Pumpkin Seed

Cucurbita pepo L. belongs to Cucurbitaceae, the gourd or melon family, which EMA’s assessment report puts at about 95 genera and 950 to 980 species. Linnaeus named it in Species Plantarum in 1753. Kew’s Plants of the World Online describes its native range as a cultigen from Mexico, meaning it is known as a crop rather than a wild plant, and lists it as introduced in dozens of regions across the Americas, Europe, Africa, Asia, and the Pacific. It is an annual. King’s American Dispensatory (1898) describes a rough, bristly plant with a trailing stem, branching tendrils, and large heart-shaped leaves with five palm-like lobes. The flowers are large, yellow, and bell-shaped, borne singly where the leaves join the stem, and the male flowers sit on long stalks. In the United States the plant flowers in July and ripens its fruit in September and October; King’s describes the fruit as very large, round or oblong, furrowed, and yellow when ripe.

The medicinal part is the whole, ripe, dried seed (EMA). King’s, quoting the US Pharmacopeia, describes seeds about 2 cm long, broadly oval, flat, and whitish, with a shallow groove running parallel to the edge, no smell, and a bland, oily taste, and estimates them at about a quarter husk and three-quarters kernel. There is no European Pharmacopoeia monograph; EMA notes that the German Pharmacopoeia defines the drug as the whole, dry, ripe seeds of Cucurbita pepo and its cultivated varieties. For medicines, the preferred variety is the Styrian oil pumpkin, Cucurbita pepo var. styriaca, because of its thin seed coat and mild taste. Its seeds grow without the usual tough white shell, leaving the green kernel exposed. The EU’s 1996 registration of Styrian pumpkin seed oil (Steirisches Kürbiskernöl) as a protected geographical indication describes a dark, viscous oil made by grinding, gently splitting, and pressing these skinless seeds. EMA adds that the seeds are roasted just before pressing and that the oil is dark red to green, fluorescent red, and nutty, and is not used for cooking because of its color and tendency to foam.

Pumpkin seeds are a dense food. USDA FoodData Central lists one ounce (28 g) of dried kernels at about 158 calories, with 8.6 g of protein, 13.9 g of fat, 1.7 g of fiber, 168 mg of magnesium, 2.5 mg of iron, and 2.2 mg of zinc. EMA’s assessment report gives an oil content of about 50% (45–60%), mostly unsaturated: linoleic acid typically makes up about 40–64% of the fatty acids and oleic acid 20–38%, with more linoleic acid in late-ripening crops. The vitamin E is mainly gamma-tocopherol rather than the alpha form, and the selenium content is among the highest found in plants. What sets the oil apart is its sterols. Most seed oils are dominated by delta-5 sterols such as beta-sitosterol, but in pumpkin seed four delta-7 sterols, including alpha-spinasterol and delta-7-avenasterol, make up 75–88% of the total, and EMA names delta-7 and delta-5 sterols as the putative active constituents. The seeds also contain cucurbitine, an unusual amino acid present at 0.18–0.66% in C. pepo and long studied for its activity against parasitic worms.

Pumpkin seed’s story begins in the Americas. Smith (Science 1997) examined squash seeds, fruit stalks, and rind fragments from Guilá Naquitz cave in Oaxaca, Mexico, and showed from their longer seeds, thicker stalks, and changed fruit shape and color that they came from domesticated Cucurbita pepo rather than wild gourds. Nine radiocarbon dates placed this cultivation between 10,000 and 8,000 years ago, more than 4,000 years earlier than maize, beans, or any other directly dated crop in the Americas. The plant was later carried to Europe: EMA’s assessment report, citing Janick and Paris, notes that New World cucurbits appear in frescoes painted in 1515–1518 at the Villa Farnesina in Rome, among the first European paintings of these species. The same report lists ‘pumpkin’ in the writings of Hippocrates and Dioscorides, but because Cucurbita is American, those ancient references must concern Old World gourds or melons. King’s American Dispensatory (1898) made a similar slip, calling the pumpkin a native of the Levant.

