In a placebo controlled trial of 6 weeks duration the consumption of dark chocolate had no beneficial effects on neuropsychological (e.g. memory, concentration) or cardiovascular (e.g. blood pressure, lipid levels) health related variables.
At least not when your healthy, well educated and above 60 (see the limitations).
Chocolate and cocoa products may promote cardiovascular and neurocognitive health and provide cardioprotective effects:
- chocolate and cocoa-related products have been shown to decrease or inhibit both LDL oxidation and platelet activation or function
- to enhance serum lipid profiles
- to lower blood pressure
- to promote vascular relaxation or dilation
- to inhibit free radicals
- cocoa flavanols or procyanidins may possess immunoregulatory effects and may help to modulate immune responses
- flavanol-rich cocoa can increase cerebral blood flow in healthy elderly subjects, as measured by transcranial Doppler ultrasound
What they did was select a sample of healthy adults above 60 yers of age (see the figure above). And they were extremely healthy. They had to stop eating regular chocolate at least a week before the trial. They used flavanoid- and procyanidin-rich dark chocolate bars and artificial sweetened cocoa beverage, as well as low-polyphenol placebos of identical taste and appearance.
The findings from this double-blind, placebo-controlled, randomized, clinical trial failed to support the predicted beneficial effects of short-term (6 wk) consumption of dark chocolate and cocoa on any of the neuropsychological, hematologic, or physiologic variables included in the investigation. The null neuropsychological and mental energy findings were in contrast to past research involving laboratory animals and humans that has shown the beneficial neuronal, neurocognitive, and neuroprotective effects of herbal compounds that are rich in antioxidants and phytochemicals.
Well this as a shock to me, so let's look at the limitations of this study.
- They surely used a to short period for their results, 6 weeks of chocolate is nothing
- The relatively high mean levels of education (>15 y) of subjects in this study may have negatively affected the results. Specifically, higher levels of education, as compared with lower levels, have been associated with greater cognitive reserve and enhanced neuropsychological test performances.
- They used a sample of healthy participants whose mean baseline serum HDL- and VLDL cholesterol, triacylglycerol, and ultrasensitive CRP concentrations fell within the "normal" reference ranges. Thus, it is possible that participants' baseline hematologic values were not elevated (or abnormal) to the degree necessary for the effects of short-term dark chocolate and cocoa to be observed
- The sample size of the current trial may not have been of sufficient magnitude
- The low quantity of dark chocolate and cocoa products consumed by participants in the present trial also may have contributed to the overall null findings
- Since the participants were so healthy it is possible that participants from both treatment groups continued to consume a diversity of other fruit and vegetables containing antioxidants or phytochemicals (or both), which may have confounded the current results to some extent
So I welcome their suggestion for future research.
Also needed are longitudinal trials that involve the consumption of dark chocolate and cocoa over extended periods (ie, several months to ≥1 y) and that result in the consumption of larger quantities of such products, which will likely promote more potent antioxidant and phytochemical effects.
Moreover participants of all kinds of health status should be included.
Related posts on this blog.
Crews, D.W. (2008). A double-blind, placebo-controlled, randomized trial of the effects of dark chocolate and cocoa on variables associated with neuropsychological functioning and cardiovascular health: clinical findings from a sample of healthy, cognitively intact older adults.. American Journal of Clinical Nutrition, 87(4), 872-880.