Plant diversity and gut health: must we choose between fibre and probiotics?

A new gut-health study has handed the internet exactly the sort of headline it enjoys:

“More than 30 plants changed the microbiome more than a probiotic.”

You can almost hear the broccoli cheering and the probiotic bottles quietly packing their belongings.

Fortunately, the real science is far more interesting—and far less dramatic.

In a six-week randomised controlled trial, researchers compared a diverse whole-food plant blend, a probiotic containing one specific strain and a control food. The plant blend changed the relative abundance of more microbial species than either comparison group.

Participants receiving the blend also reported improvements in indigestion, constipation, heartburn and flatulence compared with the control group.

Does this mean that colourful plant foods have defeated probiotics in a winner-takes-all gut-health tournament?

No.

The much more useful lesson is that plant diversity and gut health are closely connected, while probiotics and fibre can play different—and potentially complementary—roles.

What did the study investigate?

The BIOME study was a six-week, parallel, randomised controlled trial involving adults between 35 and 65 years old.

To qualify, participants had to be consuming less than 20 grams of fibre per day. This means the study deliberately recruited people whose usual fibre intake was relatively low.

A total of 399 people were randomly allocated to one of three groups:

• Plant-blend group: 30 grams per day of a whole-food blend containing more than 30 plant ingredients.
• Probiotic group: 15 billion colony-forming units per day of Lactobacillus rhamnosus.
• Control group: 28 grams per day of energy-matched bread croutons.

The plant blend contained a range of nuts, seeds, legumes, whole grains, fruit and vegetables. It was designed to provide fibre, polyphenols and micronutrients from a broad selection of plant sources.

Although 399 people entered the trial, the researchers’ main analysis included 349 participants after 50 exclusions.

Adherence was self-reported at more than 98%, meaning most participants said they followed the programme very closely. Your pharmacist will merely note that self-reported adherence and what occasionally happens beside the biscuit cupboard are not always perfectly identical.

What happened to the gut microbiome?

The plant blend produced broader measurable changes in microbial composition during the six weeks.

Researchers found changes in the relative abundance of:

• 57 microbial species-level groups in the plant-blend group;
• 4 microbial species-level groups in the probiotic group; and
• 14 microbial species-level groups in the control group.

That is an interesting result for plant diversity and gut health. It suggests that adding a wide variety of plant-derived fibres and compounds can affect numerous members of the gut microbial community.

However, “more species changed” does not automatically mean “the microbiome became healthier in every important way”.

The researchers used a proprietary microbiome ranking system to classify species as relatively favourable or unfavourable. They did not find a significant difference between the groups in the overall health rankings of the species that changed.

In plain English: the plant blend caused more movement in the microbial neighbourhood, but the study did not prove that every change was beneficial or that participants achieved a universally superior microbiome.

The microbiome is not a school report where more ticks automatically produce a gold star.

Why would a variety of plants affect gut microbes?

Different plant foods contain different combinations of:

• soluble and insoluble fibre;
• resistant starch;
• polyphenols;
• vitamins and minerals; and
• other compounds that may interact with intestinal microorganisms.

Humans do not fully digest every form of dietary fibre in the small intestine. Some reach the large intestine, where certain gut microbes can use them as substrates.

During this fermentation process, microbes may produce short-chain fatty acids and other metabolites. These compounds can interact with the intestinal lining and participate in various aspects of normal gut biology.

Different microbes prefer different substrates. That is one reason a broad variety of plant foods may support a more varied microbial community than repeatedly eating the same two vegetables because they behaved themselves once.

Plant diversity and gut health therefore involve more than achieving one heroic daily fibre number. Variety matters because different foods bring different fibres and plant compounds to the table.

What happened to digestive symptoms?

Compared with the control group, participants receiving the plant blend reported reductions in:

• indigestion;
• constipation;
• heartburn; and
• flatulence.

They also reported increased energy.

These improvements are encouraging, particularly because the participants began with relatively low fibre intake.

However, the symptoms were self-reported. Participants knew what they were consuming, and the intervention could not be fully blinded in the way that two identical medicine capsules might be.

