Moringa frequently asked questions

M.E. Olsona
Instituto de Biologı́a, Universidad Nacional Autó noma de Mé xico, Tercer Circuito s/n de Ciudad Universitaria,
Mé xico DF 04510, Mexico.

Abstract
The moringa tree Moringa oleifera is increasingly being studied for numerous
properties of applied interest. In the course of work on these properties, many
questions arise from both scientists and potential consumers. Here I address some of
the most common such questions. I explain that moringa’s correct scientific name is
Moringa oleifera Lam., and that Moringa pterygosperma is not a synonym but an
illegitimate name. The wild range of Moringa oleifera is unknown but it might be
native of lowland northwestern India. It is cultivated in all tropical countries, but it is
probably best to avoid saying that it is “naturalized” because some uses of this word
imply that the plant has become invasive. There are thirteen described species in the
genus Moringa, but additional new species probably await description, especially in
northeast Africa. Traditionally, leaves of Moringa oleifera, M. concanensis, and M.
stenopetala are eaten, and the tubers of young M. peregrina are sometimes eaten
roasted. All other species have local medicinal uses. Current commercial use so far
emphasizes M. oleifera dried leaf meal in capsules, often touting protein content.
Simple calculations show that capsules have negligible protein nutritional value. Such
use in pill form rather than as a food leads to the frequent question of whether
moringa has “side effects”. A review of studies shows that moringa has low levels of
trypsin inhibitors, tannins, saponins, and lectins, meaning that there is no reason to
expect that normal levels of consumption would lead to discomfort from these
compounds. Nearly 40% of moringa calcium may be present in the form of oxalates,
but current data suggest that these are insoluble, excreted, and do not contribute to
the formation of kidney stones. Goitrogenic glucosinolates are probably absent, and if
present are probably in very low concentrations. Moringa might have abortifacient
potential, especially in concentrates. Given its usefulness and relative lack of
antinutritional factors, there is global interest in growing moringa, so I examine its
climate preferences. Moringa oleifera is a plant of the lowland dry tropics, growing
best in places where annual low temperatures do not dip below 15°C, rainfall is less
than 1500 mm and distributed in one or two rainy seasons, and below 500 m a.s.l. I
conclude by underscoring the need for studies of all of these aspects across the entire
diversity within M. oleifera and across the genus.

Keywords: Moringa, taxonomy, nomenclature, climate preference, side effects, nutrition

INTRODUCTION
Moringa oleifera (“moringa”) is of global interest for its nutritional, nutraceutical, and
industrial applications, but there are many aspects of basic moringa biology for which
information is difficult to come by. This difficulty means that many papers in the applied
moringa literature often, and understandably, repeat some misconceptions regarding the
plants. To help make this information available in one place, I treat some of these key issues
here, as a series of questions.

WHAT IS MORINGA’S CORRECT SCIENTIFIC NAME?

As with many useful plants, there is some degree of confusion over moringa’s correct
scientific name, and, especially in the popular literature, even how to write it. It should go

