Nutritionist: look after your gut bacteria, and they’ll look after you
"Everything we eat also ends up on the menu for our gut bacteria, which are far more sensitive to food than we are. For them, a single meal can be a matter of life and death. Yet our own health and wellbeing depend heavily on how our gut bacteria are doing," says Meliva nutritionist Kaisa Kopliste.
Fibre-rich and fermented foods, for example, help beneficial bacterial communities thrive, leaving less room for harmful ones. Certain other substances — artificial sweeteners, some additives, alcohol, and pesticide or antibiotic residues in food — are directly toxic to bacteria.
Ultra-processed foods (such as crisps, soft drinks, margarine, sausages, and salty snacks) also tend to contain too little fibre, leaving beneficial bacteria starved. In a sugar-rich environment, many harmful bacterial strains tend to flourish, while beneficial ones, such as bifidobacteria, suffer.
The key is diversity
When it comes to gut health, it’s not so much about which foods to exclude or limit — even a fairly poor diet can be significantly balanced out simply by eating a large variety of different plants. Everyone seems to know that fruit and vegetables should make up at least half of what we eat. And yet, in my practice, I rarely meet people who actually follow that principle. It’s certainly the simplest and most effective change most people can make for their health.
Alongside quantity, the diversity of plants also matters — something that’s had far less attention so far. Research suggests the optimal number of different plant species to eat in a week is around thirty. Before you gasp, let me clarify: that count includes grains, nuts, seeds, and herbs too.
With a slightly more mindful approach to shopping and cooking, expanding your plant variety isn’t actually a real obstacle for most people — it just takes stepping a little outside the tomato-and-cucumber-salad comfort zone. The payoff for energy levels, the immune system, and often for body composition and weight too, is significant.
Interestingly, one US study on this topic accounted for a wide range of social and behavioural factors, such as age, education level, number of children, body weight, smoking, alcohol consumption, chronic illness, and medication use. The results showed that regularly eating a greater variety of plants had a meaningful effect on various health markers, regardless of these other factors.
To get the most benefit from plants, it helps to consume them wisely. Here are a few tips:
- Where possible, don’t peel plants before eating them. A large share of beneficial compounds is concentrated just beneath the skin of fruit and vegetables.
- Prefer steaming or baking over boiling. For example, boiling potatoes pours much of their vitamin and mineral content straight down the sink with the cooking water. Contrary to popular belief, potatoes are actually a genuinely health-supporting food — it’s peeling and boiling that stop them from shining as one.
- Choose plants by colour. Deep, dark, and vivid colours are a sign of high antioxidant and mineral content. For example, pale iceberg lettuce simply can’t compete, nutritionally, with deep-green spinach or kale. Leafy green vegetables are a category all their own — often dismissed from plates as “pointless greenery,” quite undeservedly, since those green leaves are densely packed with beneficial nutrients.
- The intensity rule applies to flavour as well as colour. Strongly flavoured plants — garlic, wild garlic, ginger, chilli, horseradish, parsley, and the like — are rich in polyphenols and other bioactive compounds. Our ancestors worked out that intensely flavoured plants tend to be either toxic or medicinal, with the line sometimes blurry between the two. “What doesn’t kill you makes you stronger,” as they say.
- There’s little point stockpiling fresh produce in the fridge or pantry for too long, since many vitamins break down and are lost over time. Vitamin C content, for example, drops by roughly half within three days. If you keep finding yourself staring at wilted salad leaves, it may be smarter to stock frozen vegetables instead — they’re picked at peak ripeness and frozen quickly, preserving much of their nutritional value. Long transport distances and time spent sitting on shelves, on the other hand, take their toll on fresh produce.
What’s the difference between prebiotics and probiotics?
Beyond increasing the share of plants in your diet, there’s another simple but regrettably underused health booster: fermented foods. Thanks to their fibre, oligosaccharide, and polyphenol content, plants are prebiotic, while fermented foods are probiotic. In Greek, “bios” means “life,” “pre” means “before,” and “pro” means “for.” So plant foods are, quite literally, “before life,” and fermented foods are “for life.” Put simply: the fibre in plant foods serves as food for our gut bacteria, while fermented foods contain live bacteria that help enrich the diversity of the gut microbiome.
Fermented plant foods combine both prebiotic and probiotic properties — sauerkraut and kimchi, for example, could reasonably appear on the menu almost every day. It’s worth noting that live bacteria die when heated, so probiotic properties are only preserved in raw, unheated food. Pickle season is coming up too — although fresh, one-day brined cucumbers are already delicious, their lactic acid bacteria content is still almost non-existent. For real health benefits, it’s worth letting them ferment for two or three days. It’s also worth noting that vinegar-pickled cucumbers are not the same thing as fermented ones.
Various fermented dairy products — kefir, buttermilk, yoghurt, cheese — also contain beneficial gut bacteria. So do fermented soy products, such as tempeh and miso, as well as kombucha and traditionally fermented, unpasteurised kali (a traditional Estonian fermented drink).
With fermented foods, it’s important to know that if a product sits on the shelf outside the fridge, it’s been pasteurised — meaning the bacteria created during fermentation have since been rendered harmless (and therefore useless) through heating. There are a few exceptions to this, in the form of new fermentation technologies, though these aren’t yet available on our shop shelves.
People usually set out to eat more healthily at the start of the year, but it’s actually much easier to enrich your diet with vegetables right now, in summer, when garden beds and market stalls turn invitingly colourful. So perhaps something in this piece has already inspired you to try something new — or something old, forgotten. And if it all starts to feel overwhelming, you can always ask a nutritionist for help.