The study therefore tells us that people taking the plant blend reported feeling better in several respects. It does not prove that a diverse plant blend will relieve every digestive symptom in every person.

It also does not mean that someone with persistent heartburn, constipation or abdominal discomfort should simply add a scoop of plants and cancel the medical appointment.

Did the plant blend outperform the probiotic?

It depends entirely on what we mean by “outperform”.

The plant blend changed the relative abundance of more microbial species than the tested probiotic over six weeks. That finding is clear.

But this was not a contest between all plant-rich diets and all probiotics.

The probiotic group received one particular organism, identified in the paper as Lactobacillus rhamnosus, at a particular dose. Probiotic effects are strain-specific, dose-specific and outcome-specific.

The trial did not compare the plant blend with:

• every Lactobacillus rhamnosus strain;
• a multi-strain probiotic;
• every possible probiotic dose;
• probiotics used for particular clinical purposes;
• synbiotics containing probiotics and selected substrates; or
• Noster ProBiotics.

We therefore cannot conclude that plant foods generally work “better” than probiotics.

That would be like testing one pair of running shoes against a bicycle and announcing that shoes are superior transport. It depends where you are going, why you are going there and whether the bicycle has a flat tyre.

Fibre and probiotics do different jobs

Dietary fibre and probiotics should not be treated as interchangeable products.

Fibre-rich plant foods provide substrates and plant compounds that can be used by various members of the existing gut microbial community. They also contribute nutrients and may support normal bowel function as part of a balanced diet.

Probiotics provide selected live microorganisms in an adequate amount. Their usefulness depends on the exact strain or strains, viable count, formulation, storage and purpose for which they are being used.

A probiotic does not supply the full nutritional benefits of vegetables, fruit, legumes, nuts, seeds and whole grains.

Likewise, eating a varied salad does not deliver a precisely identified probiotic strain at a controlled viable count.

They are different tools.

The commercially honest Noster position is simple: probiotics should complement a varied, fibre-rich diet—not compete with it or pretend to replace it.

What this study teaches us about everyday gut care

The most practical message from this research is wonderfully unglamorous: feed yourself—and your microbial passengers—a broader variety of real foods.

You do not have to find 30 exotic ingredients before lunchtime or sprinkle mysterious powder over everything you love.

Instead, gradually increase the range of plant foods you eat across the week. These may include:

• vegetables of different colours;
• fresh or frozen fruit;
• beans, lentils and chickpeas;
• oats and other whole grains;
• nuts;
• seeds;
• herbs and spices; and
• small amounts of unfamiliar plant foods introduced sensibly.

Frozen vegetables count. Tinned beans count. Oats count. Herbs count. Your gut does not demand that every ingredient arrive barefoot from an artisanal market at sunrise.

What matters is building variety into a routine you can maintain.

Increase fibre gently—your household will thank you

If your current fibre intake is low, suddenly eating enormous quantities of beans, bran and raw vegetables may increase bloating and wind.

This does not necessarily mean that fibre is bad for you. It may simply mean that your digestive system has been introduced to the entire extended plant family in one afternoon.

A more comfortable approach may include:

• increasing portions gradually;
• adding one or two new plant foods at a time;
• drinking adequate fluids;
• cooking vegetables if raw foods are uncomfortable;
• rinsing tinned beans before use;
• remaining physically active; and
• adjusting the pace according to your symptoms.

People with irritable bowel syndrome, inflammatory bowel disease, bowel narrowing, significant digestive disease or a medically prescribed restricted diet should seek individual guidance before making major changes.

Where do Noster ProBiotics fit?

Noster ProBiotics are refrigerated live culture probiotics intended to support everyday gut balance.

They do not replace vegetables, fruit, legumes or whole grains. They also cannot compensate for a consistently low-fibre diet by sending one tiny bacterial rescue squad into battle after a weekend of beige food.

Instead, a probiotic may form one part of a wider routine that includes:

• varied fibre-rich foods;
• adequate fluids;
• regular physical activity;
• appropriate sleep;
• sensible use of medicines; and
• professional care when symptoms persist.

Noster ProBiotics were not used in this trial. We therefore do not claim that Noster produces the same microbial changes or symptom results as the 30-ingredient plant blend.