a
E-mail: molson@ib.unam.mx

Acta Hortic. 1158. ISHS 2017. DOI 10.17660/ActaHortic.2017.1158.4 19

Proc. I International Symposium on Moringa
Eds.: A.W. Ebert and M.C. Palada
without saying that the correct scientific name format needs to be followed, and this is
Moringa oleifera Lam., with the genus capitalized, the species epithet in lower case, both the
genus and species italicized, and the authority not italicized but capitalized and abbreviated
following botanical convention. This means that uses like Moringa Oleifera Lam and related
variants that are found a bit too often in the moringa literature are incorrect. “Lam.” is short
for “Lamarck” and this is sometimes written out, but botanists have a conventional set of
abbreviations for authors and the correct one is “Lam.” in this case (Lamarck, 1783; McNeill
et al., 2012).
Another frequent naming issue regards Moringa pterygosperma. This name is often
cited as a “synonym” of M. oleifera, sometimes used interchangeably with it, and even as
though it were another species entirely. Moringa pterygosperma is none of these. It is an
incorrect name, not a synonym, of M. oleifera. Briefly, the situation is as follows. In the late
1600s, Adriaan van Rheede tot Drakenstein (van Rheede, 1698), posted with the Dutch East
India Company in southwestern India, published an early description and illustration of
Moringa oleifera as “mouringou” (along with the name in various languages, including
“moringa” in Portuguese). In his 1753 Species Plantarum, Linnaeus cites Rheede, and calls
the plant “Guilandina moringa,” mistaking it for a legume, Guilandina being a genus of
legumes. Soon botanists realized that Moringa was not a legume, so the genus Moringa was
erected, taking the name from Guilandina moringa (Adanson, 1763). Adanson did not assign
the plant a species name, however. Finally, in 1783, Jean-Baptiste Lamarck, of Lamarckian
evolution fame, gave the plant for first time the name Moringa oleifera, referencing Linnaeus,
Rheede, and others. In this way, the name Moringa oleifera was established as the official
name for the plant. Because it was Lamarck who first used this term, he is cited as the
“authority” or author of the name.
In 1791, Joseph Gaertner published the second volume of his De Fructibus et Seminibus
Plantarum, the most detailed work on seeds at that time. Gaertner overlooked that the plant
we know as Moringa oleifera had already been named by Lamarck. Not only did Gaertner
give a new name, Moringa pterygosperma, to a plant with a legitimate name, but he also went
so far as to cite the very publications in which the plant was given its name. Giving a new
name to a plant while blandly citing its previous legitimate publication is such an affront to
students of botanical nomenclature that these superfluous names are often not even
included in lists of legitimate botanical synonyms (e.g., Olson, 2010). Moringa pterygosperma
is thus considered not a synonym but a superfluous name for Moringa oleifera. Therefore,
there is no reason ever to use the name Moringa pterygosperma.

WHERE IS MORINGA NATIVE, CULTIVATED, AND NATURALIZED?

The introduction of nearly every paper on Moringa oleifera applied properties
includes a brief overview of moringa’s geographical distribution. Some of these are as
accurate as can be given current knowledge (e.g., Morton, 1991) and some are extravagant in
their biogeographical implausibility, often stating that moringa is native to “northern Africa”,
“eastern Asia”, “Arabia”, “Iran”, “Afghanistan” even Caribbean islands, and all number of other
places where it is definitely not native. Much of this confusion is understandable. Useful
plants are moved around by people and in highly transformed tropical landscapes that have
been inhabited for millennia, it is hard to tell wild from introduced plants. Even the concepts
of “wild” versus “cultivated” or “naturalized” are often unclear.
What is meant by the “wild” distribution of a plant is the area in which the plant
evolved and spread before humans arrived. Its wild habitat is the natural floristic
assemblage at the geographical site that the plant would grow in even in the absence of
human intervention. So, even though it is common to see moringa trees growing and re-
seeding on the outskirts of villages here in Mexico, or in Pakistan, in Madagascar, west Africa,
and many other places, this does not mean that they are growing wild in these places. I will
treat this issue in detail in a later work, but I will note that at the moment, based on the
literature and my own field work, there is so far evidence for wild stands of what is currently
regarded as Moringa oleifera only in hilly lowlands of northwestern India (Figure 1).
Innumerable reports of “wild” moringas in other parts of India have in my field and

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herbarium work turned out to be cultivated plants or remnants of old cultivation. Given its
proximity to northwestern India, it would not be surprising to find wild moringas in eastern
Pakistan but so far there are no convincing reports (Stewart, 1972; Pakistan Plant Database
www.tropicos.org/Project/Pakistan). So, though there is still much to be learned, based on
the literature (e.g., Dastur, 1951; Verdcourt, 1986; Olson, 2010) and ongoing field work, it is
safest to say that moringa is “possibly native to northwestern India”.

Figure 1. Putatively wild plants of Moringa oleifera in subtropical deciduous forest in

lowland northwest India.
That said, moringa is cultivated in all tropical countries, and it is often said that it is
“naturalized” in these countries. “Naturalized” is a vexed term because under some usages it
is synonymous with weedy or invasive. In others, it can refer to plants that reproduce
themselves in a non-native area, especially around human environments, without entering
into undisturbed habitat (Colautti and MacIsaac, 2004). This is the case of M. oleifera, which
does re-seed itself around houses, vacant lots, road, and the margins of agricultural fields in
many places in the world. What has never been observed anywhere in the world are
moringas invading intact primary habitat. This is very important because it means that there
is no reason to think that moringa will become an ecological nuisance, displacing native
flora. Plants considered weeds or other nuisances can be banned or their movements
otherwise restricted by governments, hampering research and trade. Therefore, because of
its various connotations, I suggest avoiding the term “naturalized” and using only
“cultivated.”
To summarize: moringa is putatively wild, as far as is currently known, in the lowlands
of northwestern India. Moringa is cultivated in other parts of the Indian subcontinent,
tropical Asia, Africa, Madagascar, the Americas, Australia, and Oceania. It is not known to be
invasive or a weed anywhere. Finally, it is best to avoid saying that moringa is naturalized
anywhere.

