HerbalEGram: Volume 14, Issue 12, December 2017

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 Bauman^a and Addie Abohosh^b

^a HerbalGram Associate Editor

^b ABC Dietetics Intern (Texas State, 2017)

Overview

The date palm (Phoenix dactylifera, Arecaceae) has been cultivated for more than 5,000 years.¹ Because of this long history of use and cultivation, the exact origin of the date palm is difficult to pinpoint. Dates have been harvested for centuries in northern Africa and the Arabian Peninsula, and have played a large role in the economies of countries where the plant grows.^1,2 The largest global producers of dates are Iraq, Egypt, Saudi Arabia, Tunisia, Algeria, the United Arab Emirates, Oman, Libya, Pakistan, Sudan, and the United States.³

The date palm is a large palm tree and grows about 49-82 feet tall.¹ The palm leaves are 1.5 to 11.5 inches long.¹ Around the trunk of the date tree, the palm branches grow in a spiral pattern and form a crown with hundreds of leaves that are gray in color.^2,4 The leaves have a needle-sharp point at their tips to deter predators.² The palm’s flowers are small and white or yellow in color.^2,4 The date palm is dioecious (i.e., male and female reproductive organs occur in separate individuals) and, in cultivation, one male date palm typically is grown for every 50 female date palms, which produce the date fruit.^4,5 The date fruits grow in clumps at the base of the branches, and the bunches of fruit can weigh up to 20 pounds.^1,5

Date fruit is oval in shape, 1-2.5 inches long, and 0.87-2.75 inches in diameter. The fruit can vary in color from bright yellow to bright red.¹ Each fruit contains a seed pit that also contains many vitamins and minerals.^1,6 The date fruit ripens in five stages, each with its specific flavor profile. The five stages of maturity for the date fruit include “habahouk,” in which the fruit is pea-sized and fully layered; “kimri,” in which the fruit is small, oblong, and green; “khalal” or “besser,” in which the fruit changes from green to yellow to red and reaches maximum weight and size; “rutab,” in which the flesh becomes softer and darker; and “tamar,” in which the fruit is fully ripe.^6,7 Date palms typically require hot and dry conditions and a regular water supply to the roots in order to produce a high-quality fruit.⁴ As the date fruit ripens, its sugar content increases and its protein content decreases.⁷ Dates are sold in three varieties: hard, soft, and semidry.⁵ The semidry form is most common in commerce.

Phytochemicals and Constituents

The date fruit contains about 70% digestible sugar, including glucose, fructose, and sucrose.¹ It also contains a significant amount of fiber and a small amount of fat and protein.^1,8 There are 23 amino acids present in the date fruit and 17, including all nine essential amino acids, in the date pit.^3,9 The fruits also are rich sources of minerals, including iron, calcium, magnesium, potassium, manganese, phosphorus, and zinc, as well as trace amounts of sulfur, cobalt, copper, fluorine, boron, and selenium.^1,8

The date pit contains fiber and a variety of fatty acids, including lauric, myristic, palmitic, and stearic acids.^8,10 The predominant monounsaturated fatty acids are palmitoleic and oleic acids while α-linolenic and linoleic acids are the predominant polyunsaturated fatty acids present in date pits.¹⁰ Research indicates that oleic acid has the potential to reduce low-density lipoprotein (LDL) cholesterol in the body and α-linolenic acid is similarly important for cardiovascular health. Pressed oil from date pits is shown to have a higher total tocopherol content than olive (Olea europaea, Oleaceae) oil and a higher antioxidant content than coconut (Cocos nucifera, Arecaceae) oil. However, these values can vary depending on the origin of the date.⁶ While date pit oil is unique in its fatty acid profile and tocopherol composition, the oil content in the pit is low.¹⁰ In vitro research has demonstrated that date seed extract lessened the permeability of cell membranes, which further reduced oxidative damage.

