Food as Medicine: Pumpkin (Cucurbita pepo, Cucurbitaceae)

HerbalEGram: Volume 12, Issue 10, October 2015 Editor’s Note: Each month, HerbalEGram highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets. The basic materials for this series were compiled by dietetic interns from Texas State University in San Marcos and the University of Texas at Austin through the American Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Perez, ABC Special Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to this project. By Hannah Baumana and Laura Bakerb a HerbalGram Assistant Editor b ABC Dietetics Intern (TSU, 2014) History and Traditional Use Range and Habitat Cucurbita pepo is a species in the gourd family which includes many varieties of winter squash and summer squash. Any round and orange fruit yielded by any variety or cultivar (there are many cultivars) of the species is usually called a pumpkin, even though the word has no real botanical meaning.1,2 The species is characterized by sprawling, coarse vines and climbing tendrils that are flexible, hollow, and prickly to the touch with large, oval-shaped leaves.3 Cucurbita pepo flowers are bright yellow or orange with rounded lobes that angle outwards. The species can produce a wide variety of fruits of different shapes, sizes, and colors, but pumpkins are spherical in shape, covered by a firm, ribbed, thick layer of orange or yellow skin. Inside the skin, the fleshy part of the pumpkin is mildly sweet and grainy. Each fruit contains a large quantity of seeds, which are flat and ovate-elliptical shaped, dark green in color and enclosed in a creamy white husk. The seed has a fibrous texture with a subtle sweetness and nuttiness. Pumpkins range in size from less than a pound to over 1,000 pounds, but average 7-10 pounds.4 Cucurbita pepo is native to Central America, and evidence of cultivation and use dates back to 5500 BCE.5 The United States is the top producer of pumpkins, followed by Mexico, India, and China, respectively.6 Phytochemicals and Constituents Several bioactive constituents in pumpkin exhibit medicinal properties, such as anti-diabetic, anti-fungal, anti-bacterial, anti-inflammatory, hypotensive, and antioxidant actions.3,7 The pumpkin fruit is low in fat and has protein-rich seeds, which make it a nutrient-dense food. Specific peptides and proteins found in pumpkin seeds have demonstrated broad-spectrum antimicrobial activity.7 For example, two of these proteins, alpha-moschin and beta-moschin, have exhibited inhibitory activity against fungal infections caused by Botrytis cinerea, Fusarium oxysporum, and Mycosphaerella arachidicola. Additionally, pumpkin proteins display a synergistic effect with antibiotics for the inhibition of the fungus Candida albicans, which can cause mucous membrane infections, such as thrush, in humans. Some of the bioactive compounds in pumpkin fruit flesh that offer beneficial health effects are polysaccharides, para-aminobenzoic acid, oils, phytosterols (beta-sitosterol, sitostanol and avenasterol), proteins, peptides, and lignans.3 Anti-diabetic effects are due to protein-bound polysaccharides (PBPP), which have been shown to increase levels of insulin, decrease blood glucose levels, and enhance glucose tolerance.7 Researchers theorize that this happens due to antioxidant activities which are thought to prevent destruction of pancreatic beta-cells, which produce insulin.6 Therefore, PBPP present in pumpkin may play a role in preventing the development and progression of diabetes.7,8 Additionally, the polyamine content of pumpkins may also play a role in optimizing the function of the pancreas.7 Pumpkin seeds are rich in phytoestrogen content (265 mg per 100g), specifically secoisolariciresinol.9 Secoisolariciresinol has been shown to exhibit cholesterol-lowering activity, and produce cardioprotective effects through the formation of new blood vessels and decreased apoptosis (programmed cell death). These effects are thought to be the result of antioxidant properties, which inhibit cell membrane damage and scavenge “free radicals.” Pumpkin seeds also contain beneficial compounds such as linoleic acid, essential amino acids, and vital micronutrients. Linoleic and linolenic acids exhibit oxidative mechanisms to reduce the production of inflammatory products, while oleic fatty acid is known to enhance signaling pathways of vasodilation (expanding blood vessels), promote a reduction in blood pressure levels, and