31 juil. 2025

Herbal Teas and Spice Blends to Aid Digestion

Only one preparation on this page has measured efficacy against digestive symptoms, and it is not a tea: peppermint oil in gastro-resistant capsules. Four randomised trials covering 392 patients with irritable bowel syndrome give a relative risk of symptoms persisting of 0.43, with a 95% confidence interval of 0.32 to 0.59. Every other plant here, chamomile, fennel and ginger infusions included, falls under what the European Medicines Agency calls traditional use, a category that means precisely this: the effect is plausible and the safety documented by long use, but clinical trials are lacking.

That distinction shapes everything below. It does not disqualify the evening cup, which remains pleasant and harmless at ordinary doses. It simply changes what you can honestly expect from it, and it comes with time limits, minimum ages and a contamination risk that articles on this subject almost always leave out.

Well-established use or traditional use: the distinction that matters

The Committee on Herbal Medicinal Products at the European Medicines Agency places each preparation in one of two categories, and the gap between them is wide.

Well-established use means there are bibliographic data providing scientific evidence of effectiveness and safety, covering a period of at least ten years in the EU. In other words, clinical studies have been run and assessed.

Traditional use means there is insufficient evidence from clinical trials, but the effectiveness is considered plausible and there is evidence of safe use for at least 30 years, including at least 15 within the EU. That is a safety record built on experience, not a demonstration of efficacy.

Of the four most commonly cited digestive plants, only one clears the first bar for a digestive indication, and only in a specific form.

Plant	Digestive indication	EMA status	Minimum age	Duration of use
Peppermint oil	Minor belly spasms, flatulence, belly pain, especially in irritable bowel syndrome	Well-established use	8 years	Depends on preparation
Ginger rhizome	Mild spasmodic gastrointestinal complaints, bloating, flatulence	Traditional use	18 years for this indication	2 weeks
Ginger rhizome	Prevention of nausea and vomiting in motion sickness	Well-established use	6 years	Depends on preparation
Chamomile flower	Minor gastrointestinal complaints, bloating, minor spasms	Traditional use	12 years generally	Seek advice beyond one week
Sweet fennel fruit	Mild spasmodic gastrointestinal complaints, bloating, flatulence	Traditional use	4 years	1 to 2 weeks

The ages and durations in this table are not boilerplate caution. They appear in the monographs because data beyond those limits do not exist.

Peppermint, and why the form matters

The European Medicines Agency concludes that peppermint oil preparations taken by mouth can be used to relieve minor belly spasms, flatulence and belly pain, especially in patients with irritable bowel syndrome. That conclusion rests on clinical studies showing reduced abdominal pain, discomfort and bloating.

The figure itself comes from a systematic review and meta-analysis published in the BMJ. Across four trials and 392 patients, peppermint oil produced a relative risk of symptoms persisting of 0.43 (0.32 to 0.59). In the same analysis, fibre reached 0.87 (0.76 to 1.00) with the effect limited to ispaghula, and pharmaceutical antispasmodics 0.68 (0.57 to 0.81). Peppermint oil therefore outperformed both conventional comparators in that dataset. The Canadian Association of Gastroenterology clinical practice guideline points the same way: it suggests peppermint oil while not suggesting herbal therapies in general.

Three caveats apply before you head to the pharmacy.

The form tested is the oil capsule, usually gastro-resistant so the contents release in the intestine rather than the stomach. An infusion of mint leaves is a different thing and has not been evaluated this way. It remains a pleasant drink, but the figure above does not transfer to it.

The contraindications are explicit and cover common situations: for minor gut problems, peppermint oil must not be used by people with achlorhydria, liver disease, gallstones or any other bile-related problem.

Finally, use for this indication is ruled out below the age of eight.

Ginger, effective for something other than digestion

Ginger occupies an interesting position: it has well-established use, but not for the indication usually attached to it. The Agency recognises its effectiveness in preventing nausea and vomiting from motion sickness, based on trials where it was more effective than placebo and as effective as other medicines. The mechanism is not fully understood, though a change in gastrointestinal motility is suggested.