Date fruit is rich in polyphenolic compounds, including lignans, carotenoids, and flavonoids, including anthocyanins and procyanidins.¹ Research indicates that the majority of date fruit’s health benefits can be associated with its polyphenol content. These polyphenols have synergistic effects that amplify health benefits.¹¹ Carotenoids and flavonoids in the date fruit and seed act as potent antioxidants that help protect the cells of the body from free radicals that can damage and destroy cells.^1,3 However, carotenoids and anthocyanins are most prevalent in the fresh fruit.^7,11 Procyanidins, which are condensed tannins with powerful antioxidant properties, are present in date fruits in varying amounts based on ripeness.^1,8

The beta glucans in the date fruit and palm pollen have also demonstrated antitumor activity.^1,3 Beta glucans are polysaccharides that occur naturally in some plants and fungi.¹² Beta glucans have been shown to increase immune defense and enhance macrophage activity as well as other natural cell protection mechanisms. The enhancement of protective cellular mechanisms is linked with tumor cell inhibition. There is also evidence that beta glucans can reduce high cholesterol and blood pressure levels in patients with diabetes mellitus.¹³

Historical and Commercial Uses

Traditionally, date fruit has been used to address leprosy, thirst, asthma, bronchitis, fatigue, tuberculosis, abdominal complaints, fever, vomiting, and loss of consciousness.¹ In Ayurveda, India’s oldest system of traditional medicine, date fruit was considered cooling and was used for its anti-inflammatory properties. While the fruit was the most commonly used part of the plant, the leaves, flower, gum, and seed pit have historically been used in medicinal preparations. The leaves of the date palm were traditionally used as an aphrodisiac and to support liver health. The flower was used as a liver tonic and expectorant and for fever and blood complaints; the gum was used as a diarrhea remedy; and the pit of the date fruit was used to reduce inflammation, heal wounds, move the bowels, and treat asthma and gonorrhea.

Roasted date pits have a long history of use as a caffeine-free coffee (Coffea arabica and C. canephora, Rubiaceae) substitute in the Middle East. Roasted date pit tea has traditionally been used there to stabilize blood glucose levels, improve memory, and prevent chronic diseases.¹⁰

The date fruit can also be used as a sugar source.¹⁴ The date fruit yield per plant is high; however, the labor required to process the date sugar could be a barrier to its mainstream production.

The date palm can also be of use in bioremediation and other ecological applications. The powder of date pits, or date-pit ash, can be used to filter waste water or contaminated water due to its water absorption strengths.^10,15 Date pits have also been traditionally used for compost preparation and animal feed and as an antimicrobial agent, while their oil has been used in cosmetics preparations and as a potential biodiesel product.^6,10

Modern Research

Dried dates have high antioxidant activity.¹⁶ Date fruit, pit, and pollen have been investigated for their anti-inflammatory benefits for a variety of conditions, including diabetes, gastrointestinal distress, and fertility issues.

Anti-inflammatory Properties

Date pit “tea” has been investigated for its health benefits. In rat models, the aqueous extract of dried, ground date pit has been shown to have protective effects on the liver as well as anti-inflammatory activity.⁹ Date pits are also an excellent source of potassium, magnesium, and calcium, which can decrease the risk of cardiovascular and cerebrovascular diseases.

Fiber and Digestive Health

In a rat study, aqueous date flesh extracts significantly decreased gastric transit time and occurrence of ulcers, gastrin, and histamine in the stomach.¹¹ The high fiber content of date fruit can help maintain gastric health and enhance immune functions.^1,3

Diabetes

Diabetes mellitus is characterized by high blood glucose levels,¹³ which can cause excessive thirst, urination, hunger, and weight loss. Prolonged exposure to high blood glucose levels can also cause neuropathy, eye damage, and inflammation of the body systems. However, despite their high sugar content, date fruits are characterized as a low or medium glycemic index fruit.¹⁷ (The glycemic index measures the effect of carbohydrate foods on human health, including insulinemic response.) In a clinical trial, patients with type 2 diabetes exhibited lower blood glucose levels compared to baseline after adding controlled amounts of date fruit to their diet. In patients without diabetes, date fruit consumption stimulated insulin secretion 2.7% less on average than an active amount of dextrose sugar, which suggests that date fruit consumption does not adversely affect glucose tolerance in people without diabetes. Animal studies have shown antihyperglycemic effects from date leaf extract, while date pit extract has been shown to lower blood glucose levels in rats and improve insulin resistance with its high fiber content.^3,10 Date fruit aqueous extract has been shown to improve neuropathy related to diabetes, as well.³

