Nutritive Value and Inherent Anti-nutritive Factors in Four Indigenous Edible Leafy Vegetables in Human Nutrition in Nigeria: A Review
Eroarome Martin Aregheore
Indigenous edible vegetable leaves such as fluted pumpkin (Telfairia occidentalis Hook f.), bitter leaf (Vernonia amygdalina), sweet potato (Ipomea batatas), cassava (Manihot esculenta Crantz) and Moringa oleifera are inexpensive source of cheap and abundant source of proteins, carbohydrate, minerals, vitamins and fibres to most vulnerable groups. Edible leaves from vegetable plants are rich source of beta-carotene a precursor for vitamin A. They have medicinal properties reservoir for the sick to recuperate in addition to natural source of therapeutic agents. Local vegetables are useful contributors to rural and urban peoples diets in Nigeria but some contain anti-nutritional factors such as cyanogenic glucoside; oxalate; phytate; saponin and tannin to mention but a few that make them unsafe. Traditional processing methods are used to detoxify those with anti-nutrients safe for human nutrition.
Received: November 10, 2011;
Accepted: January 14, 2012;
Published: March 08, 2012
Nigeria has rich genetic resources of cultivated, semi-wild and wild species
of crops being used as traditional vegetables and different types are consumed
by the various ethnic groups for different reasons (Denton
et al., 1983; Mensah et al., 2008).
Edible leaves from vegetable plants are eaten as supporting food or main dishes.
They may be aromatic, bitter or tasteless (Edema, 1987)
but are the cheapest and most accessible source of proteins, vitamins, minerals,
essential amino acids (Okafor, 1983; Fasuyi,
2006; Mensah et al., 2008). Also, possess
certain hormone precursors in addition to energy (Oyenuga
and Fetuga, 1975). Leaf vegetables are highly beneficial for maintenance
of health and prevention of diseases. They contain valuable source of food ingredients
that can be utilized to build up and improve the body successfully (Hanif
et al., 2006). They also maintain alkaline reserve of the body. They
contain high carbohydrate, vitamin and mineral contents.
There are different types of vegetables and each group contributes in its own
way to the diet (Robinson, 1990). Local vegetables are
useful contributors to rural and urban peoples diets in Nigeria (Barminas
et al., 1998). They play prominent roles in the traditional-food
culture and various ethnic groups consume a variety of different indigenous
types of vegetables for different reasons, some have medicinal properties reserved
for the sick and recuperation (Mensah et al., 2008)
and others natural source of therapeutic agents (Roberts and
Tyler, 1999). Non-starchy vegetables are rich sources of dietary fibre used
in treatment of obesity, diabetes, cancer and gastrointestinal disorders (Iniaghe
et al., 2009). In most local Nigerian diets, approximately half
of the leafy vegetables consumed are from indigenous sources constituting significant
micronutrient sources especially in times of drought and famine (Lockett
et al., 2000; Grivetti and Ogle, 2000). Leafy
vegetables alleviate the problems of micronutrient malnutrition dominant in
tropical Africa (Ejoh et al., 2005). Adding a
small amount of vegetable in ones food intake can prevent a disease like
river blindness from occurring. Mensah (59) posited that the use of green leafy
vegetables for the preparation of soups cuts across different cultures within
Nigeria and other parts of West Africa with similar cultural and socioeconomic
Green leafy vegetable are cheap and abundant source of proteins. They can synthesize
amino acids from a wide range of available primary materials such as water,
carbon dioxide and atmospheric nitrogen as in legumes (Lewis
and Fenwick, 1987; Aletor and Adeogun, 1995; Ladeji
et al., 1995; Fasuyi, 2006; Babu,
2000; Ajibade et al., 2006; Aregheore,
2007, 2002; Oduro et al.,
2008). They offer the most efficient and cheapest source of minerals, fibres
and vitamins to most vulnerable groups (Ejoh et al.,
2003); also, lower nutritional deficiency of people in poor countries where
millions still suffer from nutrient insufficiency despite the availability of
leafy vegetables (Ejoh et al., 2005). There are
over 40 indigenous leafy vegetables eaten in Nigeria and the southwest alone
accounted for 24 of them (Adebooye et al., 2003).
