History and Traditional Use
Range and Habitat
Okra (Abelmoschus esculentus) is a naturalized
tropical and subtropical annual grown extensively in Asia and Africa. Growing
up to 6 feet in height, okra plants have sturdy stems, long, broad, serrated, deeply-lobed
leaves, and delicate yellow flowers marked with red or purple color toward the
base.1,2 The edible portion of okra is the immature pod or fruit
which contains the seeds.3 Inside the tapering, fuzzy pod is a soft
tissue that exudes a mucilaginous (sticky) juice when cooked.4 The
pods are commonly green, but other varieties have red or burgundy pods. Considered
one of the most reliable annual edible vegetable crops of the tropics (the
Latin term esculentus means edible),
okra is tolerant of both hot, dry as well as hot, humid climates and is widely
cultivated in West Africa, India, Southern Europe, and the Americas.5
Related to hibiscus (Hibiscus sabdariffa)
and marshmallow (Althaea officinalis),
okra was originally classified in the genus Hibiscus
and was later reclassified into the genus Abelmoschus
in the 18th century.3 Okra is believed to have originated in
Ethiopia, where it still grows wild, although there is no definitive proof of
its origin.3 Okra has been cultivated by the Egyptians since the
12th century BCE. From there it traveled to central Africa, the Mediterranean,
and India.6 By the 17th century CE, okra had reached the New World
via the slave trade in Africa and by the 19th century, it had spread to China.2
Phytochemicals and Constituents
Okra is comprised primarily of water, carbohydrates, and protein with very
little fat and a fair amount of dietary fiber.3 Okra is also a
significant source of vitamin C and contains many other micronutrients such as
calcium, phosphorus, iron, beta-carotene, and B vitamins. The carbohydrate
content of okra is primarily in the form of mucilage, a long chain
polysaccharide molecule made up of sugar units and amino acids. Thin-layer
chromatography analytical methods indicate that the polysaccharides in okra gum
contain galactose, galacturonic acid, rhamnose and glucose.7 This water-soluble mucilage is the source of okra’s
viscous, slippery consistency, which is linked to okra’s effectiveness in
treating gastritis and other conditions where the mucilage acts as a demulcent
agent, i.e., it provides relief to inflamed mucous membranes.
Phytochemical studies show that okra pods contain flavonoids, tannins, sterols,
and triterpenes.5 Flavonoids are important compounds that are
responsible for protecting tissues from oxidative damage in a variety of ways.
Quercetin is the major antioxidant in okra gum, which is a key player in
controlling inflammation in the body.7
Okra contains a moderate amount of oxalate, a compound that both is created by
the human body and is present in plants. Because oxalate is excreted through
urine and can calcify in the kidneys, high levels of oxalate intake along with
genetic predisposition may lead to the development of kidney stones. Different
types of kidney stones exist, but approximately 75% of patients diagnosed with
kidney stones in the United States suffer from stones made of calcium oxalate.8
Physicians may recommend that patients with kidney stones or with a history of
kidney stones follow a low-oxalate diet; however, a food’s oxalate content does
not necessarily correlate with its oxalate bioavailability in the human body.
Okra has been shown to have low oxalate bioavailability as compared to similar oxalate-rich
foods such as peanuts (Arachis hypogaea)
and almonds (Prunus dulcis).9
Oxalate absorption from dietary sources can be reduced when paired with foods
with high calcium or magnesium content.10
Historical and Commercial Uses
Ancient cultures quickly noted okra’s mucilaginous nature and its subsequent
benefits to the digestive system. Okra was used by Egyptians to prevent the
development of kidney stones.5 In folkloric practice, fresh, tender
okra pods were consumed to cure constipation, leucorrhea (abnormal vaginal
discharge), spermatorrhea (excessive, involuntary ejaculation), diabetes, and
jaundice. The mucilage from okra is used commonly in traditional Asian and
African medicine to treat gastritis, gastric ulcers, and to lubricate the
intestines.5,11,12
The acceptance of okra as a relatively modern medicinal agent can be found in J.M. Nickell’s Botanical Ready Reference,
a book published in 1911 in the United States for physicians and pharmacists.13
Arranged alphabetically by Latin binomial, okra appears as the first entry on
the list of herbal drugs and medicinal agents. The actions noted for okra capsule
(fruit) are “mucilaginous, demulcent, and edible.”