For symptomatic treatment of mild spasmodic gastrointestinal complaints, bloating and flatulence included, the status drops back to traditional use. Use is capped at two weeks for that indication and is not recommended below 18 years of age owing to a lack of adequate data.

The widespread claim that ginger or black pepper act as natural fat burners that help regulate weight appears in no monograph and is supported by none of the trials cited here. It belongs to marketing, not pharmacology.

Fennel and chamomile, comfort documented by use

Sweet fennel fruit is traditionally used for the symptomatic treatment of mild spasmodic gastrointestinal complaints including bloating and flatulence. Preparations are generally taken three to four times a day and should not be used for more than one to two weeks. They can be used from the age of four; below that they are not recommended because there is not enough information on safe use.

One point deserves correcting, because it circulates widely: the Agency states that, since no tests have looked at the effects during pregnancy or lactation, sweet fennel fruit medicines should not be used by women who are pregnant or breastfeeding, as a general precaution. Fennel’s reputation as a lactation aid therefore comes with no authorisation in that context.

Chamomile flower is also traditional use only, for symptoms of minor gastrointestinal complaints such as bloating and minor spasms. The monograph advises consulting a doctor or qualified practitioner if symptoms persist for more than one week, and reserves most preparations for adults and adolescents over 12, with only some recommended below that age.

The risk nobody mentions: pyrrolizidine alkaloids

This is the one documented safety issue with herbal teas, and it is not a footnote.

Pyrrolizidine alkaloids are natural substances produced by many plant species, probably as a defence against pests. The Swiss Federal Food Safety and Veterinary Office explains that humans ingest them mainly through honey, spices, culinary herbs, tea, herbal infusions and food supplements. In most cases they are not a component of the plant you bought but a contamination from wild plants that enter the batch during harvest or processing.

Two consequences are documented. The 1,2-unsaturated alkaloids can damage the liver through veno-occlusive lesions and cause serious poisoning. More importantly, some of them caused cancer and genetic damage in animal studies, which leads the Swiss office to call for minimising their content in food. The office notes that in Switzerland and Europe, acute poisoning is highly unlikely at the concentrations currently measured. The European Food Safety Authority, however, pointed out in 2017 that people who drink tea and herbal infusions frequently and in large amounts may face an increased risk.

The point that bears directly on a reader of an article about herbal tea is this: according to the Swiss office’s own studies, almost all the alkaloids present in the leaves end up in the brewed drink. A measurement published in Food Chemistry in 2025, carried out under controlled conditions by UPLC-MS/MS, puts transfer rates between 30% and 68% with an average of 49%, and establishes that brewing time is not a significant factor. Polarity of the compounds and the pH of the infusion drive the transfer instead. Steeping for less time therefore protects you from nothing.

Since 2024, the Swiss contaminants ordinance has set numerical limits, expressed as the sum of alkaloids on a dry matter basis:

Product	Maximum level
Herbal infusion, except those listed below	200 µg/kg
Rooibos, aniseed, lemon balm, chamomile, thyme, peppermint, lemon verbena infusions	400 µg/kg
Tea (Camellia sinensis), including flavoured, dried	150 µg/kg
Dried tea and infusions for infants and young children	75 µg/kg
Liquid tea and infusions for infants and young children	1 µg/kg
Dried herbs, except borage, lovage, marjoram and oregano	400 µg/kg
Dried borage, lovage, marjoram and oregano	1000 µg/kg
Plant-based food supplements, extracts included	400 µg/kg
Cumin seeds	400 µg/kg

The tenfold stricter limit for dried products aimed at infants shows clearly where the concern lies, and the ready-to-drink infant product drops all the way to 1 µg/kg.

Sourcing matters too. A 2025 study in BMC Complementary Medicine and Therapies analysed 28 herbal products bought from spice shops, markets and internet sites for gas pain in children: 75% contained pyrrolizidine alkaloids above 10 µg/kg. Fennel was the most used plant at 51.3%, and 59% of parents bought from spice shops rather than pharmacies. The authors recommend obtaining such products from pharmacies and under professional advice.