Several other species have been listed in Nigeria (Okafor,
1983). For example, Mensah et al. (2008)
identified 29 different green leafy vegetables in Edo State, Nigeria. Indigenous
leaf vegetables are valuable sources of food, income and traditional medicine
in Nigeria (Okafor, 1979; Awoyinka
et al., 1995; Schippers, 2000; Mensah
et al., 2008; Adebooye et al., 2003).
This report is a review of four indigenous edible vegetable leaves; fluted pumpkin (Telfairia occidentalis Hook f); bitter leaf (Vernonia amygdalina); sweet potato (Ipomea batatas); cassava (Manihot esculenta Crantz) and Moringa oleifera in the nutrition of humans in Nigeria Although, Telfaria (fluted pumpkin) is comparatively expensive, it is ranked high by consumers because of its good taste. Although, some contain anti-nutritional factors such as cyanogenic glucoside; oxalate; phytate; saponinand tannin to mention but a few, they still play significant roles and have distinct advantages in the nourishment of humans. This report is a review on the nutritional importance of leafy vegetables in the diets of ethnic groups in Nigeria despite the presence of some fundamental anti-nutritive factors.
Fluted pumpkin (Telfairia occidentalis Hook f.): Fluted pumpkin
(Talfairia occidentialis Hoof) belongs to the family Cucurbitaceae (Aregheore,
2007). It is a valuable commercial crop grown across the low-land humid
tropics of West Africa. The leading producers of fluted pumpkin in West Africa
are Nigeria, Ghana and Sierra Leone (Nkang et al.,
2003; Aregheore, 2007). However, there is no identifiable
information on varieties of the crop (Ajibade et al.,
2006; FAO, 1992). It is a tropical vine grown primarily
for the leaves and edible seed as an important component of food of many people
in West Africa (Longe et al., 1983; Fagbemi
et al., 2005). Young shoots and leaves are the main parts used in
soup. The common names of the plant in Nigeria include fluted gourd, fluted
pumpkin, iroko and ugu.
The plant is dioecious, perennial, drought tolerant and usually grows trellised. It needs a well drained soil, some water and sunlight. The vines will climb to 1.5 m. Flowers are white and dark purple. Sex of fluted pumpkin is difficult to identify until about 4 months after planting when it produces flowers, a major obstacle to its production. Housewives prefer the female leaves leading to higher demand. The young shoots and leaves of the female plant form main ingredients in edikang ikong, a soup favoured by people in Cross River and Akwa Ibong states, Nigeria.
In Southern Nigeria, ugu is the common name for the green leaves
of fluted pumpkins. The leaves have a sweet taste. Fluted pumpkins leaves rich
source of protein, oil, vitamins and minerals enhances, nourish, protect and
heal the body. The leaves are low in crude fibre but, rich source of folic acid,
calcium, zinc, potassium, cobalt, copper, iron, vitamins A, C and K also, have
medicinal value (Ladeji et al., 1995; Ajibade
et al., 2006).
