Nasturtium

Heart and circulation The most direct human evidence for nasturtium comes from a randomized crossover pilot study in prediabetic adults. Participants consumed a standardized freeze-dried nasturtium drink delivering 15 g of nasturtium (containing 681 µmol of benzyl glucosinolate) once weekly for four weeks. The results showed significant reductions in LDL cholesterol (often called "bad" cholesterol), oxidized LDL (ox-LDL, a particularly damaging form linked to artery plaque), and two cardiovascular risk ratios — the Castelli Index I (total cholesterol divided by HDL) and the atherogenic coefficient (non-HDL divided by HDL). Total antioxidant capacity (the body's overall ability to neutralize damaging free radicals) also improved by roughly 10–21% depending on the measurement method used. These are promising findings, but important context: this was a small pilot trial in one specific population. Larger, longer studies are needed before nasturtium can be said to reliably "lower cholesterol" in a clinical sense. For now, it is more accurate to say that early evidence suggests it may support cardiovascular risk markers. Digestive health and microbiome Nasturtium has no dedicated clinical trials for digestive outcomes, but its culinary properties offer plausible support for gut comfort. The peppery phytochemicals may stimulate saliva and gastric secretion, which helps kick-start digestion. The plant also provides some dietary fibre and compounds traditionally described as carminative (helping to ease gas and bloating). People with sensitive digestion should introduce nasturtium gradually, as large amounts of pungent isothiocyanates can cause mild gastrointestinal irritation. Blood sugar and metabolism The same prediabetic crossover study explored insulin resistance and metabolic markers, but the glycaemic (blood sugar) results were exploratory rather than the primary finding. Mechanistically, BITC may influence signalling pathways involved in carbohydrate metabolism and insulin sensitivity, which makes this an area worth watching. At this stage, any blood sugar benefit should be considered speculative and secondary to broader dietary changes. Inflammation and recovery The prediabetic crossover study showed improvements in oxidized LDL and antioxidant capacity — both closely linked to oxidative stress–driven inflammation. A separately registered German cross-over intervention trial is actively investigating nasturtium's BITC content for anti-inflammatory effects, though published outcome data from that trial are limited. Laboratory studies show that glucosinolates and isothiocyanates can inhibit inflammatory responses in human immune cells, which provides a plausible mechanism. Overall: anti-inflammatory potential is supported by one pilot human trial plus mechanistic data, making the evidence promising but not yet firm. Immune and antimicrobial support In several European countries, a combination phytotherapeutic containing nasturtium and horseradish is used for acute sinusitis, bronchitis, and urinary tract infections — and in some studies these combinations have performed comparably to standard antibiotics for uncomplicated bladder infections. However, these findings come from combination products, not nasturtium alone. The plant's glucosinolates and isothiocyanates do have demonstrated broad antimicrobial activity against bacteria, viruses, and fungi in laboratory settings, which underpins traditional use. Treating it as immune-supportive food is reasonable; using it as a standalone antibiotic replacement is not supported by evidence.

Fresh leaves and flowers (the most practical choice) Raw, fresh nasturtium leaves and flowers retain the highest levels of vitamin C, glucosinolates, and heat-sensitive antioxidants. This is the form used in most traditional and culinary contexts, and it is the simplest way to add nasturtium to your diet. Look for young, tender leaves for the mildest flavour; older leaves are sharper and more peppery. Freeze-dried powder or functional drink The only form tested in human trials is a standardized freeze-dried nasturtium preparation. This concentrates glucosinolates and allows for precise dosing, but it is not widely available as a consumer product. If you see nasturtium powder supplements, check whether the glucosinolate content is standardized. Pickled seeds and buds Immature nasturtium seeds and flower buds pickled in brine or vinegar make a convincing caper substitute. They carry a punchy, briny flavour and are a useful condiment in plant-based cooking. One note: seeds and buds are relatively high in oxalic acid (a naturally occurring plant compound that can bind minerals and, in large quantities, contribute to kidney stones), so treat them as a condiment rather than a staple. Combination herbal products Registered phytotherapeutic combinations with nasturtium and horseradish are available in some European countries. These are formulated and dosed according to regulatory standards and are distinct from casual culinary use.