The practical conclusion is not to give up herbal tea. It is to rotate plants rather than drinking three litres of the same infusion daily for months, to prefer controlled supply chains, and to apply particular caution with young children.

Brewing properly, with quantities

A reliable baseline for most infusions: one tablespoon of dried plant material, or one teaspoon of seeds, per 250 ml of water.

For leaves such as mint or verbena, pour hot water over them and cover the cup while it steeps. Covering is not decorative: the aromatic compounds in these plants are volatile and escape with the steam.

For seeds such as fennel, cumin or coriander, crush them lightly before pouring on boiling water. An intact seed coat limits extraction.

For fresh ginger, cut thin slices and steep for five to ten minutes in 250 ml of boiling water.

Store dried plants away from light in an airtight container. Light and air degrade the aromatic compounds faster than time alone. Our page on keeping fresh herbs year round covers the storage methods that actually work.

Spices in cooking, and the special case of curcumin

Spice blends add flavour, which is reason enough to use them, particularly for cutting back on salt. On the digestive side, the spices in a chai, a ras el hanout or a curry do contain ginger, cinnamon, cumin and coriander, but at culinary quantities, a teaspoon spread across four portions, you are far below the doses in the preparations that were evaluated.

Cinnamon illustrates the gap between composition and effect nicely. It shows 1,230 mg of calcium and 38 mg of iron per 100 g in the Swiss Food Composition Database, impressive numbers. A teaspoon weighs about 2.5 g and therefore delivers 31 mg of calcium and 0.95 mg of iron, useful but modest. The same reasoning applies across the spice rack: these are condiments, not nutrient sources.

Turmeric deserves its own note, because the bioavailability argument is often stood on its head. A review published in Nutrients in 2019 sets out the problem: curcumin combines a broad spectrum of properties observed in the lab with a poor pharmacokinetic profile, where low absorption by the small intestine and extensive reductive and conjugative metabolism in the liver dramatically weaken oral bioavailability. Adding fat or pepper improves matters at the margins but does not turn a pinch of turmeric in a curry into an anti-inflammatory treatment.

One final safety note concerns essential oils and supplements rather than cooking. Alkenylbenzenes such as safrole, methyleugenol and estragole occur notably in basil and fennel seeds. A review published in Foods in 2021 notes that safrole and methyleugenol are genotoxic and carcinogenic, and that essential oils and plant food supplements derived from these herbs are often characterised by high alkenylbenzene content. Fennel seed in a soup does not raise this issue; essential oil taken daily is another matter.

For dosing spices in an actual dish, our guide to dosing spices in a homemade curry gives quantities and the order of addition, and the page on seven everyday spices separates what is evidenced from what is not.

What actually helps digestion

Official guidance on functional digestive symptoms leans far less on plants than on simple habits, and that is where to start.

The British NICE guideline on irritable bowel syndrome lists: regular meals eaten unhurried, without skipping meals or leaving long gaps; at least eight cups of fluid a day, preferably water or non-caffeinated drinks such as herbal tea; tea and coffee limited to three cups a day; alcohol and fizzy drinks reduced; fresh fruit limited to three 80 g portions a day. For wind and bloating, oats and up to one tablespoon of linseeds a day. On fibre, the recommendation is to review intake and usually reduce it, favouring soluble fibre such as oats or ispaghula while discouraging insoluble fibre such as bran. NICE also allows that antispasmodics may be considered, taken as required, alongside this advice.

That matters for a vegetarian reader, whose fibre intake is often high: when discomfort persists, the most productive move is rarely to add a herbal tea, it is to adjust fibre and meal rhythm. The page on the microbiota and a vegetarian diet explains what happens downstream, and the one on soaking and sprouting legumes addresses the most common cause of bloating among vegetarians.

Common mistakes

Expecting from an infusion the effect measured on a capsule. The relative risk of 0.43 applies to peppermint oil capsules, not to mint leaf tea. The two preparations share a plant name but differ in concentration and in where they act along the gut.

Believing a shorter steep reduces contamination. The available measurement establishes that brewing time is not a significant factor in alkaloid transfer. Compound polarity and pH are what count.