HOW MANY SPECIES OF MORINGA ARE THERE?

Reports of the numbers of species of Moringa vary widely, ranging up to 14
(Verdcourt, 1986). Based on my field and herbarium work, there are 13 currently described
species (Table 1). Verdcourt’s “species 14” turned out to be Moringa longituba upon visiting
the locality (Figure 2). There are probably several undescribed species, especially in
northeast Africa. Moringa rivae ssp. longisiliqua is very different in flower color from
Moringa rivae ssp. rivae and is very poorly collected. It might represent a distinct species,
but material is so fragmentary that it is difficult to say. Specimens from southeast of Berbera,
Somaliland, (Glover and Gilliland 1194, in the Kew and East African herbaria) were referred
to M. pygmaea by Olson and Carlquist (2001) but they might represent M. borziana or
possibly an undescribed species. Much more exploration is needed to map out the wild
distributions of Moringa species and the taxonomy of the species. Based on current
knowledge, though, there are 13 described species, listed in Table 1.

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Table 1. Currently described species of Moringa.
Moringa arborea Verdc.
Moringa borziana Mattei
Moringa concanensis Nimmo
Moringa drouhardii Jum.
Moringa hildebrandtii Engl.
Moringa longituba Engl.
Moringa oleifera Lam.
Moringa ovalifolia Dinter and A. Berger
Moringa peregrina (Forssk.) Fiori
Moringa pygmaea Verdc.
Moringa rivae Chiov.
Moringa ruspoliana Engl.
Moringa stenopetala (Baker f.) Cufodontis

Figure 2. Verdcourt’s “Moringa sp. 14” on the Kenya-Somalia border east of Wajir turned
out to be Moringa longituba.

WHICH SPECIES OF MORINGA ARE EDIBLE?

Moringa oleifera is the most widely grown species, cultivated around the world for a
variety of products. In addition to M. oleifera, three species are known to have some degree
of edibility, M. stenopetala, and to a lesser degree M. concanensis and M. peregrina. Moringa
stenopetala is the second most-cultivated species of Moringa. It seems to be found native
only in a handful of localities around Lake Turkana (Mbaluka and Brown, 2016), in the Great
Rift Valley of northwestern Kenya and southwestern Ethiopia. Slightly to the northeast, it
forms part of a system of permaculture agroforestry in southern Ethiopia in the region of the
Konso people. This area is at the upper elevational margin of the dry tropics, around 1600 m
a.s.l. People there grow annual vegetable crops in the rainy season, but plant Moringa
stenopetala trees abundantly in their towns. Moringa stenopetala has a very large, water
storing trunk and holds on to its leaves well into the dry season. These are eaten by the
Konso as an important dry season food (see Jahn, 1991; Fö rch, 2002; Jiru et al., 2006).
Though its growth rate and yields are impressive, M. stenopetala grows more slowly than M.

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oleifera and its yields are lower. Its seed yields are lower and the thick, spongy seed coat of
M. stenopetala makes it even harder to extract the oil, with lower yields and, apparently,
lower quality seed oil and much lower water clarification properties. Moringa stenopetala
leaves have a tougher texture to eat than the very soft leaves of M. oleifera. Whereas M.
oleifera grows tall and mast-like during its first year, M. stenopetala tends to form many
stems from the base, forming a huge shrub if it is not shaped aggressively.
Moringa concanensis is the closest living relative of M. oleifera. It is native throughout
the lowland dry tropics of eastern and southern Pakistan, much of India, and a few small
localities in Bangladesh. It looks somewhat like M. oleifera and is often confused with it. It
often has thicker outer bark than M. oleifera and the leaves have slightly longer pinna
segments that are once-pinnate as compared to M. oleifera. The common assertion that M.
concanensis has twice pinnate leaves and that M. oleifera has 3-pinnate leaves and that this
feature readily distinguishes the species (Qaiser, 1972; Bhandari, 1990; Verdcourt, 1986) is
not quite true. It is based on the small and fragmentary leaves that are often pressed for
herbarium specimens. Small leaves of M. concanensis are indeed often 2-pinnate, but the
large, mature leaves of M. concanensis often have 3-pinnate sections (Figure 3). Large,
mature leaves of Moringa oleifera are always 3-4 pinnate. What distinguishes them most
clearly are the long leaf tips in M. concanensis, which consist of a long section of pairs of
leaflets, often 3-8, in contrast to M. oleifera, which at the leaf tips usually has only 1 or 2
pairs of leaflets.

