Purslane

Purslane, Portulaca oleracea L., is a low-growing plant in the family Portulacaceae that lives for one year. Its reddish stems and glossy paddle-shaped leaves are fleshy, and its flowers are small and yellow. Three forms of the plant carry three different histories. The fresh herb, meaning leaf and tender stem, is an everyday vegetable across the Mediterranean, the Middle East, South Asia and Mexico, eaten raw in salads or cooked like spinach. The dried herb is listed in the Chinese Pharmacopoeia as Ma Chi Xian, and the seed is the form used in most modern clinical trials. Keep these three forms apart when you read about purslane.

Its best-documented feature is its composition. Fresh purslane leaves contain roughly 300 to 400 milligrams of the omega-3 fatty acid alpha-linolenic acid per 100 grams. The leaves studied contained more than spinach. They also contain potassium, magnesium, vitamin A and vitamin C. The same leaf is high in oxalic acid. In the EU purslane is a food. It has no EU herbal monograph or authorised health claim.

Purslane's written record goes back to the first century, and its classical sources can still be read today. Pliny the Elder gives porcillaca a chapter of its own in the book of the Natural History on remedies from garden plants. He lists twenty-five uses, from headache and toothache to dysentery, and notes that it was eaten in salads. Dioscorides describes the plant as andrachne in De Materia Medica, a cooling astringent for burning of the stomach, inflamed eyes, dysentery and haemorrhoids. That list comes from a 2017 review rather than from the Greek text itself. The plant then passed into Persian and Arabic medicine, where it appears as khorfeh in Avicenna's Canon of Medicine and in the works of Rhazes and Jorjani, and on into South Asian Unani practice as Khurfa. There the seed is traded separately as Tukhme Khurfa.

In China the dried herb became the medicinal drug Ma Chi Xian. It is still listed in the Chinese Pharmacopoeia, which gives 9 to 15 grams to clear heat and resolve toxins, in the language of Chinese medicine. In Mexico the plant is verdolaga, one of the classic quelites, the wild greens gathered and sold in local markets, and in Yucatán it carries Maya names such as xúukul and xanab mukuy. How it reached the Americas is disputed. Standard floras treat it there as introduced, yet Byrne and McAndrews presented evidence that purslane was present in the New World before Columbus. In German-speaking Europe it is Gemüse-Portulak or Sommerportulak, Burzelkraut in folk speech. In the mid-twelfth century Hildegard von Bingen called it Burzel in her Physica and thought little of it as food. She wrote that it was cold, made slime in the body and was of no use as food. Today it is a garden salad crop and a stubborn arable weed whose seed stays viable in the soil for decades.

Purslane contains fatty acids, pigments and other plant compounds. Fresh leaves contain roughly 300 to 400 milligrams of alpha-linolenic acid per 100 grams. The leaves studied contained more than spinach. The plant contains betacyanins, red pigments, and oleraceins, nitrogen-containing plant compounds in the cyclo-dopa alkaloid group. Dopamine and noradrenaline, two signalling molecules, are more concentrated in the leaf than in stem or seed. Its flavonoids, another group of plant compounds, include kaempferol, quercetin, luteolin and apigenin. Purslane also contains potassium, magnesium and calcium, as well as oxalic acid, which is a nutritional drawback in large amounts.

What these compounds do in the body is known mainly from laboratory and animal work. In cell cultures and animal experiments, purslane extracts neutralised free radicals, reactive molecules that can damage cells. The extracts lowered markers of fat oxidation, damped inflammatory signalling in cells of the blood vessel wall and reduced experimentally induced damage to the stomach lining. In experiments on rats, a high-dose flavonoid extract of leaf and stem reduced embryo implantation in the womb and caused pregnancy loss. This is one reason for caution in pregnancy. None of these mechanisms has been shown in people. The role of alpha-linolenic acid as a nutrient is established and has an authorised EU claim.

Purslane trials mostly measure metabolic markers, usually in people who already have a metabolic diagnosis. In 2023, Jafari and colleagues systematically reviewed the trials and combined their results in an analysis that examined dose and response. It included 16 trials with 1122 participants allocated to groups at random. Eight were in people with type 2 diabetes. Other groups had conditions including fatty liver disease, raised blood lipids or metabolic syndrome, a combination of metabolic disorders. The review also includes a trial in people with schizophrenia and one in physically inactive young women. Over 4 to 16 weeks, participants took 0.06 to 50 grams a day, the 50 grams as fresh herb. Most trials gave 7.5 to 10 grams a day, usually of ground seed rather than the leaf on a plate. The combined analysis found a statistically significant fall in fasting blood glucose. Total antioxidant capacity in the blood rose, a measure of its ability to counter oxidation. Malondialdehyde, a marker of fat oxidation, fell.

The authors rated the certainty of the evidence on fasting glucose as low, because most trials were of low methodological quality and the results varied widely. I squared, a measure of that spread, was about 86 per cent. HbA1c, the long-term blood sugar value, rested on only two trials and showed no statistically significant change, and neither did fasting insulin or HOMA-IR, a measure of the reduced response to insulin. Fourteen of the 16 trials were run in Iran, which limits how far the results carry. Individual trials also disagree with the pooled picture. A double-blind trial of 300 milligrams a day of an extract of the herb in 74 people with fatty liver found no difference from placebo in fasting glucose or insulin resistance. In a crossover trial, the same 48 people with type 2 diabetes tried both treatments in turn. With 10 grams of seed a day in yoghurt, their fasting glucose, insulin and HOMA-IR did not differ from their values after yoghurt alone. A further 2024 trial in people with fatty liver had 70 completers. For 8 weeks they took 700 milligrams a day of a water and alcohol extract of the aerial parts or placebo. Both groups followed a calorie-restricted diet. Fasting glucose was lower than with placebo, but insulin and HOMA-IR showed no statistically significant between-group difference. The findings concern blood values in defined patient groups under medical care, most of whom took seed. These studies do not show that a purslane salad does anything comparable or provide a basis for managing a diagnosed condition with purslane.

