9 août 2025

10 local medicinal herbs worth cooking with

Fresh thyme contains 20 mg of iron per 100 g, which is 143% of the nutrient reference value. That figure circulates in every article about medicinal herbs, and it is accurate.

The sprig of thyme you drop into a soup weighs about 2 g. It delivers 0.40 mg of iron, which is 2.9% of that same reference. To reach a full daily 14 mg from thyme you would need to eat 70 g of it, raw, in one sitting.

That is the central problem with this subject. Aromatic herbs are remarkable concentrates by weight and negligible nutritional contributors by portion. Both statements are true at once, and the second is almost always left out.

So this page takes a different route. What herbs genuinely do in a kitchen is flavour, and flavour lets you do measurable things, such as cutting salt. For everything else there is a precise legal framework in Switzerland, and exactly one of these ten plants has a clinically recognised effect in international guidelines, in a form that has nothing to do with cooking.

What Swiss law actually lets you claim

Before the virtues, the rule. The Swiss ordinance on food information defines a health claim in its article 31 as any message stating, suggesting or implying a relationship between a food or one of its components and health.

The essential point fits in one sentence from that article: health claims are permitted only if they appear in Annex 14. Any claim not listed there requires authorisation from the Federal Food Safety and Veterinary Office, granted only where generally recognised scientific studies provide proof.

Annex 14 lists substances, not aromatic plants: calcium, iron, magnesium, potassium, riboflavin, folates, selenium, chitosan, beta-glucans, phytosterols, guar gum, live yoghurt cultures, among others. None of the ten herbs on this page appears there by name. Not thyme, not sage, not nettle, not lemon balm.

The ordinance adds a detail aimed squarely at the usual writing style on this topic. Claims referring to non-specific benefits for general health or wellbeing are permitted only when accompanied by an authorised claim. And health claims must not be framed as recommendations from doctors or other health professionals.

A page stating that sage supports natural defences, or that rosemary stimulates circulation, is therefore not describing an established fact. It is making a claim that, on a Swiss label, would not be permitted. That is why this page deals in measured composition, culinary use and safety, and leaves the virtues to texts that never have to justify them.

The calculation nobody runs: the real portion

Composition tables give values per 100 g. Nobody eats 100 g of thyme. Here are the two columns side by side, from the Swiss Food Composition Database and the nutrient reference values used on labels.

Herb	Per 100 g	Real portion	What the portion delivers
Fresh thyme	20 mg iron, 310 mg calcium	2 g	0.40 mg iron (2.9%), 6.2 mg calcium (0.8%)
Fresh rosemary	4.8 mg iron, 210 mg calcium	2 g	0.10 mg iron (0.7%), 4.2 mg calcium (0.5%)
Fresh sage	4.5 mg iron, 270 mg calcium	3 g	0.14 mg iron (1.0%), 8.1 mg calcium (1.0%)
Fresh basil	5.5 mg iron, 250 mg calcium	10 g	0.55 mg iron (3.9%), 25 mg calcium (3.1%)
Peppermint	9.5 mg iron, 210 mg calcium	5 g	0.48 mg iron (3.4%), 10.5 mg calcium (1.3%)
Fresh parsley	5.9 mg iron, 850 mg potassium	10 g	0.59 mg iron (4.2%), 85 mg potassium (4.2%)
Dried rosemary	1280 mg calcium, 42.6 g fibre	1 g	12.8 mg calcium (1.6%), 0.43 g fibre

Dried rosemary is the clearest case. Its 1280 mg of calcium per 100 g is 160% of the reference value, which on paper would make it a spectacular calcium source. The one-gram teaspoon you actually put in a dish delivers 12.8 mg, or 1.6%. A third of a glass of milk does better.

Two herbs partly escape this rule, for a simple reason: people eat more of them. Parsley in a tabbouleh and basil in a pesto are measured in tens of grams, not pinches. At 10 g, parsley delivers 85 mg of potassium and 0.59 mg of iron, still modest but no longer symbolic. If you want herbs to count nutritionally, treat them as a leafy vegetable rather than a seasoning.

