The notion that bacteria living in your gut can affect your brain may seem odd. Yet a good deal of research indicates that intestinal bacteria are intimately entwined with the function of our bodies – and our brains. Scientists at Oxford University recently made an important advance in this field with a study demonstrating that consumption of prebiotics affects both emotional processing and stress hormone levels in healthy volunteers.
There are two ways to manipulate the microbes in the gut (collectively, the microbiome): by consuming live cultures of bacteria called probiotics; or by ingesting certain types of sugar molecules, known as prebiotics, that nurture growth of these bacteria. While previous research has established that probiotics can alter human brain function, similar effects of prebiotics have until now only been found in animals. The Oxford study is the first to show prebiotic effects on human behaviour.
The researchers were particularly interested in whether the prebiotics would affect emotion and stress, as much of the data on the microbiome-brain connection concerns the role gut bacteria play in stress-related disorders like anxiety and depression. Patients with these disorders may experience digestive as well as psychological symptoms, and studies in both humans and animals indicate that the number and type of bacteria in the gut influence anxiety levels. Probiotics appear to lower anxiety in humans, so the Oxford team set out to investigate whether prebiotics do the same.
To do so, they recruited healthy volunteers to take one of two types of prebiotic, or a placebo, each morning for three weeks. At the end of this period, the volunteers completed a series of tasks designed to test emotional processing. One of these tasks turned up a positive result: volunteers who took a prebiotic called B-GOS paid less attention to negative words, and more attention to positive ones, than those taking placebo. Volunteers taking B-GOS also had lower levels of the stress hormone cortisol in their saliva after three weeks on the prebiotic than they had at the beginning of the experiment.
Interestingly, the second prebiotic tested, FOS, affected neither emotional processing nor cortisol levels. This difference is in line with previous work showing that B-GOS more strongly stimulates the growth of intestinal microbes than does FOS. As these findings highlight, research on the microbiome must take account not just of the distinction between probiotics and prebiotics but also of differences among classes of prebiotics.
The healthy eating trends of 2015
The healthy eating trends of 2015
1/10 Acai bowls are the new green juice
Who ever thought we’d have been ok with adding spinach to our smoothies? Yet even virtuous green juices started to get something of a bad rep, as the ‘juice fast’ backlash grew and it turned out that some shop-bought juices contained as much sugar as a can of fizzy drink. Bring on Acai bowls, the new darlings of Instagram. Like a gloopier smoothie, these are made with antioxidant-rich acai berries (they are hard to come by - search for powdered or dried berries or frozen puree), which are said to aid weight loss. Blend with frozen bananas, berries and a little nut milk and top with whatever you like - seeds, nuts, cacao nibs, goji berries. A picture-perfect purple powerhouse for breakfast.
Ella Grace Denton, www.weneedtolivemore.com
2/10 Bone broth is the new Miso soup
Remember back in the day when the word ‘broth’ would conjure up visions of Dickensian orphanages? Then miso came along, Gwyneth embraced it, and we all followed suit, lauding how filling and protein rich with little wonder broth was. We’ve come full circle now, as bone broth is back on the radar. The glowing-with-health Hemsley sisters seem to use bone broth in most of their recipes, and rave about its nutritional benefits. “Bone broth is a nourishing all rounder packed with vitamins, minerals, collagen and keratin which makes it amazing for skin – including the dreaded cellulite! The healthy fats in the broth help you to assimilate important vitamins including Vit D.” There you go, something to stew over...
Food Loves Writing, Flickr
3/10 Bee pollen is the new Manuka honey
Every health hipster has a jar of manuka honey on their shelves - if they can afford it that is, a jar can cost about £15. But many claim it is worth its weight in gold, due to its unique antibacterial properties. Traditionally it was used on wounds, but many also claim that it performs miracles combatting cholesterol, diabetes, cancer and digestive problems (although the science is limited). Now bee pollen is the latest ‘superfood’ out there - thought to ward off colds, limit food cravings, improve skin tone, ward off allergies like hay fever (although some caution that it may exacerbate them) and, of course, fight cancer. Again, the science behind these claims is dubious - but it certainly adds a nice sweetness to your morning porridge.
4/10 Kelp is the new kale
Last year saw the emergence of an unassuming green leaf that was previously barely used beyond cattle feed. Now, we have kale chips in Pret, kale juices, ‘massaged’ kale salads - it’s even on the menu in fine dining restaurants. Yawn. Introducing kelp. This seaweed is high in iodine, which is said to improve thyroid function and control metabolism. It is also thought to have anti-aging properties for skin and hair. Try it in salads or add to asian-style soups.
5/10 Matcha is the new green tea
Yes, yes, yes, green tea, weightloss, yadda yadda yadda, boosts metabolism, etc etc. For 2015, though, it’s not about just any old green tea - this is matcha green tea. Made from finely milled high-grade matcha leaves, which are grown in the shade, matcha boasts 130 times more anti-oxidants than your bog standard green tea and is supposed to boost energy levels, lower stress, improve your mood and aid metabolism. It can be consumed as a regular tea, added to steamed milk for a matcha latte or even used to add a pleasant green shade and flavour to ice-cream.