Relative to most vegetables, its protein content is top (Ladeji
et al., 1995; Ajibade et al., 2006;
Aregheore, 2007). Leaves of fluted pumpkin are cheap nitrogen
and mineral source (Aregheore, 2007). Ladeji
et al. (1995) reported that the leaves contain (g 100-1
g, DM) 30.5 crude protein; 3.0 fat; 8.3 crude fibre and 8.4 total ash. Ajibade
et al. (2006) reported that the leaves contain (g kg-1
DM) 35.1 crude protein, 9.6 fat; 12.7 crude fibre. Nutritionally, leaves of
Telfairia occidentalis are rich in minerals antioxidants, vitamins (such
as thiamine, riboflavin, nicotinamide and ascorbic acid (Kayode
and Kayode, 2011). The leaf has potassium, calcium, magnesium and iron contents
of ash of 594, 144, 100 and 12.0 mg 100-1 g DM, respectively. Young
leaves also possess a high level of magnesium (8.69 mg 100-1) and
iron (3.60 mg 100-1 g) (Akwaowo et al.,
2000) and due to its richness in iron the leaves can prevent and eliminate
anaemia (Ajibade et al., 2006). The leaves have
an excellent proportion of essential amino acids to total nitrogen but methionine
is the limiting amino acid with a chemical score of 16. Badifu
et al. (1995) reported Beta-carotene content of 98.9 mg 100-1
g, for fresh leaves but on blanching the value was reduced to 86.3 for steam
blanches and 83.8 for water blanch. This demonstrated that processing has effects
on the nutritive value of leaves of fluted pumpkin. Consumption of the leaves
assist to combat certain diseases due to the presence of antioxidant and antimicrobial
properties, its minerals (especially Iron), vitamins (especially vitamin A and
C) and high protein contents (Kayode and Kayode, 2011).
Inherent anti-nutritional factors and detoxification: The leaves contain
a considerable amount of anti-nutritive factors like high level of tannic acid
and saponin. Akwaowo et al. (2000) reported that
the young leaves often preferred for human consumption, contain high cyanide
(60.1 mg 100-1 g DM) and tannin content (40.6 mg 100-1
g DM) than older ones. (Hill, 1987) reported a cyanide
content of 59.80 mg 100-1 g for Telferia occidentalis (fluted
pumpkin). Oxalate content (10.0 mg 100-1 g DM) and phytate content
(48.8 mg 100-1 g DM) are higher in the older leaves than in the younger
ones. However, the amount of phytic acid and oxalate are within the normal range
in human nutrition (Ladeji et al., 1995). Amongst
others, it contains diethylamine, dimethylamine, morpholine and ethylaniline
with its secondary amine content of between 0.80-0.91 μg N kg-1
(Uhegbu, 1997). While some of the anti-nutrients in
the leaves are above safety limits in human consumption, most are not harmful
but rather have some health benefits to its consumers (Ladeji
et al., 1995; Ajibade et al., 2006).
However, the young leaves should be properly cooked in order to remove any inherent
anti-nutrient effects before consumption.
Bitter leaf (Vernonia amygdalina): Bitter leaf (Vernonia amygdalina)
is a green shrub with petiole leaf of about 6 mm diameter. The leaf has a characteristic
odour and bitter taste. Vernonia amygdalina grows under a range of ecological
zones in Africa being drought tolerant and produces large fodder biomass for
both human and animal nutrition (Bonsi et al., 1995;
Aregheore, 1998; Daodu and Babayemi,
2009). Vernonia amygdalina plant commonly found around homes in Southern
Nigeria as a green vegetable or spice especially in the popular bitter-leaf
soup (Igile et al., 1995) also widely used
for both therapeutic and nutritional purposes.
Vernonia amygdalina used as a fence post and pot-herb in the home and
villages is one of the most widely consumed leafy vegetables in most countries
in West and Central African being an excellent source of vitamin C and total
carotenoid (Ejoh et al., 2005). Ejoh
et al. (2005) reported a vitamin C value and total carotenoid level
of 197.5 and 30.0 mg 100-1 g, respectively for bitter leaf. Besides
it use as an indigenous vegetable in human nutrition, the plant has also acquired
significant relevance in human medicine having been proven to possess potent
antimalarial and anti-helmintic properties as well as anti-tumorigenic properties
(Izevbigie, 2003) laxative and fertility inducers in
infertile women (Igile et al., 1995). Its therapeutic
constituent (quinine) cures malaria cleans the liver and lymphatic system and
lungs for smokers. It could also be given to patients suffering from hyperglycemia
(excessive sugar) as in diabetes mellitus and diabetes insipidus (Akah
and Okafor, 1992; Nwachukwu et al., 2010).
