We were not joking in our Nutrition Newsmakers when we said 2012 was the year of the Gut Microflora! These unsung heroes of your intestine have been linked to a multitude of digestive health benefits but it turns out they are influencing much more than just what happens in your colon. There has been a boom in research looking at the far-reaching, whole-body effects of your microflora – from weight loss and metabolism, to arterial plaque formation and risk of stroke.
We’ve previously brought you posts on gut microbiota and weight (Probiotics and Weight Loss?), and probiotic use in intestinal disorders (A Gut Feeling) but there is so much more! Here are a few additional reasons to keep your microflora flourishing.
1. They are key for immune function
You are first “colonized” by bacteria when you are born, that’s why the method of your birth (vaginal vs. caesarean) has a huge impact on the type of gut bacteria you have, just as your first food does – breast milk is best!
From birth onwards, the bacteria in your gut play an essential role not only in the development of your young immune system, but they continue to fend off pathogenic, bad-guy bacteria to reduce your risk of bacterial infections. Studies have shown that germ-free animals without gut bacteria (usually mice) show poorly developed immune systems and reduced immune response and resistance to infection (1).
Some researchers now argue that the rise in inflammatory bowel diseases and immune function-related diseases like type 1 diabetes and asthma is due to the North American diet and its negative effects on the beneficial bacteria in the gut (2). If you don’t give the gut bacteria food (read: fibre), they cannot do their job properly!
2. They might lower your cholesterol
New research has demonstrated that the gut bacteria of those with heart disease differs dramatically from healthy individuals (3). While the possible impact of gut microflora on obesity – a significant risk factor for heart disease – offers an easy explanation for this link, it appears now that the gut bacteria are able to regulate cholesterol metabolism all on their own, so much so that probiotic supplements have been successful in reducing cholesterol levels in human trials (4).
While the precise mechanism remains unknown, there are a few different possibilities. Researchers at Oklahoma State argue that a healthy microflora population actually uses up dietary cholesterol for their own cell growth, preventing absorption in the gut. Other recent studies have shown that intestinal microflora, at least in mice, is capable of regulating bile acid metabolism (5); this is a similar mechanism to how soluble fibre is able to lower cholesterol by preventing bile reabsorption.
3. They up your antioxidants
While we know that higher intake of antioxidant-rich foods is linked to reduced risk of chronic disease, the relationship may not be as simple as we thought (5). Turns out the actual absorption of some antioxidants is quite limited and blood levels remain very low despite intake. This is particularly relevant in the case of polyphenols, specifically the anthocyanins found in red wine, chocolate and berries. But how can these compounds have been linked to health benefits if we cannot absorb them? The answer – your microflora help you out (6).
Some antioxidant compounds are actually transformed by your gut microbiota, and these resulting compounds are absorbed easily and are able to act in the body. This begs the question – without microflora, would you derive the same benefits from your dark chocolate? Some argue that a significant amount of the benefit we derive from eating a plant-based diet rich in vegetables, fruit and other antioxidant-rich foods like tea and chocolate is all thanks to the bacteria in our colon. Without them, a lot of the good stuff would end up down the drain.
4. They could impact your mental health
“Microbes Manipulate Your Mind” – catchy title, but could it really be true? Before we get all science fiction-y, your gut bacteria are NOT going to turn you into a mindless robot, but they do seem to help regulate neurotransmitters in your brain. The “gut-brain axis” is nothing new – research suggests the microbes living in our intestine may be able to alter the production of hormones involved in brain function, mood, stress and anxiety (8-10).
Keep in mind, much of the research has been done in mice and is by no means cause-and-effect but does support other findings showing altered gut bacteria in mental illnesses like depression and schizophrenia. Clark et al. (11) looked at germ-free mice before and after they introduced bacteria into their system – they showed altered serotonin (the “happy” hormone) transmission, as well as anxiety levels.
No Baloney’s advice? Respect and nurture your gut bacteria – they are doing a lot more than producing vitamin K down there! There is growing evidence that your intestinal microflora has effects throughout the body, so we think this takes a whole-diet approach. Taking a probiotic supplement or a scoop of prebiotic fibre while eating a bacon cheeseburger is not going to cut it! We know that Europeans tends to have higher concentrations of beneficial gut bacteria (12), so eat like they do!
- Boost your fibre intake: think vegetables, fruit and whole grains. Limit the white, refined stuff as much as possible.
- Seek out soluble fibre and resistant starches: this is the stuff gut bacteria love because they can ferment it. Best sources include oats, barley, beans and lentils, bananas and even *potatoes*. Take that low-carb diets! Dietitians of Canada has some good info on fibre sources.
- Add dietary sources of probiotics: we are big fans of going with food first, so rather than starting a probiotic supplement, try to find sources to add to your diet like plain yogurt or kefir. Other probiotic foods like miso, kimchi and sauerkraut are also good choices but watch the salt.
- Think about prebiotic / probiotic supplements: although these supplements are unlikely to hurt you, they are generally not necessary for healthy individuals – go with food first. Those with high cholesterol, digestive concerns or routine antibiotic use, however, may want to consider supplementation. Make sure to talk to your health professional before starting any new supplements, particularly for children, the elderly or anyone with a weak immune system. And drink lots of water if you start a fibre supplement or you will get constipated!
- Round JL, Mazmanian SK.The gut microbiota shapes intestinal immune responses during health and disease. Nat Rev Immunol 2009; 9:313-23.
- Maslowski KM, Mackay CR. Diet, gut microbiota and immune responses. Nat Immunol 2011; 12:5-9.
- Wong JM, et al. Gut microbiota, diet, and heart disease. J AOAC Int. 2012 Jan-Feb;95(1):24-30.
- Kumar M, et al. Cholesterol-lowering probiotics as potential biotherapeutics for metabolic diseases. Exp Diabetes Res 2012 [epub ahead of print].
- Sayin SI, et al. Gut microbiota regulates bile acid metabolism by reducing the levels of tauro-beta-muricholic acid, a naturally occurring FXR antagonist. Cell Metab 2013; 17:225-35.
- Quiñones M, et al. Beneficial effects of polyphenols on cardiovascular disease. Pharmacol Res 2013; 68:125-31.
- Williamson G, Clifford MN. Colonic metabolites of berry polyphenols: the missing link to biological activity? Br J Nutr 2010;104 Suppl 3:S48-66.
- Foster JA, et al. Gut-brain axis: how the microbiome influences anxiety and depression. Trends Neurosci 2013; [epub ahead of print].
- Diaz Heijtz R, et al. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA 2011; 108:3047-52.
- Cryan JF, Dinan TG. Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour. Nat Rev Neurosci. 2012; 13:701-12.
- Clarke G, et al. The microbiome-gut-brain axis during early life regulates the hippocampal serotonergic system in a sex-dependent manner. Mol Psychiatry 2012; [epub ahead of print].
- Delzenne NM, et al. Gut microbiota and metabolic disorders: how prebiotic can work? Br J Nutr 2013;109 Suppl 2:S81-5.