6/10 Whole 30 is the new Paleo diet
Thought you were a culinary champ with your caveman-style eating plan? Well, think again, paleo is for wimps! Ok, not quite, but while people on the paleo plan cut out grains, legumes, sugar and processed foods, there is an increasing trend to paleo-fy your treats, with almond-flour pancakes, banana bread and a lot of brownies. The Whole 30 plan is a purer, stricter version of Paleo and really takes you back to basics when it comes to eating natural foods. The 30-day plan bans scales as well as sugar and alcohol, so that you can concentrate on nourishment rather than weight.
7/10 Fermenting is the new sprouting
Just when we thought we were ahead of the game by starting to sprout our own seeds and with sprouted flours creeping on to the market, the health set had to kick it up a notch. Now it’s all about making your own kombucha (fermented tea), sauerkraut or kimchi (both kinds of pickled cabbage). Fermented foods are said to aid digestion thanks to the creation of enzymes and probiotics in the process. Plus they tend to be high in B-vitamins and Omega-3 fatty acids. Think of it as the new jam-making, and break out those mason jars.
8/10 Banana flour is the new coconut flour
Coconut flour was one of the coolest baking ingredients of the year, beloved by Paleo fans. Its highly absorbent qualities mean you only need a tiny bit for baking, keeping your creations low carb but resulting in the odd dry-crumbly-mess baking fail. Banana flour is the next flour to experiment with. Made from green bananas (and no, not banana-flavoured), it is gluten free and light in texture, so ideal for baking. High in resistant starch, which is effective against colon cancer, obesity, and diabetes, it is already being lauded for its nutritional benefits in Africa and South America, and will surely start to become much more visible on health-food shop shelves in the near future.
9/10 Bulletproof coffee is the new soy latte
Nowadays it is possible to walk into almost any cafe and order a soy latte without being eyeballed as a lunatic by the person behind the counter. But would you have the guts to request a stick of butter in your morning brew? Well, some coffee shops are offering exactly that. Bulletproof coffee is a paleo-friendly invention which involves a black coffee with a dollop of coconut oil or butter. Bleurgh. But advocates say it gives you more slow-release energy, sharpens your brain and helps you to focus - and even that it is delicious. Now the theory has been expanded into a whole ‘Bulletproof’ diet plan, rich in fat. Who wants to bet on when Starbucks will give it a shot?
10/10 Tiger nuts are the new almonds
2014 was a good year for almonds. Gym-goers and raw foodists alike carried around a stash for healthy, protein-rich snacking, almond-milk lattes were quaffed, and almond flour featured in so many paleo and gluten-free treats. Now tiger nuts, or ‘earth almonds’ (yes, really), are about to vie for snacking superiority. Tiger nuts are not nuts, but the tubers of the sedge plant. Originally a key food source for Paleolithic Indians, they have until recently been used as animal feed or a side dish in South America, Africa and the Middle East, or in Hispanic companies made into a sweet, milky drink called horchata. But now the hipsters have got their hands on it, drying, roasting and flavouring with the likes of sweet chilli for an on-the-go snack. High in healthy fats, protein and natural sugar, it is rich in energy content, and thought to help prevent heart disease and improve circulation.
The effect of B-GOS on the attention task is similar to results found when healthy volunteers were given anti-anxiety or anti-depressant medication and asked to perform the task. The way attention is caught by emotionally charged stimuli (like the positive and negative words used in the test) is thought to be a key feature of anxiety disorders and depression. If attention too easily latches onto negative or threatening thoughts, or if it stays stuck on those thoughts for too long, this may contribute to anxious or depressive symptoms. The finding that prebiotics shift attention from the negative towards the positive thus suggests that they might have therapeutic uses. As the study’s senior author Dr. Philip Burnet notes, however, prebiotics and probiotics are likely to be administered as adjunct therapies alongside current pharmacological and psychological treatments rather than on their own.
Prebiotic effects on cortisol are similarly intriguing. The body’s stress response system shares a close relationship with the microbiome. In fact, animal studies indicate that the bacteria present in the gut in early life affect the development of the stress system and shape how the animal responds to stress in adulthood. The dampening effect of prebiotics on cortisol levels seen in the Oxford study are evidence of the microbiome’s continued influence over the stress response system and, given the role stress plays in psychiatric disorders, further supports the potential use of prebiotics as adjunct therapies for anxiety or depression.
The relationship between stress and gut bacteria may be relevant for diseases of the gastrointestinal tract as well as of the brain. Stress is thought to play a role in disorders like irritable bowel syndrome, Crohn’s disease, and colitis. The question of how the microbes fit into this picture is a hot one, and much of the data on probiotics and prebiotics comes out of studies of such disorders.
Mounting evidence thus indicates that manipulations of the microbiome affect both the brain and the body. The influence of probiotics on brain function has been demonstrated, and this latest research from Oxford has now opened the door for investigation of prebiotic effects. The study of the microbiome-brain connection will likely intensify in coming years given its potential to contribute to treatment of stress-related diseases.
Clio blogs at Neurobabble http://neurobabble.co.uk/