In Europe and North America the seeds became a household remedy for worms. EMA records traditional European use as a diuretic and as a remedy to expel tapeworms, and King’s lists the seed as Pepo in the US Pharmacopeia. King’s calls the seeds long popular with the public for worms and describes the method then favored: the patient fasted for a day, took a saline purgative, and then drank three doses of an emulsion of fresh seeds pounded with sugar and diluted with milk or water, two hours apart, followed by castor oil to expel the worm. King’s also recommended the seeds as a diuretic for ‘scalding of urine’ and spasm of the urinary passages, an early hint of the modern use. Later reports summarized by EMA were uncontrolled: a pumpkin seed preparation cleared tapeworms in 50–70% of 150 patients in one series, and pumpkin seeds combined with areca nut cured 95% of beef tapeworm infections but only 40% of pork tapeworm infections in another. Martindale’s reference book, EMA notes, now describes the seeds as formerly used to expel tapeworms.

The urinary use grew in twentieth-century Central Europe. Madaus’s German textbook of 1938 already listed pumpkin seeds for symptoms of an enlarged prostate as well as for tapeworm (EMA). Germany’s Commission E published a monograph in 1985, revised in 1991, for irritable bladder and urination problems in early-stage BPH, cautioning that pumpkin seed relieves symptoms without reducing the enlargement and that a doctor should be consulted at regular intervals; ESCOP and the World Health Organization published similar monographs. Styria, meanwhile, built a regional industry around its oil pumpkin. The 1996 EU registration of Styrian pumpkin seed oil states that oil was pressed from pumpkin seeds there as early as the eighteenth century and that the skinless seeds were developed in Styria, and it describes about 10,000 hectares under cultivation and some 70 commercial oil mills supporting small farms in southern Styria and southern Burgenland. EMA’s Committee on Herbal Medicinal Products adopted its monograph on 20 November 2012, granting traditional use only, and in a 2021 periodic review agreed by consensus that no revision was needed.

No one knows exactly how pumpkin seed might ease urinary symptoms, and EMA found no data on how its constituents are absorbed in people. Attention has focused on the delta-7 sterols. In a small German study summarized by EMA, Schilcher and colleagues (1987) gave six men awaiting prostate surgery 90 mg a day of five delta-7 sterols from Styrian pumpkin seeds on the third and fourth days before their operations. Their removed prostate tissue contained less dihydrotestosterone (DHT), a more potent androgen made from testosterone, than tissue from untreated men. In laboratory work by Schmidlin and Kreuter (2003), a pumpkin seed extract inhibited 5-alpha-reductase type II, the enzyme that converts testosterone to DHT, and aromatase in placental tissue, though only at high concentrations. In castrated rats given testosterone, the extract reduced prostate enlargement by 31%, against 76% with finasteride. Such experiments suggest a weak hormonal effect at most, and none has been confirmed in men at normal doses.

Other findings point in different directions. An ethanol extract containing triglycerides, sterols, and tocopherol showed no anti-androgen activity in a laboratory test of androgen-receptor signaling (Schleich and colleagues 2006, cited by EMA). The European Association of Urology (EAU) notes that plant extracts can show many laboratory effects, from anti-inflammatory and anti-androgen activity to action on enzymes and receptors, but that their effects in the body are uncertain and their mechanisms unclear. EMA’s assessors suggested instead that any benefit comes from a toning effect on the bladder, relaxation of the sphincter, and easing of urination symptoms, an explanation that fits the parallel traditional use for an overactive bladder. What pumpkin seed does not appear to do is shrink the prostate: in the year-long Bach trial summarized by EMA, prostate volume, urine flow, and the amount of urine left in the bladder did not differ from placebo, consistent with Commission E’s warning that it relieves symptoms without reducing the enlargement.