Forms and preparation

As a vegetable, purslane needs almost nothing. Cut young shoots before flowering and wash them well, because the plant grows close to the soil. Raw in salads, the thick leaves are crisp, slightly sour and salty. Cooked, purslane behaves like a cross between spinach and okra, wilting quickly and lightly thickening soups and stews. In Turkish, Greek, Levantine and Mexican cooking it is stewed with onion and tomato, folded into yoghurt, or simmered with pork or beans as verdolagas. If you eat it often or in quantity, blanch or boil it and pour the water away, which lowers the oxalate. Raw juices and green smoothies keep the oxalate in. In Chinese practice the dried herb, Ma Chi Xian, is boiled in water, and fresh herb is crushed and applied to skin complaints and insect bites. Supplements and trials mostly use ground seed, in capsules or stirred into yoghurt, sometimes an extract of the herb. These are concentrated products with their own dosing and their own cautions, not a portion of vegetables. Whatever the form, check that the label names the plant part, because the leaf, the dried herb and the seed are not interchangeable.

Dosage

There is no official European dosage, because purslane has no EU herbal monograph. As a vegetable it is eaten in ordinary portions. Because of its oxalate, vary it with other vegetables rather than eating a daily bowlful, especially raw. For context rather than as a recommendation, there are three reference points. In Chinese practice, 9 to 15 grams of the dried herb are made into a decoction. The trials pooled in the 2023 meta-analysis used 0.06 to 50 grams a day for 4 to 16 weeks, most often 7.5 to 10 grams of ground seed. One trial used 300 milligrams a day of a water and alcohol extract of the herb. Those are study doses in patients under medical supervision, not amounts for everyday use. If you are considering a purslane supplement, follow the label, and if you take glucose-lowering medicines or have had kidney stones, talk to your doctor first.

Special populations

Pregnancy and breastfeeding. Avoid concentrated preparations during this time. In experiments on rats, a high-dose flavonoid extract of leaf and stem reduced embryo implantation in the womb and caused pregnancy loss. Health Canada's monograph covering Ma Chi Xian as a traditional Chinese medicine ingredient lists pregnancy and breastfeeding as a contraindication for all products under that monograph. Discuss food amounts with your doctor or midwife. If you are prone to calcium oxalate kidney stones or have been advised to follow a low-oxalate diet, handle purslane like spinach, with modest portions, cooked with the water discarded rather than raw. If you take glucose-lowering medicines, do not add purslane seed preparations without medical advice, because in trials they lowered fasting glucose. Children can eat purslane as a vegetable. Seed powder was tested in a small, one-month trial in adolescents with obesity and raised blood lipids. A general dosage for children remains undefined. Health Canada’s monograph on traditional Chinese medicine ingredients applies to adults aged 18 and over. Do not give purslane supplements to children.

Drug interactions

The main interaction to watch follows from its own trials and concerns glucose-lowering medicines. In the pooled trial literature, purslane seed preparations lowered fasting blood glucose in people with type 2 diabetes, so adding such a preparation to insulin, metformin, sulfonylureas or similar medication could add to their effect. If that applies to you, talk to your doctor before you start, and do not change prescribed doses yourself. For products covered by its monograph on traditional Chinese medicine ingredients, Health Canada requires medical advice before use if you take prescription medicines. Two further points belong here. Because the leaf is high in oxalate, large intakes matter for anyone under care or on a diet for kidney stones. And because the plant contains potassium, people on a potassium-restricted diet or taking medicines that raise potassium should keep portions in mind. These cautions concern possible risks inferred from composition and the cited trial results.

Contraindications

Pregnancy and breastfeeding, for medicinal and concentrated preparations. The Health Canada monograph covering Ma Chi Xian as a traditional Chinese medicine ingredient states that the product is not to be used if pregnant or breastfeeding. In experiments on rats, a high-dose flavonoid extract of leaf and stem reduced embryo implantation in the womb and caused pregnancy loss. Known hypersensitivity to purslane or to other members of the Portulacaceae. Existing calcium oxalate kidney stones or a prescribed low-oxalate diet. Avoid large amounts and raw preparations unless your dietitian advises otherwise. Children, for medicinal preparations. Seed powder was tested in a small, one-month trial in adolescents with obesity and raised blood lipids. A general dosage for children remains undefined. Health Canada’s monograph on traditional Chinese medicine ingredients applies to adults aged 18 and over. Do not give purslane supplements to children. The vegetable in normal food amounts is a different matter.

Side effects

Oxalate is the main nutritional caution when purslane is eaten as a vegetable. In the clinical trials, which gave seed powder or extract for 4 to 16 weeks, it was well tolerated, and constipation was the most common complaint. Allergic reactions are possible. Very large amounts of any oxalate-rich leaf are inadvisable for people prone to kidney stones. If you notice an unexpected reaction, stop taking it and seek medical advice.