Furthermore, the leaves used as local medicine against leech that transmits
bilharziose. The leaves used as vegetable stimulate the digestive system, as
well as reduce fever. The tops of the shrub have some trado-medicinal value,
also used instead of hops to make beer in Nigeria.
The broad macerated green leaves used as vegetables and condiments especially
in cooking soup. Arhoghro et al. (2009) posit
that the water extract serves as tonic for the prevention of certain illnesses.
In addition, the aqueous leaf extract exhibited hepatoprotective activity due
to its antioxidant property attributable to its flavonoid content, as a result
of the sesquiterpene lactone present in the leaves (Babalola
et al., 2001; Arhoghro et al., 2009).
The broad greenish leaves contain natural quinine with a bitter taste due to
anti-nutritional factors such as alkaloids, saponins, tannin and glycoside also
sesquiterpene lactone and flavonoids (Akah and Okafor, 1992).
Ohigashi et al. (1991) and Jisaka
et al. (1992) reported the isolation of extremely bitter steroid
glycoside and Vernonioside A from the leaves of V. amygdalina. Washing
of the young leaves often preferred for human consumption get rid of the bitter
Inherent anti-nutritional factors and detoxification: The young leaves
have higher cyanide (60.1 mg 100-1 g DM) and tannin content (40.6
mg 100-1 g DM) than older ones. Hill (1987)
reported a cyanide content of 95.50 mg 100-1 g for Vernonia amygdalina
(bitter leaf), Oxalate content (10.0 mg 100-1 g DM) and phytate content
(48.8 mg 100-1 g DM) were higher in the older leaves than the younger
ones. Okoli et al. (2003) reported 0.38% tannin;
21.10 mg g-1 Phytin and HCN content of 6.40 mg g-1 for
bitter leaf. Vernonia amygdalina amongst other foodstuffs contains diethylamine,
dimethylamine, morpholine and ethylaniline and its secondary amine content ranged
between 0.80-0.91 μg N kg-1 (Uhegbu, 1997).
Bitter leaf also contains saponins, sesquiterpene lactone, steroid glycosides,
alkaloids, tannins and flavonoids (Akah and Okafor, 1992).
Some of the anti-nutrients in the leaves are above safety limits for human consumption;
therefore, young leaves should be properly cooked in order to remove anti-nutrient
effects before consumption. The local processing method of squeeze-washing raw
or boiling helps to remove the bitter taste and foam. Washed bitter leaf can
be preserved by freezing or drying, however, processing results in loss of some
nutrients and anti nutritional factors (Ejoh et al.,
2003; Bender, 1966).
Sweet potato (Ipomea batatas):
The leaves have a CP content of 25.6
to 32.4% DM (Woolfe, 1992
; Ishida et
; Oduro et al., 2008
). The leaves
in particular contain a large amount of protein with a high amino acid
The leaves of the sweet potato are highly digestible, fairly rich in protein,
a dietary source of vitamins, minerals, antioxidants, dietary fiber and essential
s and free from toxins. In comparison with other vegetables, minerals
and vitamins such as A, B2, C and E are high in sweet potato leaves (An,
). The leaves also an excellent source of beta-carotene, thiamine (vitamin
B1), folic acid and ascorbic acid
(Villareal et al.,
; Woolfe, 1992
, CIP, 2004
The young leaves serve as a nutritious vegetable source for man, contain several
nutrients such as appreciable amounts of zinc, potassium, sodium, manganese, calcium,
magnesium, iron, vitamin C
and fiber (Antia et al.,
). However, as vegetable it is considered a poor mans vegetable
being traditionally, used as feeds for domestic animals (Oyenuga,
). Antia et al. (2006)
posited that sweet
potato leaves contain high concentrations of magnesium (340 mg 100-1
g) and phosphorus (37.28 mg 100-1
g), with levels for calcium, iron,
sodium, potassium and manganese at 28.44, 16.00, 4.23, 4.05 and 4.65 mg 100-1
g, respectively. However, the leaves contain remarkably little of zinc (0 .08
g) while copper is totally absent (0.00 mg 100-1
g). The Efik-Ibibio people of South-Eastern Nigeria use sweet potato leaves as
vegetable in cocoyam porridges (Eka and Edijala, 1972
The high concentration of anthocyanin and beta-carotene combined with the high
stability of color extract make sweet potato leaves healthier alternative to
synthetic coloring agents in the food chain systems (Bovell-Benjamin,
2007). Ipomoea batatas leaves are excellent source of anti-oxidative
polyphenolics compared to other commercial vegetables (Islam
et al., 2002). Polyphenols have many physiological functions such
as cancer-fighting properties (Ishiguro et al., 2004).