For protein and minerals the contributions that matter come from elsewhere on the plate anyway, as our plant protein guide sets out.

None of this takes anything away from herbs. It simply moves their value to where it actually sits.

The one solid clinical effect in this group, and its exact form

Of the ten plants on this page, one appears in international guidelines with randomised trial data behind it.

A systematic review with meta-analysis published in Phytotherapy Research in 2026 gathered 60 eligible studies covering 6329 patients with irritable bowel syndrome. For peppermint oil, across seven studies, the relative risk of symptom improvement was 1.63 with a 95% confidence interval of 1.33 to 2.00. The authors also note that the quality of many studies was limited.

A 2026 review in Nutrients is more explicit still about where this plant stands: peppermint oil is the only plant-based therapy consistently acknowledged across adult and paediatric international recommendations.

The detail that changes everything is the form. Those trials use peppermint essential oil in enteric-coated capsules, dosed and standardised. Not leaves in a salad, not a herbal tea. The menthol in a leaf infusion bears no relation to the amount in an enteric-coated capsule, and neither does the site of release.

Put plainly: peppermint has a demonstrated effect in a specific indication, in a specific pharmaceutical form, which is not the form in your kitchen. The mint leaf remains an excellent mint leaf.

Content varies enormously between batches

A composition table figure assumes all sage is alike. It is not.

A study published in Molecules in 2025 analysed thirteen dried sage products sold in Poland by HPLC. Carnosic acid ranged from 1.25 to 32.42 mg/g, carnosol from 0 to 9.06 mg/g, rosmarinic acid from 3.2 to 20.6 mg/g. On carnosic acid, the richest batch holds 26 times the poorest. The authors note that current standardisation and quality assessment procedures do not specify the content of these substances in dried sage.

The variability also comes from the plant. Work published in Food Chemistry in 2026 on 32 sage genotypes grown under homogeneous environmental conditions identified four distinct chemical groups, some dominated by camphor and 1,8-cineole, others by alpha-thujone and viridiflorol. Same soil, same climate, different profiles.

And it comes from growing conditions and harvest date. A 2026 study in Plants on sage grown under shading nets reports thujone content of 24.1 to 36.1% for cis-thujone and 4.9 to 13.1% for trans-thujone of the essential oil, depending on harvest and shading.

The practical consequence is not to give up on herbs. It is to understand that no precise numerical recommendation can apply to a herb bought in a packet, because nobody knows what that packet contains.

Sage, thujone, and the difference between a dish and an infusion

Sage contains thujone, a compound that is neurotoxic at high doses, and its share of the essential oil can exceed 40% depending on the harvest, according to the measurements above.

What matters here is the concentration factor. A few leaves fried on a risotto is one or two grams of fresh leaf. A concentrated infusion drunk several times a day, or worse an essential oil taken by mouth, changes the scale of exposure entirely, because the essential oil concentrates precisely the volatile compounds thujone belongs to.

The safety rule is therefore simple and rests on one distinction:

sage in cooking, a few leaves in a dish, remains ordinary food use
sage as a prolonged daily infusion leaves that frame
sage essential oil taken orally is not a cooking act and calls for professional advice

The same logic applies to every plant on this page. The question is never “is this plant toxic”, it is “what dose, in what form, for how long”.

Parsley: why the culinary amount and the extract are unrelated

Parsley illustrates the same mechanics with numbers.

Its essential oil contains apiol and myristicin. A 2026 study in Food Science and Nutrition on harvest stage shows apiol reaching 43.69% of the essential oil at the latest harvest, against profiles dominated by monoterpene hydrocarbons at earlier stages.

These compounds are the source of parsley’s reputation as a plant to avoid during pregnancy. A review published in Frontiers in Medicine in 2024 on parsley’s renal effects sums up the state of knowledge with the caution the subject demands: animal studies show reductions in oxidative stress and improvements in metabolic biomarkers, the limited human studies show only modest improvements in urinary composition, and parsley’s safety profile, particularly at high doses, requires further investigation, including potential herb-drug interactions and safety during pregnancy.

