HerbalEGram: Volume 15, Issue 5, June 2018

Editor’s Note: As the Food as Medicine project has evolved at the American Botanical Council (ABC), the editors of HerbalEGram will revisit previous articles in this series and update them with current research. This effort will hopefully improve the accuracy and relevance of these articles, in keeping with our commitment to education and empowerment. Food as Medicine: Butternut Squash was originally published in the March 2015 issue of HerbalEGram.

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 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 Bauman^a and Sarah Edwards^b

^a HerbalGram Associate Editor

^b ABC Dietetics Intern (Texas State, 2013)

Overview

Cucurbita moschata (Cucurbitaceae), which is referred to as butternut, winter, or pumpkin squash, is a trailing annual with lobed leaves and yellow flowers.¹ Mature fruits that are peanut- or bottle-shaped are harvested for their rich orange flesh and edible seeds. Native to tropical and subtropical regions of the American continents, butternut squash requires warm climates for cultivation.^1,2 Butternut squash grows best in rich and well-drained soil in full sun.² It can be stored for extended periods, and, in fact, has one of the longest shelf lives of edible fruits in the Cucurbitaceae family.³

Phytochemicals and Constituents

Butternut squash contains high amounts of complex carbohydrates and provides vitamin C, potassium, iron, riboflavin, and magnesium.³ Additionally, butternut squash is an excellent source of carotenoids such as alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, and zeaxanthin. While it is a low-fat food, butternut squash does contain some healthy fats in the form of alpha-linolenic acid, a beneficial omega-3 fatty acid.⁴ Omega-3 fatty acids possess a variety of health benefits, including anti-inflammatory properties.

The vitamin C content of butternut squash is unusually stable during storage and processing.⁵ As the squash ripens, the flesh produces more vitamin C; if stored properly at cool temperatures (12-14° C, or 54-57ᵒ F), squash retains most of its vitamin C content. While this level of retention is common in produce with long shelf lives (e.g., other types of winter squash and potatoes [Solanum tuberosum, Solanaceae]), butternut squash also retains approximately 80% of its vitamin C content after 30 minutes of cooking at 95° C (203ᵒ F). This indicates that both fresh and processed butternut squash are good, stable sources of vitamin C.

Boiled butternut squash has an intermediate glycemic index value at 66 (compared to the reference glucose value of 100).⁶ Butternut squash’s complex carbohydrate content slows the breakdown of carbohydrates into simple sugars, thereby delaying the release of insulin in the human body.

The edible seeds of the squash can be roasted like pumpkin (Cucurbita pepo) seeds. The seeds contain linoleic acid, a polyunsaturated omega-6 fatty acid, and oleic acid.⁴ Butternut squash seeds contain a higher amount of carotenoids as well as alpha-, beta-, and gamma-tocopherols per serving than pumpkin seeds. These tocopherols are precursors of vitamin E.⁷ The seeds also contain a high amount of zinc.

Historical and Commercial Uses

Cultivation of butternut squash dates back more than 10,000 years in Central America.⁸ The use of the plant spread to the north and south, with evidence of use from 4900 BCE in southern Mexico and 3000 BCE in coastal Peru.¹ Millennia later, Christopher Columbus and other European explorers brought squash from the Americas to Europe.⁸

Squashes initially were cultivated for their seeds; in early varieties, the sparse flesh was bitter and inedible.⁸ The seeds traditionally have been used in the squash’s native habitat as a diuretic and for the treatment of intestinal parasites.^2,9

Trade brought butternut squash from the American continents through Europe to China, where it was incorporated into the practice of traditional Chinese medicine (TCM) in the 17th century. TCM practitioners consider squash to be a warming food that aids digestion,^3,10 improves qi (vital energy) deficiency in the spleen/pancreas,¹¹ and alleviates pain. Application of fresh squash juice was used to reduce inflammation and relieve burns, and its slightly acidic nature led to its incorporation as an ingredient in bone marrow or “longevity” soup.¹¹ Intercontinental trade likewise brought butternut squash to India, where it, too, was adopted as a functional food. In the Indian traditional medicinal practice of Ayurveda, winter squash has a history of use to treat vata (conditions that are dry and cold) and pitta (conditions that are inflammatory and hot).³

Modern Research

Research on the therapeutic properties of butternut squash has largely been limited to in vitro cell studies and animal studies. Their relation to human physiology is not certain.

