Nutrients for the Gut: Fibre, Cultures & More

Hardly any topic is discussed as often in connection with nutrition as the gut. That's understandable: the digestive tract deals daily with everything we eat and drink. Around fibre, cultures and fermented foods, a lot of promises circulate that go far beyond what can seriously be claimed. This guide takes a factual look at the key building blocks of a gut-friendly diet and explains which claims about individual nutrients are actually approved in the EU.

Important upfront: this is about diet and food supplements, not about treating symptoms. If you have persistent or severe digestive problems, you should have them checked out by a doctor. Food supplements are no substitute for a varied diet or a medical diagnosis.

Gut and Diet: What It's Really About

The gut processes a considerable amount of food and fluid every day. What ends up on your plate influences, among other things, how much fibre you get and how varied your diet is overall. Nutrition societies such as the German Nutrition Society (DGE) have long recommended a plant-forward, varied diet with plenty of vegetables, fruit, legumes and wholegrain products.

This recommendation is deliberately kept general, because there is no single miracle substance for the gut. Rather, it's the interplay of many foods and nutrients that matters. Below, we take a closer look at the individual building blocks that keep coming up in this context.

Building Blocks of a Gut-Friendly Diet

Fibre and Prebiotics

Fibre consists of indigestible components of plant-based foods. It's found in vegetables, fruit, legumes, nuts, seeds and wholegrain products. As a guideline, the DGE cites an intake of at least 30 grams of fibre per day – a figure many people in Germany don't reach.

Some fibre is described as prebiotic, because these fibres are used by microorganisms in the large intestine. Well-known examples include inulin and oligofructose, found in chicory, Jerusalem artichoke, onions, leeks and bananas, among others. From a strictly legal standpoint, however, no health-related effect claims are approved for prebiotics – so the description here is deliberately kept factual. If you'd like to understand the difference between these terms in more detail, our article Prebiotics or Fibre? The Difference Explained offers a detailed look.

In practice, this means: increasing your fibre intake is easiest through food choices – for example wholegrain instead of white flour, an extra portion of vegetables, or legumes several times a week. If you increase your fibre intake, do so gradually and make sure to drink enough fluid at the same time.

A rough distinction is made between soluble and insoluble fibre. Soluble fibre is found, for example, in oats, apples, carrots and legumes, while insoluble fibre is found mainly in wholegrain products, nuts and the outer layers of vegetables. A varied selection of foods provides some of each – which is more convenient than relying on individual fibre sources. In practice, this simply means: eat as varied a plant-based diet as possible, rather than isolating individual ingredients.

Lactic Acid Bacteria and Cultures

Foods such as yoghurt, kefir, sauerkraut or kimchi contain live cultures, often lactic acid bacteria. In advertising, this is often linked to the term “probiotic”. An honest clarification is important here: in the EU, the term “probiotic” is not approved as a health claim. This means products may not simply be advertised with this term, and no guaranteed digestive or immune benefits can be derived from it.

What can be said descriptively is this: fermented foods and corresponding food supplements contain certain bacterial cultures. Whether and how these have an effect in individual cases has been studied very unevenly in the scientific literature and cannot be promised across the board. If you want to try such products, you can do so as part of a varied diet – without inflated expectations. Our guide Gut & Microbiome: Probiotics, Fibre & Diet offers a broader look at the topic.

Fermented Foods in Everyday Life

Fermented foods are a traditional part of many cuisines. These include natural yoghurt, kefir, buttermilk, sauerkraut, lacto-fermented vegetables, kimchi and miso, among others. Depending on the product, they provide live cultures and can easily be worked into your meal plan – for example, yoghurt for breakfast or a small portion of sauerkraut as a side.

The main advantage of these foods is that they increase the variety of your diet. Instead of individual, isolated substances, a broad range of ingredients ends up on your plate. It's precisely this variety that nutrition experts recommend.

Drinking Enough

Fluid intake is often underestimated when it comes to gut health. Especially as fibre intake increases, drinking enough is important so the fibre can swell properly in the digestive tract. As a guideline, the DGE recommends adults drink around 1.5 litres of fluid per day, mostly from water and unsweetened drinks – correspondingly more in heat, during physical exertion, or when requirements are increased.

