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 Zachary Brownb
a HerbalGram Associate Editor
b ABC Dietetics
Intern (TSU, 2015)
Overview
Mustard plants are herbaceous perennials (though
often grown as annuals or biennials) and belong to the Brassicaceae, or cabbage,
family.1 The three types of mustard most commonly consumed today are
brown mustard (Brassica juncea),
black mustard (B. nigra), and white
mustard (Sinapis alba). This paper is
concerned only with the brown and black species.
Native to temperate regions in Europe, mustard was
one of the continent’s first domesticated crops, and thereafter became a
cultivated food crop in Asia, North Africa, and North America.2 All
species yield edible leaves, while their seeds are used whole, powdered, or
pressed to produce oil.1 Annually, the United States produces
160,000 tons of mustard seed.3 Mustard plants have alternate leaves
with ruffled margins and produce the small, yellow four-petaled flowers typical
of members of the Brassicaceae family (formerly referred to as the Cruciferae
family due to the cross-like pattern of the four petals). Upon pollination,
each seedpod elongates into an oblong fruit capsule that contains up to 20
spherical seeds, which can be dark brown or yellow depending on the species.4
Black mustard is sparsely branched and erect. It
grows up to three meters in height and produces very small, pungent seeds (1.5
grams per 1,000 seeds) that are shed by the plant as the seedpod matures.1
Black mustard is grown for its edible greens in Argentina, Chile, and the
United States, but it is rarely cultivated as a seed crop due to difficulties
with the harvesting process and has largely been replaced by brown mustard because
of this. Brown mustard, also known as Indian or Oriental mustard, originated in
the Himalayan region of central Asia. Brown mustard grows 1-2 meters tall, has
larger seeds (three grams per 1,000 seeds), and produces seedpods that are
easier to mechanically collect and process. Brown mustard is commercially grown
in North America, specifically in parts of the United States and Canada.3
Phytochemicals and Constituents
Phytochemical
differences in black mustard and brown mustard are minor, since B. juncea evolved from its ancestor B. nigra. The primary components of interest
in mustard are the glucosinolates such as sinigrin, which are believed to be responsible for many of mustard’s
health benefits.5 Mustard seed oil contains 90% allyl isothiocyanate
(AITC). The seed contains 27% non-volatile oils (fixed oils), 30% proteins, and
small amounts of lecithin, inositol, albumin, gums, mucilage, and pigments.
Sinapine, an alkaloid, is also present in trace amounts. The fixed oils are
composed of oleic, stearic, erucic, or brassic acids. Mustard seeds also
contain terpenes, which have anti-inflammatory properties and are the primary
constituents of mustard essential oil.
Other constituents in significant amounts include
flavonoids and other phenolic compounds. The concentrations of these compounds
can vary widely based on the growing conditions of the mustard plant. Pathogenic
attacks on the plant also result in an altered phytochemical profile. Thus, it
is possible that the health effects of mustard can vary due to the different
farming practices used to grow the mustard. It would be beneficial to
standardize farming practices to maximize yields of specific plant chemicals.6
Mustard
greens are nutrient dense and contain high amounts of vitamins, such as vitamin
A, vitamin K, and vitamin C, and minerals, such as calcium. Mustard seeds
contain fewer vitamins but are a good source of iron, calcium, magnesium, and
other minerals. Mustard seeds are also a good source of omega fatty acids, as
they contain an almost 1:1 ratio of omega-3 and omega-6 fatty acids. Both the
seeds and greens can offer health-protective effects through their impressive
nutrient profiles, although prepared mustard as a condiment should be used sparingly,
since many commercial brands can contain high amounts of sodium.1
Historical and Commercial Uses
The
recorded use of mustard as a medicinal plant dates back to the first century CE
in Greece, where the physician Dioscorides recommended the topical application
of a mustard seed poultice to reduce inflammation in his herbal medicine
encyclopedia De Materia Medica.7
In Unani literature (the Greco-Arabic system of traditional medicine), mustard
seed is recommended for a variety of conditions, including neuralgia, epilepsy,
sciatica, leprosy, gout, pleurisy, and pneumonia.5
In
Ayurveda, the system of traditional medicine practiced for thousands of years
in India, the therapeutic uses of mustard are well documented. The Ayurvedic
practice considers mustard seed oil derived from the brown mustard plant to be pungent
and warming, and documents external uses such as a massage oil and a hair
tonic; for skin diseases like vitiligo; skin infections like acne; and
hemorrhoids.8 Mustard seeds were processed into a paste and used as
a poultice to treat internal conditions such as tumors of the thyroid gland and
lymphadenitis (swelling of lymph nodes). Mustard seeds were also decocted in
water and used as a poultice for cracked skin, leprosy, rheumatoid arthritis,
acne, and as a rinse for mouth sores.
