Scientific Name(s): Cucurbita pepo L.
Common Name(s): Acorn squash, Butternut squash, Chilacayote, Field pumpkin, Fig-leaf gourd, Pepo, Pumpkin, Squash, Yellow summer squash, Zucchini
Pumpkin is a dicotyledonous vegetable that develops long vine-like stems with trifoliate leaves and edible large, fleshy fruits. The rapid-growing plant can climb to 5 m. The large, yellow flowers are eaten in some Mediterranean and Mexican cultures, and the fruits are eaten worldwide. Many cultivated varieties can be found throughout the world.1, 2, 3 Other members of the genus include Cucurbita digitata, Cucurbita ficifolia, and Cucurbita maxima species.
The seeds of several species of pumpkin have been used in traditional medicine for centuries. Traditionally, the seeds of the Cucurbita species are ingested as a tea or after grinding. They have been used to immobilize and aid in the expulsion of intestinal worms and parasites. In some cultures, small amounts of the seeds are eaten on a daily basis as a prophylactic against worm infections. The seeds also have been used in the treatment of prostate disorders. Pumpkin flowers are sometimes added to tacos or soup as a source of protein.2, 3, 4
The fleshy pulp of Cucurbita is primarily consumed as a vegetable. Investigational interest centers on polysaccharide and pectin content, as well as the presence of triterpenoids, cucurbitan glycosides, carotenoids, including lutein and beta-carotene, and cucurmosin, a ribosome-inactivating protein.3, 5, 6, 7, 8, 9, 10, 11
The pumpkin flower is a source of protein. Glutamic and aspartic acid, leucine, valine, phenylalanine, and tryptophan are among the amino acids identified. Phytosterols, such as spinasterol, have been identified, as well as trypsin-inhibitors.4, 12, 13
Lipids comprise up to 50% of the seed and around 30% is protein. Pumpkin seeds can be a nutritional source of iron and potassium. Phytosterols (eg, beta-sitosterol, stigmasterol), antioxidant tocopherols, antihelminthic cucurbitin, squalene, and cardioprotective fatty acids have been isolated from the seeds and seed oil. The presence of squash inhibitors (serine protease inhibitors) is thought to confer a protective effect to the plant against pests and pathogens.3, 14, 15, 16, 17, 18, 19, 20
Uses and Pharmacology
In vitro experiments and animal studies have demonstrated anthelmintic action of dried seeds and extracts against some Schistosoma japonicum and malarial parasites, but not all parasites (eg, tapeworm).21, 22, 23
A preclinical study demonstrated an anthelmintic effect with pumpkin seed 23 g in 100 mL water; however, cucurbitin has been generally supplanted by more effective single-dose vermifuges.3
Benign prostatic hyperplasia (BPH)
Pumpkin seed extract may have antiandrogenic and anti-inflammatory activity.24
A protective effect on testosterone-induced prostatic hyperplasia was seen in rats fed pumpkin seed oil.25
Trials are limited and the results conflict. A large clinical trial (N = 476) found an improvement in symptoms associated with BPH as determined by the International Prostate Symptom Score (IPSS), but no change in objective measures, such as p-vol or post-void residual urine.24 Another clinical trial found that a preparation of C. pepo (curbicin) improved certain parameters of BPH, including urinary flow, micturition time, residual urine, and urinary frequency versus placebo.26 A sponsor-funded phase 2 placebo-controlled, randomized clinical trial (n = 57) conducted in men with benign prostatic hypertrophy (BPH) found a commercially available herbal formulation containing pumpkin seed oil, lycopene, saw palmetto, pygeum, and Epilobium parviflorum to significantly reduce median prostate specific scores as well as day time and night time urinary frequency. Improvements were progressive and were observed in several scores at 1 month and in all scores at 3 months.45 IPSS was not shown to differ among 1,431 men with BPH-related lower urinary tract infections randomized to be treated for 12 months with pumpkin seed 5 g twice daily, pumpkin seed extract 500 mg twice daily, or placebo. All individual symptoms improved in all groups; no clinically significant changes in prostate volume, post-void residual volume, or prostate-specific antigen levels were observed.48
In rats, pumpkin seed oil improved the plasma lipid profile3, 29 and exhibited antioxidant activity in the heart and liver.30 In these experiments, a hypotensive action was demonstrated by the oil alone, and in combination with captopril and felodipine.29, 30
Defatted squash seed is rich in tryptophan.31, 32 Limited clinical trials have been conducted comparing plant-based tryptophan with the pharmaceutical grade chemical. Modest improvements were demonstrated in social anxiety disorder (social phobia) and insomnia when squash-derived tryptophan was administered with glucose to improve CNS blood levels.31, 32