Since the leaves contain a significant amount of nutrients; they contribute
to health requirements (Antia et al., 2006). The
low levels of anti-nutrients except for oxalate can be reduced by cooking the
Bioactive compounds contained in sweet potato leaves contribute to health promotion
and chronic disease prevention. Increased consumption of this vegetable is advocated
because it reduces the prevalence of chronic diseases of public health concern.
The consumption of sweet potato leaves warrants further and more extensive research
study (Johnson and Pace, 2010).
Inherent anti-nutritional factors and detoxification: Tannins inhibit
the bioavailability of protein and minerals however, sweet potato leaves have
little tannins (0.21 mg 100-1 g), cyanide (30.24 mg 100-1
g) and phytic acid (1.44 mg 100-1 g) (Antia et
al., 2006). The leaves have unusually high value of oxalate (308 mg
100-1 g) that may constitute potent human poisons (Akwaowo
et al., 2000). Proper cooking before consumption significantly reduces
the total oxalate content of the leaves (Akwaowo et al.,
2000). Besides the high level of oxalate, the leaves contain a sufficient
amount of nutrients, vitamins and mineral elements. The leaves in the human
diet increase the daily allowance of the aforementioned nutrients needed by
Cassava (Manihot esculenta Crantz): Leaves of cassava are a significant
source of potential alternative protein resource for both humans and animals
(Fasuyi, 2005). Cassava leaves, depending on the varieties
are rich in protein (14-40 or 20-35% DM), minerals, Vitamin B1, B2, C and carotenes
(Eggum, 1970; Adewusi and Bradbury,
1993). The high-protein content and nutritive value of cassava leaves alleviate
nutritional deficiency in poor countries (Brown and Kane,
1994; Aletor and Adeogun, 1995). Apart from lower
methionine, lysine and perhaps isoleucine content, the amino acid profile of
cassava leaf protein compares favourably with those of milk, cheese, soyabean,
fish and egg. The leaves contained a high level of crude protein (29.3-32.4%
dry weight) compared to a conventional vegetable (Awoyinka
et al., 1995). The leaves have ash content of 4.6% and remarkably
high dietary fibre that ranges between 26.9-39% dry weights. However, young
leaves are low in crude fibre and relatively high in calcium and phosphorus
(FAO, 1990). Pregnant women in some African countries
such as Sierra Leone and Liberia consume cassava leaves to increase breast milk
production and control of stomach worms. Cassava leaves contain high profile
of most mineral particularly calcium and trace minerals. The leaves are high
in phosphorus, magnesium, manganese and adequate source of calcium; however,
potassium and sodium are low. With leaf maturity the value for Potassium (P),
Magnesium (Mg), Phosphorus (P), Zinc (Zn) and Manganese (Mn) decreases while
Ca, Na and Fe increases (Ravindran and Ravindran, 1988).
