I was at a friend's place when this argument occurred 'again'; "garri causes eyesight problems, true or not?". I used the word 'again' as this is not a new topic of argument.
This topic has been successful at gaining itself much popularity as it's been widely debated for decades; by our great grannies - who (may) know little or nothing about medicine - among scholars, and even among medical experts.
But with critical examination, we're going to take a look into this topic together.
A QUICK LOOK INTO THE SUBJECT MATTER
This is for the benefit of non-Nigerians who might be reading this, for better understanding.
Garri is a popular West African food made from cassava tubers.
Garri is a food hated by few, but loved by much. Virtually every home in Nigeria has it in their store.
It has so much fan base that if possible, a facebook or twitter account would have been opened on it. I for one would have been the guy with the most visits.
I can remember vividly sometime around 2012, a tweet got trending on twitter; "RETWEET if you agree! #Garri Ijebu Saving Lives Since 1400!". Very funny.
Some of it lovers have even anglicized it by calling it Cassava Flakes. Much of love, you see!
NOW, TO THE ROOT OF THE MATTER
As earlier stated, garri is a food made from cassava tubers.
Cassava roots and tubers contain what is known as CYANOGENIC GLYCOSIDES (i.e cyanides bound to sugar molecules in some plants), which helps defend them against herbivorous animals. But the main element in that compound is CYANIDE.
According to the American Cancer Society, the cyanide produced in cassava plant is poisonous, can be deadly to humans, and also pose serious health hazard IF NOT PROPERLY PROCESSED.
Proper garri processing should reduce the concentration of this acid to a harmless level, but impatience on the part of its producers make them employ inappropriate processing methods which give rise to "cyanide-laden garri poison" as a friend calls it.
A BRIEF ON CYANIDE
Cyanides can be produced by certain bacteria, fungi and algae and are found in a number of plants (spinach, bamboo shoots, almonds, cassava, etc).
People may be exposed to low levels of cyanides in their daily lives from foods, smoking and other sources. Eating or drinking cyanide-containing foods may cause health effects.
After ingestion, cyanide quickly enters the bloodstream. The body handles small amounts of cyanide effectively and differently than large amounts:
• In small doses, cyanide in the body can be changed into thiocyanate, which is less harmful (about seven times less toxic than cyanide) and is excreted in urine.
• In the body, cyanide in small amounts can also combine with the hydroxycobalamin form of vitamin B12 to form cyanocobalamin, thus altering the cyanide into a safe vitamin which helps maintain healthy nerve and red blood cells.
These two reasons explain why most medical experts argue against this topic and call it a fallacy. But. . .
• In large doses (which can cause chronic cyanide poisoning), the body’s ability to change cyanide into thiocyanate is overwhelmed. Increased thiocyanate concentrations in the body can adversely affect the body. Large doses of cyanide prevent cells from using oxygen and eventually these cells die.
Chronic cyanide exposure is linked to demyelination, lesions of the optic nerve, ataxia, hypertonia, Leber's optic atrophy, goiters and depressed thyroid function.
Don't forget, most garri drinkers are addicts. And also considering the economic situation of the country, some people drink it three times a day.
HOW IT AFFECTS THE EYE
The body has several mechanisms to effectively detoxify cyanide. The majority of cyanide reacts with thiosulfate to produce thiocyanate in reactions catalyzed by sulfur tranferase enzymes such as rhodanese. The thiocyanate is then excreted in the urine over a period of days.
Although thiocyanate is approximately seven times less toxic than cyanide, increased thiocyanate concentrations in the body resulting from chronic cyanide exposure can adversely affect the thyroid.
The 'thio' of thiocyanate comes from the sulfur amino acids, cysteine and methionine, which are also essential to a number of vital enzymes, including glutathione peroxidase, the major natural enzyme antioxidant of cell membranes.
Thiocyanate carries similar electronic charge, size and characteristics as iodide; hence it substitutes or competes with iodide by entering the thyroid gland, and blocking the production of the thyroid hormone, thyroxine.
A low thyroid state interferes with vitamin A production, essential to regeneration of the retinal pigments and healing of the retina. Night blindness and retinal damage are the most obvious of the consequences, and vitamin A is required for healing and repair in every cell of the body.
Another way is that, as large doses of cyanide prevent cells from using oxygen, suffocation occurs at the cellular level. The nervous system is particularly vulnerable and sub-clinical cases damage the eyes and nerves. Demyelination of the brain, similar to multiple sclerosis, can also occur.
FURTHER WORSENING CONDITIONS
Thiocyanate levels can increase after cigarette smoking or exposure to cigarette smoke, because of cyanogens in tobacco leaf.
Thus, thiocyanate can amplify retinal damage along with carbon monoxide.
Carbon monoxide, however, blocks the transport of oxygen from hemoglobin to the tissues, and this adds to the damage caused by cyanide, which blocks the cytochrome enzymes within cells, thus preventing oxygen transfer inside the mitochondria of the cells.
The combination of carbon monoxide and cyanide is worse than either alone so that even at relatively low doses of dietary cyanides, irreversible damage to the retina of the eye can and does occur in smokers.
So smokers who drink garri are at greater risk of having eyesight problems.
OTHER COMPLICATIONS
There are also some people who are allergic to cassava, and some to garri. Allergies manifest in different ways including itchy eyes, red eye, itchy skin, skin rashes, coughing, etc. Drinking garri for this set of individuals isn't a good idea.
BENEFITS
Notwithstanding, plants that contain cyanide have medical value and may be used as therapy for malaria, sickle-cell disease, boils, diarrhea, flu, hernia, inflammation, sores, etc.
It has also been theorized that cyanide may be useful as a type of gene therapy to treat cancer.
To all garri fans (like me) out there, I'm so sorry if this breaks your heart, but I just have to do my job, and that's to tell you the truth.
For more on cassava, READ HERE
REFERENCES:
NEW YORK STATE
DRINK YOUR VITAMINS
International Cyanide Management Code
