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Skip to 0 minutes and 15 secondsDavid T.

Skip to 0 minutes and 15 secondsField: In this video, I'm going to talk about scientific evidence that flavonoids can influence psychological or mental functioning when added to your diet or when the level in your diet is increased. I'll actually start by mentioning one of the most striking scientific studies that I've ever come across. This is to do with the Nobel Prize. What's been found is that countries where there's a much higher level of chocolate consumption, have over the last century won far more Nobel Prizes for literature and science than those countries where less chocolate is eaten. Of course, the Nobel Prize is an indication of the human mind functioning at its most efficient in a way.

Skip to 1 minute and 14 secondsDoes this indicate to us that the flavonoids contained in chocolate can help people become geniuses if you like? If you look at what the Nobel Prize is awarded for. For avoidance of any doubt, I want to be clear that this study, while it's very eye-catching, is just presenting a correlation. The correlation doesn't tell us that one thing the chocolate consumption is causing the other, the rate of winning Nobel prizes. To move on from these correlational observations as interesting as they are, we can look at experimental studies that are being carried out in the laboratory where we can manipulate people’s diets according to how the scientists running the study chooses.

Skip to 2 minutes and 6 secondsWhat the scientists will usually do, is choose to randomly allocate a group of people to either a high flavonoid meal or a low flavonoid meal. Some studies have looked at the effect of a single high flavonoid meal on outcome variables, and others have looked at longer-term interventions spanning weeks or even months of daily high flavonoid meals compared to low flavonoid meals. What outcomes have been measured? The most frequently measured outcome is what we might call cognitive tests. These tasks look at measuring things like people's short-term memory, their ability to ignore distraction, their attention. The results of all these studies have been a mixed picture.

Skip to 2 minutes and 54 secondsThere are quite a few published studies that do show a positive effect of either a single high flavonoid meal or a series of them over days and weeks on mental performance as assessed by cognitive test batteries. There are also some that haven't found an effect. However, one thing that should be emphasized is that we don't find ever that the flavonoids have a negative effect. That's important from an ethical point of view when recommending these to people. There are no studies published finding negative effects of flavonoid. Recently, some studies have started looking at emotional and mood-based effects of high flavonoid meals instead of the more like IQ test type of situations.

Skip to 3 minutes and 50 secondsThere has been some evidence, though again the picture is a bit mixed, for the idea that mood is improved by consumption of flavonoids. There is a way of overcoming this limitation called meta-analysis, which is a way of statistically analyzing across the results of different studies in a way that allows you to do things like estimate the real effect size from a set of small studies that all produce quite different effect sizes. It also allows you to estimate the number of unpublished studies in the file drawer that have shown no effect. This meta-analysis has been carried out for those studies of flavonoids that have looked at cardiovascular reflects of flavonoids. This clearly concluded that there are real effects.

Skip to 4 minutes and 50 secondsHowever, in the year 2018, we're still waiting for that meta-analysis to be performed on those studies that look at the cognitive and other psychological outcomes of high flavonoid meal consumption. In a sense, the jury is still out.

Flavonoids effect on cognition

Can an increased flavonoid intake affect our cognitive performance?

Just as scientists are interested in the effect on bodily functions, such as blood pressure, of flavonoids, they are also interested in finding out whether mood, memory or attention can be improved by increasing our dietary intake of flavonoids.

To do so, they use batteries standardized test, administered before and after the consumption of high levels of flavonoids. The test can be quite taxing and are commonly used to measure cognitive performances in a variety of different conditions and of experimental settings.

Unfortunately, it is often the case that multiple studies carried out by different people and with different methodology do not agree on the result - that is why scientists regularly adopt a statistical technique, called meta-analysis, to reach an answer that summarizes the available evidence.

In this video we briefly discuss the state of the art of this field of research, while in the next (and last) video of the week we will present the studies that use neuroscientific techniques to assess the effect of flavonoids on the brain, rather than on cognitive functions.

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