There is no formally established daily dose for nasturtium consumed as a food. Here is a practical guide based on available evidence: Culinary use (everyday baseline): A small handful of fresh leaves and flowers — roughly 5–15 g — a few times per week is a reasonable starting point. This is consistent with traditional and culinary use and is the amount that provides a meaningful hit of vitamin C and K without risk of overconsumption. What human trials used: The only published randomized crossover trial used a standardized freeze-dried drink delivering 15 g of nasturtium once weekly (not daily) for four weeks. This is not a daily dose recommendation — it was a research protocol designed to measure acute effects. Seeds and pickled buds: Treat these as condiments. A teaspoon to a tablespoon at a time is appropriate. Avoid eating large quantities of seeds or buds daily given their oxalic acid content. Start low: If nasturtium is new to your diet, begin with a few leaves in a salad and increase gradually. Very large amounts eaten at once can cause stomach upset in sensitive individuals due to the pungent isothiocyanate content. No upper limit is established for culinary nasturtium consumption in healthy adults, but common sense applies: variety in your diet matters more than maximizing any single ingredient.

The salad-as-meal cook Wants more nutritional depth from fresh vegetables without taking supplements Enjoys bold, peppery flavour as an alternative to rocket or watercress Benefits from nasturtium's vitamin C and K in combination with legumes and whole grains The heart-health-focused eater Already eating a mostly whole food, plant-based diet and looking for functional additions Interested in foods that may support healthy cholesterol ratios and antioxidant status Can incorporate nasturtium into regular meals knowing early human trial data exist for cardiometabolic markers

Nasturtium leaves and flowers are highly nutritious, providing up to 465 mg of vitamin C per 100 g, which is more than four times the amount found in oranges. They are also an excellent source of vitamin K, offering over 100% of the daily value per 100 g.

Nasturtium leaves and flowers can be eaten raw in salads, blended into a peppery pesto, or used as a garnish for soups and grain bowls. The seeds can also be pickled in a vinegar brine for two weeks to create a flavorful substitute for capers.

People taking warfarin or other blood thinners should be cautious because nasturtium is exceptionally rich in vitamin K, which can interfere with how these medications work. Those with a history of kidney stones or gout should also limit their intake of seeds and buds due to their oxalic acid content.

Nasturtium contains benzyl isothiocyanate (BITC), a compound that drives the plant's antimicrobial, anti-inflammatory, and metabolic-regulating properties. It also provides antioxidants like phenolic compounds, flavonoids, and anthocyanins that help neutralize cell-damaging free radicals.

Nasturtium pairs exceptionally well with avocado, where its sharpness cuts through the richness, and with cucumber or white beans for a cooling, high-protein salad. Another effective combination is roasted beetroot and walnuts, which balances the plant's peppery bite with earthy sweetness.

While nasturtium compounds show antimicrobial activity in laboratory settings, eating the leaves is not a direct replacement for prescribed antibiotic treatment. A regulated combination of nasturtium and horseradish is used clinically in Europe, but you should never delay medical treatment in favor of the herb.

Nasturtium flowers contain high levels of lutein, a fat-soluble carotenoid pigment that is well known for protecting the macula of the eye. Lutein plays a critical role in maintaining overall eye health and protecting the central part of the retina.

You should only eat nasturtiums that are specifically labeled as food-grade and pesticide-free, as ornamental varieties from garden centers are often treated with toxic chemicals. Additionally, ensure you are eating the leaves and flowers rather than large quantities of seeds, which are higher in oxalic acid.

Nasturtiums are widely available at local farmers markets and specialty retailers like Whole Foods Market or Sprouts, typically during the spring and summer months. Because they are delicate, they are rarely found in the produce aisles of conventional grocery chains and are most easily sourced from local growers or home gardens.

In the US, nasturtium is a hardy annual that thrives during the spring and fall in warmer climates like California (Zones 9-11) or as a summer staple in northern states. They are particularly popular in Pacific Northwest and New England gardens because they prefer cooler roots and consistent moisture to produce the best-tasting leaves.

Under USDA regulations, nasturtium sold for consumption should be labeled as "edible flowers" to distinguish them from ornamental plants treated with non-food-safe pesticides. When buying at US farmers markets, look for "Certified Organic" labels to ensure the blooms haven't been exposed to systemic chemicals commonly used in decorative horticulture.

In American culinary culture, nasturtium seeds are often pickled to create "poor man’s capers," a traditional substitute for imported Mediterranean capers. This practice gained popularity in US farm-to-table cooking as a way to utilize the entire plant and provide a local, pungent alternative to imported pantry staples.