Diabetes, the body's failure to metabolize blood sugar properly, now strikes Americans at the rate of one new case every 52 seconds. Diabetes threatens to overwhelm developing nations as they switch to Westernized lifestyles that emphasize rich foods and sedentary living.
.....
I. DIABETIC DISEASE
There are two widely known forms of diabetes. TYPE 1 is a failure of the pancreas to produce insulin. Daily injection of insulin replacement is the treatment, itself a triumph of twentieth century science. TYPE 2 is insulin resistance or impaired glucose tolerance. This model of two forms of diabetes may be too simple. Diabetes may be a whole family of related diseases. (My note: a previous article called Type 2 NIDDM.)
.....
II. THE ROLE OF INSULIN
Insulin appears to be the key factor in developing Type 2 diabetes. Some people have impaired glucose tolerance. What happens is that there is just a moderate rise in blood sugar--enough so that it silently triggers heart disease. In others, they develop insulin resistance. The insulin is produced in adequate quantity, but the body no longer responds effectively to it.
A growing trend (no pun intended) is obesity particularly in children Recent surveys suggest as many as 20% of children are overweight. As people become fatter, insulin has a harder time doing its job. Insulin resistance means a person has to produce more insulin than normal to push glucose into muscle cells. When they can't produce enough insulin because they have become heavy, their blood-sugar levels rise and they get diabetes.
Some suspect that the increase in insulin with weight gain over the long term is doing things that are bad for people. High blood pressure, high triglycerides, lower HDL (the protective) cholesterol, changes in blood clotting factors, a whole series of things linked to excessive insulin. Three out of four diabetics die of heart attacks.
(My note: why is insulin injected instead of taken in pill form? Insulin is a large molecule that isn't absorbed from the digestive tract. Merck & Co. has announced discovery of a rain forest fungus substance L-783,281 which targets insulin receptors on cells, causing large reductions in blood-sugar levels. The substance would be clinically useful in both Type 1 and Type 2 diabetes. It could be taken in pill form.)
Diabetes isn't limited to humans. All animals use insulin to exchange food for energy. But other animals stop eating when their appetites are satisfied. When animals do overeat, particularly when pets eat the same foods as their owners, they develop glucose and insulin problems. Pets can develop diabetes just like humans.
.....
III. THE CULTURAL CONNECTION
The trend toward obesity is evident here and other parts of the world. In the U.S., one of three Americans is obese. Two of three teenagers don't engage in any regular vigorous physical activity.
Asians who still have traditional lifestyles of frugality and hard work experience adult diabetes at a rate of just 1% of adults. Once Asians adopt Western diets and lifestyles, diabetes becomes rampant. Among Chinese immigrants living a modernized life in Mauritius, the diabetes rate already is up to 20% of the population.
The incidence of Type 2 diabetes among Pima Indians between the ages of 30-64 years of age in the United States today is an astonishing 50%--the highest in the U.S. When you include impaired glucose intolerance, the rate becomes 65% for contemporary Pima Indians.
Latinos, particularly Mexican-Americans acquire Type 2 diabetes when they trade health indigenous diets for fast food and sedentary lifeways. Studies cited in 1998 revealed an incidence of stress-induced psychological disorders, substance abuse, heart disease, and diabetes is twice as high for native-born and naturalized Mexican-Americans than it is for other recent immigrants.
.....
IV. "THRIFTY GENES'" A LEGITIMATE EXPLANATION?
Endocrinologists argue that our modern diet is abnormal. Most animals don't overeat: you have to force-fed them to make them fat-or put them on a human diet. The trouble in humans starts with what some call 'thrifty genes,' the ability to gain weight quickly when food is abundant in those brief periods between times of famine and want. (My note: the increased incidence of diabetes and other diseases brought on by over consumption in Native Americans is sometimes labeled as the "Native American Syndrome" in some literature.)
Diabetes is a hereditary disease. Statistics that it 'runs in families' support that comment. What happens is this: the genes that make a person vulnerable to it may be passed from generation to generation. But even if diabetes is common in a family, only the risk of diabetes is passed on to the children, NOT the certainty of developing the disease. The potentially harmful genes are expressed only in conditions of stresses such as when a person is overweight and inactive.
