Intended for healthcare professionals

Rapid response to:

Clinical Review

Myopia

BMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7347.1195 (Published 18 May 2002) Cite this as: BMJ 2002;324:1195

Rapid Response:

Myopia Possible LInk to Increased Refined Carbohydrate Intake and Hyperinsulinemia

Dr. Fredrick’s excellent review of myopia fails to acknowledge that
diets high in refined starches such as breads and cereals increase insulin
levels that can adversely affect ocular development and predisposition to
myopia.

Studies(1)carried out in hunter-gatherer societies and in recently
westernized hunter-gatherer groups indicate that the prevalence of myopia
normally occurs only 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.

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.

Cordain’s review (1) of 229 hunter-gatherer societies 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.

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.
In the islands of Vanuatu they have eight hours of compulsory schooling a
day, 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.

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 number of studies (1) 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.

(1) Cordain L, Eaton SB, Brand Miller J, et. al. An evolutionary
analysis of the aetiology and pathogenesis of juvenile-onset myopia. Acta
Ophthalmol Scand. 2002 Apr;80(2):125-35. National Library of Medicine
Link

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&lis...

Competing interests: No competing interests

18 May 2002
Joseph Mercola
Medical Director Optimal Wellness Center
Schaumburg, IL 60194