reduce effects of vasoconstriction (narrower diameter of blood vessels). Pumpkin seeds are also a good source of trace minerals including magnesium, zinc, copper, and selenium.3 The bright orange color of pumpkin indicates elevated levels of beta-carotene, a vital antioxidant and precursor to vitamin A, which maintains vision and the health and function of bones, skin, and mucous membranes.4,10 Additionally, the fruit contains gamma-aminobutyric acid (GABA; a neurotransmitter that has inhibitory effects on the nervous system) and modest levels of carbohydrates, vitamins, and minerals.3 Historical and Commercial Uses The name “pumpkin” originates from the Greek word pepon, which means “large melon.”4 The French modified this name to pompon and the British changed it to pumpion, which was later changed by the American colonists to pumpkin.6 Pumpkin has a traditional history as a food and medicine. Some Native American tribes dried the skins of pumpkins into strips and wove them together into mats.4 The modern pumpkin pie has its origins in colonial New England, where colonists cut off the top of the pumpkin, removed the seeds, filled the fruit with milk, spices, and honey, and baked the fruit over hot ashes.4,5 Pumpkins are highly valued in Chiapas, Mexico, where they are combined with honey for the preparation of the dessert palanquetas.3 Though native to Central America, the pumpkin was one of the first foods from the “New World” to be brought back to Europe, and cultivation spread quickly thereafter.5 Pumpkins have been used as a medicine in several countries. For example, the former Yugoslav Republic of Macedonia, Argentina, India, Brazil, and Mexico have traditionally used pumpkins as a treatment for diabetes.11 In addition,7 pumpkin seed oil from a particular variety known as the Styrian pumpkin (C. pepo subsp. pepo var. styriaca) produced in southern Austria and Slovenia is a European Union Protected Designation of Origin product. Nicknamed “green gold,” the dark green oil has culinary and medicinal applications and is an integral part of the local culture throughout Eastern Europe.12 The seeds of pumpkins have also been used as a vermifuge for intestinal parasites and worms. In addition to the many health benefits offered by pumpkin, it also is used as an ornamental decoration during the US holidays Halloween and Thanksgiving and has recently become a crop of interest in agritourism (defined broadly, agritourism is the act of visiting any agricultural operation or business in order to be educated or entertained).13 Currently, pumpkin farms in California are considered to be one of the most popular and lucrative agritourism attractions, commonly offered in conjunction with pony rides and corn mazes. Modern Research Current research on the medicinal possibilities of C. pepo focuses heavily on pumpkin seeds and pumpkin seed oil (PSO). Studies show that pumpkin seeds have therapeutic potential for a variety of conditions, including benign prostatic hyperplasia (BPH), urinary tract infections associated with BPH, hypertension, diabetes, and microbial infections. Researchers theorize that the phytosterol content of pumpkin seeds can prevent testosterone-induced BPH by inhibiting the conversion of testosterone to dihydrotestosterone.14 Male rats with testosterone-induced BPH given a daily dose of pumpkin seed oil were found to have reduced levels of hyperplasia. This further indicates that PSO may be directly involved in prostate health. Pumpkin seeds have been shown to be an effective alternative treatment for lower urinary tract symptoms (LUTS) secondary to BPH.13 BPH is characterized by an enlargement of the prostate gland, which commonly results in the constriction of the lower urinary tract in men.15,16 Fifty percent of men over the age of 60 report having BPH, with 15%-30% of these men also having LUTS.16 A 12-month study of men diagnosed with BPH/LUTS was conducted to analyze the health effects of pumpkin seeds.16 Doses of purified pumpkin seed, pumpkin seed extract, or placebo were administered twice daily. Both treatment modalities exhibited statistically significant improvements as measured by the International Prostate Symptom Score screening tool (I-PSS) and quality of life (QoL) scores. Additionally, the pumpkin seed group revealed greater improvements in IPSS-related QoL scores than the placebo group. QoL scores were enhanced 36% for pumpkin seed, 33.4% for pumpkin seed extract, and 