Figure 3. Moringa concanensis leaves. On the left, a small twice pinnate leaf. On the right, a
very large leaf, showing that when large, there are often 3-pinnate sections, even
in M. concanensis.
The young pods, and sometimes leaves and flowers of M. concanensis are occasionally
eaten locally (e.g., Arinathan et al., 2007), but in general this species is regarded as
medicinal, including intervening in cholesterol levels, diabetes, and parasite infections, much
like other species of Moringa (e.g., see Anbazhakan et al., 2007, though their description of
the species seems at odds with its morphology).
Moringa peregrina is, in turn, the closest living relative to M. oleifera and M.
concanensis (Olson, 2002). It is a slender trunked or bushy tree with wispy leaves that drop
their leaflets at maturity. In this way, the mature leaves are made up of just the naked, woody
rachises. The oil contained in the hard-shelled, wingless seeds is laboriously collected and
saved for medicinal use, at least in Oman, where it is reportedly taken by the cupful for
stomach complaints. The only edible part seems to be the tubers of young plants, which are
roasted and eaten (Miller and Morris, 1988).
Only M. oleifera, M. stenopetala, M. concanensis, and M. peregrina are known to have
any degree of edibility. The other species are all used medicinally locally, though. In
Madagascar Moringa drouhardii and M. hildebrandtii are classic tomb ornamentals in
southern and western Madagascar (see Olson and Razafimandimbison, 2000). The bark of

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the trees is often scraped and gouged. Local people told me that they use the bark in
decoctions for bronchial complaints. I asked them if they ever ate the leaves or the seeds,
and they told me that they are regarded as poisonous. Moringa ovalifolia, from Namibia and
Angola, also seems to be used medicinally but never as food. The northeast African endemics
M. arborea, M. borziana, M. longituba, M. rivae, and M. ruspoliana are all used medicinally.
The roots all seem to be used to treat intestinal parasites in goats and camels, and skin
afflictions in animals. Moringa pygmaea is so geographically restricted and so poorly known
in general that, while it might be used similarly, there is no documentation of this. No part of
any of these species is known to be eaten.

DO MORINGA PILLS OR CAPSULES HAVE PROTEIN NUTRITIONAL VALUE?

The most common product on the moringa market comes in the form of dried leaves
in capsules. A very common claim in support of the sale of these capsules is that Moringa
oleifera leaves have high levels of protein. Examining these claims makes it clear that
moringa capsules are unlikely to provide dietarily significant amounts of protein. Moringa
capsules usually contain about 400 mg of dried moringa leaf powder. Moringa leaf powder
that includes mostly leaflets, and not the woody petiole and leaf rachises, contains about 20-
30% protein. 25% of 400 mg = 100 mg protein. World Health Organization standards
suggest that an average adult needs 105 mg protein kg-1 body weight day-1. Therefore, an 80-
kg adult needs some 8,400 mg protein day-1. Assuming that all of the protein in moringa is
available to the body, dividing the average daily need by the amount of protein in moringa
(100/8400×100) shows that a moringa capsule contains about 1.2% of the protein needed
every day. Meeting daily protein intake would require more than 80 moringa capsules.
Therefore, it is clear that moringa capsules are neither a significant protein source and nor a
cost-effective one.

DOES INGESTING MORINGA PRODUCE SIDE EFFECTS?