Internally,
mustard oil traditionally was used to lower blood lipid levels, reduce build-up
of fat or adipose tissue, treat intestinal worms, and assist detoxification of the
body. Mustard seeds were also included in traditional herbal formulas used to
induce vomiting and cleanse the cranial cavity via nasal irrigation, and as a
decoction in an enema therapy.8 Though mustard leaves were more
commonly consumed as a vegetable, they were also used as an ingredient for
steam fomentation and to cleanse the cranial cavity.
Other
ethnobotanical uses of the mustard plant exist in cultures around the world.1
In Africa, the roots are used as a galactagogue to stimulate milk production. Dried
leaves and flowers are burned in Tanzania in spiritual rituals. The essential
oil has been used to relieve constipation and as a counterirritant. In Java, the
leaves are used internally to treat syphilis and stimulate blood flow to the
pelvic area and topically to treat headaches. In Korea, the seeds are used for
abscesses, colds, lower back pain, rheumatism, and stomach disorders. The oil
of mustard has been used to treat skin eruptions and ulcers throughout Asia.
In North
America, black mustard has a history of use among indigenous tribes.9
It was used by the Cherokee to stimulate the appetite, treat fever and “nervous
fever,” heal the kidneys, and treat various other diseases such as malaria. It
was also used to treat palsy and asthma, and as a tonic for overall wellness.
The Meskwaki used mustard due to its pungent nature to treat head colds. The
Mohegan tribe applied mustard leaf poultices as an analgesic for body pains,
headaches, and toothaches. The Shinnecock used it similarly to the Mohegan, but
also mixed it with flour and water to induce vomiting. Brown mustard seed powder also has a widespread use as an emetic to treat acute and narcotic poisoning.10
Modern Research
In recent
studies, mustard has shown antitumor effects and other beneficial properties against
chronic conditions, including diabetes, cardiovascular disease, weight gain,
and neuropathic disease. It might also act as a protective agent against acute conditions
such as fungal infection and influenza.
Cytotoxic and Anti-Tumor Effects
The
anticancer effect of mustard may be due to the anti-proliferative activity of
constituents such as sinigrin, the precursor to AITC. Many cytotoxicity studies
have been performed in vitro to investigate how mustard and its constituents act
against cancer cell proliferation. A hydrolyzed mustard seed powder that
contained AITC caused cell cycle arrest and apoptosis (programmed cell death) in
bladder cancer cell lines.11 This was further observed in rats,
where an oral dose of the hydrolyzed mustard seed powder inhibited bladder
cancer growth and blocked muscle invasion of cancerous cells. AITC specifically
is thought to be selectively delivered to the bladder through urinary
excretion. The mustard powder produced more significant results than pure AITC,
suggesting that ingestion of the whole seed is more beneficial than ingestion
of any isolated constituents. In an animal model, injections of mustard
essential oil rich in AITC inhibited cell proliferation and blood vessel creation
(angiogenesis, which is required for tumor growth).12 The oil also
induced apoptosis, a pathway for cancer chemoprevention.
Another
study examined the effects of sinigrin on liver tumors in rats. This
three-month study found that oral sinigrin administration significantly
inhibited proliferation of tumor cells in the liver and reduced the number of
tumors in the rat liver. The response was dose dependent, with the highest
tumor suppression at 25 mg/kg of body weight. However, the lowest dose, 10 mg/kg,
still caused a significant reduction of tumors on the liver surface compared to
the positive control, reducing tumor size by half.13
An in
vitro study examined the effects of several mustard extracts and found a
dose-dependent protective response in human hepatocytes, colorectal cells,
cervical cells, breast cancer cells, and larynx cells.5 The juice of
the mustard leaf was also found to protect against induced DNA damage in human
cells, again in a dose-dependent manner. These cancer chemopreventive effects
were thought to be mediated not through inherent antioxidant properties of
mustard extract, as is often seen with many plant materials, but by increasing
expression of detoxification enzymes.
