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Dietary Causes of Myopia (Short Sightedness) Information
Introduction
There are many conditions in Western industrialised societies today that were unheard of, or at least very rare, just a century ago. The same conditions are still unheard of in primitive peoples who do not have the 'benefits' of our knowledge. There is a very good reason for this: They eat what Nature intended; we don't. The diseases caused by our incorrect and unnatural diets are those featured on these pages.
Myopia (short sightedness) in childhood
Dietary causes of myopia:
High-carb diet — sugars and starches — in infancy.Introduction to Myopia
Our eyes were developed for an environment very different from that in which we now live. In prehistoric times we needed to be able to perceive a predator or other danger throughout our lives. With no doctors or opticians, our eyes had to last and be able to see clearly. And, judging from studies of peoples who still eat a 'stone-age diet' today, their eyes did a very good job for a whole lifetime. But many of us are plagued from birth to old age with a variety of sight defects. This is because the type of food we eat now has a profound effect on our eyes.
Myopia's not caused by reading!
Have you noticed how many children wear glasses these days? Myopia, or short-sightedness, is very common. There has been a dramatic increase in myopia in developed countries over the past two-hundred years. In the USA, myopia affects around 25 to 35% of people of European descent and up to half or more of Asian descent populations. It is also increasingly common in Britain.
For many years myopia in children was thought to be caused by excessive reading. This was because rates were typically less than 2% among populations with no formal programme of education and who didn't read books. Other research found that myopia afflicted as many as one in three children brought up in towns and cities and where they went through a course of formal education. These observations combined were used to justify the conclusion that myopia must be caused by reading. Wearing glasses became synonymous with intelligence. In mid-twentieth century films, brainy children were always portrayed wearing glasses.
But then anomalies were noticed: There were places in the world where myopia was rare despite their having compulsory education programmes; children who skipped school or who had no formal education in civilised societies also had high rates of myopia. And focussing on reading did not explain why the levels of short-sightedness were low in societies that adopted Western lifestyles but not Western diets.
Except for the past few thousand years since the advent of agriculture, all our ancestors were hunter-gatherers. It was a lifestyle in which accurate distance vision was essential for survival.[1] Indeed, we find that all mammalian and bird species tend to be long-sighted or emmetropic, which means that they can see any object further than six metres clearly without any effort needed to focus. They rarely develop myopia. This makes evolutionary sense. If we did not have compensatory mechanisms for myopia and were left to mere Palaeolithic resources, it is likely that short-sighted individuals would not survive very long as clear distance vision is required for escape from predators, location of food, recognition of other species members and awareness of environmental dangers and benefits. Consequently, any gene or genes that favoured myopia would be lethal and rapidly eliminated by natural selection. So that rules out a genetic defect as a cause of short-sightedness.
Myopia is not genetic
It was just possible that the discrepancies in susceptibility to myopia may have been due to genetic differences, but studies showed that when groups migrated from primal living to a more urbanised existence, rates of myopia shot up within a single generation. That is far too quick to be a genetic mutation and so completely ruled out a genetic susceptibility. It seemed that myopia occurred only when new environmental conditions associated with modern civilisation were introduced into the hunter-gatherer lifestyle.
This is confirmed if we look at hunter-gatherer populations today. Again we find little evidence of myopia where these peoples eat their traditional diet. Of some 3,624 eyes examined in a 1936 study of 20- to 65-year-old hunter-gatherer tribes-people in Gabon (then French Equatorial Africa), only 14 were classified as myopic.[2] That's just 0.4%. Similarly low rates for myopia were reported amongst Angmagssalik Inuit in 1954:[3] an examination of 1,123 eyes, found only 13 (1.2%) to be myopic.
But things were to change. In 1969 a group of scientists compared the eyes of older and younger Inuit.[4] They found an astonishing difference between the two groups. Testing the right eyes of 131 adults over 41 years of age, the scientists led by Dr F A Young discovered only two myopic eyes amongst them. But over half — 149 out of 284 — of the right eyes of 11- to 40-year olds were myopic. As most of the older Inuit had grown up and lived most of their early lives in isolated communities in the traditional Inuit lifestyle with little or no schooling, whereas many of their children and grandchildren grew up in Barrow and had compulsory American style schooling, Dr Young and his colleagues suggested that this was the reason for the huge difference in incidence rates of myopia between younger and older Inuit. It was simply that the younger ones had to learn to read.
But they were wrong. The Inuit have been studied in great depth. Vilhjalmur Stefansson wrote in 1919 that both women and men engaged in work which could strain the eyes in a similar way to reading with such occupations as sewing and tool making for hours on end in dimly lit snow houses during the long arctic winter yet did not develop myopia.[5]
It's caused by incorrect diet — carbs
In 1966, Dr E Cass suggested the reason for myopia in younger Inuit was that they had been born and brought up in an increasingly western dietary environment so that they ate imported cereals, bread, potatoes and sugar rather than the fish and seal meat that their elders had eaten as youngsters.[6] It was this, he suggested, that may have been associated with the rapid increase of myopia noted in these aboriginal people.
In 2002 a group of scientists led by Professor Loren Cordain, an evolutionary biologist at Colorado State University, published a review of the literature.[7] They looked at 229 hunter-gatherer tribes and confirmed that primitive populations had low rates of myopia even in those receiving formal education. It was all down to food. Cordain was clear that cereals were to blame. 'In the islands of Vanuatu', he said, 'they have eight hours of compulsory schooling a day. Yet the rate of myopia in these children is only two percent.' The difference between them and Europeans was that the Vanuatuans ate fish, yam and coconut rather than white bread and cereals.