Because moringa is often commercialized as a capsule rather than as a vegetable,
many consumers ask whether “taking” moringa produces side effects. In answering this
question, it is helpful to stop thinking of moringa as a medicine and think of it as a nutritious
vegetable. This will help think properly how to eat moringa, as well as guide expectations
regarding “side effects”. Briefly, there are generally no side effects to eating a vegetable, but
people have different reactions. Soybeans, for example, provide high quality protein, but
many people are allergic to them. I am unaware of any reports of moringa allergy, but there
is no reason to assume that it is impossible (though there is some evidence to suggest that
moringa actually helps counteract some allergic responses, see for example Mahajan and
Mehta, 2007; Agrawal and Mehta, 2008). But “side effects” refer to a reasonably dependable,
undesirable secondary effect, and there are numerous compounds in plants that can cause
such unwanted effects. I briefly examine the contents of Moringa oleifera and conclude that
there is little reason to expect side effects from eating moringa, though its abortifacient
potential at high concentrations requires more research. I examine several antinutritional
compounds as follows:

Trypsin inhibitors
Trypsin is an important digestive protease. Natural selection has favored the
production of protease inhibitors in plants, apparently as a defense mechanism, deterring
animals from eating them. There have not been many studies on trypsin inhibitors in
Moringa, and those that have been done have been carried out only on very limited samples.
Based on these studies, though, protease inhibitors seem to be found only in moderate
amounts in M. oleifera leaves, and the ones that are there seem to be very heat-sensitive, so a
quick cooking deactivates most of them (Vanderjagt et al., 2000). Some nutritious foods,
such as soybeans, are notorious for their trypsin inhibitors (e.g., Guillamó n et al., 2008). In
fact, many legumes with very high protein contents are not eaten precisely because they
have such high levels of trypsin inhibitors and other antinutritional factors. Unlike these
species, Moringa oleifera is not known for its indigestibility. So, based on the available

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evidence and a long history of consumption by people, trypsin inhibitors do not seem to be
present in side-effect producing quantities in M. oleifera.

Tannins
Tannins are polyphenols that interact with proteins, often binding to them and making
them insoluble. When proteins are not in solution, they cannot be digested. So, like protease
inhibitors, tannins appear to have arisen and been maintained in plants as antiherbivory
agents. Makkar and Becker (1997) found tannins in concentrations of about 12 g kg-1, which
the authors regarded as only representing a moderate concentration. Note, though, that the
studies that have been conducted on moringa have been carried out on samples gathered
only in a few geographical regions and therefore might not reflect the variability found
across the species. Also, the results of chemical studies can vary tremendously depending on
the exact extraction and sample preparation method used (Hagerman, 1988). This also
means that it is sometimes hard to compare between studies. For example, Albrecht and
Muck (1991) measured tannin contents in a variety of legumes and found that tannin
contents varied from 0 to 27 g kg-1. This would seem to bear out Makkar and Becker’s (1997)
conclusion that the 12 g kg-1 in Moringa oleifera leaves is indeed “moderate”. However, given
that their methods differed slightly, it is hard to know just how Moringa oleifera tannin levels
compare to those in other foods. In addition, because Makkar and Becker only used a single
sample, it is hard to know how much variation there is in tannin concentrations across
Moringa oleifera and the different products made from moringa that people consume.
However, in contrast to things like grapes, persimmons, or raw nuts, which are notorious for
their tannin content, moringa has no such reputation despite millennia of consumption. So,
given the information available, the tannin concentrations seem low enough that they are
unlikely to produce unwanted reaction under normal consumption.

Saponins
Fungi seem to be particularly susceptible and saponins might be an evolutionary
response by plants to fungal attack (Osbourn, 1996). They apparently act by disrupting lipid
cell membranes. Like tannins, they are unpleasant tasting and potentially toxic. Makkar and
Becker (1996) showed that Moringa contained some saponins (see also Richter et al., 2003).
They found saponin levels higher than those in soybean, but reported that the toxicity of the
saponins in moringa seems to be very low. Like all aspects of moringa, systematic studies
across the variability within M. oleifera and across the genus are needed, but based on the
available evidence there would seem to be no reason to avoid eating Moringa in a normal
diet because of its saponin content (see also Makkar and Becker, 1997; Gidamis et al., 2003).

Lectins
Lectins are glycoproteins that, when eaten by people, bind to the mucopolysaccharides
protruding from the membranes of the cells in the intestinal wall. Well known lectins include
ricin and phytohemagglutinin. Lectins are again compounds that plants, being sessile
organisms that cannot run away when confronted by a predator, defend themselves against
attack (Peumans and Van Damme, 1995). Makkar and Becker (1996) found no traces of
lectins in their analysis, though the seed does, famously, have coagulating proteins. These are
the proteins that are used in moringa water purification (see Sutherland et al., 1994, also
Coelho et al., 2009 for other moringa lectin uses). So, even though moringa is so rich in
proteins, lectins do not seem to be important components of the chemical repertoire of
moringa leaves.