Multiple open-label clinical studies report reduced postprandial serum and fasting glucose levels in patients with type 2 diabetes given pumpkin juice or pumpkin powder, but quality clinical trials are lacking.3 A small clinical trial (N = 10) demonstrated decreases in fasting blood glucose levels 3 to 5 hours after consumption of the juice of fresh immature C. ficifolia fruit; 4 mL/kg of body weight of the juice was administered (100 g crushed fruit was equivalent to 75 mL of juice).34 A cross-sectional and follow-up dietary intervention study in hemodialysis patients (n = 30) documented significantly improved blood pressure, total cholesterol, triglyceride/HDL cholesterol ratio, serum triglycerides, glucose tolerance, serum fatty acid composition, and inflammatory markers (ie, interleukin [IL]-6, tumor necrosis factor [TNF]-alpha, high-sensitivity C-reactive protein [hs-CRP]) after 12 weeks of dietary supplementation with 30 g/day of a milled flax-sesame-pumpkin seed (3:1:1) mixture added to 200 mL of fat-free milk before dinner. Pruritis also improved in all patients.46
Lower urinary tract symptoms
The European Association of Urology guidelines on the management of lower urinary tract symptoms (LUTS) in males (2013) discuss but do not make any specific recommendations on phytotherapy for the treatment of male LUTS because of variability of products, lack of regulatory infrastructure, and variability in methodologies in the available literature. C. pepo (pumpkin seeds) is recognized as one of the most widely used plants.44
Limited high-quality clinical trials exist to support therapeutic dosing. Fresh pumpkin juice 4 mL/kg of body weight was administered in a study conducted among patients with type 2 diabetes.34 However, it would take 100 g of crushed fruit to equal 75 mL of juice.35 Pumpkin seed 30 g provide approximately 4 mg of iron. When administered to nonpregnant adults for 4 weeks, iron status improved.14 Pumpkin seed 23 g per 100 mL was used in a study of anthelmintic action.3
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Anti-nutrients (eg, oxalates, cyanide, tannin) have been identified in pumpkin seeds and leaves, with detrimental effects on growing rats and chickens.3, 19
In an experiment conducted in rats, pumpkin seed oil potentiated the hypotensive effect of captopril and felodipine.30 Two men stabilized on warfarin experienced an increase in the international normalized ratio (INR) after taking an herbal combination containing Cucurbita, saw palmetto, and vitamin E.36 In both patients, the INR returned to previous values when the herbal product was discontinued. Although neither Cucurbita nor saw palmetto can be ruled out as the cause of the INR increase, it is more likely that vitamin E interfered with vitamin K-dependent clotting factors, adding to the anticoagulant effects of warfarin.36
Methemoglobinemia has been reported in infants 2 months of age or younger who were given zucchini soup for constipation. The adverse reaction was attributed to the high nitrate content of the vegetable.37 The importance of considering cross-contamination between foods grown in the same fields was demonstrated when hemolytic crisis was reported in an 8-month-old infant with undiagnosed glucose-6-phosphate dehydrogenase (G6PD) deficiency after eating pumpkin for the first time. DNA analysis of the pumpkin sample revealed it was cross-contaminated with fava bean DNA; the hemolytic reaction was attributed to substances present in the fava beans that are known to trigger hemolytic crisis, especially in children with G6PD deficiency.47
Vitamin A toxicity, with abnormal liver function tests, has been reported with prolonged and excessive pumpkin consumption.38
IgE-related allergy to zucchini has been reported. Oral allergy syndrome, nausea, diarrhea, and pruritus have also been described in a number of patients. Cross-reactivity to watermelon, cucumber, and pumpkin has occurred.39, 40, 41
A number of pathogenic fungi causing the deterioration of carved pumpkins have been identified. These fungi could cause severe infection in immunocompromised individuals.42
Severe toxicity has not been reported with the use of Cucurbita extracts. Ingestion of C. maxima seeds by rats and pigs during a 4-week period resulted in no changes in most laboratory parameters.43 The median lethal dose of freeze-dried C. ficifolia juice in mice was 650 mg/kg.35
Antinutrients (eg, oxalates, cyanide, tannin) have been found in pumpkin seeds and leaves, having detrimental effects on rats and chickens.3, 19 Trypsin inhibitors have been described in flowers of pumpkin varieties, but were not considered antinutritional.4
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