Experts interviewed by the BBC had mixed reactions to this review. Dr Nick Astbury, vice-president of the Royal College of Ophthalmologists, told BBC News Online 'It's an interesting theory, but it needs more evidence to support it.' Although he did admit that the reasons for short-sightedness were 'multi-factorial' so diets high in refined starches could play a part. And James Mertz, a biochemist at the New England College of Optometry in Boston, remarked: 'It's a very surprising idea.'
However, Bill Stell of the University of Calgary in Canada said: 'It wouldn't surprise me at all. Those of us who work with local growth factors within the eye would have no problem with that — in fact we would expect it.'
When hunter-gatherer societies changed their primitive existence to a more Western lifestyle during the nineteenth and twentieth centuries, they not only became literate and began reading within one or two generations, they also altered the type of food they had previously consumed. Hunter-gatherer diets typically consist of high levels of protein and fats, and low levels of carbohydrate compared to modern western diets.[8] Even those carbohydrates that are present in hunter-gatherer diets are less concentrated. They are absorbed slowly and produce only a gradual and minimal rise in blood glucose and insulin levels.
Dr. Cordain's team found that although refined cereals and sugars were rarely if ever consumed by groups living in their traditional manner, these foods quickly became dietary staples following contact with Western influences. When these societies changed their lifestyles and introduced grains and other carbohydrates, they rapidly developed myopia rates that equalled or exceeded those in Western societies.
How carbs could cause myopia
As well as stimulating the production of insulin, diets high in refined starches such as sugar and cereals also stimulate production of a related compound called insulin-like growth factor 1 (IGF-1). Too much IGF-1 stimulates excess growth of the eyeball during its development. This affects the development of the eyeball, making it abnormally long. And this is the fundamental defect in myopia.
As with so many other conditions, far-sighted scientists suspected diet — and processed carbohydrates in particular. Professor Jennie Brand-Miller links the dramatic increase in myopia in developed countries on childhood over-consumption of bread. Short-sightedness is extremely rare in societies where the diet does not contain processed carbohydrates. It is also noticeable that short-sighted individuals are more susceptible to other conditions associated with the excessive consumption of sugar or starch: diseases such as diabetes and dental decay.
Confirmation
That diet could be the reason was confirmed in 1999. Short-sightedness is a uniquely human trait. It was completely unknown in the animal kingdom — until recent evidence came to light with domesticated dogs, in a study of Labrador dogs.[9]
Dogs don't read; that could not be the reason that the Labradors had myopia. But while wild dogs do not get myopia, they aren't fed by civilised humans. Domesticated dogs are — and the difference between the wild and domesticated animals is that wild dogs eat meat and Man's best friend is fed on wheat-based dog biscuits. It's exactly the same pattern as was found in the comparisons between the traditional Inuit and their younger offspring.
Myopia is a modern trend. Although highly refined sugars and cereals are common elements of our diet today, such foods were eaten rarely or not at all by the average citizen in seventeenth and eighteenth century Europe. Their availability to the masses only increased after the industrial revolution, and wheat flour of a low extraction became widely available with the advent of steel roller mills in the late nineteenth century.
Over the last two centuries the carbohydrate content of foods in urban areas of industrialised countries has risen steadily, primarily because of increasing consumption of refined cereals and sugars. This is consistent with observations that people are more likely to develop myopia if they are overweight or have adult-onset diabetes, both of which involve elevated blood glucose and insulin levels. The progression of myopia has been shown to be slower in children whose protein consumption is increased.
Taken as a whole, then, the research which suggested that reading was the prime cause of myopia was a bit, well, short-sighted. Conventional dietetic wisdom makes claims for the health-promoting effects of a diet rich in starchy staples such as breakfast cereals. Perhaps they are unable see the effect it is having.
References
[1]. Nesse RM, Williams GC. Why We Get Sick. Times Books, New York, USA. 1994, pp 91–106.
[2]. Holm S. The ocular refraction state of the Palae-Negroids in Gabon, French Equatorial Africa. Acta Ophthalmol 1937; Suppl 13: 1–299.
[3]. Skeller E. Anthropological and ophthalmological studies on the Angmagssalik Eskimos. Meddr Gronland 1954; 107: 167–211.
[4]. Young FA, et al. The transmission of refractive errors within Eskimo families. Am J Optom Arch Am Acad Optom 1969; 46: 676–685.
[5]. Stefansson V. My Life with the Eskimo. MacMillan Co. New York, USA, 1919.
[6]. Cass E. Ocular conditions amongst the Canadian western arctic Eskimo. In: Weigelin E (ed.). Proceedings of the XX International Congress of Ophthalmology. Excerpta Medica Foundation. New York, USA. 1966. pp 1041–1053.
[7]. Cordain L, et al. An evolutionary analysis of the etiology and pathogenesis of juvenile-onset myopia. Acta Opthalmolgica 2002; 80:125-135.
[8]. Cordain L. Cereal grains: humanity's double-edged sword. World Rev Nutr Diet 1999; 84: 19-73.
[9]. Mutti DO, et al. Naturally occurring vitreous chamber-based myopia in the Labrador retriever. Invest Ophthalmol Vis Sci 1999; 40: 1577–1584.
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