Calcium oxalate
It is often said that moringa has “more vitamin C than oranges, more calcium than
yogurt, etc…” Olson and Carlquist (2001) showed that there was abundant calcium in all
moringa parts – but in the form of calcium oxalate crystals. These crystals are another line of
plant defense, this time against chewing or piercing insects. For humans, calcium oxalate is
worrisome because in the best case it is not available to the body and in the worst case can

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contribute to formation of kidney stones (Finkielstein and Goldfarb, 2006). For years it was
not clear how much of the “more calcium than yogurt” was actually nutritionally inaccessible
calcium oxalate. Radek and Savage (2008) quantified the proportion of calcium in moringa
in the form of oxalate, and it turned out to be a 38%. This percentage would seem
dismayingly high, but two important observations emerge from their study. First, Radek and
Savage showed that moringa leaves contain only non-soluble oxalates. This means that even
though there are large amounts of oxalates in moringa leaves, it is found in a form that is
simply excreted by the body. Oxalates that are excreted do not circulate in the body, and
therefore cannot contribute to kidney stone formation. Second, Radek and Savage showed
that moringa has total calcium values that are extremely high (>20 mg g-1 of dry leaf). So,
even with more than a third of the calcium being unavailable, moringa offers substantial
levels of calcium that are potentially bioavailable. Powdered milk has approximately 13 mg
g-1 of calcium (USAID, 2006). So, moringa leaf powder would seem to compare favorably not
only with powdered milk in terms of protein content but also in terms of calcium. Even if all
of the protein or even all of the non-oxalate calcium in moringa turns out not to be readily
digestible (and here more research is needed), the much lower cost of moringa means that it
is a protein and calcium source that is more inexpensive and with a much lower
environmental impact than milk. Thus, although a large proportion of the calcium in
moringa is bound up in oxalates, most of these oxalates are likely simply excreted, meaning
that they do not contribute to kidney stones. And, in addition to calcium oxalate, there is still
a substantial amount of calcium that is probably bioavailable.

Glucosinolates
Beyond its well-proven nutritional benefits, one of the main promising aspects of
Moringa oleifera is its battery of antioxidant glucosinolates, or mustard oils. Glucosinolates
are the spicy, sulfur-containing compounds that give radish, cabbage, wasabi, papaya, and
other Brassicalean plants their spiciness, pungency, or sometimes slightly fetid smell. They
are what seem to give moringa its potential promise in cancer chemoprevention (Guevara et
al., 1999; Fahey et al., 2004; etc.), glucose regulation for diabetics (Kar et al., 2003; Ndong et
al., 2007), and other potential applications.
Glucosinolates are potentially important in connection with side effects because some
of them lead to the formation of goiters. Therefore, a natural question is whether
glucosinolates in Moringa oleifera have the potential to cause goiters (Abuye et al., 2003).
Moringa is a member of Brassicales, the great order of mustard-oil producing plants. This
means that it is a relative, though a bit distant, of the mustard family, Brassicaceae. Many
Brassicaceae are well known for containing progoitrin, which, when eaten and then split
apart in the initial stages of digestion, releases goitrogenic oxazolidonethiones. However,
progoitrin has never been identified in any Moringa species. Likewise, no Moringa species is
known to have high levels of glucosinolates constructed around an indole group (Faizi et al.,
1995; Guevara et al., 1999). Indole glucosinolates are also important goiter-causing
compounds. As a result, there is no evidence that points decisively toward a risk of goiters
from consuming moringa. However, it could be that some thiocyanates, the sulfur- plus cyan-
group containing compounds common in moringa, just might be goitrogenic in very high
concentrations, well beyond those found in a normal diet. This is significant because some
commercial moringa products include concentrates that very well might concentrate some
substances excessively, an issue potentially of concern also with regard to abortifacient
potential.

Abortifacient potential
One aspect of moringa biology that requires attention is its potential to provoke
abortion. Moringa is a traditional abortifacient in India (Nath et al., 1992) and does seem to
provoke uterine changes in rats that have had their ovaries removed and so otherwise lack
female hormones (Shukla et al., 1989). In addition, there is a fair amount of research
examining the ability of moringa to cause abortions in rats. As with most research on
moringa’s medical and nutritional potential, many have methods that are hard to interpret.