Arizona's Pima Indians are a striking example of how genes can interact with a lifestyle. Historically lean and healthy when they foraged or gardened in their sparse Southwestern environment, most have become very obese after adopting the high fat diet of deep fat-fried foods and sedentary living. Half of the Pima adults are now diabetic. Although their overall cholesterol levels are generally normal, heart attack deaths have skyrocketed. (My note: how are such statistics available? Registered tribal member Indians have access to the Indian Health Service which maintains excellent health records.)
.....
V. A CRITICAL REVIEW
'Thrifty genes' and the 'discordance hypothesis' make nice reading and clever teaching. These ideas have value only if they stimulate further thinking. In science, a hypothesis should tie together existing evidence and suggest new ways of verifying or refuting the hypothesis.
Here is the 'thrifty gene' hypothesis as I understand it: Humans have genes which enable fat storage when food is plentiful. By extension, IF food is too plentiful, THEN diabetes can be a result. Are you comfortable this?
Let us look at available data and see how it supports the 'thrifty gene' hypothesis. Warning: I am making this up as I go along, so be prepared to disagree! (My note: The 'thrifty gene' idea is called Neel's hypothesis. Stated briefly, it says that the diabetic tendency is an advantage in situations where people experience frequent famine cycles. )
(1) Native American Indians have lived the foraging lifestyle more recently than the American population as a whole; therefore, they should be more susceptible to an overabundance of food (and diabetes). Abundant statistics exist for various groups. The combined rate of diabetes for American Indians and Alaska Natives is over twice the rate for the U.S. population as a whole. Further, their mortality rates have increased by 550% for females and 249% for males. The highest rates are 35% for Pimas, 29% for Cherokees, 17% for Navajo, on down to under 9% for Eskimos. (My note: the cited statistics for Blacks is 10.2% and non-Hispanic Whites is 6.4%.) Our opening statement has many assumptions; however, these data suggest at least that something is going on with these groups.
(2) As people shift from low sugar/low fat diets to contemporary Western eating habits, diabetes should increase. What do we see? Diabetes rates are rising in such diverse groups as Asian Indians, Australian Aborigines, Chinese, Eskimo, mainland and migrant Japanese, and Polynesians. These rates seem to come more from environmental factors than biologic differences. Dietary change is suggested as a major culprit.
(3) Obesity, a consequence of food abundance, should correlate with diabetes. Actually, obesity doesn't correlate as well as does the diet itself. Said differently, obesity's relationship to diabetes is NOT as clear is it is for diet. Obese individuals whose fat is concentrated in the upper body are more susceptible to diabetes than individuals whose fat is concentrated below the waist. Read this slowly: body fat deposition varies for Whites, Blacks, and other groups. Low economic status and low education correlate with fat distribution. Duration of obesity is also positively correlated with diabetes.
(4) The lower incidence of diabetes in Whites and Blacks is because of natural selection: before insulin treatment, diabetics died before reproducing. This is theory; I have no numbers to verify or refute this one. Sorry.
(5) Increased consumption of sugar should associate with diabetes. Sugar can contribute to weight gain and require more insulin, a possible detriment to our bodies. Diets high in simple carbohydrates are positively associated with diabetes while diets high in complex carbohydrates are negatively associated with it. (A quick primer on carbohydrates: They are complex molecules formed by photosynthesis. A large part of our diet is carbohydrates in the form of starch and sugar. We cannot digest complex ones such as cellulose )
.....
Viable research in this field now focuses on the molecular genetic mechanisms that contribute to increased susceptibility to Type 2 diabetes. Epidemiology has made its case.
.....
VI. FETAL PROGRAMMING?
Epidemiologic research has focused new interest in the influence of the in utero environment on subsequent health. The mother's health during pregnancy can leave a lasting legacy in a person' life. See "Where Health Begins" Newsweek September 27, 1999.
..... CJ'99
Resources
Gorner, P. "Scientists find trigger for juvenile diabetes" Chicago Tribune Augst 31, 1999
Haynes, V. "Immigrants pay for American way" Chicago Tribune October 12, 1999.
Kotulak, R. "Deadly downside for good life--diabetes" Chicago Tribune February 5, 1995.
Langreth, R. "Merck Discovery May Lead to Pills for Diabetes" Wall Street Journal, May 7, 1999
Nickter & Nickter Anthropology and International Health Australia: Gordon Breech, 1996.
"Obesity-linked diabetes rising in kids" Kankakee Daily Journal November 6, 1998.
Overfield, T. Biologic Variation in Health and Illness 2nd ed. Boca Raton: CRC Press, 1995.
"Studies find more adult-type diabetes in minors" Chicago Tribune June 20, 1999.