29.2% for the placebo treatment group. Another 12-month study revealed similar results, with I-PSS scores significantly enhanced after administration of 320 mg of PSO twice daily.17 This study also showed a decrease in prostate volume and a significant increase in maximal urinary flow rate. The intervention resulted in an average increase from 14 mL/second at baseline to 17 mL/second after taking PSO for an improvement of 14.9% in urinary flow rate. Pumpkin seed oil enhances cardiovascular health through its antihypertensive and atheroprotective characteristics.6 Hypertensive rats fed either 40 mg/kg/day or 50 mg/kg/day of PSO for six weeks exhibited cardioprotective effects.18 The study showed that use of PSO resulted in a significant reduction of high systolic blood pressure and proved to be as effective as a common antihypertensive medication (amlodipine) in reducing high blood pressure by producing close to normal levels of nitric oxide.6,18 This mechanism may be a result of the linoleic, linolenic fatty acid and/or oleic fatty acid content of pumpkin seeds.18 PSO also exhibited antioxidant effects by increasing low levels of nitric oxide metabolites back to normal and significantly reduced indicators of oxidative stress known as malondialdehydes (MDAs). A study of post-menopausal women found that consumption of pumpkin seeds increased levels of high-density lipoprotein (HDL) cholesterol by 16% and decreased diastolic blood pressure by 7%.6,9 These effects may be attributed to the high content of the phytoestrogen secoisolariciresinol, which has been shown to exhibit cardioprotective properties through its antioxidant content.9 Subjects also experienced a decrease in severity of hot flashes, decreased occurrence of headaches, and reduced joint pain. These findings provide supporting evidence of PSO supplementation for improved cardiovascular health. Pumpkin seeds traditionally have been used for their anti-diabetic properties and are a promising area of research in diabetes treatment. Due to the hypoglycemic activities observed in animal and human studies, PSO may eventually be considered as an alternative modality of treatment. Hypoglycemic effects are due to bioactive constituents such as polysaccharides, para-aminobenzoic acid, oils, sterols, proteins, peptides, and macromolecules such as trigonelline, nicotinic acid, and D-chiro-inositol. D-chiro-inositol is classified as an insulin sensitizer and plays a vital role in the anti-diabetic properties of pumpkin.3 A study done on diabetic rats with orally administered polysaccharides isolated from pumpkin fruits revealed improvements in insulin regulation and glucose levels.7 These animal studies offer intriguing evidence of pumpkin’s anti-diabetic properties, though additional research and human clinical trials are needed to support the implementation of pumpkin as a medicinal alternative for glycemic control.11 Pumpkin seed oil has exhibited broad spectrum antimicrobial effects in cell culture studies with the following organisms: Acinetobacter baumannii, Aeromonas veronii biogroup sobria, Candida albicans, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype typhimurium, Serratia marcescens, and Staphylococcus aureus.3,7 These findings hold a twofold benefit for developed and developing countries: as antibiotic-resistant bacteria grow more prevalent, scientists are working to identify plant-based compounds with antimicrobial actions; additionally, pumpkin consumption in countries with insufficient health care infrastructures may serve as a protection against harmful organisms that result in infectious diseases.3 Pumpkin and PSO should be further researched to validate these possible uses. Nutrient Profile19 Macronutrient Profile: (Per 1 cup raw 1” cubes [approx. 116 g]) 30 calories 1.16 g protein 7.54 g carbohydrates 0.10 g fat Secondary Metabolites: (Per 1 cup raw 1” cubes [approx. 