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For example, Sethi et al. (1988) appear to have ground up moringa leaves, extracted the
contents with ethanol and then dried this tincture down (see also Nath et al., 1992). They
then administrated 175 mg of this paste per kg of rat body weight. For a 65-kg human, this
would mean taking 11 g of this hyper-concentrate. It is not at all clear how many kilos of
fresh moringa leaves would be needed to make 11 g of such an extract, but it likely exceeds
the amount that a person would ingest in any meal. Centuries of use as an edible food have
established moringa as a nutritious addition to human diets, apparently including pregnant
women, but it is clear that more research would be helpful. Moringa’s potential abortifacient
potential at very high doses illustrates the important point that well-meaning usages such as
concentrates that go far beyond proven dietary doses could reveal potential undesirable
effect. Given this evidence, it seems clear that dietary use of moringa should concentrate on
moringa as a vegetable, a use that is known to be safe and nutritious; concentrates and
extracts should be avoided until more is known about abortifacient potential.

WHERE CAN MORINGA BE GROWN?

Because moringa is such a useful plant, people worldwide would like to grow it. Here I
provide some information regarding where moringa grows best, its climate preferences, and
considerations for growing in marginal areas. First, moringa is a tropical plant. It only grows
truly well in the tropics, and the dry tropics at that. The key factors are temperature and
moisture; latitude and elevation inevitably intervene as well. We will look at these
individually.
The first key aspect is the annual low temperature. Just because it gets hot in Death
Valley, or Iowa, or Paris does not mean moringas will grow well there. This is because what
limits moringas most severely is the yearly absolute (not mean) low temperature. Moringas
do not tolerate frost well. More importantly, they do not grow well in places that get below
10°C or so, and only then when such low temperatures are rare. 15°C as a general low is
ideal. On the Jalisco coast, at the site of the International Moringa Germplasm Collection
(www.moringaceae.org), the lowest low is 17°C, ideal for moringa. There are occasional
lows, at 3 am at the coldest time of year. Ten (10) degree weather for days on end is as bad
for moringas as a frost. Good average daily temperature ranges are in the 20- to 35-degree
range. The annual high is important insofar as it is related to the average, but is not an
important consideration in selection areas for growing moringa. Moringas in general do not
suffer from high temperature, and often do not even drop their leaves under high
temperature if there is water in the soil. In any case, tropical areas have more moderate
climates than deserts and other extreme places, so anywhere with the minimum that is high
enough for a moringa will have absolute high temperatures that are also in the correct range.
As to rainfall, practically any tropical area that meets the temperature requirements
will meet the minimum rainfall needs of moringa. The problem in the tropics is likely to be
too much rainfall. Moringas do best in areas that receive less than 1.5 m of rain per year and
where the rain falls in one or two concentrated seasons during the year, not evenly all year
round. The wet tropics, as in rainforest areas, places where things like cacao, mangosteen,
tea, oil palms, or allspice grow well are usually too wet for moringas to grow satisfactorily.
Moringas do not tolerate well water puddled around their roots, or heavy, fine soil with little
oxygen around the roots. On the other hand, they respond well to well drained, well aerated
soil. Fast draining gravelly soil is ideal, and they will also do well in sandy soils. However,
they will do poorly even on the best soils if they remain waterlogged. For example, deep
volcanic soils are often perfect for moringas, but if they are in a high rainfall area the plants
will suffer anyway.
With regard to latitude and elevation, moringa is a tropical lowland plant. Moringas in
general grow best from sea level to 500 m a.s.l. or so. In some places, moringas can grow
acceptably up to about 1000 m. Growth at these elevations will generally not be acceptable
for commercial production but might be satisfactory for domestic use or as an ornamental.
The trees can often survive but definitely not thrive between 1000 and 1500 m. Above 1500
m is completely out of the question as far as serious moringa cultivation goes. Remember
that moringa is a tropical plant and these elevations apply to tropical latitudes, between 23

