Newsletter #136: Good Sleep and Cocoa Flavanols for a Better Brain?
Welcome to the latest edition of the humanOS newsletter!
This week, we got some insight into how aspects of sleep affect brain function, especially as we age, as well as how certain plant-derived compounds can enhance blood flow to the brain and boost cognitive performance.
Scroll down to learn more 👇
This Week’s Research Highlights
😴 Aspects of sleep change with age and some of these features are linked to cognitive performance.
Researchers analyzed data on sleep neurophysiology from two cohorts of older adults (n = 3819). In addition, the participants completed various tests of cognitive function, processing speed, working memory, attention, and psychomotor ability. Out of more than 150 objective sleep metrics, the researchers identified 23 metrics that were linked with measures of cognitive performance. For instance, greater duration of REM sleep was associated with better cognitive performance, as was higher sleep efficiency (meaning more of your time spent in bed is spent asleep). Unsurprisingly, many of these measures appeared to be influenced by age, as we have discussed previously on the podcast. Further analysis of the datasets revealed that older individuals who had sleep metrics that are more similar to that of younger people also tended to have better cognitive performance. Furthermore, older people with more youthful sleep patterns also had a lower incidence of diabetes and hypertension, when compared to similarly aged peers whose sleep metrics more closely reflected their age.
🧠 Differences in sleep habits are associated with differences in brain structure, which in turn are related to cognitive performance.
Researchers assessed data on cognitive function, as well as sleep quality and duration, from 1065 healthy young adults. The participants also underwent diffusion tensor imaging, which provides imaging and analysis of white matter integrity. After examining the brain scans, the researchers found that shorter sleep duration was associated with decreased white matter integrity in a fiber tract known as the superior longitudinal fasciculus (SLF), which is thought to be important for working memory and language processing. Furthermore, alterations in white matter microstructure in the SLF, impacted by short sleep duration, were in turn linked to poorer cognitive scores. Curiously, unusually long sleep duration was also associated with worse cognitive performance, though underlying mechanisms are unclear.
🍫 Cocoa flavanols boost brain oxygenation and aspects of cognition in healthy adults.
Researchers recruited 18 healthy participants and tested them in two different conditions: one in which they received flavanol-rich cocoa (total flavanols = 681 mg), and another in which they consumed a processed form of coca with negligible amounts of flavanols. Two hours after consuming the cocoa, the participants breathed air with 5% carbon dioxide - around 100 times as much as we normally experience - resulting in a state known as hypercapnia.
This is a standard procedure to challenge brain vasculature, and normally elicits an increase in blood flow to the brain to help clear the CO2. The researchers used non-invasive near-infrared spectroscopy to track changes in brain oxygenation levels and had the participants complete a series of cognitive tests. The scientists found that participants consuming the flavanols exhibited more efficient tissue oxygenation in the frontal cortex, a part of the brain that is important in planning and decision-making. Levels of maximal oxygenation were more than three times higher when the subjects consumed the flavanol-enriched beverage, and the oxygenation response was about a minute faster. This was accompanied by better performance on the most challenging cognitive tests, correctly solving these problems 11% faster than at baseline or while drinking the flavanol-depleted cocoa. There was no difference in performance for the easier tests.
Question of the Week
The holidays can be pretty stressful (even in a non-pandemic year). What are you grateful for right now?
Podcasts We Loved This Week
- James Hamblin & Katherine Wells: Misinformation Mailbag - How do you talk with a loved one who believes pandemic conspiracy theories? Via Social Distance.
- Alan Flanagan: Public Health Policy vs. Personal Responsibility - Evidence vs. Ideology. Via Sigma Nutrition Radio.
Products We Are Enjoying
Terrasoul Superfoods cacao nibs
If you are looking for a good source of cocoa flavanols, this is a pretty efficient way to get them. So why this brand in particular? The reason has to do with a fundamental characteristic of cacao. The leaves and beans are naturally prone to accumulating heavy metals from the soil, particularly cadmium, which is potentially problematic. This process probably isn’t fully preventable, but it can be monitored. That’s what I like about Terrasoul - their third-party lab test for heavy metals in their products. And if you want to know a little more about the benefits associated with chocolate, check out these blogs addressing how cocoa flavanols can improve exercise performance, and how dark chocolate boosts cognition. 👀