What 100 trillion organisms want you to eat — part 1
One of the things I hear most often from new clients, usually within the first couple of weeks of working together, is some variation of ‘I had no idea how much better my digestion could feel.” Or, slightly more bluntly: “I’m going to the bathroom properly for the first time in years.’
Good digestion is so often overlooked in standard health consultations. But as anyone who has lived with slow, unpredictable, or uncomfortable digestion knows — bloating, cramping, gassiness and just not being able to go to the bathroom consistently can affect your energy levels, your mood, your concentration, your skin, and even your ability to just get through a day feeling good. I know this, because I’ve been there — years of digestive discomfort during my teens and twenties that I simply accepted as normal, until I understood what the problem actually was. It wasn’t until I began studying nutrition twenty years ago that I realised that all these issues largely stem from the same place: not paying proper attention to your gut microbiome — that vast, largely invisible ecosystem of approximately 100 trillion bacteria, fungi and other microorganisms living in your large intestine, which most of us never even think about.
When this ecosystem is diverse and in good balance — with around four times as many beneficial bacteria as those with the potential to be pathogenic or ‘bad’ — it functions well; breaking down food, producing anti-inflammatory compounds, regulating your immune system, and even manufacturing certain hormones and vitamins that your body depends on. However when it falls out of balance, a condition known as dysbiosis, the consequences can be surprisingly far-reaching: weakened immunity, systemic inflammation, digestive discomfort, low mood, brain fog, and a general sense of not quite feeling yourself.
The question, then, is what tips the balance — and how can we restore it?
Here is the uncomfortable truth: most people in the Western world, including New Zealand where I live, are not eating nearly enough of the foods that their beneficial gut bacteria need to thrive. Not because good food is hard to find, but because the way that most people now eat has drifted a long way from the kinds of varied, traditionally prepared foods that our microbiomes evolved alongside.
Previous generations just didn’t eat ultra-processed foods; refined grains; industrial seed oils; and foods high in excess sugar — which all create the conditions in which harmful bacteria flourish and beneficial ones decline. In addition, regardless of where they were in the world, they were much more likely to be eating the type of high-quality fermented and cultured foods that are necessary to maintain a healthy gut microbiome. If I think back to my own grandparents for example, who were born just after the turn of the 20th century, they grew all their own vegetables, baked all their own bread, and my grandmother also made the most delicious red sauerkraut.
Fortunately, the microbiome is highly responsive to change, and even small steps in the right direction will begin to shift its balance — often within a matter of weeks.
Let’s start with foods classified as prebiotic — those that nourish the beneficial bacteria already living in your gut — and next week we’ll explore probiotics, which are more familiar to most people. There are several different sources of prebiotics, each acting in a slightly different way, but all of which are fermented by beneficial bacteria in the colon which then produce short chain fatty acids such as butyrate, an important molecule that most people have never heard of.
Butyrate plays several important roles in keeping us healthy, most importantly by strengthening the lining of your large intestine, helping to prevent leaky gut syndrome, where undigested particles pass through the wall of the colon into the bloodstream and trigger an inflammatory response. Butyrate also influences mood, focus and our emotions through the gut-brain axis — the two-way communication network between your digestive system and your central nervous system. So for anyone recovering from surgery, or simply looking to strengthen their immunity overall, making sure that your diet regularly includes butyrate-producing foods pays real dividends.
One principle worth keeping in mind as you read through what follows though, is that diversity matters as much as quantity. Researchers are increasingly finding that eating a wide variety of different plant foods — ideally around 30 different species a week — is one of the best ways that you can build a resilient, well-functioning microbiome. This sounds hard to do, but it’s actually very achievable (and fun to participate in!) once you start counting everything: not only vegetables and fruits but also herbs, spices, nuts, seeds, and grains.
So what should you be eating?