Okra mucilage has been used traditionally in Arabic, West African, Caribbean,
and Eastern Mediterranean cooking.6 The most common culinary
application of okra is as a thickener for soups and stews. The most well-known
application may be in Louisiana’s Creole gumbo stew, which may derive its name
from a corruption of the Bantu word for okra: kingombo. It is also used as a substitute for egg whites and as a
fat replacement in chocolate bars, cookies, and frozen dairy desserts.7
Okra can be boiled, baked, sautéed, stuffed, or fried. Sautéing or quickly
frying the okra reduces the sticky texture significantly.4 The gummy
texture can also be mitigated by cooking okra with cornmeal.14
The water extract of okra, also known as okra gum, is used as an industrial
lubricant and as an emulsifier to stabilize foams and suspensions.9
It is also utilized medically in plasma replacement therapy.3 The
seeds of the okra pods are roasted and powdered into a flour for use as a
coffee substitute in Turkey, and in Nigeria, the nutritious flour is an
important staple and often added to soups and other foods.4,15
In vitro studies done on the chemical composition and antioxidative properties
of Nigerian okra seed flour demonstrated that antioxidant activity correlated
positively with roasting time.15 This study showed that antioxidants
within the okra seeds had the greatest benefit in protecting the human large intestine from oxidative damage.
Modern Research
Laboratory research suggests that okra and its extracts can be useful in the
treatment of a variety of disease states. A recent in vitro study indicated
that Abelmoschus esculentus lectin
(AEL), a protein extracted from okra, binds carbohydrates on the surface of
cancer cells, thus causing apoptosis (programmed cell death) and significantly
and selectively inhibiting breast cancer cell proliferation.16
Modern research suggests that okra’s effectiveness in the treatment of gastrointestinal
complaints can be attributed to the presence of rhamnogalacturonan
polysaccharides, which disrupt the adhesion of Helicobacter pylori bacteria to stomach tissue;11 these
bacteria are associated with stomach ulcers.
The polysaccharide compounds bind
non-specifically to different strains of H.
pylori, inhibiting the binding of the pathogens to gastric cells. The
rhamnogalacturonans appear to interact with H.
pylori’s surface proteins, potentially providing a preventative treatment
approach. Okra’s mucilage could also inhibit the recurrence of H. pylori infections by preventing
re-colonization of the stomach following antibiotic eradication therapy.
An in vitro study published in 2007 by the USDA Agricultural Research Service
compared the effectiveness of the bile acid-binding, cholesterol-lowering drug
cholestyramine to the natural bile acid-binding ability of the common
vegetables okra, beets (Beta vulgaris),
asparagus (Asparagus officinalis),
eggplant (Solanum malongena), turnips
(Brassica rapa subsp. rapifera), green beans (Phaseolus vulgaris), carrots (Daucus carota subsp. sativus), and cauliflower (B. oleracea var. botrytis).17 Okra was found to be more effective at
binding bile acids than any other vegetable evaluated in the study, and 34% as
effective as cholestyramine.
An animal study
conducted in 2011 found that okra peel and seed powder had the ability to
normalize blood levels of both lipids and sugars in diabetic rats.18
Oral administration of okra significantly reduced blood levels of total
cholesterol, triglycerides, low-density lipoproteins (LDL), very low-density
lipoproteins (VLDL), and hemoglobin A1C as well as significantly increased
blood levels of high-density lipoproteins (HDL) and hemoglobin. While both
parts of the plant were effective in a dose-dependent manner, the seed powder
had a more pronounced effect than the peel, especially on blood glucose levels.
These results indicate that consumption of okra may help reduce hyperlipidemia
and hyperglycemia in diabetics, thus helping to prevent cardiovascular disease
and other comorbidities associated with diabetes. These effects could be
related to okra’s ability to bind bile acids.
Among other factors (e.g.,
soil, climate, season, etc.), cooking and preparation methods can impact the
nutrient content of vegetables. A study on the effects of different cooking
methods on the nutrient content of okra pods compared the mineral content of
raw and cooked okra of both organic and conventional varieties.19 Raw
okra had the highest concentration of all elements tested, indicating some
degree of nutrient losses during cooking, with the most pronounced difference
found in potassium concentration, while calcium losses were relatively minimal.
