I write this comment below to a request and question via
Whatsapp on a video narrated in Chinese
Mandarin. It was sent to me for advice by a friend called Sister Sonia Soon
from Bahhma Kimaris on behalf of her sister and someone else from a cancer
society (CanSurvive) in Malaysia
They solicited my opinion that garlic when overcooked causes
cancer
Dear sister Soon
Thank you sister Soon for soliciting my personal view once
again on this video claim
This video in Chinese Mandarin emphasizes on overheating the
garlic (Allium sativum) that it claims can cause cancer, but it says garlic is
cancer-protective if eaten uncooked.
If you were to solicit my opinion on this, let me tell you a
lot of foods containing complex starches such bread when toasted, cakes, traditional
kuih, coffee (after roasting its beans), potatoes chips, pop corns, fried rice,
fried mee, fried rice noodles and any foods containing starches (almost all
foods do) when cooked above 120 degrees Celsius produces this acryloyl group called acrylic amide or
acrylamide or prop-2-enoyl in short
We are not too clear on the mechanism how this substance is
formed when almost all starchy foods, not just garlic alone, are heated to above 120
0 C. Food scientists think
this may be a by-product of Maillard reaction.
Maillard reaction:
Maillard reaction is a chemical reaction between amino acids
and reducing sugars that gives food its brown colour and distinctive flavor
when foods like bread, buns, and cakes are heated at a high temperature. It is
a non-enzymic browning reaction, a very well-known reaction in food chemistry.
This reaction does not occur when starchy foods are boiled
such as in boiled potatoes and rice. But in fried or baked goods, acrylamide
may be produced by the reaction between asparagine (an amino acid from protein)
and reducing sugars (fructose, glucose, etc.) or by reactive carbonyls at
temperatures above 120 °C.
Unfortunately some later studies showed that acrylamide was also present in black olives, prunes, dried pears for
reasons not clear to us.
The Decomposition of Acrylamide:
However, we also know that acrylamide decomposes in the
presence of acids, bases, oxidizing agents, iron, and iron salts. This means
that even if starchy foods are baked, acrylamide may not be present if they are
cooked at high temperatures in the presence of vinegar (acetic acid), lime
juice (citric acid) or if baking powder (sodium bicarbonate, a mild alkaline) has
been added.
The baking powder itself will decompose into carbon dioxide
and sodium carbonate which is even more alkaline than baking powder. This may
block the formation of acrylamide, but we need studies to show this.
But even if acrylamide is present, this compound can decompose
even without heating into ammonia, and with heat, it decomposes into carbon
monoxide, carbon dioxide, and oxides of nitrogen after some time. Again we need
to conduct studies on this.
Discovery of Acrylamide:
Acrylamide was discovered in April 2002 by a scientist in
Sweden when she found the chemical in starchy foods, such as, French fries
(potato chips), and bread that had been heated higher than 120 °C, but was not found in food that had been boiled or
in foods that were not heated.
The discovery of acrylamide in some cooked starchy foods
provoked worries about the cancer-causing effects of these foods.
However as today (Friday, June 1, 2018), food scientists,
nutritionists, toxicologists, and medical scientists are still uncertain whether
or not acrylamide in foods put us all at risk of developing cancer.
Tumors in Experimental Animals:
In experimental animals, exposure to acrylamide was shown to
causes tumors in the lungs, thyroid, adrenal glands, and testes.
This concern is not just through ingestion, since acrylamide
can easily be absorbed by the skin and distributed throughout the body.
It was demonstrated that the highest levels of acrylamide
after exposure were found in the blood, non-exposed skin, liver, the kidneys,
in the testes, and spleen.
The mechanism how the carcinogenicity of glycidamide is
triggered in animal models is through a gene called cytochrome P450 which
transfers its metabolism into a genotoxic metabolite called glycidamide.
However, people who worked in food manufacturing industry
and were exposed to twice the average level of acrylamide do not exhibit higher
cancer rates.
Detoxification of Acrylamide:
Interestingly, acrylamide and glycidamide can also be detoxified
by conjugation with glutathione (an antioxidant produced by the body) to form
isomeric glycidamide-glutathione conjugates, and these are subsequently metabolized to mercapturic acids and excreted harmlessly
in the urine.
Neurotoxic Effect:
Acrylamide has also been found to have neurotoxic effects in
humans who have been exposed. Animal studies also show the same neurotoxic
effects.