Isothiocyanates
may also decrease multidrug resistance in human cancer cell lines and inhibit
the efflux (simply put, the removal of compounds from cells) of cancer-treating
drugs, which enhances the effect of chemotherapy treatment. In an in vitro
study, isolated compounds, including isothiocyanates and sulforaphane, increased
the accumulation of chemotherapeutic drugs in multidrug resistant cancer cells
through the inhibition of efflux of these drugs.14 Researchers also
found that the isothiocyanates inhibited tumor formation in breast, colon, lung,
and skin tissue.
Diabetes, Cardiovascular Disease, and Neuropathic
Effects
Mustard
leaves and seeds both can induce hypoglycemic effects in animals with type 2
diabetes. One rodent study found that administration of an extract made from
mustard leaves significantly reduced lipid peroxidation, reduced free radicals,
and ameliorated the damage caused by oxidative stress.15 Researchers
speculated that mustard enhances glycolysis and glycogenesis, and decreases
glycogenosis. These data were further confirmed by a follow-up study that also
showed reduced levels of superoxide and nitrite/nitrates in a dose-dependent
manner after oral administration of a mustard extract.16 Mustard may
also delay or prevent the onset of diabetes in addition to mitigating its
effects. A study examined the effects of feeding high-fructose diets to rodents
for 30 days and found that the inclusion of mustard powder over the study
period significantly decreased fasting serum glucose, insulin, and cholesterol
levels, although not enough to normalize them.17 Researchers
concluded that mustard powder may be beneficial for pre-diabetic patients and
those who are genetically prone to the disease.
Cardiovascular
disease (CVD) is often studied in tandem with diabetes, as individuals with
diabetes tend to suffer from CVD as well. One study examined the effects of two
doses of mustard seed powder on serum cholesterol and triglycerides in diabetic
rats.18 The lower dose did not significantly affect these markers;
however, a higher dose (8 g/kg of body weight) significantly and consistently
lowered both. The authors suggested that mustard might mimic or enhance the
effectiveness of insulin, lowering the necessary amount and reducing insulin’s anabolic
effect.
There are
often neurological complications associated with diabetes. In a rat model,
researchers examined the effects of an ethanol mustard extract and found
dose-dependent improvements in brain chemistry and cognitive function, and
speculated that non-diabeties-induced neurological problems could be improved
with mustard consumption or supplementation.19 The effect of mustard
on the depletion of neurotransmitters norepinephrine, serotonin, and dopamine
was further researched.20 Mustard was found to compensate for
depleted levels of neurotransmitters in the brain, resulting in improvement of
behavioral outcomes such as feelings of helplessness and despair, as well as
impaired locomotion. Mustard’s rich polyphenol content may be the source of its
therapeutic effects on cognitive issues.
Antimicrobial Properties
Mustard
has antimicrobial and antiviral properties and shows protective effects against
microbe- and virus-induced damage. One rodent study on viral hepatitis found
that mustard extract protected against liver and kidney damage. The mechanism
of this protective action is thought to be related to the anti-inflammatory
activity of the compounds in mustard such as terpenes.21 This is of
specific interest because it shows that the protective properties of mustard go
beyond antibiotic properties and may protect against viruses as well.
Mustard
has also been shown to have antifungal properties. Mustard essential oil was
able to inhibit or delay the growth of several types of fungi and prevent
further growth even if mustard essential oil was in contact with the fungi
through vapors.22 Furthermore, mustard was found to recognize the
structural differences of microbes and targeted sphingolipids, specific regulators
of pathogenicity unique to fungal pathogens.23
Consumer Considerations
Mustard
as a food generally is considered safe. There are no known nutrient-drug
interactions with mustard, although high levels of vitamin K in the leaves
could interact with certain blood-thinning medications such as warfarin due to
vitamin K’s blood-coagulating properties. The vitamin K content could also be a
concern to individuals with existing untreated thyroid issues or an iodine
deficiency. Due to the high oxalate content of the leaves, those with a history
of oxalate-containing kidney stones may wish to limit their intake of mustard
leaves.24
Mustard
essential oil can be highly irritable to the skin and mucous membranes. It is
not recommended to use mustard oil either internally or externally. However,
mustard oil must be specifically extracted and these side effects are not a
concern when consuming the condiment, seeds, or leaves.25 While there
is little concern about adulteration of culinary mustard, there is a history of
adulterating mustard seed oil with argemone (Argemone mexicana, Papaveraceae) oil. In 1998, 2,300 people were
affected and 41 people died from adulterated mustard oil in India, resulting in
a complete ban of mustard seed oil.26 The ban was subsequently
lifted after the adulteration was discovered and corrected. However, mustard seed
oil for edible consumption is not recognized as safe in the United States,
Canada, and European Union due to its high erucic acid content.27
Nutrient Profile28
Macronutrient Profile: (Per 1 cup [approx.
56 grams] chopped mustard greens, raw)
15 calories
1.6 g
protein
2.6 g
carbohydrate
0.2 g
fat
Secondary Metabolites: (Per 1 cup [approx.
56 grams] chopped mustard greens, raw)
Excellent source of:
Vitamin
K: 144.2 mcg (180.3% DV)
Vitamin
C: 39.2 mg (65.3% DV)
Vitamin
A: 1,693 IU (33.9% DV)
Very good source of:
Manganese:
0.3 mg (15% DV)
Good source of:
Dietary
Fiber: 1.8 g (7.2% DV)
Calcium:
64 mg (6.4% DV)
Potassium:
215 mg (6.1% DV)
Vitamin
E: 1.13 mg (5.6% DV)
Iron:
0.92 mg (5.1% DV)
Also provides:
Vitamin
B6: 0.1 mg (5% DV)
Magnesium:
18 mg (4.5% DV)
Riboflavin:
0.06 mg (3.5% DV)
Thiamin:
0.05 mg (3.3% DV)
Phosphorus:
32 mg (3.2% DV)
Niacin:
0.45 mg (2.3% DV)
Folate:
7 mcg (1.8% DV)
DV =
Daily Value as established by the US Food and Drug Administration, based on a
2,000-calorie diet.
Recipe: Saag Paneer
Adapted from Anita Jaisinghani29
Ingredients:
- 1/4
cup ghee or neutral vegetable oil, divided
- 1
medium yellow onion, chopped
- Salt
and pepper to taste
- 3
garlic cloves, minced
- 2
serrano chilies, stems and seeds removed, minced
- 2-inch
piece of ginger, peeled and minced/grated
- 1
pound of mustard greens, stems removed and leaves chopped
- 1
pound baby spinach leaves
- 2
teaspoons garam masala spice blend
- 3/4
cup heavy cream or plain, unsweetened yogurt
- 1
pound paneer or halloumi cheese, diced into 1-inch pieces
Directions:
- In a
large saucepan, heat 3 tablespoons of the ghee or oil. Add the onion and season
with salt and pepper. Cook over moderately low heat, stirring occasionally,
until soft and golden brown, about 20 minutes.
- Add
the garlic, chilies, and ginger. Cook over moderate heat, stirring
occasionally, until softened, about 5 minutes. Stir in the garam masala and
cook until fragrant.
- In
batches, add the mustard greens and spinach, letting each batch wilt before
adding more. Season with salt and pepper.
- In a
food processor, pulse half of the greens with half of the heavy cream or yogurt
until finely chopped. Return to the saucepan and repeat with the remaining
greens and cream/yogurt. Alternatively, use an immersion blender to process the
greens and dairy in the saucepan. Keep the saag warm over very low heat,
stirring occasionally.
- In a medium nonstick skillet, heat 1/2 tablespoon
of the ghee or oil over moderate heat. Add half of the paneer and cook, turning
once, until golden brown, about 5 minutes. Transfer to a paper towel-lined
plate to drain. Repeat with the remaining ghee and paneer.
- Fold the paneer into the saag and cook over
low heat until warmed through, 2 to 3 minutes. Season with salt and pepper.
Serve with steamed basmati rice.
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