They blame sugars/insulin and also lack of sunlight/dopamine on the
excessive growth of eyes.

Taka

Near-Sightedness Appears Linked to Excess Sugar in Diet

Myopia or near-sightedness is extremely prevalent. It affects more
than 25 - 35% of European descent populations and up to 50% or more of
Asian descent populations.

If we did not have compensatory mechanisms for myopia and were left to
mere Paleolithic resources, it is likely myopic 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.

Studies carried out in hunter-gatherer societies and in recently
westernized hunter-gatherer groups indicate that the prevalence of
myopia normally occurs in 0-2% of the population, and most refractive
errors are less than minor. Moderate to high myopia is either non-
existent or occurs in about one person out of a thousand.

Diets high in refined starches such as breads and cereals increase
insulin levels. This affects the development of the eyeball, making it
abnormally long and causing short-sightedness, suggests a team led by
Loren Cordain, an evolutionary biologist at Colorado State University
in Fort Collins.

When these hunter-gatherer societies change their lifestyles and
introduce grains and carbohydrates, they rapidly develop (within a
single generation) myopia rates that equal or exceed those in western
societies.

In Dr. Cordain's study of 229 hunter-gatherer societies, he 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 western contact.

Hunter-gatherer diets are typically characterized by high levels of
protein, moderate levels of fat and low levels of carbohydrate when
compared to modern western diets.

The carbohydrates present in hunter-gatherer diets are of a low
glycemic index: they are slowly absorbed and produce a gradual and
minimal rise in plasma glucose and insulin levels when compared to the
sugars and refined starches in western diets.

Studies of recently acculturated hunter-gatherer populations that have
adopted western dietary patterns frequently show high levels of
hyperglycemia, insulin resistance, hyperinsulinemia and type II
diabetes. Conversely, hunter-gatherer populations in their native
environments rarely exhibit these symptoms.

In industrialized countries, this dietary shift from hunter-gatherers
occurred more slowly over the 200 or so years since the advent of the
industrial revolution as more and more refined sugars were gradually
included in the diet along with increasingly greater levels of refined
cereals.

Although highly refined sugars and cereals are common elements of the
modern urban diet, these carbohydrates were eaten sparingly or not at
all by the average citizen in 17th and 18th century Europe and only
started to become available to the masses after the industrial
revolution.

Only with the widespread introduction of steel roller mills in the
late 19th century did fiber-depleted wheat flour of a low extraction
become widely available.

Hence, over the last 200-250 years the average glycemic load of foods
in urban areas of industrialized countries has risen steadily,
primarily because of increasing consumption of refined cereals and
sugars. This increase in sugars is clearly related to increased levels
of insulin.

"Overnight Epidemics"

While fewer than one per cent of the Inuit and Pacific islanders had
myopia early in the last century, these rates have since skyrocketed
to as high as 50 per cent. These "overnight epidemics" have usually
been blamed on the increase in reading following the sudden advent of
literacy and compulsory schooling in these societies.

But while reading may play a role, it does not explain why the
incidence of myopia has remained low in societies that have adopted
Western lifestyles but not Western diets, says Cordain.

"In the islands of Vanuatu they have eight hours of compulsory
schooling a day," he says, "yet the rate of myopia in these children
is only two per cent." The difference is that Vanuatuans eat fish, yam
and coconut rather than white bread and cereals.

The theory is also 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 insulin levels. The
progression of myopia has also been shown to be slower in children
whose protein consumption is increased.

High Carbohydrate Intake Increase Insulin Levels.

This elevated level of insulin from consumption of excess grains and
sugars will serve to increase free insulin like growth factor (IGF-1)
which can then accelerate scleral tissue growth during critical
developmental stages thus leading to myopia.

A variety of studies also suggest that high carbohydrate diets may
cause permanent changes in the development and progression of
refractive errors, particularly during periods of early growth and
development.

High insulin levels from the carbohydrate loads could disturb the
delicate choreography that normally coordinates eyeball lengthening
and lens growth. And if the eyeball grows too long, the lens can no
longer flatten itself enough to focus a sharp image on the retina,

Population studies have demonstrated that people of Asian and Chinese
descent tend to be more insulin resistant than people of European
descent. The prevalence of myopia is also higher in Asian populations
than it is in European populations; it is possible that the higher
rates of myopia in Asian populations may, in part, be due to their
increased genetic susceptibility to insulin resistance.

Acta Ophthalmologica Scandinavica March 2002 vol 80, p 125
SOURCE: http://www.mercola.com/2002/apr/17/near-sightedness.htm

Sunlight may save kids' sight

Exposure to sunlight could be a critical factor in stopping children
from becoming short-sighted, Australian researchers have found.

The findings, presented to the Australasian Ophthalmic and Visual
Sciences Meeting in Canberra this week, appear to overturn the long-
held view that education and close work are the key drivers of myopia.

Instead they suggest the ability to develop myopia is strongly
influenced by environmental factors.

They will also be a boon to public health officials in the region as
myopia is reaching epidemic proportions across urban Asia.

Dr Ian Morgan, of the Australian Research Council Centre of Excellence
in Vision Science, says there has been a dramatic escalation in myopia
rates in East Asia during the past 30 years.

Morgan says 90% of conscription-aged males in Singapore are now
myopic.

This compares with figures from the 1960s to the 70s when only 20-30%
of 17-year-old males had myopia.

During the same period, rates of myopia in Australia have increased
from about 15% to 20-25%.

Morgan says it has been suggested there may be an East Asian genetic
susceptibility to environmental risk factors associated with intensive
education and urbanisation.

But he says this can be discounted because those of South Asian, or
Indian, ethnicity growing up in Singapore are as myopic as the Chinese
and Malay populations.

"This phenomenon cannot plausibly be explained in terms of changes in
gene pools," the Australian National University researcher says.

"A gene pool doesn't change that fast."

Playing outside

Instead Morgan and colleague Dr Kathy Rose, of the Faculty of Health
Sciences at the University of Sydney, have found the time children
spend outdoors is the critical factor.

A comparison of children of Chinese origin living in Singapore and
Sydney, which matched the subjects for age and parental myopia, shows
the rate of myopia in Singaporean children is 10 times higher.

But Morgan says the Sydney-based children spend significantly more
time in near-work activity, reading twice as many books per week.

The key difference in their weekly activities was in time spent
outdoors with Sydney-based children outside almost four times longer
than their Singapore counterparts.

"What children are doing in Australia at the moment seems to be
right," he says.

Dopamine

Morgan believes the exposure to sunlight cuts myopia rates by
encouraging the release of dopamine.

Dopamine is known to inhibit eye growth and myopia is a condition
caused by excessive eye growth.

Morgan says while they will begin experiments to assess this theory,
the findings are concrete enough to inform public health policy.

"The findings provide a means of prevention and are enough to start
authorities thinking about time outdoors as a public health strategy."

Morgan says a prevention strategy is needed because severe myopia
increases the risk of retinal detachment, which can lead to
blindness.

He says Singapore faces the serious public health threat of having as
much as 10% of its population developing a serious retinal problem
later in life.

SOURCE: http://www.abc.net.au/science/articles/2007/12/05/2110197.htm?topic=health