Future Outlook

Areas of research that merit further investigation include the use of date palm pollen for fertility, date fruit’s potential for the inhibition of tumor growth, and the neuroprotective nature of the date seed and fruit. Traditionally, date palm pollen was used as an aphrodisiac and to increase fertility in both men and women. A recent animal study demonstrated an increase in sperm count, serum testosterone, and spermatogenesis in male rats and an increase in testosterone, estrogen, and progesterone production in female mice.¹⁹ Both the date fruit pollen as well as the fruit itself contain immune-stimulating beta glucans. In a mouse study, date fruit extract significantly inhibited tumor growth.¹¹ Additionally, the seed extract and date fruit have been shown in animal models to significantly reduce damage to neurons and oxidative stress in the brain.³ However, data for the efficacy of these treatments in humans is lacking.

Consumer Considerations

The tannin, phytate, and oxalate levels present in date fruit have the potential to damage the stomach, kidneys, and liver, as well as cause mineral deficiencies.^3,10 Tannins are polyphenols that can interfere with the absorption of nutrients in the body.¹⁰ However, the levels of tannins in the fruit decrease as the fruit ripens, and the consumption of ripe fruit should not cause any adverse effects on nutrient absorption. Additionally, it has been shown that dates in general, and four varieties in particular (Aseel, Dhakki, Hallavi, and Dora), are safe to consume as part of a regular diet without this potential for health complications due to low levels of anti-nutrients.^3,19

Nutrient Profile²⁰

Macronutrient Profile: (Per 100 grams [approx. 4 dates])

277 calories
1.8 g protein
75 g carbohydrate
0.2 g fat

Secondary Metabolites: (Per 100 grams [approx. 4 dates])

Excellent source of:

Dietary Fiber: 6.7 g (26.8% DV)

Very good source of:

Potassium: 696 mg (19.8% DV)
Manganese: 0.3 mg (15% DV)
Magnesium: 54 mg (13.5% DV)
Vitamin B6: 0.25 mg (12.5% DV)

Good source of:

Niacin: 1.6 mg (8% DV)
Calcium: 64 mg (6.4% DV)
Phosphorus: 62 mg (6.2% DV)
Iron: 1 mg (5.6% DV)

Also provides:

Folate: 15 mcg (3.8% DV)
Riboflavin: 0.06 mg (3.5% DV)
Vitamin K: 2.7 mcg (3.4% DV)
Thiamin: 0.05 mg (3.3% DV)
Vitamin A: 149 IU (3% DV)

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

Recipe: Goat Cheese-Stuffed Dates Adapted from Martha Stewart21 Ingredients: 12 large Medjool dates, pitted 1/4 cup (2 ounces) soft goat cheese 12 pecan halves (for more information about pecans, click here.22) Directions: Make a lengthwise slit through each date without cutting through it entirely. Fill each date with a teaspoon of the goat cheese and top each with a pecan half.

Photo credits:

Top: Date fruit at the Mercat Central de València, Spain. Photo courtesy of Hans Hillewaert.
Middle: Date palm illustration from The New Student's Reference.
Bottom: Fruiting date palm in Las Vegas, Nevada. Photo courtesy of Stan Shebs.

References

1. Ateeq A, Sunil SD, Varun SK, Santosh MK. Phoenix dactylifera Linn. (Pind Kharjura): A review article. Int J Res Ayurveda Pharm. 2013;4(3):447-451.

2. El Hadrami A, Al-Khayri JM. Socioeconomic and traditional importance of date palm. Emir J Food Agric. 2012;24(5):371-385.

3. Mallhi TH, Imran M, Qadir MI, Ali M, Ahmad B, Khan YH, Rehman AU. Ajwa date (Phoenix dactylifera): An emerging plant in pharmacological research. Pak J Pharm Sci. 2014;27(3):607-617.

