In this blog, Clinical Neuroscientist Miguel Toribio-Mateas discusses how certain super-concentrated sources of nutrients can help you be the most resilient version of yourself, and how both your gut and your brain are involved in the emotional responses and mental wellbeing.
Life has become really stressful, uncertain and challenging for us all as a result of the COVID-19 pandemic. Our lives have changed dramatically, and we are surrounded by blatant uncertainty and subliminal negativity. Combined, these two emotions give us that kind of funny “gut feeling” that tells us something really bad may be just round the corner. Will we lose our jobs? Will the house market crash? Will we get so annoyed with our other halves that we may end up divorcing them? We are certainly anticipating stress – a normal physiological response to the world around us – in a completely different way as a result of COVID-19, and many of us aren’t coping well with the feelings of and anxiety that this bringing out in us. So what can we do in order to optimise our stress response or, in other words, optimise our psychological resilience? When it comes to food, there are certainly some “stars of resilience” that are loaded with nutrients known to support our gut and our brain to make us more flexible, more “plastic”, less easy to be broken by the surrounding frazzled world we are living in. Here are my top picks:
Tea, including green tea and matcha
Green tea is gaining popularity throughout the world in recent years and is frequently referred to as a mood-and-brain food. Previous research has demonstrated that three constituents present in green tea, l-theanine, epigallocatechin gallate (EGCG), and caffeine, affect mood and cognitive performance.
Our research found green tea as one of the key individual sources of nutrients in the literature we reviewed. As an example, a recent randomised controlled trial of 12 people who drank green tea or an equivalent drink reported that those who actually had the green tea experienced benefits in cognitive functioning, in particular on working memory. Working memory refers to the ability to remember and use relevant information while in the middle of an activity. The effects might be driven by a combination of tea-specific antioxidants (epigallocatechin gallate or EGCG) and the amino acid L-theanine, which tend to decrease anxiety and improve response to stress1. Of particular interest is matcha green tea, ground powder of specially grown and processed green tea leaves farmed from green tea plants that are shade-grown for three to four weeks before harvest, thereby enabling higher production of theanine and caffeine.
A recent randomised, placebo-controlled, single-blind study found matcha drinkers to experience slight benefits in speed of attention and episodic memory2. But how does green tea work? How do its anti-inflammatory compounds get to the brain? You’ll be glad to know that your gut microbes are involved in this process. A systematic review of 6 human trials and 18 mechanistic studies published in the journal Trials last year, found that people who drank up to 1000 mL daily (4-5 cups) reported to increase proportions of Bifidobacterium. And it also seems that other types of tea work too, i.e. green tea gets all the compliments, but your regular Yorkshire tea cuppa may be as good as. In fact, mechanistic studies show promise suggesting that black, oolong, Pu-erh and Fuzhuan teas (microbially fermented ‘dark tea’) are able to positively influence microbial diversity and the ratio of Firmicutes to Bacteroidetes. So drinking tea (whichever type, but green tea “topping the evidence charts”) could favourably regulate your gut microbiome, helping offset the derangement triggered by typical British diets, which is great news!
So how much matcha should you drink? Literature seems to point to 3 to 4 grams of matcha per day as a sufficient quantity to support cognitive function. This is equivalent to 1 tablespoon of powder. 3-4 cups of regular black tea seem to be comparable in many respects, so if that’s your preferred drink, own it with pride!
Turmeric as a source of curcumin
BDNF stands for Brain Derived Neurotrophic Factor and affects global cognitive function, learning, and memory. In fact, when people experience low BDNF levels, this affects cognitive function, learning and memory, and also causes behavioural disorders. Several randomised controlled trials have examined the neuroprotective effects of curcumin and its ability to increase BDNF levels, with inconclusive results, but a recent systematic review of four randomised control trials with 139 participants documented how curcumin supplementation (200 to 1,820mg day) for a period of 8 to 12 weeks has the ability to improve BDNF levels3.