In short: the parsley in a tabbouleh is not the subject, the concentrated extract is. The distinction between the food and the extract is the only one that counts in this field, and it is the one that lists of virtues systematically skip.

One more point worth knowing if you take a vitamin K antagonist anticoagulant. Parsley and green herbs are rich in vitamin K1. A 2026 composition study in the Journal of Advanced Pharmaceutical Technology and Research measured 71.3 to 212.5 µg per 100 g fresh weight across five indigenous vegetables in northern Thailand, against a benchmark intake of 150 µg a day, and the authors specify that these values are descriptive intake estimates for dietary counselling and not evidence of altered anticoagulation outcomes.

What destabilises vitamin K antagonist therapy is not the presence of vitamin K in the diet, it is sudden variation in intake. Regular, stable consumption is the principle used in clinical practice, and this is a conversation for the doctor managing the treatment, not for an article.

Nettle: the only one on the list that carries nutritional weight

Nettle deserves separate treatment, because its composition puts it in another category.

A study published in the Journal of the Science of Food and Agriculture in 2026 analysed blanched, dried nettle leaf powder: 23.99% protein, 14.91% fibre, 347.46 mg calcium and 52.11 mg iron per 100 g. The authors incorporated this powder at 7% into a traditional savoury snack, which improved protein, iron, calcium, phenolics and flavonoids without compromising sensory acceptability.

Those figures describe a dried powder, dehydrated material rather than a fresh leaf. But unlike thyme, nettle gets eaten in quantity: a nettle soup starts from a good handful of leaves, not a pinch. That difference in use is what makes it nutritionally relevant where the others remain seasonings.

A 2026 review in Antioxidants details its composition: polyphenols including rutin, quercetin, kaempferol and chlorogenic acid, sterols including beta-sitosterol and stigmasterol, vitamins, carotenoids, and a lectin, Urtica dioica agglutinin. The review describes molecular mechanisms studied in vitro, which documents biological activity rather than a clinical effect in people.

Cooking it takes two steps. Pick young shoots before flowering, wearing gloves. Blanch for a minute in boiling water, which neutralises the stinging apparatus and lets you handle the leaves bare-handed afterwards. The rest is ordinary cooking: soup with potato, pesto with garlic and oil, tart filling.

Foraging: the only genuine danger in this subject

Every other precaution on this page is about dose. This one is about mistaking one species for another, and it is the only one that can kill.

A 2026 article in the International Journal of Emergency Medicine reports two patients admitted to the emergency department of a university hospital in Istanbul after sharing a meal prepared from wild greens later identified as poison hemlock, Conium maculatum. Despite the shared exposure, their courses diverged sharply: one developed early respiratory muscle involvement with progressive ventilatory failure requiring intubation and intensive care, the other had only mild, self-limiting neuromuscular symptoms. The authors stress that the exposure is often unrecognised on arrival.

Poison hemlock resembles wild parsley, chervil and other umbellifers. Nettle, by contrast, is hard to mistake. That is why the foraging rule is not a formality:

pick only species you identify with certainty, without any hesitation whatsoever
never rely on a general resemblance or on a photo recognition app alone
be especially wary of umbellifers, the family of parsley, fennel and hemlock
if there is any doubt about what was eaten, call the Swiss Toxicological Information Centre immediately on 145

The WHO five keys to safer food apply to herbs as well: wash with clean water, separate raw from ready-to-eat, and remember that raw leaves can carry contamination. A 2026 study in the International Journal of Food Science found inoculated Escherichia coli persisting at 6.5 log CFU/g in soil and 5.15 in coriander seeds, with a peak of 9.61 log CFU/g in the plants at day seven, a reminder that contamination of fresh leaves happens well upstream of your kitchen.