There were significant
mineral losses following boiling and baking, but the effect was less pronounced
with sautéing.19 This could be due to the water solubility of
nutrients found in okra, including but not limited to its mucilage. While the
loss of mineral content may seem undesirable, the marked reduction of minerals
from cooking could be beneficial for those with kidney disease. For example,
potassium levels can be reduced by up to 60% by boiling okra and pouring off
the water, making boiled okra safer than raw okra for a potassium-restricted
diet.
An in vitro study in
2011 examined the effects of okra gum extract on both cell viability and
bacterial growth.7 Okra gum extract had antibacterial effects on
seven of eight strains of bacteria tested, and was most effective against Staphylococcus aureus, Mycobacterium sp., M. aurum, Xanthobacter Py2, and Pseudomonas aeruginosa. In fact, okra gum extract was completely
effective in inhibiting growth of S.
aureus (which can cause skin infections, pneumonia, meningitis and
septicemia) as well as P. aeruginosa
(known for causing fatal lung infections in patients with cystic fibrosis).
Major lipid fractions isolated from okra gum extract were 34% palmitic acid and
26% stearic acid, both of which have antibacterial properties against S. aureus and Listeria monocytogenes. The results of this study demonstrate the
potential use of okra extract as an antibacterial agent with possible
applications in the food and pharmaceutical industry.
A study on rats explored
the traditional uses of okra in liver disease.5 Hepatotoxicity was
induced in rats that were then given an okra gum extract that quenched all free
radicals present, thus preventing lipid peroxidation of liver cell membranes.
The hepatoprotective and antioxidant activities of the okra extract are
comparable to standard silymarin, isolated from milk thistle (Silybum marianum) fruit, making okra
extract a potentially important substance for protecting chemically-damaged
liver tissue. Human clinical trials are needed to explore this potential
therapeutic application.
Nutrient Profile20
Macronutrient
Profile: (Per 1 cup
[approx. 100 g] raw okra pods)
33 calories 2 g protein 7.5 g carbohydrate 0.2 g fat
Secondary
Metabolites: (Per 1
cup [approx. 100 g] raw okra pods)
Excellent
source of:
Vitamin K: 31.3 mcg (39.1%
DV) Vitamin C: 23 mg (38.3%
DV)
Very
good source of:
Folate: 60 mcg (15%
DV) Vitamin A: 716 IU
(14.32% DV) Magnesium: 57 mg (14.3%
DV) Thiamin: 0.2 mg (13.3%
DV) Dietary Fiber: 3.2 g (12.8%
DV) Vitamin B6: 0.22 mg (11%DV)
Good
source of:
Potassium: 299 mg (8.5%
DV) Calcium: 82 mg (8.2%
DV) Phosphorus: 61 mg (6.1%
DV) Niacin: 1 mg (5% DV)
Also
provides:
Zinc: 0.6 mg (4% DV) Iron: 0.6 mg (3.3% DV) Vitamin E: 0.27 mg
(2.5% DV)
DV = Daily Value as
established by the US Food and Drug Administration, based on a 2,000-calorie
diet.
Recipe: Spicy Okra Stew
Adapted from New Flavors for Vegetables21
Ingredients:
- 3
large ripe tomatoes
- 1
lb fresh okra, stems removed, sliced 1/4-inch thick
- 2
tablespoons canola oil
- 1
yellow onion, diced
- Salt
and freshly-ground black pepper, to taste
- 2
cloves of garlic, minced
- 1/2
teaspoon cayenne pepper
- 1/2
teaspoon ground coriander
- 1/2
teaspoon ground cumin
- 1/4-1/3
cup fresh parsley, chopped
Directions:
- Prepare a small saucepan of boiling
water and a separate bowl of ice water. Blanch the tomatoes: cut a shallow “x”
at the bottom of each tomato, then cook in boiling water for 10 seconds.
Immediately submerge in the ice water, let stand for 10 more seconds, then
drain. Peel the skin from the tomatoes and chop the flesh.
- Heat the oil in a saucepan over
medium heat. Add the onions and cook until just softened, 2-3 minutes. Add the
okra and sauté until lightly browned, approximately 10 minutes, then lower the
heat to medium-low and cook until tender.
- Add the garlic, salt, pepper, and
spices, stirring until combined and fragrant, then add the tomatoes and 1 cup
of water. Simmer until the tomatoes have broken down and the mixture begins to
thicken. Adjust seasoning to taste, then remove from heat and stir in the
chopped parsley.
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