HerbalEGram: Volume 12, Issue 9, September 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) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We thank Ashley Schmidt (TSU, 2014) for her research and work on prickly pear.
History and Traditional Use
Range and Habitat
The cactus genus Opuntia encompasses a large group of species characterized by flat, jointed or segmented pads known in botany as cladodes and in Spanish as nopales (singular: nopal).1 The cladodes are cylindrical or conical in shape, covered with clusters of spines, and are uniquely adapted to a dry desert climate due to thick, waxy stems that store water and minimize water evaporation in much the same way that leaves do.2 Yellow, orange, pink, and red flowers grow on the plant. Pear-shaped fruits, called tunas, mature on the cactus pads in early fall. Two types of spines grow on the pads: large, fixed spines, and small, barbed spines that detach from the plant easily.3 The fruit often has clusters of smaller, inconspicuous spines and vary in color from green, yellow, red, orange, and purple. The fruit contains hard seeds surrounded by a fleshy portion. These succulent shrubs are drought-tolerant and grow in arid and semiarid climates. The prickly pear is native to Mexico but now grows across the United States, Australia, and South Africa.4 Prickly pear can be cultivated and propagated easily because the pads can be removed from the plant and replanted, forming a new growth.
Phytochemicals and Constituents
Opuntia species contain a variety of nutrients and bioactive compounds that are beneficial for human health. The pad and fruit compositions differ, but both provide various levels of macronutrient distribution, vitamins, minerals, and phytochemicals.
The fruits of the Opuntia species are rich in antioxidant pigments called betacyanins.5 Betacyanins from cactus pear fruit have been found to reduce low-density lipoprotein (LDL) cholesterol levels after consumption and protect against oxidation.6 Numerous flavonol glycosides, plant-derived secondary metabolites with important antioxidant properties, have been isolated from O. ficus-indica fruit concentrates.7
Pads of the Opuntia species contain manganese, which is essential for glucose metabolism8; magnesium, which helps the body regulate protein synthesis, muscle and nerve function, blood glucose, and blood pressure9; and vitamin C.
Historical and Commercial Uses
The prickly pear has been used traditionally in a variety of ways, including the treatment of digestive problems, edema, and topically for burn and wound care.10 The bitter plant also has been used as a diuretic, a fever reducer, for vitiligo (localized loss of pigmentation in the skin), urinary problems, tumors, abdominal fluid build-up, inflammation, liver problems, anemia, ulcers, bronchitis, hemorrhoids, bladder stones, inflammation of the eyes, lower back pain, spleen enlargement, and management of human immunodeficiency virus (HIV).3,11 Mashed pads historically were used to relieve heat and inflammation. They were also applied to boils for quick removal of pus. The flowers were used for lung problems, including bronchitis and asthma. The fruit of the plant was used to cool the body, treat gonorrhea and whooping cough, expel phlegm from the lungs, control excessive coughing, and increase bile secretion. Indigenous tribes in Mexico and the Pima tribe in central and southern Arizona use the cactus as a treatment for diabetes. Additional historical uses of the species include treatment of hangovers, prostate enlargement, and rabies.12
Opuntia cacti played an important role in the daily life and economy of the Aztec and Maya, since they served not only as sources of food for humans and livestock, but also as host plants for the cochineal insect (Dactylopius coccus).13 Cochineals are used to make carmine dye, a highly prized red dye for textiles. Carmine-dyed wool and cotton remain important mediums in Mexican folk art.