Cassava leaves are accepted as vegetable in Nigeria, Sierra Leone and Zaire
where its use in combination with nontoxic indigenous vegetables in yam porridge
still remain dominant (UNV, 1980). In the cassava region
of Africa that ranges from Senegal to Mozambique, humans use cassava leaves
as vegetable in nutrition. Bokanga (1994) reported that,
in much of East Africa, Central Africa and some countries in West Africa such
as Sierra Leone and Liberia, cassava leaves constitute a significant component
of the diet as a source of dietary protein, minerals and vitamins. In Indonesia,
for example, young cassava leaves compared to other vegetables, are a popular
vegetable due to their high content of protein, minerals and vitamins (Wargiono
et al., 2002). Malnutrition, such as anaemia, vitamin A and protein
deficiencies in millions of people in tropics and sub-tropics can be reduced
by introducing young cassava leaves as a vegetable in human diets (Hidajat
and Wargiono, 2002). The use of cassava leaves as a human-food stand on
value as a source of protein and vitamins for supplementing mostly starchy diets.
The high-protein content and nutritive value cassava leaves (Aletor
and Adeogun, 1995) may contribute to alleviate nutritional deficiency in
poor countries (Brown and Kane, 1994; Hidajat
and Wargiono, 2002) also fight against micronutrients undernourishment due
to the high vitamins and minerals in the leaves. The major drawback to the widespread
use of cassava leaves as food is cyanogenic glucosides scare that may be 6 times
higher than the root (Yeoh and Chaw, 1976). This may
limit the nutritional value of cassava leaves but if sweet cassava cultivars
with low HCN content and high protein in leaves are consumed it could offer
a valuable protein and other nutrients (Nassar and Marques,
2006) in the nutrition of humans in Nigeria other poor countries.
Inherent anti-nutritional factors and detoxification: Variation in the
chemical composition and inherent anti-nutritional substances, in different
cultivars, may restrict usage. Principal problems that could undermine its potential
include high fibre content and anti-nutrients typified by cyanide, tannin and
phytin. Cassava leaves have cyanide content of 52.9 mg HCN 100 g-1,
high tannin and phytin levels of 9.7 g 100-1 DM and 192.0 mg 100-1
gm, respectively (Fasuyi, 2005). Independent of cultivar
and age of the plant, saponin levels ranged from 1.74 to 4.73 g 100 g-1
DM. The level of tannin and phytin retention remained high (>41%) demonstrating
that residual tannin and perhaps, to a lesser extent, phytin could pose greater
problem in processed cassava leaves based diets (Mkpong
et al., 1990). Phytin chelate with certain mineral elements, such
as Ca, Mg, Fe and Zn which render them metabolically unavailable (Fasuyi,
2005). Tannins binds with dietary proteins and digestive enzymes to
form complexes (Makkar, 1991, 1993)
not easily digestible by humans.
Toxicity problems that affect nutritive value of cassava leaves can be reduced
by traditional preparation methods such as drying, pounding and long periods
of boiling (Lancaster and Brooks, 1983; Lewis
and Fenwick, 1987; Aletor and Adeogun, 1995; Fasuyi,
2005; Ajibade et al., 2006). Sun-drying is
an inexpensive effective method of preserving surplus micronutrient-rich foods
(Tontisirin et al., 2002). However, loss of nutrients
particularly vitamins, occurs during processing but remaining levels still contribute
to the diet. Cassava leaves are highly nutritious but have anti-nutrients that
cause toxicity (Achidi et al., 2008). The presence
of the two cyanogenic glycosides, linamarin and lotaustralin, limits the leaves
as food (Padmaja, 1995). Bokanga
(1994) reported the cyanogenic potential of cassava leaves being 5 to 20
times greater than that of roots. Therefore, for a 70 kg weighed individual,
the maximum reliable consumption of cassava leaf powder is about 110 g which
is bulky because the powder presents low density (Wobeto
et al., 2007). Osuntokun (1981) however,
indicated that chronic toxicity may also occur due to the consumption of lower
cyanide doses at longer timer intervals. The risk of intoxication from consuming
cassava leaves reduces because during processing leaves quickly loose cyanogens
(reduces HCN levels) (Lancaster and Brooks, 1983). Linamarase
activity in the leaves is over 200 times greater than in the roots. The high
concentration of the enzyme linamarase present in cassava leaves detoxifies
the cyanogens. Although, cyanide content in pounded cassava leaves ("pondu"
or "sakasaka") remains high at 8.6 mg 100-1 g, about 95.8% of total
cyanide in leaves can be removed through further processing into soup (Mahungu
et al., 1987). The African traditional processing techniques of pounding,
crushing and cooking reduce cyanogenic and tannin levels to >99 and 55.2%,
respectively (Padmaja, 1995). The different processing
methods have no effect on ash, lipids, protein, fiber, total carbohydrate, carotene,
calcium, magnesium, potassium, sodium, phosphorus, copper, zinc and manganese
contents (Mahungu et al., 1987). Processing does
offer a reduction in free sugars (23.2% reduction), ascorbic acid (77.7% reduction)
and thiamine (37.1% reduction) levels, respectively. Grinding increases iron
level three to five fold but not with pounding process.