We can, however, agree wholeheartedly with the study’s broader reminder: your resident gut microbes need a varied food supply too.

Eat the rainbow. Consider an appropriate live culture probiotic. Pop it in the fridge. Keep the claims sensible.

Important limitations of the study

This was a randomised controlled trial, which is a useful and comparatively strong design. Even so, several limitations matter:

• The intervention lasted only six weeks.
• The participants were healthy adults between 35 and 65 years old with fibre intake below 20 grams per day.
• Fifty of the 399 randomised participants were excluded from the main analysis.
• Digestive symptoms, adherence, energy and other experiences were self-reported.
• The intervention could not be completely blinded.
• The plant product was a proprietary blend rather than an ordinary food-based dietary programme.
• The microbiome health ranking used in the study was proprietary.
• Many of the researchers were affiliated with ZOE, the company connected to the blend and ranking studied.
• The research did not test Noster ProBiotics or every probiotic strain and formulation.

The paper reports the competing interests and commercial affiliations. That does not automatically invalidate the research, but readers should know who developed the product, who conducted the study and what system was used to judge the microbiome changes.

Good science deserves attention. Commercial science deserves the same attention—with the reading glasses cleaned first.

When digestive symptoms need more than dietary advice

Persistent digestive symptoms should not be blamed automatically on a “bad microbiome”. Arrange an assessment with a healthcare professional if you experience:

• blood in the stool;
• black or tarry stools;
• unexplained weight loss;
• persistent vomiting;
• difficulty swallowing;
• severe or worsening abdominal pain;
• anaemia or unusual fatigue;
• a persistent change in bowel habits;
• ongoing diarrhoea or constipation; or
• heartburn that occurs frequently or does not settle.

Food and probiotics can support a sensible health routine. Neither should delay diagnosis or replace prescribed treatment.

Frequently asked questions

Did the plant blend improve the gut microbiome?

The blend changed the relative abundance of more microbial species than the probiotic or control food. However, there was no significant between-group difference in the overall health ranking of the species that changed. “More change” should therefore not be interpreted automatically as “a healthier microbiome”.

Did the plant blend improve digestive symptoms?

Participants receiving the blend reported less indigestion, constipation, heartburn and flatulence than the control group. These outcomes were self-reported, and the study does not prove that the same intervention will relieve symptoms in every person.

Does this prove that fibre is better than probiotics?

No. The study compared one proprietary plant blend with one particular probiotic organism at one dose. Fibre and probiotics have different roles, while probiotic effects depend on the exact strain, formulation, dose and intended outcome.

Should I aim to eat 30 different plants?

Eating a broad range of vegetables, fruit, legumes, whole grains, nuts, seeds, herbs and spices is a sensible goal. However, this study tested a particular blend containing more than 30 ingredients; it did not establish a universal minimum number that every person must eat.

Can I take probiotics if I eat plenty of fibre?

For many generally healthy adults, a suitable probiotic may complement a varied, fibre-rich diet. It does not replace that diet. Seek professional advice if you have a serious illness, a weakened immune system or an important underlying medical condition.

Was Noster ProBiotics tested in this trial?

No. Noster ProBiotics were not used in the study, so the microbial and symptom findings cannot be attributed to the Noster formulation.

The friendly pharmacist’s final word

This trial gives us another good reason to care about plant diversity and gut health.

A blend containing more than 30 plant ingredients produced broader microbial changes than one probiotic strain or a control food over six weeks. Participants also reported several improvements in digestive comfort compared with the control group.

Those results are encouraging—but they do not prove that plants have defeated probiotics, that every microbial change was healthier or that one commercial blend is essential for good gut health.

The sensible lesson is much better:

Feed your existing microbial community with a varied selection of fibre-rich plants, and use an appropriate probiotic as a complement where it makes sense.

Your carrots and your probiotics do not need boxing gloves. They are quite capable of working on the same team.

Resources

• British Journal of Nutrition: BIOME randomised controlled trial
• Study DOI and publication record
• NHS: How to include more fibre in your diet
• NCCIH: Probiotics—usefulness and safety

This article provides general educational information and does not replace individual advice from your doctor, pharmacist or dietitian.