Be good to your gut
Being good to your gut takes many forms – one of the most important being your diet. So how can you nurture your gut microbes with the foods you eat?
Shake up your diet
By our very nature we are creatures of habit. In fact, an estimated 90% of what we do each day is routine – and that includes the foods we eat. Hands up who opts for the same brekkie or lunch most days? While this helps prevent umming and ahing about what to eat at 7am, your gut bacteria prefer a shake up, ‘coz variety is their jam.
In fact, studies suggest the diversity of our diet (the number of different foods or food groups we eat) may have more influence on the health of our microbiome than the type of diet we follow (meat eater vs vegetarian).
Eating a varied diet (lots of different types of fruits, vegetables, grains, proteins and healthy fats) encourages the growth of a diverse range of gut bacteria, which seems important when it comes to reducing the risk of disease. In one study, people regularly munching on 30 types of plant foods per week had a more diverse microbiome than those eating 10 or fewer (read more about this here).
I like the analogy of likening your diet to a kaleidoscope – making sure it has lots of different parts and colours, which are constantly changing. Try varying the fruits on your breakfast (check what’s in season here) and use different grains with your meals – instead of pasta, try wild rice, polenta, buckwheat, quinoa or teff (a seed which is fab in porridge soups, stews and pancakes). Opt for plant based proteins a few times a week, and mix up your snacks – this could be as simple as swapping the nuts or fruits you eat.
Up the F word
So far as your gut microbes are concerned fibre is the food of the Gods. Without it your gut bacteria start to shrink in number and diversity. On the contrary, upping your fibre intake can increase the variety of species in your gut garden. A richer and more diverse microbial garden seems to defend against a range of health conditions, thanks to protective compounds that your bacteria produce when they consume fibre.
The recommended intake of fibre is 30 grams, but most of us don’t get this amount. At last count, the average was 17 grams a day for women and 20 for men. Increasing your intake to the 30 gram target is one positive step you can take for your gut health. But – here’s the key – make sure you add fibre slowly to give your digestive system a chance to adapt. Too much too quickly, and you can end up with tummy cramps and wind.
My advice is to start from the top down by boosting the fibre in your breakfast (add oats, chia, flax or fruits), and then after a week of this new habit, make a change to your snacks, then your lunch, and so on. Make sure you drink plenty of water alongside the extra fibre too, as this will help it move through your digestive system.
One extra word of warning – if you have IBS or another gut condition, adding more fibre to your diet can aggravate symptoms… so work with a dietitian or adjust slowly to tolerance, as some types of fibre will less aggravatory than others.
Plants and polyphenols
Polyphenols are naturally occurring compounds found in many plant foods including tea, coffee, berries, herbs, veggies, cocoa and red wine (yes, wine!). They’re responsible for giving fruit and veg their bright colours – think the bright orange hue of an apricot or the shiny purple skin of an aubergine.
Most polyphenols are not well absorbed in the small intestine, so they travel to the colon (large intestine) where they are broken down by your gut bacteria into compounds which exert antibacterial and antiviral effects.
Foods rich in polyphenols include berries, apples, aubergine, black grapes, cherries, red wine, beans, kale, black tea, green tea, and extra virgin olive oil. Boost your intake by choosing a wide range of colours, eating your fruit and veggies with their skins on where possible, and steaming instead of boiling to prevent losses.
The good news is that by adding more polyphenol rich foods to your diet, you’ll naturally be feasting on more plant foods – which means more fibre – and that’s a win win for your microbes.
The bad and the ugly…
Now you know the foods that can give your gut health a helping hand, what about the foods that are less helpful?
Junk the junk
Eating lots of fast and processed food isn’t good for your mental or physical health – and neither is it good for your gut bacteria. Junk foods often contain ingredients (like emulsifiers) that seems to suppress the growth of ‘good’ bacteria.
It makes sense that the more processed food you eat, the less room for the more nutritious stuff – the absence of fibre in processed and junk food can shrink the numbers of friendly bifidobacteria in your gut, altering the balance of your ‘biome in a relatively short space of time.
This isn’t to say you should never touch a takeaway pizza again or avoid all preservatives (which isn’t possible or necessary), but your gut bacteria will be happier if the majority of your calories come from nutrient rich foods.
Balance the booze
The occasional glass of polyphenol packed red wine arguably has benefits for your microbes, but bathing your gut bacteria in alcohol isn’t a smart idea. Drinking lots of alcohol can disrupt the movement of food through the digestive system, and can alter the balance of gut bacteria. High levels of alcohol can also increase the permeability of your gut lining, which may trigger inflammation.
The best advice is to moderate your measures, and savour the flavour.
Ditch the restrictive diets
Diets which eliminate whole food groups seem to have an adverse effect on gut bacteria. In particular, the trend for low carb diets may be impacting the environment in our gut in some unwanted ways.
In a recent study from the American Society for Microbiology, switching to a carb free diet resulted in lower levels of short-chain fatty acids, which are made when gut bacteria consume fibre. These fatty acids are known for their ability to regulate inflammation, so having fewer of them could be problematic.
The smart choice it seems, is to make your diet as varied as possible, and not to exclude food groups unless necessary (due to food intolerances or allergies for example), or to limit any exclusions to the short-term.
1. Mcdonald D, Hyde E, Debelius JW, et al. American Gut : an Open Platform for Citizen Science. Am. Soc. Microbiol. 2018;3(3):1-28.
2. Shen Q, Zhao L, Tuohy KM. High-level dietary fibre up-regulates colonic fermentation and relative abundance of saccharolytic bacteria within the human faecal microbiota in vitro. Eur. J. Nutr. 2012;51:693-705. doi:10.1007/s00394-011-0248-6.
3. Hervert-Hernández D, Goñi I. Dietary polyphenols and human gut microbiota: A review. Food Rev. Int. 2011;27(2):154-169. doi:10.1080/87559129.2010.535233.
4. Agans R, Gordon A, Kramer DL, Perez-Burillo S, Rufián-Henares JA, Paliy O. Dietary Fatty Acids Sustain Growth of Human Gut Microbiota. Appl. Environ. Microbiol. 2018;(September). doi:10.1128/AEM.01525-18.