-treated (also known as Dutch), high-temperature roasted, or fermented cocoa can have very low flavanol concentrations.
Shorter roasting and fermenting durations can help make up for this loss, however. Simply buying dark chocolate does not guarantee that it has appreciable amounts of flavonoids.
Cocoa percentage is also not a reliable indicator of flavanol content. Additionally, cocoa flavanol concentrations can vary from batch to batch depending on growing conditions. Therefore, the actual flavanol intake of the study participants is uncertain.
It is not known if the vision improvements seen in this trial will last beyond 2 hours, if long-term cocoa flavonoid intake would have a clinically relevant impact on vision, or if the same improvements would be seen in people. with poor vision or eye diseases.
The results of this study should be viewed as very preliminary. Much more research is needed before safe conclusions can be made about cocoa flavanols and visual performance.
It’s too early for the headlines “eating dark chocolate improves eyesight.” There was some improvement in small print contrast sensitivity, but that was only measured within two hours of eating chocolate. Much more research needs to be done in this area.
