Phytobiotics as natural antibiotics? Fact check on effects, benefits and risks

Phytobiotics have the reputation of being natural antibiotics. They’re said to support digestion, the immune system and metabolism, and to reduce inflammation. Often, the term refers to extracts from herbs, spices or other plants. But what exactly are phytobiotics – and what does the science really say?

Dr Melanie Loessner

17 February 2026 | 3 Min. Reading Time

Frequently asked questions about phytobiotics

The term phytobiotics refers to plant-based bioactive substances. In science, it’s often used in animal nutrition, where they’re known as phytogenic feed additives. When it comes to human nutrition, we usually speak of secondary plant compounds.

Phytobiotics primarily act through the gut: Plant-based substances can influence gut bacteria and their metabolic products in beneficial ways.

No. Probiotics are live micro-organisms, while prebiotics are indigestible food components (such as certain fibres) that serve as food for gut bacteria. Phytobiotics, by contrast, are plant compounds – some with antimicrobial or anti-inflammatory properties.

Phytobiotics aren't essential nutrients like vitamins or minerals. They’re plant compounds that can have an influence on the body – but you don’t need them to stay healthy.

Phytobiotics are found in plant-based foods: vegetables, fruits, pulses, whole grains, nuts, as well as herbs, teas and spices.

Supplements in capsule or extract form often contain higher and more precisely measured amounts. However, how effective they are depends on the specific substance, on the dosage and on the duration of their consumption. Much of the current evidence also stems from lab and animal studies and can't be directly transferred to humans.

It’s wise to be cautious with high-dose extracts – especially if you’re taking medication, are pregnant or breastfeeding, or have an existing medical condition.

Phytobiotics: What are they?

The term phytobiotics isn't clearly defined or protected. In scientific literature, it’s mostly used to describe plant-based additives in animal feed: extracts or essential oils that may influence feed efficiency, gut health or susceptibility to infections.

For humans, the term secondary plant compounds is more commonly used. Their effects on humans vary widely depending on the specific substance.

Possible effects of phytobiotics on gut health

A large part of the potential effects of phytobiotics is linked to the gut. Many plant substances aren't fully absorbed in the small intestine during digestion and therefore reach the large intestine. There, they can interact with gut bacteria and influence the composition of the gut microbiome. A stable and diverse gut microbiome is associated with good health, but research in this area is still at an early stage.

Effects of phytobiotics and examples

Beyond gut health, a number of other effects for certain phytobiotics have been debated, although these are usually considered indications rather than firmly established benefits.

Polyphenols (e.g. flavonoids from berries, cacao, tea): act as antioxidants (protecting cells), may reduce inflammation and support the cardiovascular system.
Carotenoids (e.g. beta-carotene from carrots, lycopene from tomatoes): may act as antioxidants and protect cells against oxidative stress.
Glucosinolates / isothiocyanates (e.g. in cabbage, broccoli): belong to the bitter compounds, give these vegetables their characteristic bitterness and are being studied for their potential cell-protective effects.
Sulphur-containing plant compounds (e.g. in garlic and onions): some evidence of antimicrobial and anti-inflammatory properties, as well as possible effects on blood pressure and blood lipid levels.
Terpenes / essential oils (e.g. in herbs such as thyme, oregano, peppermint): often show antimicrobial or antispasmodic effects in laboratory studies.
Tannins (e.g. in tea, cacao, pulses): may have antioxidant effects but can also impair the absorption of certain minerals (such as iron).
Lignans (e.g. in flaxseed, sesame, whole grains): have strong antioxidant properties and also exert hormone-like effects. They also have a calming effect.

Phytobiotics as natural antibiotics?

Phytobiotics are sometimes marketed as natural antibiotics, which is misleading. Some plant compounds do indeed show antimicrobial properties. However, this doesn’t mean that they have the same effects as antibiotics (for example in treating infections or existing illnesses in humans). For this reason, antibiotics prescribed by a doctor must never be replaced with phytobiotics, herbal extracts or other natural remedies.

Plant compounds as add-ons to antibiotics

In laboratory studies, some plant compounds appear to enhance the effects of antibiotics when used in combination. Researchers are therefore investigating whether and how they might support antibiotic treatment. However, much more research is needed in this area.

Phytobiotics in our food

A diet rich in fruit, vegetables, whole grains and herbs provides a wide range of secondary plant compounds and as part of a healthy lifestyle, these may contribute to overall health. However, whether specific phytobiotics offer additional, distinct benefits beyond this remains the subject of ongoing research.

What's clear, though, is that anyone wishing to make sensible use of phytobiotics doesn’t need to turn to supplements. A predominantly plant-based, varied and healthy diet with plenty of colourful vegetables and fruits, pulses, whole grains, good-quality nuts and generous amounts of herbs and spices provides many secondary plant compounds in everyday, practical amounts.

When is caution advisable?

Although phytobiotics are derived from plants, they’re not harmless natural remedies. It’s well documented, for example, that some plant compounds or products can weaken or enhance the effects of medicines. In the following situations, it's advisable to discuss the use of high-dose herbal and plant extracts with your doctor: