Overview
Buckwheat
(Fagopyrum esculentum and F. tataricum) belongs to the
Polygonaceae, or knotweed, family, a plant family with 40 known genera and approximately
1,200 species, which includes other edible plants such as common sorrel (Rumex acetosa) and rhubarb (Rheum rhabarbarum).1,2 Plants in this family have polygonum, or “many knees,” referring to
the swollen nodes of the leaf stems.1
Commercially,
buckwheat is grown for its fruits, leaves, and flowers that are obtained from either
Fagopyrum esculentum, often referred
to as common or sweet buckwheat, or F.
tataricum, known as Tartary or bitter buckwheat.2-6 Both species
are annual herbaceous plants that grow erect from a single hollow stem, which
is succulent and smooth except at its characteristic swollen nodes.4
The plant grows rapidly to an average height of 1-3 feet and has soft,
heart-shaped leaves and clustered groups of five small white to dark pink
petal-like sepals.4,7 Its small dry fruits, botanically known as
achenes, are grey to black and have a distinct triangular shape, a hard shell,
and a starchy endosperm inside.7 These achenes are known
commercially as “groats.”
Despite
its common name, buckwheat does not belong to the cereal grain family (Poaceae)
but is considered a pseudocereal due to its similarities to wheat (Triticum aestivum, Poaceae) in terms of chemical
characteristics and dietary uses.3 However, buckwheat does not
contain gluten. The name buckwheat comes from the Dutch boekweit (boeke: “beech”
and weite: “wheat”), which describes
the resemblance of buckwheat seeds to beech (Fagus spp., Fagaceae)
nuts as well as the wheat-like nature of buckwheat flour.7,8
Phytochemicals and Constituents
Buckwheat groats and flour are considered important nutritional foods because
of their high levels of protein, polyphenols, and minerals.5 Starch
is the major nutritional component of buckwheat seed. The groats are high in B vitamins,
including thiamin (B1), riboflavin (B2), and pyridoxine (B6), and they provide
an array of minerals such as potassium, calcium, magnesium, zinc, copper,
manganese, and selenium.3 In fact, buckwheat is considered a very
good source of dietary magnesium, which is required for healthy nerves and
muscles, and contains considerably more calcium than most cereal grains.8,9
Buckwheat’s fatty acid profile and total dietary fiber content is also considered
superior to cereal grains.3 However, the high fiber content (17.8%) of
buckwheat impedes the digestibility of its proteins.4
The protein
content in buckwheat groats is well-balanced and extremely high compared to true
cereal grains, and it has a biological value above 90%.3,6 (Biological
value is a measure of how much protein is absorbed and integrated into the human
body.) Buckwheat contains all nine essential amino acids and is particularly
high in lysine, an amino acid found in limited quantities in cereal grains.3,4,8
Buckwheat also contains high amounts of arginine, tryptophan, and
thiamine-binding proteins (TBPs), which act to stabilize and enhance the
biological activity of thiamine.3 Foods that contain TBPs can be used
to prevent dietary thiamine deficiencies.2,3 Despite the high
protein content of buckwheat groats, the presence of trypsin inhibitors, fiber,
and tannins lowers enzymatic availability, which can impede digestion and
absorption of protein.3
The
high antioxidant capacity and flavonoid content of buckwheat groats qualify
buckwheat and buckwheat-enriched products as functional foods.3 Buckwheat
groats are rich in antioxidant compounds, including glutathione, and have a
very high polyphenol content, including catechins and flavonoids (e.g., rutin
and quercetin).2,3 Rutin and quercetin are biosynthesized by plants
in order to protect themselves from UV radiation, diseases, and predators.10
Buckwheat
is among a few other field-grown crops that contain rutin, which is considered
to be an important component of a heart-healthy diet.3,4 The leaves
of buckwheat contain the highest amount of rutin in the plant.10 Tartary
buckwheat contains more rutin than common buckwheat.2 Rutin has
significant antioxidant and anti-inflammatory effects, and may also have antidiabetic
and anti-hypertensive effects.2-4 Consuming 100 g (3.5 oz) of
buckwheat flour or grains delivers roughly 10% of the daily therapeutic dose of
rutin, which is considered to be between 180 and 350 mg.5
Buckwheat’s rutin levels decrease when exposed to heat; however, quercetin
levels remain stable when heated. Although heat-treatment results in lower
rutin levels in buckwheat breads and noodles, they are still considered
nutrient-dense compared to raw flour.5
Historical and Commercial Uses
Buckwheat, grown mainly for its groats, has been cultivated in China for at least
1,000 years.4,5 Buckwheat initially spread to Asia, reaching Japan 3,000
years ago from northern China via the Korean Peninsula.4 Buckwheat
cultivation then spread to the Middle East and subsequently to Europe and
Russia during the Middle Ages.7 From Europe, buckwheat arrived in
North America in the 1600s, and early immigrants cultivated buckwheat on
cleared lands to smother weeds and build soil.4,8 Today, Russia and
China are the biggest producers of buckwheat globally.2,6
In traditional
Chinese medicine (TCM), the leaf of the Tartary buckwheat is used to treat
choking, ulcers, and hypertension, and to cleanse wounds. The flavonoid-rich
leaves are also considered a nutritious food used to improve vision and
hearing.4 Buckwheat is considered blood-building and detoxifying as
it neutralizes acidic metabolic waste, and it is a staple of macrobiotic diets.9
In Nepal, Tartary buckwheat leaves are consumed to alleviate stomach
disorders.4
Buckwheat
groats are prepared raw or roasted, whole or powdered.11 To process
buckwheat, the hulls enclosing the seeds are removed, and the seeds are
typically roasted.3,11 Raw, hulled buckwheat seeds have a subtle
flavor, while roasted, hulled buckwheat has an earthy, nutty flavor.8,11
Roasted, cooked groats have the consistency of porridge and are the basis of kasha, a traditional Russian dish cooked
and served much like rice.7,11 In medieval Russia, the word kasha meant “meal” or “feast,” which
referred to the belief that no meal was complete without buckwheat.9
Buckwheat
flour is made from unroasted groats and typically includes a mixture of both
hulled and unhulled buckwheat seeds. Depending on the amount hulled and
unhulled seeds, buckwheat flour is graded light, medium, or dark.9
Unhulled buckwheat seed flour is the darkest in color and most nutritious,
while flour made from hulled ground groats is the lightest in color and
contains fewer nutrients.8,9 Buckwheat
flour is used by a variety of diverse cultures, alone or as an ingredient in pancakes,
French crepes, Southeast Asian unleavened breads (chapattis) and fried snacks (pakora),
as well as Japanese soba noodles.4,7 To prevent rancidity, buckwheat
seeds are stored with hulls and de-hulled shortly before use.4
A
balanced amino acid profile can be achieved by mixing buckwheat with cereal
grains, which are typically low in lysine.4 In Europe, buckwheat
bread is gaining popularity as a nutrient-dense, antioxidant rich, gluten-free
alternative to common cereal grains.5 Food science studies indicate
that making wheat bread with 15% buckwheat flour functionally enhances its
nutrient content and natural antioxidant capacity without compromising texture
or flavor.3 In Europe and North America, buckwheat flour is
typically blended with wheat flour to prepare pancakes, biscuits, noodles, and
cereals.3
Aromatic
buckwheat flowers provide both pollen and nectar for honeybees.3,8,11
Because honey production comes late in the season when other nectar sources are
scarce, buckwheat is an important warm-weather, late-season crop for honeybees.4,11
Buckwheat honey has dark color, a distinct spiced flavor, and confirmed health
benefits (see “Buckwheat Honey” section below).3
Modern Research
A Gluten-free
‘Grain’
Unlike wheat, barley (Hordeum vulgare,
Poaceae), and rye (Secale cereale,
Poaceae), buckwheat grains lack α-gliadin and are low in prolamins (seed
storage proteins that act as food antigens).3 These factors make buckwheat
a healthy alternative for individuals with Celiac disease or non-Celiac gluten
sensitivity (NCGS). Celiac disease is an autoimmune disease with both genetic
and environmental components.3 Chronic intestinal inflammation can
lead to malabsorption of several important nutrients, including iron and folate,
which can lead to anemia and other ill effects.3 Strict adherence to
a gluten-free diet is crucial to effectively treating Celiac disease and other
gluten-sensitive individuals.3
A
randomized, crossover trial with two intervention phases was conducted on 19 patients
with NCGS over a period of 12 weeks.12 Participants either consumed
a diet that consisted of buckwheat products or maintained their normal
gluten-free diet without buckwheat supplementation. During the intervention period,
those consuming buckwheat products experienced not only a significant reduction
in the severity of abdominal pain and bloating, but also a significant increase
in blood levels of magnesium and a reduction in pro-inflammatory cytokines.12
Type
2 Diabetes
Dietary approaches are highly recommended for managing chronic diseases like
type 2 diabetes mellitus (T2DM) and its associated cardiovascular, renal, and
ocular complications.13 In many places where buckwheat is
cultivated, it is traditionally used as both a food and a medicine. For
example, in Taiwan and China, Tartary buckwheat is consumed daily to treat
T2DM.5 Regular consumption of buckwheat products is strongly
correlated with lower incidence of hyperglycemia and improved glucose
tolerance.6 Buckwheat contains D-chiro-inositol (DCI), which is a
primary mediator of insulin metabolism and has the ability to enhance glucose
utilization and decrease blood pressure, plasma triglycerides, and glucose
concentrations.6
Replacing
or partially substituting buckwheat flour for white rice or wheat flour is a
practical approach to disease management for patients with T2DM and those with
a high risk of developing T2DM.13 Among all of the grains, buckwheat
has the longest gastrointestinal transit time, which is associated with
stabilized blood sugar levels and feelings of satiety.9 In a four-week
clinical trial, 165 participants with T2DM who consumed Tartary buckwheat (>
110 g/d) experienced a 2.85% reduction in insulin, a 6.3% reduction in total
cholesterol levels, and a 7.0% decrease in low-density lipoprotein (LDL) levels
compared with the control group.13 Additionally, those who consumed
buckwheat as part of their staple diet had a 15% increase in daily protein
intake and a 25% increase in daily dietary fiber intake compared to baseline.13
A small clinical study of analyzed the effects on glucose and insulin on 10
healthy volunteers who consumed a single dose of boiled buckwheat groats, bread
enriched with 50% buckwheat flour, or white wheat bread on separate days. Data
showed that postprandial blood glucose and insulin production were lower when the
subjects consumed buckwheat, especially buckwheat groats, than when the
subjects consumed white wheat bread.2
Cardiovascular
Health
The bioflavanoids in green buckwheat tea may play a role in improving
circulatory health.9,10 Rutin, for example, has been shown to
increase the elasticity of blood vessels and arteries, enhance peripheral
circulation, lower the risk of atherosclerosis and hypertension, and reduce
capillary fragility.2-4,10 Two other compounds in buckwheat —
γ-aminobutyric acid (GABA) and 2”-hydroxynicotianamine (H2N) — have been shown
to possess blood pressure-reducing activity in vitro and in animals, possibly
by inhibiting the action of angiotensin converting enzyme (ACE)-inhibitors.2,6
The
use of buckwheat leaf and flower tea was investigated for its effects on leg
adema in a randomized, double-blind, placebo-controlled trial of 67 patients
with chronic venous insufficiency. Individuals who consumed buckwheat tea reported
significant improvements in edema symptoms and less discomfort.5 Other
studies have reported a rise in serum quercetin levels after consuming
buckwheat tea, which may contributing to its potential anti-inflammatory and
antioxidant effects.10
Buckwheat
has also been studied for its ability to reduce unhealthy cholesterol levels
including LDL and very low density lipoproteins.6 Buckwheat’s high
fiber content helps lower cholesterol by increasing fecal excretion of sterols
and decreasing absorption of dietary cholesterol.6,13 In a 2011
randomized, double-blind, placebo-controlled crossover study, 62 healthy
volunteers were divided into two groups that consumed four cookies daily for
four weeks. The active group received cookies enriched with buckwheat flour,
and the control group were given cookies contained no buckwheat flour. After
two weeks, the groups switched cookie types.2 The participants in
the active group experienced significant decreases in levels of total
cholesterol and myeloperoxidase (MPO), an enzyme that contributes to oxidative
stress and inflammation.2
Oral
Health
In many traditional cultures, the seeds, roots, and bark of polyphenol-rich
herbs are powdered and used as natural antibacterial and anti-inflammatory
toothpowders to maintain oral hygiene and gum health. A clinical study reported
a 62% improvement in periodontitis and bleeding gums in patients who brushed
their teeth twice daily with Tartary buckwheat flour toothpowders.4 The
improvements in gum tissue integrity were attributed to buckwheat’s vitamin and
mineral contents, as well as the protective anti-inflammatory effects of rutin
and quercetin.4
Buckwheat
Honey
Buckwheat honey provides antioxidant and antibacterial protection similar to
New Zealand’s Manuka honey and has been studied for its powerful internal and
external healing properties.14 Despite its own therapeutic benefits,
buckwheat honey is not widely consumed due to its dark amber color and its
strongly spiced odor and malty flavor.14 The flavor, composition,
and biological activities of honey vary upon type of botanical forage and
geographical location. Research indicates that dark-colored honey contains
higher levels of phenolic compounds and has, therefore, a more potent
antibacterial and antioxidant capacity.14 Higher mineral content in
honey is also associated with a darker color and stronger flavor. Buckwheat
honey has a higher protein content than most honeys and delivers more iron,
calcium, magnesium, manganese, and zinc.14
A
2007 clinical study of 105 children with acute nocturnal cough due to upper
respiratory illness were randomly assigned to one of three groups: an active group
given a single nocturnal dose of buckwheat honey, an active control group given
single nocturnal dose of artificial honey-flavored dextromethorphan (an
over-the-counter antitussive), or the control group which received no
treatment.15 Results indicated that the group treated with buckwheat
honey had significantly greater symptom relief (reduced cough severity, and
frequency while improving child’s sleep quality) than participants in the other
two groups.15
In
vitro, both Manuka and buckwheat honey have been shown to inhibit Staphylococcus aureus, a bacteria that
causes a wide range of common skin infections and life-threatening illnesses
such as pneumonia and sepsis.14 Studies by Zhou et al. have demonstrated
buckwheat honey’s ability to prevent hydroxyl radical-induced DNA damage
through its inherent antioxidant components.2
Consumer Considerations
Buckwheat’s nutritional, dietetic, and therapeutic properties make it an
important global food crop to cultivate especially as access to arable land and
water become more challenging.2 Compared to cereal grains, buckwheat
requires fewer soil nutrients and less water, and has the additional benefits
of naturally suppressing weeds, improving soil health, fostering beneficial
insects, and providing forage for livestock and poultry.2,7,11 Due
to its very high protein content, buckwheat complements cereal grains and helps
provide a more complete protein when combined with typical cereal grains and
flours.8
Consuming
buckwheat or buckwheat-containing foods frequently and in high amounts can
cause IgE antibody-mediated allergic reactions.2 Additionally, it is
important to be aware that buckwheat sprouts, despite their growing popularity,
contain napthodianthrones, more specifically the fagopyrins that can cause
photosensitization or skin irritation after sunlight exposure.5 Buckwheat
sprouts should not be consumed in excess by poultry, livestock, or humans.5
Consumers
should be aware that gluten-free products tend to be deficient in B vitamins,
calcium, iron, zinc, magnesium, and fiber while also containing higher amounts
of added sugar or fat.12 The dietary use of pseudocereals, like
buckwheat, could improve dietary intake of protein, iron, calcium, and fiber.12
Nutrient Profile16
Macronutrient Profile: (Per 100 grams
buckwheat groats)
343
calories 13.3
g protein 71.5
g carbohydrate 3.4 g
fat
Secondary Metabolites: (Per 100 grams
buckwheat groats)
Excellent source of:
Manganese:
1.3 mg (56.5% DV) Magnesium:
231 mg (55% DV) Dietary
Fiber: 10 g (33% DV) Riboflavin:
0.43 mg (33% DV) Niacin:
7.02 mg (43.9% DV) Phosphorus:
347 mg (27.8% DV)
Very good source of:
Vitamin
B6: 0.21 mg (12.4% DV) Iron:
2.2 mg (12.2% DV)
Good source of:
Potassium:
460 mg (9.8% DV) Thiamin:
0.101 mg (8.4% DV) Folate:
30 mcg (7.5% DV)
Also provides:
Calcium:
18 mg (1.4% DV)
DV =
Daily Value as established by the US Food and Drug Administration, based on a
2,000-calorie diet.
Recipe: Kasha
Cereal9
Ingredients:
- 1
cup buckwheat groats
- 4-5
cups boiling water
- 1/2
onion, diced (optional)
- Salt
to taste
Directions:
- Place
all ingredients in a large pot and bring to a boil.
- Cover,
reduce heat to low, and simmer for 30 minutes until soft.
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Photo credit: Buckwheat (Fagopyrum esculentum) All photos ©2018 Steven Foster
References
- Elpel
T. Botany in a Day: The Patterns Method
of Plant Identification. Pony, MT: HOPS Press LLC; 2004.
- Gimenez-Bastida
JA, Zielinski H. Buckwheat as a functional food and its effects on health. J Agr Food Chem. 2015;63:7896-7913.
- Wronkowska
M, Soral-Smietana M, Krupa-Kozak U. Buckwheat, as a food component of a high
nutritional value, used in the prophylaxis of gastrointestinal disease. Eur J Plant Sci Biotech. 2010;4(Special
Issue 1):64-70.
- Campbell
CG. Buckwheat (Fagopyrum esculentum).
International Plant Genetic Resources Institute. 1997. Kade Research Ltd.
Morden, Manitoba, Canada.
- Kreft
M. Buckwheat phenolic metabolites in health and disease. Nutr Res Rev. 2016;29:30-39.
- Zhang
ZL, Zhou ML, Tang Y, et al. Bioactive compounds in functional buckwheat food. Food Res Int. 2012;49:389-395.
- Van
Wyk B. Food Plants of the World: An
Illustrated Guide. Portland, OR: Timber Press; 2006.
- Murray
M, Pizzorno J. The Encyclopedia of Healing
Foods. New York, NY: Atria Books; 2005.
- Pitchford
P. Healing with Whole Foods: Oriental Traditions and Modern Nutrition.
Berkeley, CA: North Atlantic Books; 1993.
- Kreft
I, Fabjan N, Germ M. Rutin in buckwheat – Protection of plants and its
importance for the production of function food. Fagopyrum. 2003;20:7-11.
- Buckwheat.
Encyclopedia Britannica website. Available at: www.britannica.com/plant/buckwheat. Accessed on October
2, 2018.
- Dinu
M, Macchia D, Pagliai G, et al. Symptomatic efficacy of buckwheat products in
Non-Celiac Gluten Sensitivity (NCGS). Asian
Pac J Clin Nutr. 2017;26(4):630-636.
- Qiu
J, Liu Y, Yue T, et al. Dietary Tartary buckwheat intake attenuates insulin
resistance and improves lipid profiles in patients with type 2 diabetes: a
randomized controlled trial. Nutr Res.
2016;36:1392-1401.
- Deng
J, Liu R, Lu Q, et al. Biochemical properties, antibacterial and cellular
antioxidant activities of buckwheat honey in comparison to Manuka honey. Food Chem. 2018;252:243-249.
- Paul
IM. Therapeutic options for acute cough due to upper respiratory infections in
children. Lung. 2012;190:41-44.
- Agricultural
Research Service. National Nutrient Database for Standard Reference Legacy
Release. United States Department of Agriculture website. April 2018. Available
at: https://ndb.nal.usda.gov/ndb/foods/show/20008. Accessed October
5, 2018.
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