||Natural Toxins in Sprouted
Seeds: Separating Myth from Reality
By Warren Peary and William Peavy, Ph.D.
Natural toxins in food has become a hot and controversial subject recently.
In the last few years, some popular writers have attacked sprouts (particularly alfalfa
and legume sprouts) as containing natural toxins. These writers may have heard something
about a lathyrogen toxin, saponins, canavanine, and mabbe some other nasty-sounding
toxins, and concluded that the sprouts of legumes are toxic in the raw state and so should
not be eaten. These statements are taken out of context.
Toxin One of the natural toxins that has been mentioned comes from the peas of the
genus Lathyrus. It is blamed for causing a disease known as lathyrism. Lathyrism causes
paralysis in the legs in susceptible individuals and is believed to be caused by a toxic
amino acid. This sounds scary, but its not, because peas of the genus Lathyrus are
not edible peas. The toxin is only found in the seeds of certain Lathyrus species (L.
sativus, L. cicera, L. clymenun)! Edible peas and beans are of the genera Cicer, Glycine,
Phaseolus, Pisum, and Vigna. They do not contain any such toxin. Non-edible peas of the
genus Lathyrus include sweet peas, which are ornamentals grown for their scented flowers.
In India, where food is often scarce, some people have resorted to eating a non-edible pea
known as Lathyrus sativus. It is often called "chickpea" but is NOT the same
chickpea eaten in this country or any other developed country.The edible chickpea is of
the genus Cicer and in botany is known as Cicer arietinum. Outbreaks of lathyrism in India
have been blamed on eating large amounts of the non-edible chickpea without proper
cooking. Well-cooked, it is safe to eat. But it shouldnt matter to us at all because
it is considered an inedible species.
There are at least 1.500 species of legumes within one of
three subfamilies of the family Leguminosae (Latin for Legume). Of these 1.500 species,
only a few dozen are regularly used as human food. Of course there are toxins in many of
the raw legumes usually used for human food; thats why humans have learned not to
eat them. This is the first mistake sometimes made in warning about natural toxins ¾
talking about a toxin thats found in some non-edible species people shouldnt
eat to begin with!
The second mistake often made in talking about natural toxins is to call something
toxic that, in the body, is not toxic at all but rather, is beneficial. Such is the case
with saponins. Saponins are a compound found in legumes and legume sprouts. They are toxic
to red blood cells only in vitro (outside the body in a test tube) but harmless when
ingested. In fact, Saponins appear to be beneficial, being responsible for a major part of
the cholesteral-lowering effect of legumes. Perhaps it is more than coincidence that the
increase in the increase of heart disease in the 20th century in the Western countries
coincides with the with a decline in the consumption of saponin-rich legumes. Saponins
also seem to be anticarcinogens; in one study they inhibited colon cancer. Even some of
the most beneficial nutrients, such as vitamin C, can be shown to be toxic under certain
laboratory conditions. Vitamin C is concidered an important antioxident, and substantial
evidence shows that it is involved in cancer prevention. Yet under the right experimental
conditions, in the presence of iron (Fe III) or copper (Cu II) ions, ascorbic acid can
actually cause the formation of harmful free radicals. Does this mean you should try to
avoid vitamin C? Absolutely not! These experimental conditions do not appear to be
relevant to what goes on in our bodies.
The third mistake made in the warning about some natural toxins is failing to say
that the amount encountered in food is so miniscule that it is completely insignificant.
Such is the case with a toxin called canavanine, which is found in alfalfa seeds. While
some writers may make canavanine sound like a dangerous carcinogen ¾ it isnt.
Canavanine is a non-protein amino acid thats toxic in high amounts. In the dry seed
it serves as storage protein, a growth inhibitor, and a defense against natural predators.
As you might guess, as a sprout grows, canavanine falls rapidly to insignificant levels.
