MadSci Network: General Biology

Re: Can iris color change ( become lighter) in humans to do to raw food diets?

Date: Sat Dec 18 15:35:13 2004
Posted By: Peter Bosani, Independent
Area of science: General Biology
ID: 1102720503.Gb

Hello, from Idaho.
They say the eyes are the window of the soul.  Doctors can tell a lot when 
looking into the eyes of their patients.  A whole pseudoscience has 
developed around this practice, called iridology, the study of the iris as 
associated with disease.  Dr. Stephen Barret, who runs an 
excellent web site on, has called iridology a dubious 
Color changes in the iris begins after birth.  For example, most Caucasian 
babies have blue eyes and begin to darken as they age, whereby their true 
color usually sets in by 6 months.  Afro-Americans and some other darker skinned
peoples are born with brown eyes and their eyes remain brown for life.  The 
pigment in the eyes are due to cells known as melanocytes, and heredity 
determines one's eye color.  The more melanin, the darker the color.  When 
these cells are deeper in the eye, the color produced is blue or green, 
resulting from the way lightwaves are scattered by the melanocytes.  When 
they are closer to the surface, the eye is brown.  Albinos have eyes that 
appear pink, because the melanocytes which ordinarily masks blood vessels, 
are lacking.
The reason you've never noted any contrary evidence to the claim that 
eating raw food causes the eyes to change color is because this doesn't 
happen.  If there were such a link, scientists and the general population 
would have noticed this connection by now.  There is no scientific 
evidence that eating any type of diet, raw or otherwise, will change one's 
eye color.
A quick perusal of the web quickly elucidates where this claim is coming 
from.  Practitioners of iridology, naturopathy and 'New Age', are just a 
few.  There are many claims and anecdotes that's made by members of such 
groups, however, they are hard pressed to prove these claims when measured 
against rigorous scientific studies.
Many foods are eaten raw, such as fruits, nuts and vegetables.  The 
Japanese culture eats many raw foods, such as sushi.  There are those who 
like steak tartare, or savor eating raw oysters, clams or other mollusks, 
while others prefer drinking 'raw' milk or downing raw eggs.  The problem 
with eating raw foods, in general, is a significantly higher risk of food 
poisoning from bacteria, which otherwise would be killed by cooking.
Cooking helps break down fiber, carbohydrates and protein, making for 
easier digestion and release.  It increases the nutritive value of foods, 
making them more bioavailable, such as in carrots, spinach and tomatoes, 
by releasing greater amounts of carotenoids.  It makes food edible that 
would otherwise be inedible or unpalatable.  It brings out the aroma and 
flavor of food, enhancing appetite and contributes to the pleasure of 
eating.  Although cooking, and especially overcooking, has its drawbacks, 
its benefits outweigh the risks.  In short, cooking improves one's health.
Indeed, the late Carleton Coon, an American anthropologist and leading 
authority on the peoples and cultures of North Africa and the Middle East 
wrote, that cooking was "the decisive factor in leading man from a 
primarily animal existence into one that was more fully human."
Be careful when reading from the web, and try to search out scientifically 
based organizations for more accurate information.  I strongly recommend, -
Hope that helps,
Peter Bosani.

References:  The Family Health and Medical Guide - Publisher - Doubleday
             Food in History - Author - Tannahill
             Food and Nutrition- Life Science Library

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