What herbs genuinely do well: replacing salt

Here is the use where the effect is real, measurable and immediate.

The WHO recommends staying below 5 g of salt a day in adults. Most populations sit well above that, and the bulk of that intake comes from salt added in cooking and from processed foods.

Herbs work on this through a simple mechanism: they occupy the aromatic space salt used to occupy. A dish with thyme, garlic and lemon stays interesting in the mouth with considerably less salt, because there is something else to perceive. That is sensory substitution, not a medicinal property, and it is probably the most concrete service these plants do your health. The subject has its own page on seasoning without salt.

Three principles make the substitution work:

Acidity amplifies. A squeeze of lemon or a splash of vinegar at the end of cooking wakes the herbs up and compensates for the flatness of a lightly salted dish.

Fat carries aroma. The aromatic compounds in herbs are fat-soluble, which is why a rosemary-infused oil is more fragrant than a water infusion.

Timing matters, which is the next point.

When to add which herb

The useful classification in a kitchen is not medicinal, it is thermal. Herbs split according to how well their aromatic compounds survive heat.

Woody herbs, early in cooking: thyme, rosemary, sage, oregano, bay. Their tough leaves release compounds slowly and tolerate long cooking. They go into the stock, the stew, the marinade, the tomato sauce that simmers.

Tender herbs, at the end or raw: basil, parsley, mint, coriander, chives, lemon balm. Their volatile compounds leave with the heat. Added twenty minutes too early, they leave nothing but a tired green colour. They go in off the heat, at the last moment.

The commonest mistake is treating basil like thyme. A cooked pesto is not a pesto, it is green purée.

For drying, the usual ratio is one to three: a teaspoon of dried herb for a tablespoon of fresh. That holds for woody herbs. Dried basil, coriander and chives lose so much that they do not replace fresh at any ratio. Our page on preserving herbs covers the methods that hold on to the most.

The ten, in culinary use

Thyme. Woody, robust, goes into anything that simmers. The lemon variety suits root vegetables.

Rosemary. Powerful, worth restraint: one whole sprig in a dish for four is often enough. Excellent as an infused oil, with potatoes and roast vegetables.

Sage. Leaves fried in fat until they crisp, over pasta or risotto. Precautions on form as described above.

Oregano. The one tender herb in the group that gains from drying, which explains its place on pizza. Its dried flavour is rounder than fresh.

Basil. Raw, at the end of service. Several varieties exist with distinct profiles: lemon, purple, Thai.

Mint. Tabbouleh, yoghurt sauces, desserts. Planted in open ground it takes over: a pot is wiser.

Parsley. Treat it as a leafy vegetable rather than a garnish. It becomes interesting in quantity, in a tabbouleh or a chimichurri, which puts it alongside the essential spices and herbs of a vegetarian kitchen.

Coriander. Divisive for real genetic reasons, tied to the perception of certain aldehydes. Leaves raw, seeds early in cooking: these are two different ingredients.

Nettle. Blanch for a minute, then cook it like spinach. The only one in the group with nutritional weight, because you eat it in quantity.

Lemon balm. A fragile citrus note that vanishes with heat. Fruit salads, infusions, syrups.

Storage: what degrades, and how fast

Fresh herbs lose water and volatile compounds above all. A 2026 study in Foods on hydroponically grown nettle leaves compared ambient and modified atmosphere: leaves packed in modified atmosphere retained significantly more phenolic compounds, ascorbic acid, total chlorophylls and antioxidant capacity, with the highest values after 17 days without moisture absorbers. Adding moisture absorbers was associated with a general decline in metabolite content.

That result is interesting for a counter-intuitive reason: trying to dry out the storage environment degraded quality. For a home kitchen the practical translation is to keep tender herbs damp and cold, standing in a glass of water or wrapped in a damp cloth, rather than storing them dry. The subject is developed in keeping fresh herbs all year round.

For dried herbs, airtight jars away from light slow oxidation, but aromatic content declines over a few months regardless. A dried herb that smells of nothing when rubbed between your fingers will season nothing. On a commercial blend, the only useful information is the ingredient list, and reading one is covered on our page about reading a nutrition label.