Currently, Opuntia is cultivated in arid and semiarid climates across the world including Mexico, Argentina, Brazil, Tunisia, Italy, Israel, China, Spain, and California.3,14 Uses of different components of the prickly pear encompass traditional uses as well as use for food and beverages, for livestock fodder, dye, soap, drinking water purification, thickening agent, and as a protective hedge for fencing.10 Mexico, Spain, Italy, northern Africa, and the United States commonly use the plant for food, consuming both the pad and the fruit.3
Treatment of diabetes has been cited as a traditional use for Opuntia, prompting research on its effects on various health parameters associated with diabetes. Rats with induced diabetes fed nopal flour from medium-sized pads followed by glucose were found to have a reduced post-meal glucose peak.15 A 40% reduction in fasting blood sugar was also seen in rats that consumed nopal flour, and a 30% decrease from treatment with nopal flour made with smaller pads. The results suggest that the maturity (as indicated by the size) of the pad modifies the blood sugar-lowering effects of Opuntia. The fiber found in the pad could be the primary component responsible for its blood sugar-lowering effects, delaying the absorption of carbohydrates from foods. Additional benefits have been found in animal studies: concentrated juice from the fruit of O. ficus-indica has been found to protect against ulcer formation in rats.7
Studies in humans have also explored the antidiabetic properties of prickly pear. A recent small study of type 2 diabetics found that consumption of steamed nopales significantly reduced spikes in blood glucose levels and serum insulin levels up to one hour after consumption of a high-carbohydrate breakfast.16 The study also found a significant decrease in glucose-dependent insulinotropic peptide (a hormone released from the small intestine that stimulates insulin production17) after consumption of nopales and a high-carbohydrate breakfast. In pre-diabetics, a product formulated with both cladode and fruit skin extract of O. ficus-indica, named OpunDia™ (Martin Bauer Group, Vestenbergsgreuth, Germany), has been found to reduce blood glucose spikes 60, 90, and 120 minutes after ingestion followed by 75 g of a glucose solution.18
Studies have found additional uses for the fruit and cladodes of the prickly pear. The cladodes of the prickly pear cactus contain high levels of calcium and have been studied for their effects on bone mineral density. Urine calcium/creatinine levels decreased (increased urinary excretion of calcium can be a symptom of bone-destroying diseases, among other physiological abnormalities), and bone mineral density in the total hip region was increased in women 35 to 55 years old after daily consumption of 55 g of dehydrated nopal.19 Premenopausal women consuming 15 g of dehydrated nopal also had increased bone mineral density of the lumbar spine region. The 15 g of dehydrated nopal contained 500 mg of calcium and used nopales harvested at a high maturity stage. Furthermore, consumption of tortillas filled with cactus fruit jam increased blood antioxidant levels, blood vitamin C levels, and protected lipids from oxidation in human participants.20 The jam-filled tortillas also significantly reduced blood glucose, total cholesterol, and triglyceride levels. Some evidence of antiviral properties, immunomodulation, improvement of platelet function, and neuroprotection have also been noted.3
Interestingly, some research suggests that prickly pear may be a useful and practical tool for water filtration. A study from 2010 found that prickly pear gel filtered out 98% of bacteria in a contaminated water sample. The researchers noted that the cactus could “become a sustainable and affordable water purification method in the rural communities of developing countries.”21
Macronutrient Profile: (Per 100 g [approx. 1 1/4 cup sliced] raw nopal)
1.3 g protein
3.33 g carbohydrate
0.1 g fat
Secondary Metabolites: (Per 100 g [approx. 1 1/4 cup sliced] raw nopal)
Very good source of:
Calcium: 164 mg (16.4% DV)
Vitamin C: 9.3 mg (15.5% DV)
Magnesium: 52 mg (13% DV)
Good source of:
Vitamin A: 457 IU (9.1% DV)
Dietary Fiber: 2.2 g (8.8% DV)
Potassium: 257 mg (7.34% DV)
Vitamin K: 5.3 mcg (6.63% DV)
Vitamin B6: 0.07 mg (3.5% DV)
Iron: 0.6 mg (3.33% DV)
Riboflavin: 0.04 mg (2.35% DV)
Niacin: 0.41 mg (2.05% DV)
Zinc: 0.25 mg (1.67% DV)
Phosphorus: 16 mg (1.6% DV)
DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000 calorie diet.
Cactus Casserole with Rice, Ancho Chili, and Cheese