The different processing methods tremendously reduced ant-nutrients with minimal
loss in the nutrients. Adequate processing detoxifies cassava leaves for human
consumption with considerable nutrient retention (Mahungu
et al., 1987; Bokanga, 1994; Achidi
et al., 2008). Processing methods reduces available cyanide to harmless
levels but less effective with tannin and phytin. Dietary phytin is of importance
in humans nutrition. However, human lacks the enzyme phytase to break
down phytin to release phosphorus for metabolism (Fasuyi,
2005). However, there should be no danger in direct use of cassava leaves
as a good source of leafy vegetable. The nutrient value of processed cassava
leaves makes it a potential source of raw material for formulating weaning foods
especially for the underdeveloped world (Mahungu et al.,
1987; Bokanga, 1994; Achidi
et al., 2008). Drying is most prevalent processing method used in
many tropical countries as it eliminates more cyanide than oven drying. Also,
sun drying prolongs exposure time between linamarase and glucosides in detoxifying
the leaves (Padmaja, 1995).
Moringa oleifera: Moringa oleifera tree is the most underutilized
tropical shrubs. Traditional dishes around the world include green leafy vegetable
sources substituted or augmented with M. oleifera leaves (Lockett
and Grivetti, 2000). M. oleifera is a nonconventional plant with
substantial nutritional value (Sanchez-Machado et al.,
2010). Barminas et al. (1998) compared other
nutrient-dense leafy vegetables in Nigeria and posited that no other plant,
compares favorably with that of M. oleifera, nutritional profile or match
its combination of overall utility, micro and macronutrient composition, rapid
growth habit, high yield leaf production and survival in harsh climates which
suggest that M. oleifera is a unique pan-tropical dietary plant.
Among leafy vegetables, the cost of nutrients is the lowest in Moringa (Babu,
2000) and for all age groups, leaves of M. oleifera serve as a valuable
source of nutrient (Oduro et al., 2008). The
young leaves are edible and can be consumed fresh, cooked and eaten like spinach
or used for soups and salads. The powder has the highest protein content than
any other vegetable. Fresh leaves of Moringa oleifera contain at least
twice more proteins than milk and half the proteins of eggs (DSouza
and Kulkarni, 1993; Broin, 2006).
Moringa oleifera leaves have nine essential amino acids that comprise
the sulphur-containing amino acids methionine and cystine (Makkar
and Becker, 1997; Sena et al., 1998) higher
than levels recommended by the Food and Agriculture Organization (Ferreira
et al., 2008; WHO, 1985) with patterns similar
to those of soybean seeds. Its beta-carotene content is 3 to 5 times more than
in carrots. Beta carotene is extremely beneficial in healing and bone development,
control of cholesterol and anti-cancer protection. The leaves are exceptionally
reliable source of minerals. Its iron content is richer than lentils and beef
meat. The iron is three times higher than the level found in spinach. The potassium
content is also three times more than in bananas; also richer in calcium than
milk. Lockett et al. (2000) reported that in
North Eastern Nigeria; zogale (Moringa oleifera) serves as a good source
of protein, fat and an excellent source of calcium and iron or copper and zinc.