The text, Seed Physiology, clearly states that "Canavanine
is non-toxic to
mammals at low concentration." Canavanine is so irrelevant that in the 1980 text,
Toxic Constituents of Plant Foodstuffs, doesnt even mention it. A 150-pound human
would have to consume 14,000 milligrams of canavanine all at once for it to be toxic at
the same level it is toxic in mice. This is an incredible amount! It is doubtful that with
a generous helping of alfalfa sprouts, you would get no more than a few milligrams. There
is NO canavanine at all in other legumes that are commonly used as human food. Even in
toxic amounts, canavanine has nothing to do with cancer. In very high, toxic amounts it
can cause a lupus-like anemia in susceptible animals due to an alteration in the red blood
cells. These studies are not relevant to the human diet. The minute doses found in the
diet are completely irrelevant and harmless. Just remember that most substances can show
some kind of toxic effect at a high enough dose. Vitamin A, selenium, copper, zinc, and
iron will all kill you at a high enough dose. So dont stop eating alfalfa sprouts
any more than you would any other food because of some minute toxin that might be present.
They are a good source of vitamin C, folic acid, and othe protective compounds.
ANTI-NUTRIENTS IN SPROUTED LEGUMES
As far as the sprouts of other legumes go, the only other toxins for which any
concern has been raised is for a class know as anti-nutrients. These are substances that
bind enzymes or nutrients and inhibit the absorption of the nutrients. The commonly
alleged anti-nutrients are protease inhibitors, amylase inhibitors, phytic acid, and
polyphenolic compounds such as tannins. With proper soaking and germination, none of these
are anything to worry about. Around the world, studies have been and are being conducted
on the use of germinated seeds as a low-cost, highly nutritive source of human food. It is
well established that when legumes are properly soaked and germinated, their nutritive
value increases greatly, usually to levels equal to or exceeding those of the cooked bean.
(Nutritive value is the ability of food to provide a usable form of nutrients: protein,
carbohydrates, vitamins, and minerals). This has been shown for mung bean, lentil,
chickpea (garbanzo bean), cowpea (blackeye pea), pigeon pea, fava bean, fenugreek seeds (a
member of the pea family), green & black gram, kidney bean, moth bean, rice bean,
soybean, and legumes in general. The increase in nutritive value in the raw sprouted seed
is due to an explosion of enzyme activity, which breaks down the storage-protein and
starch in the seed into amino acids, peptides, and simpler carbohydrates needed for the
seed to grow. The seed is literally digesting its own protein and starch and creating
amino acids in the process. Because of this process, sprouted seeds are essentially a
predigested food. At the same time, the anti-nutritional factors such as enzyme inhibitors
and other anti-nutrients are greatly decreased to insignificant levels or to nothing.
Soaking alone causes a significant decrease in anti-nutrients, as the anti-nutrients are
leached into the soak water. Soaking for 18 hours removed 65% of hemagglutinin activity in
peas.Soaking for 24 hours at room temperature removed 66% of the trypsin (protease)
inhibitor activity in mung bean, 93% in lentil, 59% in chickpea, and 100% in broad bean.
Then as germination proceeds, anti-nutrients are degraded further to lower levels or
nothing. Soaking for 12 hours and 3 4 days of germination completely removed all
hamagglutinin activity in mung beans and lentil. Soaking for 10 hours and germination for
3 days completely removed amylase inhibitor in lentils. Normal cooking removes most or all
of the anti-nutrients.
ANTI-NUTRIENTS AS PROTECTORS
Some of the substances commonly referred to as anti-nutrients are actually powerful
cancer-protecting phyto-chemicals. These include protease inhibitors and tannins. The
problem in most diets is that we dont get enough of these substances. Substantial
research shows that protease inhibitors are one of the most powerful anti-carcinogens we
have in our arsenal. They have proven to be particularly protective against cancer of the
colon, breast, and prostate. Tannins have also been shown to give substantial protection
against cancer (including cancer of the stomach and lungs) when ingested orally. Tannins
and other polyphenols may play a role in fighting tooth decay. Evidence shows that some
tannins inhibit the growth of bacteria that cause tooth decay. Phytates, like tannins, may
also interact with digestive processes in a beneficial way. Small amounts in food slow
down the absorption of sugars and regulate insulin levels. This is beneficial in the
prevention and treatment of diabetes and hyperlipidemia (high blood fats). Small amounts
of protease inhibitors, tannins, and phylates are beneficial and can be considered to be a
normal part of nutritional ecology.
Warren Peary is an investigative health journalist. William
S. Peavy holds a doctoral degree from Kansas State University in horticultural science.
They can be reached at 316 Horton Lane NW, Albuquerque, NM 87114.