Drinking the same herbal tea daily for months. That is exactly the consumption pattern the European Food Safety Authority flagged as potentially risky. Rotating plants spreads the exposure.

Giving a digestive tea to a young child without checking. Fennel is not recommended below four years, peppermint oil is excluded below eight for the digestive indication, and the legal maximum for alkaloids is ten times stricter for products aimed at infants.

Taking fennel during pregnancy or breastfeeding. The European monograph explicitly rules it out in those situations, as a precaution, for want of trials.

Confusing composition with effect. Cinnamon contains plenty of iron per 100 g, but a teaspoon supplies less than a milligram. Judge spices by the flavour they bring to the dish.

Depending on your situation

You get occasional bloating after a heavy meal. A fennel, chamomile or ginger infusion is reasonable, over a few days rather than continuously. If the discomfort is regular, the dietary route will be more productive than the teapot.

You have diagnosed irritable bowel syndrome. Peppermint oil capsules are the only option on this page backed by trials, and they are suggested by the Canadian guideline. Discuss them with a doctor or pharmacist, given the liver and bile contraindications.

You are pregnant or breastfeeding. Sweet fennel is explicitly advised against by the European monograph in these situations. For any other plant, ask before making it a routine.

You are preparing teas for a child. Respect the minimum ages, buy from a pharmacy rather than a market stall or website, and do not extend use beyond a few days without professional advice.

You take long-term medication. Some plants, ginger among them, interact with medicines. Ask the pharmacist beforehand rather than afterwards.

You mainly want to drink more. That may be the best use of everything above. Infusions count towards fluid intake, carry no sugar and no caffeine, and NICE recommends at least eight cups a day. Our page on hydration over 24 hours covers how to spread that out.

The limits of this page

The statuses, ages and durations cited come from monographs published by the Committee on Herbal Medicinal Products at the European Medicines Agency. They apply to herbal medicinal products, whose concentration and quality are controlled, not to a tea brewed at home, whose actual dose is unknown. That difference cuts both ways: it makes the effect less predictable, and it also makes most adverse effects less likely.

The relative risk of 0.43 for peppermint oil comes from a meta-analysis of four trials only, conducted in people with irritable bowel syndrome. It says nothing about the effect in someone without a diagnosed digestive disorder.

The maximum alkaloid levels are regulatory limits for products sold in Switzerland, not measurements taken on the products you buy. The contamination data cited come from Turkish analyses and European laboratory measurements.

This page makes no diagnosis and does not replace medical advice. Persistent digestive discomfort, weight loss, blood in the stool or a lasting change in bowel habit warrant a consultation.

Frequently asked questions

Does peppermint tea really work? The trials tested peppermint oil in capsules, not leaf infusion. The tea remains pleasant and harmless at ordinary doses, but the efficacy figure does not transfer to it.

How long can you drink a digestive tea? The European monographs limit sweet fennel to one to two weeks and ginger to two weeks for mild spasmodic complaints. For chamomile, medical advice is recommended if symptoms persist beyond one week.

Are herbal teas risk free? At ordinary doses and with rotation between plants, the risk is low. The genuine watch point is pyrrolizidine alkaloid contamination among heavy daily consumers, whom EFSA explicitly identified in 2017.

Should I steep for less time to limit contaminants? No. The available measurement shows brewing time is not a significant factor in transfer.

Does ginger help with weight loss? No European monograph carries that indication, and none of the trials cited here supports it.

Is turmeric in a curry anti-inflammatory? Curcumin is poorly absorbed and rapidly metabolised by the liver. At culinary quantities, treat it as a condiment rather than a treatment.

Which tea for a child? Respect the monograph ages, sweet fennel from four years, chamomile generally from twelve depending on the preparation, and buy from a pharmacy. The legal alkaloid limit is ten times stricter for products aimed at infants, which indicates the expected level of caution.

What if nothing helps? Go back to the NICE basics, regular meals, fluid intake, shifting fibre towards soluble sources, and see a clinician if the discomfort persists.

Sources

To go further, see how to season without salt using herbs, spices and citrus and the guide to edible wild herbs.