We have unnatural and incorrect diets. Prehistoric people didn’t have supermarkets or McDonald’s; they had to live off from the land. None of our ancestors had supermarkets and fast food restaurants. They grew their own vegetables, baked their own bread and killed their own meat. We’re not really adapted to doing all that today, but we could still eat a natural diet.
The other factor which our ancestors did not have was TV and computers. The kids didn’t spend all day in front of the boob tube or playing computer games. They were out working and getting exercise.
Myopia is becoming a worldwide condition. No one race seems more susceptible than another. For many years it was thought that myopia was caused by reading, because the myopia rate was lower in the population with no formal education and didn’t read books. So, wearing glasses was a sign of intelligence. They didn’t even realize that the people in the two groups ate different diets. The people with no formal education were the poor people and they ate food they grew and hunted. The formal education group could afford to eat more processed foods.
Studies have shown that when groups of people left primal living behind and moved on to a more urbanized existence, myopia rates increased within a single generation. This happened too quickly to be genetic. Certain hunter-gatherer tribes have very low rates of myopia, but when given a western diet of highly refined carbs, their myopic rate was equal to those who had never eaten a natural diet.
It has been argued that the different lifestyle between our long ago ancestors and the people of today could also be based on the fact that we do a lot more reading, TV watching and computer work. So, the diet cannot be the deciding factor.
However, the diets that are high in proteins and fats and low in carbohydrates don’t produce a spike in blood glucose and insulin levels in our bloodstream. We know that high glucose levels leads to diabetes and diabetes raises havoc with our eyesight. When societies that previously had low myopic rates, changed their lifestyles and introduced a high carbohydrate diet, they rapidly developed myopia rates that equaled or exceeded those in western societies.
Christopher Hammond conducted a study in the Twin Research and Genetic Epidemiology Unit of St. Thomas’ Hospital in London (which was published in the American Journal of Human Genetics), of 506 pairs of unselected twins. This study inferred the heritability of refractive error. Refractive error is a common complex trait measured on a continuous scale, with myopia affecting 25-61% of the population. This is taking environment out of the equation and just using genes as a measurement. The study has identified several genes that may be involved including PAX6, known to be important in the development of the eye.
Even with this study, overwhelming evidence points to the fact that our unhealthy lifestyle is the leading cause of myopia. An astounding thing came to light recently that confirmed this. Dogs don’t read, watch TV or use the computer. Wild dogs do not have myopia but some domesticated dogs do. Why, because wild dogs eat meat and domesticated dogs are fed high carb based dog food and table scraps. Exactly the same pattern found between our hunter-gatherer ancestors and our own couch-potato, high carb lifestyle. Maybe when we have to start buying glasses for our pets, we will change our not so healthy habits.