Five common mistakes

Reading the per-100 g figure as an intake. This is the error that structures nearly everything published on the subject. Thyme’s 20 mg of iron becomes 0.40 mg in the sprig you actually use.

Confusing the food with the extract. Peppermint oil in enteric-coated capsules has trial data behind it. A mint leaf in a tea has neither the same data nor the same dose.

Cooking tender herbs. Basil, coriander and lemon balm lose most of their aroma to heat. They go in off the heat.

Foraging without certain identification. This is the only serious risk in the subject, and the poison hemlock case is the reminder.

Taking a herb as a prolonged course for a health problem. None of the ten appears in Annex 14 of the Swiss food information ordinance. If a symptom warrants treatment, it warrants medical advice.

When medical advice comes first

These plants are ordinary foods in culinary amounts. Three situations fall outside that frame and deserve a conversation with a health professional rather than a reading:

pregnancy and breastfeeding, for concentrated infusions and extracts, particularly of parsley and sage
vitamin K antagonist anticoagulant therapy, for stability of vitamin K1 intake
long-term medication, because of possible interactions with concentrated extracts

None of these situations rules out cooking with herbs. They concern concentrated forms and repeated therapeutic use.

What this page cannot tell you

The composition values come from generic categories in the Swiss database. The Polish sage data show a factor of 26 between two commercial batches on carnosic acid, and nothing suggests the other herbs are more uniform.

The portion sizes used here are estimates of common practice, not measurements. Two grams for a thyme sprig and ten grams for a handful of parsley match what goes into a dish, but your hand is not mine.

The nettle data concern a blanched, dried leaf powder analysed in an Indian study, not fresh nettles picked in Switzerland. The order of magnitude is useful, the exact value is not.

Finally, the mechanisms described in the nettle and sage reviews come largely from in vitro and animal work. Biological activity observed in cells does not predict an effect in a person eating soup.

Frequently asked questions

Do herbs count towards five portions of fruit and vegetables? Not at the usual amounts. Swiss dietary recommendations count 3 portions of vegetables and 2 of fruit a day, and a vegetable portion is measured in tens of grams. A parsley-heavy tabbouleh can contribute; a pinch of thyme cannot.

Does a thyme tea cure a sore throat? A hot drink soothes mechanically, which is already something. No health claim for thyme appears in Annex 14 of the Swiss ordinance, and a sore throat that persists or comes with fever is a matter for medical advice.

Fresh or dried herbs? It depends on the herb. Drying suits woody herbs: thyme, rosemary, oregano, bay. It destroys most of the point of basil, coriander and chives.

Does mint really help digestion? Peppermint essential oil in enteric-coated capsules has randomised trial data in irritable bowel syndrome, with a relative risk of 1.63 across seven studies. That result does not transfer to a leaf infusion, which is a different dose in a different form.

Can I pick nettles by a path? Technically yes, but the location matters more than the plant: avoid roadsides, treated areas and places dogs frequent. Young shoots before flowering, gloves, blanching.

Is parsley a good iron source for a vegetarian? Marginally. A 10 g handful delivers 0.59 mg, or 4.2% of the reference value. Absorption of plant iron depends mainly on other factors, set out on our page about plant iron absorption.

Are supermarket potted herbs as good as garden ones? For cooking, yes, provided you repot them and do not leave them in their original compost too long. Our page on growing herbs on a balcony explains how to settle them in.

How long does a jar of dried herbs last? Until it stops smelling of anything. In practice a few months for leaves, longer for whole seeds, which degrade more slowly than crushed leaves.

Can herbs be frozen? Yes, and it usually beats drying for tender herbs. The methods are compared on our page on preserving herbs.

Which wild herbs are safe to start with? Nettle, which is hard to mistake, and wild garlic provided you check each leaf for the garlic smell. The subject has its own page: edible wild herbs.