Garlic, onions, leeks, asparagus, chicory root (not that common in New Zealand), Jerusalem artichokes (which have a lovely nutty flavour and are well worth seeking out at farmers markets, or growing your own), and green or greenish bananas. These foods all contain inulin, a soluble fibre that travels undigested to the colon, where it is fermented by beneficial bacteria such as bifidobacteria and lactobacilli.
Other fibrous vegetables like carrots, broccoli, green peas and leafy greens, whose fibre can also be broken down to provide food for beneficial bacteria.
Cooked and cooled starches such as rice, potatoes, kumara, quinoa, barley, wheat and oats, which contain resistant starch — a natural prebiotic. I now always pre-cook and cool my grains so that they’re ready to use in salads and stir-fries or can be reheated (even from frozen) in a steamer basket.
Dried pulses, including lentils, chickpeas, and all of the many different types of dried beans, which are all excellent sources of both resistant starch and other fermentable fibres. Soak them overnight in plenty of warm water before cooking to reduce phytic acid, a compound that can interfere with mineral absorption.
Wholegrain oats, barley, and rye, which all contain beta-glucans, a specific kind of soluble fibre that not only encourages butyrate production but also directly interacts with immune cells in the gut lining. Always choose organic where possible, as glyphosate — a commonly used agricultural chemical — is a known microbiome disruptor, and as with pulses, soak them overnight before cooking.
Beta-glucans are also found in certain varieties of mushroom, including fresh or dried shiitake, as well as powdered extracts of medicinal mushrooms such as Reishi, Lion’s Mane, Chaga, Tremella, Cordyceps, and Turkey Tail.
Flaxseeds, chia seeds, and walnuts, all excellent sources of prebiotic fibre as well as omega-3 fatty acids, which have their own anti-inflammatory benefits. Soaking seeds and nuts overnight improves their digestibility as well as mineral absorption.
Apples also deserve a special mention as they are one of the best sources of pectin, another soluble fibre that acts as a prebiotic. An apple a day, as it turns out, may have been better advice than anyone fully understood at the time!
And lastly, the inner gel or mucilage from fresh aloe vera leaves, which contains polysaccharides including acemannan and fructans that not only stimulate the growth of bifidobacterium and lactobacillus, but also soothe the intestinal lining.
In addition to these prebiotics, there are also some foods that supply butyric acid (the same molecule as butyrate) directly, with perhaps the most surprising being dairy fats, especially butter or ghee from grass-fed animals, and smaller amounts being found in red meat and fermented foods like sauerkraut. This is not a licence for excess, but it is a good reason to stop feeling guilty about butter on your vegetables!
It is also worth mentioning polyphenols, which are compounds found in foods like dark chocolate, green tea, berries, and extra virgin olive oil. While these are not classic prebiotics, they still feed beneficial bacteria, and are increasingly recognised as being important for microbiome diversity. Including a variety of these foods in your diet adds another layer of support that compounds over time.
If much of this is new to you, the most important thing is not to overhaul everything at once. The gut microbiome responds well to gradual, consistent change, and introducing too many new foods too quickly, particularly high-fibre prebiotic foods, can cause temporary bloating and discomfort as your bacteria adjust. For those with existing gut sensitivities, it is also worth knowing that some of these prebiotic-rich foods are high in fermentable carbohydrates that can be difficult to process if your microbiome is already significantly imbalanced. If that sounds familiar, a low FODMAP approach, which temporarily limits these fermentable compounds while your gut adapts, may be worth exploring. More information can be found at www.monashfodmap.com.
Start with just one or two changes that feel easy to do — cook a batch of lentils at the weekend and make a soup; if you eat rice, get in the habit of always cooking, cooling and then reheating it before eating, make a commitment overall to eat more fibrous vegetables — all minor changes, but they add-up. Within a few weeks, most people notice a difference that surprises them. Your 100 trillion microorganisms aren’t asking for very much — just a little more of the right food, a little more often.
I hope you’ve enjoyed reading this article. In the next one I’ll be talking about probiotics — the fermented and cultured foods that actively replenish your gut microbiome, and how to include more of them in your everyday meals.