116 g]) Excellent source of: Vitamin A: 9,875 IU (197.5% DV) Very good source of: Vitamin C: 10.4 mg (17.3% DV) Potassium: 394 mg (11.26% DV) Good source of: Iron: 0.93 mg (5.2% DV) Phosphorus: 51 mg (5.1% DV) Also provides: Folate: 19 mcg (4.75% DV) Vitamin E: 1.23 mg (4.6% DV) Thiamin: 0.06 mg (4% DV) Magnesium: 14 mg (3.5% DV) Niacin: 0.7 mg (3.5% DV) Vitamin B6: 0.07 mg (3.5% DV) Calcium: 24 mg (2.4% DV) Dietary Fiber: 0.6 g (2.4% DV) Vitamin K: 1.3 mcg (1.6% DV) DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet. Recipe: Pumpkin-Shiitake Risotto Ingredients: 4-5 cups vegetable stock 2 tablespoons olive oil 1 medium yellow onion, finely chopped 2 cups shiitake mushroom caps, sliced 2 garlic cloves, minced 1 cup uncooked Arborio or other short-grain rice ½ cup dry white wine ½ teaspoon kosher salt 1 cup fresh or canned unflavored pumpkin puree 2 tablespoons fresh chives, chopped Directions: In a medium saucepan, heat the broth until simmering. Reduce heat to low and keep warm. In a large nonstick pan, heat the oil over medium heat until shimmering. Add the onions, mushrooms, and garlic and cook, stirring occasionally, until softened, about 6-7 minutes. Add the rice to the pan and cook, stirring constantly, until the rice is lightly toasted and coated in oil, about 1 minute. Add the wine and reduce until nearly evaporated. Ladle 1 cup of the warm broth into the rice and stir constantly until the rice absorbs most of the liquid. Reduce heat, if necessary, to maintain a simmer. Continue adding the broth in 1-cup increments, each time waiting for the rice to absorb most of the liquid, approximately 20-30 minutes. The rice will slowly become creamy and cooked, with tender grains and a loose sauce. Reduce heat to low. Stir in the salt and pumpkin puree and heat through. Garnish with chives and serve immediately. References What is the difference between pumpkins, squashes and gourds? Missouri Botanical Garden website. Available here. Accessed October 15, 2015. Cucurbita pepo. Missouri Botanical Garden website. Available here. Accessed October 15, 2015. Yadav M, Jain S, Tomar R, Prasad GB, Yadav H. Medicinal and biological potential of pumpkin: An updated review. Nutr Res Rev. 2010;23(2):184-190. Pumpkins and More. University of Illinois Extension website. Available here. Accessed September 16, 2015. Barksdale N. The History of Pumpkin Pie. History website. November 21, 2014. Available here. Accessed September 16, 2015. Gamonski W. The true potency of the pumpkin seed. Life Extension. 2012;18(10):95-98. Caili F, Huan S, Quanhong L. A review on pharmacological activities and utilization technologies of pumpkin. Plant Foods Hum Nutr. 2006;61(2):70-77. Quanhong L, Caili F, Yukui R, Guanghui H, Tongyi C. Effects of protein-bound polysaccharide isolated from pumpkin on insulin in diabetic rats. Plant Foods Hum Nutr. 2005;60(1):13-16. Gossell-Williams M, Hyde C, Hunter T, et al. Improvement in HDL cholesterol in postmenopausal women supplemented with pumpkin seed oil: Pilot study. Climacteric. 2011;14(5):558-564. Weil A, Becker B. Supplements and Herbs: Facts about Vitamin A. Andrew Weil, MD website. October 29, 2012. Available here. Accessed September 23, 2015. Adams GG, Imran S, Wang S, et al. The hypoglycemic effect of pumpkin seeds, trigonelline (TRG), nicotinic acid (NA), and D-chiro-inositol (DCI) in controlling glycemic levels in diabetes mellitus. Crit Rev Food Sci Nutr. 2014;54(10):1322-1329. Košťálová Z, Hromádková Z, Ebringerová A. Chemical evaluation of seeded fruit biomass of oil pumpkin (Cucurbita pepo L. var. Styriaca). Chemical Papers. 2009;63(4):406–413. Aegerter B, Smith R, Natwick E, Gaskell M, Rilla E. Pumpkin Production in California. Richmond, CA: University of California Vegetable Research and Information Center; 2013. Available here. Accessed September 16, 2015. Gossell-Williams M, Davis A, O'Connor N. Inhibition of testosterone-induced hyperplasia of the prostate of sprague-dawley rats by pumpkin seed oil. J Med Food. 2006;9(2):284-286. Vahlensieck W, Theurer C, Pfitzer E, et al. Effects of pumpkin seed in men with lower urinary tract symptoms due to benign prostatic hyperplasia in the one-year, randomized, placebo-controlled GRANU study. Urol Int. 2015;94(3):286-295. Coulson S, Rao A, Beck SL, et al. A phase II randomised double-blind placebo-controlled clinical trial investigating the efficacy and safety of ProstateEZE Max: A herbal medicine preparation for the management of symptoms of benign prostatic hypertrophy. Complement Ther Med. 2013;21(3):172-179. Hong H, Kim CS, Maeng S. Effects of pumpkin seed oil and saw palmetto oil in Korean men with symptomatic benign prostatic hyperplasia. Nutr Res Prac. 2009;3(4):323-327. El-Mosallamy A, Sleem AA, Abdel-Salam OM, Shaffie N, Kenawy SA. Antihypertensive and cardioprotective effects of pumpkin seed oil. J Med Food. 2012;15(2):180-189. Basic Report: 11422, Pumpkin, raw. Agricultural Research Service, United States Department of Agriculture website. Available here. Accessed September 16, 2015.