The bioavailability of curcumin has been studied extensively in humans and scientists know that it is poor, i.e. you need a lot of it for it to do anything substantial enough to be measurable. However, we now know that the transformation of curcumin does not occur only by enzymes produced by the enterocytes or by hepatocytes, but also by enzymes produced by the gut microbiota. When you eat turmeric, the curcumin in it provides food to support the growth of many species of the beneficial genus Bifidobacteria and Lactobacilli, feisty bugs that produce natural microbial regulators within the gut, helping you get the most of your curcumin whilst keeping your gut ecosystem in check by staving off pathogenic and opportunistic bacteria naturally4. So how much turmeric do you need? The equivalent of 1 teaspoon of turmeric powder a day, or to a couple of inches of fresh turmeric root which can be used in cooking or added to juices, smoothies or even a turmeric latte.
Antioxidants in cocoa called flavanols have been found to improve spatial memory, the part of memory responsible for the recording of information about one’s environment and spatial orientation5. In fact, cocoa flavanols influence physiological processes in ways that suggest their consumption may improve aspects of how neurones function, as reported by studies that have found positive influences of consuming cocoa products on cognitive performance.
This is great news for chocolate lovers, as confirmed by a large cross-sectional analysis undertaken on 968 participants aged 23-98 years as part of the Maine-Syracuse Longitudinal Study where researchers created associations between dietary patterns and cognitive outcomes. For people who ate chocolate frequently there was a significant association with better performance on global cognition scores, as well as on visual and spatial memory and working memory.
Cocoa flavanols are believed to work on the dentate gyrus, a part of a brain region known as the hippocampus where memories are “stored”. The dentate gyrus is thought to contribute to the formation of new episodic memories, the specific part of memory that relates to the spontaneous exploration of novel environments.
But benefits may not be limited to this area of the brain. In a randomised controlled trial of healthy 50-69-year-old people who consumed either a high or low cocoa flavanol-containing diet for 3 months, research showed that those who had higher levels of cocoa flavanols experienced improve visual search efficiency, reflected by reduced reaction time. However, cocoa flavanols did not enhance attention. This suggests that flavanols may affect some aspects of cognition, but not others6. Cocoa flavanol have also been seen to improve blood flow to the brain both at rest and after exercise (Decroix et al., 2016).
Chocolate and stress
Cortisol, known as the stress hormone, activates the limbic system or “impulsive brain” and inhibits the prefrontal cortex, the area of the brain that enables us to plan ahead, to focus and to think strategically. In a recent clinical trial 26 participants consumed 25 grams of a high flavanol dark chocolate daily or a similar amount of a control dark chocolate containing negligible flavonoids for four weeks. The people who ate the high flavanol chocolate presented with lower cortisol levels (measured in saliva, the most reliable way of doing this) compared with those who ate the regular chocolate.
Based on the evidence of cognitive benefits of cocoa flavanols, it seems a sensible recommendation to switch to a good quality dark chocolate (with a minimum 70% cocoa mass is the recommended standard) as a source of cocoa flavanols, and to eat about half a small bar (around 25g) daily as part of a healthy balanced diet.
About the author
Miguel Toribio-Mateas is a clinical neuroscientist and nutrition practitioner, currently working towards a professional doctorate in health neuroscience, using health-related quality of life outcome measures alongside biomarkers from microbiome analysis to assess the complex effects of food on cognitive function and mental health via the gut brain axis.
With many thanks to Miguel for this blog. If you have any questions regarding the health topics that have been raised, please don’t hesitate to get in touch with Amanda via e-mail or phone:
Amanda Williams and the Cytoplan Editorial Team
- Unno, K., et al., Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials. Nutrients, 2018. 10(10).
- Dietz, C., M. Dekker, and B. Piqueras-Fiszman, An intervention study on the effect of matcha tea, in drink and snack bar formats, on mood and cognitive performance. Food Res Int, 2017. 99(Pt 1): p. 72-83.
- Sarraf, P., et al., Short-term curcumin supplementation enhances serum brain-derived neurotrophic factor in adult men and women: a systematic review and dose-response meta-analysis of randomized controlled trials. Nutr Res, 2019. 69: p. 1-8.
- Di Meo, F., et al., Curcumin, Gut Microbiota, and Neuroprotection. Nutrients, 2019. 11(10): p. 2426.
- Field, D.T., C.M. Williams, and L.T. Butler, Consumption of cocoa flavanols results in an acute improvement in visual and cognitive functions. Physiol Behav, 2011. 103(3-4): p. 255-60.
- Brickman, A.M., et al., Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults. Nat Neurosci, 2014. 17(12): p. 1798-803.