In addition, it has a high level of pro-vitamin A and C; at least as rich as
carrots in vitamin A. Vitamin A is the most prominent vitamin essential for
immune protection against all infections. The vitamin C in the leaves is 6 to
7 times more than the amount of vitamin C in orange juice. The vitamin E is
10 times more than the daily recommendation of vitamin E. It also has high levels
of vitamins B (Vitamin B1, B2 and B3) among many other medicinal benefits. The
most notable feature is the sustainability of the vitamins with cooked leaves
(Ferreira et al., 2008; De
Moringa oleifera has exceptionally high nutritional value and this position
it high in the table of Healthy Edible Plants and Vegetables (http://www.themoringa.com/nutritional-value).
In populations that practice traditional medicine they preferred, M. oleifera
as a way of treating under-nutrition. The leaves nutritionally prevent malnourishment
in children and have the capacity to boost the immune system.
Moringa oleifera leaf powder prevents malnutrition in developing countries
that usually appear in children during the weaning period, between 1 and 3 years
old. Broin (2006) reported that 30 g of leaf powder can
cover one third of the daily allowance for proteins, 75% of the calcium needs
and more than half of iron necessary for children under than three years in
age. In addition, it provides the totality of the recommended dietary allowance
for vitamin A and nearly one third of the needs in vitamin C. The leaf powder
also is a fascinating dietary supplement for pregnant and lactating women to
increase milk production and expel intestinal worms. Mosquin
(2008) reported that the leaves can be used to complement modern medicines
in chronically ill people including those suffering from AIDS and HIV related
Research has proved the leaves as a bio-enhancer of drugs and nutrients due
to its antibiotic activity.
For centuries, people in many countries have used Moringa leaves in
traditional treatment for various common ailments. Traditionally, fresh or dried
Moringa oleifera leaves treat different ailments such as anaemia, abnormal
blood pressure, blood impurities, headaches, hysteria, anxiety, cholera and
diarrhoea, eye and ear infections, fever, respiratory disorders and asthma,
bronchitis, catarrh, chest congestion, cough, tuberculosis and inflammation
of mucous membranes. The leaves are also used to treat hepatitis, impotency,
infertility and low sperm count, in addition to treating glandular swelling,
sprain, joints pain, pimples and psoriasis. The plant is rich in compounds containing
the sugar, rhamnose, also rich in a unique group of compounds called glucosinolates
and isothiocyanates (Fahey, 2005).
Inherent anti-nutritional factors: In relation to antinutritional factors,
the leaves have a small proportion of tannins (12 g kg-1 dry matter);
saponin content (5.0% as diosgenin equivalent), phytate (21 g kg-1)
and lack of trypsin and amylase inhibitors, lectins, cyanogenic glucosides and
glucosinolates (Makkar and Becker, 1997). In addition,
the low anti-quality factors contribute to the wide acceptance of Moringa
oleifera as a leaf vegetable.
Wild and cultivated indigenous vegetables contribute to food security in times
of hunger (Humphry et al., 1993; Zinyama
et al., 1990; Grivetti and Ogle, 2000; Ogle
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traditional vegetables contain much more vitamin A and other micronutrients
than introduced exotic vegetables. Also, have medicinal values, not restrict
to treat disease but also improve overall health due to their vitamin and other
nutrient contents. However, some contain anti-nutrients typified by cyanide,
tannin and phytin, lectins, saponins. Several traditional methods that include
drying are used to detoxify those with anti-nutrients to make them safe in human
nutrition. However, Aletor and Adeogun (1995) posited
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