4. van Wyk B-E. Food Plants of the World. Portland, OR: Timber Press; 2006.

5. National Geographic Society. Edible: An Illustrated Guide to the World’s Food Plants. Lane Cove, NSW, Australia: National Geographic Society; 2008.

6. Abdul Afiq MJ, Abdul Rahman R, Che Man YB, Al-Kahtani HA, Mansor TST. Date seed and date seed oil. Int Food Res J. 2013;20(5):2035-2043.

7. Ashraf Z, Hamidi-Esfahani Z. Date and date processing : A review. Food Rev Int. 2011;27:101-133. doi:10.1080/87559129.2010.535231.

8. Taleb H, Maddocks SE, Morris RK, Kanekanian AD. Chemical charaterisation and the anti-inflammatory, anti-angiogenic and antibacterial properties of date fruit (Phoenix dactylifera L.). J Ethnopharmacol. 2016;194:457-468.

9. Shi LE, Zheng W, Aleid SM, Tang ZX. Date pits : Chemical composition, nutritional and medicinal Values, utilization. Crop Sci. 2014;54:1322-1331. doi:10.2135/cropsci2013.05.0296.

10. Hossain MZ, Waly MI, Singh V, Sequeira V, Rahman MS. Chemical composition of date-pits and its potential for developing value-added product – a review. Pol J Food Nutr Sci. 2014;64(4):215-226. doi:10.2478/pjfns-2013-0018.

11. Yasin BR, El-Fawal HAN, Mousa SA. Date (Phoenix dactylifera) polyphenolics and other bioactive compounds : A traditional Islamic remedy’s potential in prevention of cell damage, cancer therapeutics and beyond. Int J Mol Sci. 2015;16:30075-30090. doi:10.3390/ijms161226210.

12. Akramiené D, Kondrotas A, Didžiapetriené J, Kévelaitis E. Effects of β-glucans on the immune system. Medicina (Kaunas). 2007;43(8):597-606.

13. Chen J, Raymond K. Beta-glucans in the treatment of diabetes and associated cardiovascular risks. Vascular Health and Risk Management. 2008;4(6):1265-1272.

14. Samarawira I. Date palm, potential source for refined sugar. J Econ Bot. 1983;37(2):181-186.

15. Ahmad T, Danish M, Rafatullah M, et al. The use of date palm as a potential adsorbent for wastewater treatment : a review. Environmental Science and Pollution Research. 2012;19(5):1464-1484. doi:10.1007/s11356-011-0709-8.

16. Chang SK, Alasalvar C, Shahidi F. Review of dried fruits: Phytochemicals, antioxidant efficacies, and health benefits. J Funct Food. 2016;21:113-132.

17. Vayalil P. Date fruits (Phoenix dactylifera Linn): An emerging medicinal food. Crit Rev Food Sci Nutr. 2012;52:249-271.

18. Tahvilzadeh M, Hajimahmoodi M, Rahimi R. The role of date palm (Phoenix dactylifera L ) pollen in fertility : A comprehensive review of current evidence. J Evid Based Comp Alt Med. 2016;21(4):320-324. doi:10.1177/2156587215609851.

19. Nadeem M, Rehman S, Anjum FM, Zahoor T, Saeed F, Ahmad A. Anti-nutritional factors in some date palm (Phoenix dactylifera L.) varieties grown in Pakistan. Internet Journal of Food Safety. 2011;13:386-390.

20. United States Department of Agriculture Agricultural Research Service. Basic Report: 09421, Dates, medjool. National Nutrient Database for Standard Reference Release 28. Available at: https://ndb.nal.usda.gov/ndb/foods/show/2424. Accessed November 22, 2017.

21. Stewart M. Martha Stewart’s Dinner at Home: 52 Quick Meals to Cook for Family and Friends. New York, NY: Penguin Random House; 2009.

22. Bauman H, Royer H. Food as medicine: Pecan. HerbalEGram. 14(11). Available at: http://cms.herbalgram.org/heg/volume14/11November/FAM_Pecan.html. Accessed November 20, 2017.