A simple everyday tip: have a glass of water with every meal, and keep a filled bottle visibly within reach at your workplace. That way, drinking doesn't get forgotten, and your higher fibre intake is matched by an appropriate amount of fluid.

Nutrients Related to Digestion and Mucous Membranes

Besides fibre and cultures, there are individual nutrients for which specific, approved claims exist in the EU. These so-called health claims are recorded in the EU Register of Nutrition and Health Claims. They describe contributions to normal bodily functions – not healing effects.

• Calcium contributes to the normal function of digestive enzymes. Calcium is found in, among other things, dairy products, calcium-rich mineral water, and certain vegetables such as kale and broccoli.
• Vitamin A contributes to the maintenance of normal mucous membranes. The body forms vitamin A, among other ways, from beta-carotene, which is found in orange and green vegetables.
• Riboflavin (vitamin B2) contributes to the maintenance of normal mucous membranes. It's found, for example, in dairy products, wholegrains and legumes.
• Niacin contributes to the maintenance of normal mucous membranes. Niacin is found in, among other things, meat, fish, peanuts and wholegrain products.
• Biotin contributes to the maintenance of normal mucous membranes. Good sources include eggs, nuts, oats and legumes.

These claims refer explicitly to the maintenance of normal functions as part of a balanced diet. They do not mean that a particular product relieves digestive complaints or “restores” the gut. The mucous membranes these claims refer to also concern the body in general, not exclusively the gut.

It's important to understand the difference between an approved claim and a promise of healing. A statement like “contributes to the maintenance of normal mucous membranes” describes a contribution to a function that already exists – it does not promise improvement of a symptom. These nutrients are also found in everyday foods, so with a balanced diet they're usually supplied in sufficient amounts. Deliberately reaching for a single supplement is therefore only necessary in exceptional cases, such as a proven insufficient supply.

Diet as the Foundation

As appealing as individual nutrients may sound: the foundation remains a varied, predominantly plant-based diet. If you regularly eat vegetables, fruit, legumes, nuts and wholegrain products, you automatically get plenty of fibre as well as many of the vitamins and minerals mentioned above – with no need for individual supplements.

A few practical pointers for everyday life:

• Choose wholegrain versions of bread, pasta and rice.
• Include a portion of vegetables or salad with every main meal.
• Add legumes like lentils, chickpeas or beans several times a week.
• Use nuts and seeds as a topping for muesli, yoghurt or salads.
• Include fermented foods like natural yoghurt or sauerkraut on a regular basis.
• Drink enough water or unsweetened tea.

These changes may seem unspectacular, but they are exactly what nutrition societies recommend. If you also make sure to get enough exercise, you support your overall daily routine.

When Supplementation Can Make Sense

Food supplements are meant to complement a normal diet – not replace it. In certain situations, targeted supplementation can make sense, for example with a doctor-diagnosed deficiency, a one-sided diet, or during particular life phases. Whether and what makes sense in an individual case is best clarified with the support of a doctor or nutrition professional.

Specifically for the gut: no supplement can compensate for an unbalanced diet. If you want to improve your fibre intake, you'll generally achieve more through food than through capsules. And if you're considering culture supplements, keep the legal context described above in mind and don't expect exaggerated promises. Related topics such as L-glutamine are also frequently discussed in connection with the gut – here, too, it's worth taking a sober look at the actual evidence.

Another point: the gut is closely linked to general wellbeing. If you feel tired or low on energy, you might sometimes look for the cause in your gut, even though other factors are at play. Our article Nutrients for More Energy, as well as the guide on Magnesium, Iron and B Vitamins, offer a factual overview of this.

Putting It Honestly

The gut cannot be “optimised” with a single nutrient. What can be said is this: a fibre-rich, varied, predominantly plant-based diet with enough fluid matches the recommendations of nutrition societies. Individual nutrients such as calcium and certain vitamins do, under EU law, contribute to normal functions – but as part of your overall diet, not as isolated miracle cures.

When it comes to heavily advertised cultures and the term “probiotic”, some caution is warranted, because no health claims are approved here. And as a general rule: persistent, recurring or severe digestive complaints should be checked out by a doctor. Food supplements and a mindful diet are supportive building blocks in everyday life – they do not replace a diagnosis or treatment.