Butternut squash pulp is a potential source for the production of prebiotics used in functional food and nutraceutical products. When butternut squash pulp oligosaccharides were analyzed in vitro to determine their potential for prebiotic production, they demonstrated resistance to hydrolysis by artificial human gastric juice and alpha-amylase when compared to inulin, a reference prebiotic.¹² These oligosaccharides also stimulated the growth of lactobacilli more than inulin. Prebiotics must withstand the gastric digestion process to reach the colon where they serve as a source of nutrition to stimulate growth of beneficial bacteria or microbiota.

Analyses of bioactive compounds in butternut squash also have focused on cucurmosin, which can be isolated from the fleshy part of the fruit.¹³ Cucurmosin can inhibit the proliferation of cancer cells by inducing apoptosis (normal, programmed cell death). An in vitro study showed that cucurmosin inhibits cell proliferation in a time- and dose-dependent manner and induces apoptosis specifically in human pancreatic cancer BxPC-3 cells. Cucurmosin downregulates, or decreases the quantity of epidermal growth factor receptor (EGFR) protein expression. EGFR overexpression is associated with promoting pancreatic tumor growth and metastasis.

In a separate study, human liver carcinoma cells (HepG2 cells) were treated with cucurmosin, which resulted in an increase of cell apoptosis in a concentration-dependent manner.¹⁴ Additional studies, particularly human clinical trials, are needed to assess the potential therapeutic potential of butternut squash in greater detail.

Several uses for butternut squash have been studied in animal models. Rats that were fed a high-fat diet supplemented with a fermented extract of butternut squash fruit exhibited less weight gain and lower levels of serum lipids over baseline when compared to a group of rats fed the same diet without the extract supplementation.¹⁵ Researchers hypothesized that fermentation improved the functional properties of the squash flesh and increased the beneficial probiotic bacteria, which they further hypothesized was a mechanism of action in the decrease of serum lipid levels exhibited in the study.

Taking a cue from a traditional Persian use for butternut squash, the efficacy of butternut squash peel extract to heal burn wounds was assessed.¹⁶ A burn cream containing a 20% concentration of peel extract exhibited more substantial reduction of wound area by day 10 of application compared to control, and significantly decreased lipid peroxidation in the skin tissue compared to control on day 14. A dose-dependent effect was observed, as the test cream with 10% extract concentration did not produce significant results. Researchers attributed these anti-inflammatory effects to the potent antioxidant content in butternut squash.

Nutrient Profile¹⁷

Macronutrient Profile: (Per 1 cup cubed squash [approx. 140 grams])

63 calories
1.4 g protein
16.4 g carbohydrate
0.1 g fat

Secondary Metabolites: (Per 1 cup cubed squash [approx. 140 grams])

Excellent source of:

Vitamin A: 745 mcg (82.8% DV)
Vitamin C: 29.4 mg (32.7% DV)

Very good source of:

Vitamin E: 2 mg (13.3% DV)
Manganese: 0.3 mg (13% DV)
Vitamin B₆: 0.22 mg (12.9% DV)
Thiamin: 0.14 mg (11.7% DV)
Magnesium: 48 mg (11.4% DV)
Niacin: 1.7 mg (10.6% DV)
Potassium: 493 mg (10.5% DV)

Good source of:

Folate: 38 mcg (9.5% DV)
Dietary Fiber: 2.8 g (9.3% DV)
Iron: 1 mg (5.6% DV)
Calcium: 67 mg (5.2% DV)

Also provides:

Phosphorus: 46 mg (3.7% DV)
Riboflavin: 0.03 mg (2.3% DV)
Vitamin K: 1.5 mcg (1.3% DV)

DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.