The hair-loss idea borrows the prostate theory. Cho and colleagues (2014) chose pumpkin seed oil because animal studies suggested it might inhibit 5-alpha-reductase, and DHT is a major player in male-pattern hair loss; but they measured neither DHT nor PSA and said they could not explain how the oil worked. For worms, EMA reviews animal studies: cucurbitine, an amino acid isolated from the related Cucurbita moschata, reduced worm numbers by about half at high doses in mice infected with the blood fluke Schistosoma japonicum, but not when it was started two to three weeks after infection, and powdered pumpkin seeds sharply reduced nodular worms in experimentally infected piglets. Pumpkin seeds also contain proteins that inhibit trypsin and other protein-digesting enzymes, and ribosome-inactivating proteins with antiviral and antifungal activity in the test tube, at levels EMA considers harmless in food. None of these laboratory findings has been tied to a proven clinical effect in people.

Enlarged prostate symptoms, the largest trial: in GRANU (German Research Activities on Natural Urologicals), Vahlensieck and colleagues (Urologia Internationalis 2015) randomized 1,431 men aged 50 to 80 with lower urinary tract symptoms suggestive of BPH to pumpkin seed (5 g twice daily), capsules of pumpkin seed extract (500 mg twice daily), or matching placebo for 12 months, in a partially blinded design. A man counted as a responder if his International Prostate Symptom Score (IPSS) fell by at least 5 points. The extract did no better than placebo. Among men eating the seeds, 58.5% responded, against 47.3% on placebo, a difference the authors described as only descriptively significant, and they concluded that it must be confirmed in another study or a systematic review before pumpkin seed can be fully recommended. Both products were well tolerated. GRANU is also a reminder of how much men improve on placebo: nearly half of the placebo group met the response target.

Other BPH trials are smaller or weaker. EMA’s assessment report summarizes a 65-center, double-blind trial by Bach (2000) in 476 men with early-stage BPH given a 500 mg pumpkin seed extract capsule or placebo for 12 months: symptom scores improved more than with placebo, but urine flow, quality of life, prostate volume, and residual urine did not, and EMA judged the effect small. Hong and colleagues (Nutrition Research and Practice 2009) assigned 62 Korean men, by order of enrollment, to placebo, 320 mg of pumpkin seed oil, 320 mg of saw palmetto oil, or both daily for a year. Symptom scores fell within each active group, but only 47 men finished, 13 of those who left did so because their symptoms worsened, and the paper reports no statistically significant differences between groups on any measure. In an Iranian trial by Zerafatjou and colleagues (BMC Urology 2021), 73 men took 360 mg of pumpkin seed oil twice daily or the alpha-blocker tamsulosin for three months; both groups improved, but tamsulosin reduced symptom scores significantly more.

Overactive bladder: EMA’s indication also covers urgency and frequency from an overactive bladder, in women as well as men, but the human evidence is uncontrolled. Nishimura and colleagues (Journal of Traditional and Complementary Medicine 2014) gave 45 adults, 25 men and 20 women aged 41 to 80, 10 g a day of oil from a different species, Cucurbita maxima, for 12 weeks and reported lower overactive bladder symptom scores; the authors acknowledged that the study was small and was not randomized or placebo-controlled. Gauruder-Burmester and colleagues (Planta Medica 2019) followed 117 women taking a combination of pumpkin seed oil with fragrant sumac bark and hop extracts for 12 weeks: daytime urination frequency improved in 77 of 99 women and leaks fell from 0.9 to 0.4 a day, but the product contained three herbs and there was no comparison group. Leibbrand and colleagues (Journal of Medicinal Food 2019) reported a 30% fall in symptom scores and fewer night-time trips to the toilet in 60 men with BPH taking an oil-free hydroethanolic pumpkin seed extract at bedtime for three months, again without a control group. Without a placebo group, none of these studies can separate the effect of pumpkin seed from placebo and natural ups and downs.