27
north and south latitude or so. Moringas really do not grow well outside of these latitudes
and certainly not at higher elevations.
I offer some tables (Tables 2-4) giving combinations of temperature and rainfall in
areas where I have seen moringa growing well. These illustrate the point that M. oleifera
prefers warm climates with very high low temperatures. The highs can be high, but the lows
need to be high. Rainfall tends to be low, 1500 mm or often much less, and is highly seasonal,
usually with 8 months or so of very dry weather. Moringa is a lowland plant, growing best
below 500 m a.s.l.
Moringa oleifera will hang on in many marginal places, even flower and fruiting
sparingly in places like southern California, the Mexican or Kenyan high plateaus, or the
Canary Islands. They can be cultivated, at great expense and massive carbon footprint, in
greenhouses in cold places like Europe (Fö rster et al., 2015), or, perhaps even more
unsustainably, with outdoor gas heaters (Figure 4). Given the very fast growth rates of
Moringa oleifera, it seems possible that it could be cultivated as an annual in temperate
regions with adequate yield. Some cultivars are grown in India as annuals for their edible
pods, so with their long summer day lengths it could be possible to reach adequate
temperate zone yields despite the inappropriate climate.

Table 2. Moringa oleifera temperature preferences in degrees Celsius, showing that

moringas grow best in areas with very high minimum temperatures.
Locality Mean annual temp. Max. temp. Min. temp.
Tiruchirappalli, India 29 37 21
Rupnagar, India 24 40 7
Tehuantepec, Mexico 28 35 20
Antanimeva, Madagascar 24 33 13
IMGC, Jalisco, Mexico 26 33 16
Mandera, Kenya 29 40 20
Kitui, Kenya 25 35 16
Accra, Ghana 27 32 22
Barranquilla, Colombia 28 33 23
Chiquimula, Guatemala 26 35 18
Depto. León, Nicaragua 27 35 20

Table 3. Moringa oleifera precipitation preferences (ppt in cm), showing that moringas
grow best in areas that have relatively low and seasonal rainfall.
Locality Mean Ann Ppt Ppt wet Mo Ppt dry Mo Ppt wet qtr Ppt dry qtr
Tiruchirappalli, India 860 192 9 453 39
Rupgnagar, India 944 307 8 694 55
Tehuantepec, Mexico 860 216 2 511 7
Antanimeva, Madagascar 665 165 2 457 10
IMGC, Jalisco, Mexico 818 225 1 566 13
Mandera, Kenya 247 85 1 138 3
Kitui, Kenya 421 128 1 205 5
Accra, Ghana 786 194 10 421 57
Barranquilla, Colombia 778 192 0 437 2
Chiquimula, Guatemala 696 158 0 384 3
Depto León, Nicaragua 1458 386 0 855 1
Mean Ann Ppt = Mean annual precipitation; Mo = month and Qtr = quarter, i.e. 3 month period, so it rains 192 mm in the
wet month in Barranquilla, 437 in the wet quarter, 0 mm in the driest month, and 2 mm in the driest quarter.

28
Table 4. Moringa oleifera elevational preferences in m a.s.l.
Locality Elevation
Tiruchirappalli, India 84
Rupnagar, India 260
Tehuantepec, Mexico 41
Antanimeva, Madagascar 146
IMGC, Jalisco, Mexico 74
Mandera, Kenya 221
Kitui, Kenya 574
Accra, Ghana 8
Barranquilla, Colombia 40
Chiquimula, Guatemala 339
Depto León, Nicaragua 87

Figure 4. Moringa drouhardii being grown outside with the benefit of gas heaters, The
Huntington, San Marino, California.

CONCLUSIONS – THE NEED FOR FURTHER STUDIES

Even though people have been eating moringa for thousands of years, all aspects of
moringa need more study. Most of the studies that have been carried out have examined
very small samples of moringa germplasm. Virtually no effort has been made to study
samples from across the entire genus Moringa and including the full genetic diversity of M.
oleifera. The studies that have been carried out are hard to compare with one another and
their methods make their relevance to human nutrition difficult to interpret at times (for
example, the massive abortifacient doses given to rats). Any studies in humans have involved
very few subjects. Relatively few of these studies are in prestigious international journals.
With the ease of communication afforded by tools such as email and videoconferences, plus
the relative ease of sending material or traveling, there is every reason to expect that
moringa scientists can forge a global collaboration to produce globally comprehensive

29
applied and basic data. Only in this way can we take moringa science from its current
situation of indicating great promise but based on very local studies; only in this way can we
take moringa from being a plant of great promise and much anecdotal evidence to one with
the full backing of solid scientific research.

ACKNOWLEDGEMENTS
This work was supported by Trees for Life and by project IT200515 of the Programa
de Apoyo a Proyectos de Investigació n e Innovació n Tecnoló gica, UNAM.

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