Nonetheless, we cannot translate experimental results based
on animal studies into human. First of
all, human life span is far longer than smaller animals like rats, rabbits and
guinea pigs.
Secondly, the dose normally given to animal models are far
higher and fed continuously than those consumed unintentionally by human in
their daily diet.
What we are unsure of is the accumulative effects of
acrylamide in humans even at low doses, but over a long period of our life span. So far we have no evidence on its
correlation with cancer in humans
Nutrigenetic:
Thirdly, how our human body reacts to acrylamide and other
substances may not necessary be the same as those in animals. There are a lot
of other factors such as nutrigenetics to be considered.
Nutrigenetics is a sub-specialization of the science of nutrition
on how nutrients have variations in
genetic responses, and thus the onset of disease and their outcome such
as cancer.
Food substances such as acrylamide may influence gene
expression and gene behavior and also their epigenetics. The branch of
molecular medicine called epigenetics refers to external modifications to DNA
that turn genes "on" or "off."
These modifications do not change the DNA sequence, but may
trigger off disease like metabolic syndrome and cancers, and the way we respond
to acrylamide or other poisons are different from individuals to individuals, not
just among human or among animals, but even among individual humans.
In short, you and I are entirely different even though we
share almost exactly the same genome, and we respond to disease, their
treatment including cancer and their outcome differently.
Absorption through Skin:
Acrylamide has been found to be a skin irritant. Thus being a
chemical irritant, this may act as a tumor initiator on skin tissues, giving an
increased risk to skin cancer. Clinical presentations of acrylamide exposure
include dermatitis in the exposed area, and subsequent peripheral neuropathy.
But what we are concern is not so much the presence of acrylamide in heated garlic,
but by the loss of a lot of valuable suphur-containing allicin and other
functional active components in garlic, one of the most important medicinal principle
is ajoene when garlic is cooked at home,
or processed into pills by other means through food technology
Allow me to briefly explain
this in a simple language for the benefit of my gentle lay readers.
Ajoene:
Ajoene has medicinal properties. It is an antioxidant that
is able to block the formation of free radicals like superoxide. Ajoene also
acts as an antithrombotic agent that prevents platelets in the blood from
forming blood clots. This means that regular consumption of raw garlic reduces
the risk of heart disease and stroke in humans due to blood clots
Ajoene processes anti-viral properties against a number of
viruses such as those that cause vesicular stomatitis, para-influenza, vaccinia
virus, human rhinovirus, and herpes simplex.
It was shown that when cells are infected by a human
immunodeficiency virus (HIV), ajoene in garlic was able to block the
integrin-dependent processes as shown by Tatarintsev AV, et al.
Ajoene also exhibits broad-spectrum antibacterial and
antifungal properties, and garlic has been used traditionally as a natural
antibiotic and fungicide against many types of infections since ancient times
by all civilizations for thousands of years.
Phyto-dynamics:
The mechanism how ajoene acts as natural antibiotics is its
ability to inhibit genes expression controlled by quorum sensing. Quorum sensing is a communication system used
by pathogenic bacteria like Pseudomonas aeruginosa to synchronize the
expression of specific genes involved in pathogenicity.
Cancer therapeutics:
In cancer therapeutics too, ajoene has been found to exhibit
anti-leukemia properties against acute myeloid leukemia and it was found to
decrease basal-cell carcinoma tumor size by inducing apoptosis (induced cell
suicide)
This was shown that ajoene was able to effectively inhibit
tumor cell growth by targeting the microtubule cytoskeleton of cancer cells and
through other phyto-pharmaco dynamics.
Like its action against pathogenic microorganisms, in cancer
management where gene expression, epigenetic, and nutri-genetic are of
paramount importance to our understanding on the biology of malignant growth
and their spread, garlic and other natural medicines are of current interest
to scientists in their search for cancer
treatment.
Garlic Pills vs. Raw Garlic:
Unfortunately this extremely useful cancer fighting and
cardio-protective sulphur-containing ajoene in garlic was found to be absent in
all 20 brands of garlic pills manufactured by 20 different countries
This strongly suggests to us that when foods are processed
by extraction, heating, cooking or by other means, a lot of valuable nutrients
and medicinal properties are lost.
Hence, as a general rule, wherever, and whenever possible,
bearing in mind hygiene, digestibility, toxicity and other factors when some
foods are consumed raw, plant-based foods generally are best consumed raw or
lightly cooked such as in blanching of vegetables where most of the nutritive,
medicinal and health-protective properties are retained
By lim ju boo