Hair loss: Cho and colleagues (Evidence-Based Complementary and Alternative Medicine 2014) randomized 76 Korean men with mild to moderate male-pattern hair loss to 400 mg a day of pumpkin seed oil, as a branded capsule product, or placebo for 24 weeks. Hair counts rose by 40% with pumpkin seed oil and 10% with placebo, blinded investigators rated 17 of 37 treated men as improved against 3 of 39 on placebo, and self-rated improvement and satisfaction were higher; hair thickness did not change, and side effects were similar in both groups. Twelve men dropped out, and the authors called for replication. The trial compared the oil only with placebo, not with minoxidil or finasteride, the approved treatments the authors mention. Until it is repeated, pumpkin seed oil is an interesting lead for hair loss rather than an established treatment.

Other uses: the traditional tapeworm use rests on uncontrolled mid-twentieth-century case series, often with areca nut, whose alkaloid arecoline caused side effects (EMA). In a small Thai study summarized by EMA, pumpkin seed snacks given to 10 adolescents with bladder stones for two days changed their urine chemistry in ways expected to discourage calcium oxalate crystals, too short a study to show any effect on stones. Guidelines remain cautious. The 2026 EAU guideline on male lower urinary tract symptoms lists the EU pumpkin seed monograph but makes treatment recommendations only for hexane-extracted saw palmetto, warning that extracts of the same plant from different manufacturers do not necessarily have the same effects. EMA’s assessors, citing Madersbacher and colleagues, considered pumpkin seed’s mild effect suitable only for men without significant obstruction and at low risk of their BPH progressing.

EMA’s monograph (EMA/HMPC/136024/2010, adopted 20 November 2012) covers four oral forms for adults and older people: whole or comminuted (crushed or ground) dried seeds, 2.5–7.5 g twice daily; a soft extract made with 92% ethanol (drug-to-extract ratio 15–25:1), 500 mg twice daily; a dry extract made with 60% ethanol (15–30:1), 105 mg three times daily or 152 mg twice daily; and the fatty oil, 1–1.2 g three times daily, or 3–4 g a day. Long-term use is possible, and it is not recommended under 18. Users should see a doctor if symptoms worsen or if fever, spasms, blood in the urine, painful urination, or urinary retention develop. For comparison, GRANU used 5 g of seeds or 500 mg of extract twice daily, Bach a 500 mg extract capsule, and the oil trials 320 to 720 mg of oil a day, well below EMA’s 3–4 g; Nishimura’s bladder study used 10 g of oil a day.

As food, the doses are modest. GRANU’s 10 g of seeds a day is about a third of an ounce of kernels, roughly 56 calories by USDA figures, and EMA’s top herbal dose of 15 g a day is just over half an ounce. Seeds bought in the shell deliver less kernel per gram, since King’s estimated the husk at about a quarter of the seed’s weight. Roasting is the usual way to eat them, but EMA cites a study in which roasting cut the seeds’ total tocopherol (vitamin E) content by 36%. Styrian pumpkin seed oil is a salad oil rather than a cooking oil, according to both its EU registration and EMA. In Europe, pumpkin seed oil has also been sold in combination with vitamin E and with zinc- or selenium-enriched yeast (EMA), and EMA’s 2021 review noted that some single-ingredient products have been withdrawn from the market, so check exactly what a product contains.

Practical points: allow about three months before judging any effect, since trials measured results over 12 weeks to a year and EMA judged the benefits small. A simple diary of daytime and night-time toilet trips, kept before and during use, makes it easier to tell a real change from the natural ups and downs that make placebo responses so large in BPH trials. Pumpkin seed does not shrink the prostate, so it should not replace a prescribed alpha-blocker or 5-alpha-reductase inhibitor without your doctor’s agreement. If you prefer to eat the seeds, choose shelled kernels rather than large quantities of whole seeds in their shells, given reports of seed masses blocking the rectum. Keep seeing your doctor at intervals, as Commission E advised, and report any new or worsening symptoms promptly.