Food to Feed Good Bacteria

5 Ways to feed your good bacteria6 minute read

Food to Feed Good Bacteria

Put your hand just below your belly button—and say hello. Resting under there, inside your intestines, are approximately 3 pounds (or roughly 1kg) of bacteria, viruses and fungi and protozoa.

It’s a mind-boggling state of affairs, but we carry around more bacterial DNA than human DNA [1]. Or, to put it more visually, you have more bacteria in you than there are stars in the observable universe.

Freaked out yet?

You need not be, as these little critters—collectively known as our ‘microbiome’—are essential to our health and wellbeing. New and exciting research is uncovering their many functions, including:

– Digesting our food

– Synthesising vitamins

– Producing neurotransmitters

– Regulating immune responses

– Maintaining gut integrity [2]

And that’s just what we’ve discovered so far.

The majority of these bacteria are what’s known as commensal organisms. We give them a place to live and, in return, they provide us with functions that we wouldn’t otherwise be able to carry out. It’s a happy state of affairs that has developed over millennia of evolution.

We do, however, also have a certain number of pathogenic or ‘bad’ bacteria. These are certain strains of bacteria that aren’t too bothered about providing us with a service, instead taking whatever they can from our internal environment to our detriment.

Normally, the ‘bad’ bacteria are kept in check by the ‘good’ bacteria. We can run into trouble when this balance is upset, as it gives the bad bacteria the chance to exert dominance. An example of this is the digestive upset caused by food poisoning.

On the less extreme end of the spectrum, everyday signs of an imbalance in bacteria include bloating, nausea, gassiness, constipation and/or loose stools. Studies have also linked the composition of the microbiome to conditions that appear separate from the gut, such as psoriasis, dermatitis and even type-2 diabetes [3].

But, aside from picking up a bad bacterium from some dodgy food, what else can affect this delicate balance of bacteria in our guts? There are lots of influencing factors, such as drinking excess alcohol, taking a course of antibiotics, eating foods with high levels of pesticides, consuming lots of sugar and feeling chronically stressed. Taking the oral contraceptive pill has even been found to affect the gut microbiome [4].

It’s neither realistic nor advisable to immediately cease all these behaviours, and you certainly should never stop any medications without first consulting your doctor.

Instead, we should focus on the things we can do to cultivate an environment that favours the good guys. And it’s surprisingly easy—studies suggest that dietary alterations can produce large microbial shifts within 24 hours [5].

So, for smoother digestion, clearer skin and a better mood, follow these 5 simple steps for feeding a health-boosting microbiome:

1) Focus on fibre

We cannot break down certain fibres—but our gut bacteria can. They turn soluble and insoluble fibre into a special substance called butyric acid, which in turn provides fuel for our intestinal cells [6]. It’s like a clever sort of upcycling!

We should be consuming at least 30g of fibre daily, but surveys suggest most people only manage around 18g.

A simple way to turn this around is to increase your intake of fruits and vegetables. Aim to eat at least 2 cups (or two heaped handfuls) of vegetables with each meal, and enjoy 1 or 2 servings of fruit daily. These are a valuable source of soluble and insoluble fibre, and will have your gut bugs happily munching away.

2) Rediscover fermented foods

Before the refrigerator entered kitchens roughly 100 years ago, fermented foods were a much more common part of people’s diets. Pickling or fermenting food was an easy, natural way to extend its shelf life.

Fermented foods are now back in vogue, and for good reason. By eating them regularly, you’re supplying your gut with a steady stream of good bacteria. Over time, these will help to both crowd out the bad bacteria and lower inflammation [7].

There are lots of fermented foods to choose from: kefir (fermented milk), kombucha (fermented tea) and sauerkraut (fermented cabbage) can be found in many health-food stores. Aim to drink 200ml or eat 2tbsp daily.

3) Pay attention to your sugar intake

It’s an unfortunate truth, but bad bacteria (and some yeasts) love to feed on sugar [8]. If you eat too much sugar, you’re providing fuel for the bad bacteria to proliferate and take precedence.

The issue here, however, is not having a piece of birthday cake, the odd cocktail, or the occasional dessert after dinner. The issue with sugar comes when we eat it without realising. Look at ingredients labels. As a general rule of thumb, if ‘Sugar’ appears within the first three ingredients, that food is best avoided.

However, don’t be tempted to swap sugar for sweeteners. Research also shows that consumption of artificial sweeteners (such as aspartame) causes negative shifts in gut bacteria [9].

The best thing to do is gradually reduce your sugar and sweetener intake. Over time, your palate resets, and you’ll find you no longer crave such sweet flavours.

4) Find your zen

‘Reduce stress’ is such common advice that it’s easy to ignore it. Most people become accustomed to living at a certain pace, and it takes a serious event to make them reconsider their ways.

However, even if you feel you’re coping, your gut bacteria may not be. Animal models show that even low-level stress causes shifts in the gut microbiome [10]. Certain bacteria can then affect the ongoing stress response, and it becomes a catch-22 situation.

So how, in practice, do you reduce your stress levels?

A key step is to get yourself in a sense of ‘flow’—when you’re completely absorbed, relaxed and don’t notice time passing—for at least half an hour a day. For some people, this can mean mediation. For others, simply reading a good book will do the trick. Whatever works for you, make it a non-negotiable part of your day.

5) Choose organic when possible

Just as there’s a two-way mechanism between stress and gut bacteria, there’s also a bidirectional relationship between pesticides and the gut microbiome. Pesticides have been found to alter gut bacteria and, at the same time, the way in which gut bacteria react to pesticides may increase the toxicity of these chemicals [11].

None of this sounds good, does it?

You can’t avoid all traces of these substances, but you can choose the food you eat. As much as you can afford, buy organic food. If your budget is limited, prioritise buying organic meat, poultry and dairy. The concept of bio magnification means that pesticides accumulate in animals and their products, so simply switching to organic meat can dramatically reduce your load and protect your microbiome. Of course, choosing organic fruit and vegetables will help too.

For bespoke nutrition recommendations, book in for your free 10-minute exploratory call.

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Dr Thivi Maruthappu


Dr Thivi Maruthappu is the UK’s first and only dual-qualified Consultant Dermatologist and Nutritionist, and the pioneer of the (much-needed!) Nutritional Dermatology field. She runs busy NHS dermatology clinics, conducts academic research and delivers lectures worldwide. She’s also recently authored her first book, Skin Food, which aims to make holistic skincare accessible for everyone.



Porter magazine called her a ‘Global Skincare Expert’, and Caroline Hirons described her as ‘one of the best facialists in the world’. In the skincare industry, Marie Reynolds is in a league of her own. I had the privilege of experiencing one of Marie’s facials as a young journalist—and I can still remember every exquisite detail more than a decade later.

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