Recipe: Butternut Squash Soup Courtesy of Sarah Edwards Ingredients: 1 head of garlic, cloves separated and peeled 2 medium butternut squash, peeled 2 medium carrots, peeled and roughly chopped (Learn more about the benefits of carrot here18) 1 medium onion, peeled and quartered 4 tablespoons of extra virgin olive oil 1 teaspoon salt 8 cups vegetable broth 2 teaspoons of minced ginger (Learn more about the benefits of ginger here19) 2 tablespoons coconut milk (or more, to taste) 1 bunch cilantro, chopped (Learn more about the benefits of cilantro here20) Directions: Preheat oven to 350°F. Slice butternut squash in half and scoop out the seeds. Cut off the bulbous ends where the seeds have been scooped out and place peeled whole cloves of garlic in each cavity. Place squash pieces cut side down in a large baking dish. Cut the rest of the squash into large cubes and place in the baking dish with onion and carrot. Drizzle with olive oil and season with salt. Roast for 1 hour, until tender. Heat broth in a large pot over medium heat. Add the butternut squash sections and garlic into the saucepan along with the roasted vegetables and minced ginger, then bring to a boil and simmer for 10 minutes. Turn off the heat. Stir in the coconut milk and allow to cool slightly. Blend the soup in batches in a blender or in the pot with an immersion blender until thick and creamy. Garnish with cilantro.

Image credits (top to bottom):

Cucurbita moschata fruit. Image courtesy of George Chernilevsky.
Cucurbita moschata flower. Image courtesy of Jeantosti.
Cucurbita moschata fruit. Image courtesy of the Missouri Botanical Garden.

References

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6. Bahado-Singh PS, Wheatley AO, Ahmad MH, Morrison EYSA, Asemota HN. Food processing methods influence the glycemic indices of some commonly eaten West Indian carbohydrate-rich foods. Brit J Nutr. 2006;96:476-481.
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12. Du B, Song Y, Hu X, Liao X, Ni Y, Li Q. Oligosaccharides prepared by acid hydrolysis of polysaccharides from pumpkin (Cucurbita moschata) pulp and their prebiotic activities. Int J Food Sci. 2011;46:982-987.
13. Zhang B, Huang H, Xie J, et al. Cucurmosin induces apoptosis of BsPC-3 human pancreatic cancer cells via inactivation of the EGFR signaling pathway. Oncol Rep. 2012;27:891-897.
14. Xie J, Que W, Liu H, Liu M, Yang A, Chen M. Anti-proliferative effects of cucurmosin on human hepatoma HepG2 cells. Mol Med Rep. 2012;5:196-201.
15. Hossain MA, Lee SJ, Park NH, et al. Enhancement of lipid metabolism and hepatic stability in fat-induced obese mice by fermented Cucurbita moschata extract. Evid Based Complement Alternat Med. 2018;2018: 3908453.
16. Bahramsoltani R, Farzaei MH, Abdolghaffari AH, et al. Evaluation of phytochemicals, antioxidant and burn wound healing activities of Cucurbita moschata Duchesne fruit peel. Iran J Basic Med Sci. 2017;20(7):798-805.
17. Basic report: 11485, Squash, winter, butternut, raw. United States Department of Agriculture Agricultural Research Service. National Nutrient Database for Standard Reference Legacy Release. April 2018. Available at: https://ndb.nal.usda.gov/ndb/foods/show/302080. Accessed May 17, 2018.
18. Bauman H, MacLean K. Food as Medicine Update: Carrot (Daucus carota subsp. sativus, Apiaceae). HerbalEGram. 2018;15(4). Available at: http://cms.herbalgram.org/heg/volume15/04April/FoodAsMedicineCarrot_Update.html. Accessed May 17, 2018.
19. Bauman H, Hill K. Food as Medicine: Ginger (Zingiber officinale, Zingiberaceae). HerbalEGram. 2015;12(3). Available at: http://cms.herbalgram.org/heg/volume12/03March/March2015_FaM_Ginger.html. Accessed May 17, 2018.
20. Bauman H, Seibert J. Food as Medicine: Coriander/Cilantro (Coriandrum sativum, Apiaceae). 2015;12(6). Available at: http://cms.herbalgram.org/heg/volume12/06June/June2015_FaM.html. Accessed May 17, 2018.