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News

Affluence bringing increase in diabetes, researcher says

University Of Chicago : 05 June, 2004  (Technical Article)
Soaring global rates of adult-onset diabetes will shorten the lives of hundreds of millions of people unless humanity starts to grapple with a deadly genetic legacy from its stone-age past, a prominent evolutionary biologist suggested Wednesday in the British journal Nature.
Looking at diabetes rates among nine different populations in 24 regions, along with their food history, including farming techniques, westernization and urbanization, Jared Diamond found that diabetes rates have risen in lockstep with living standards for the populations most prone to the disease.

'Diabetes is a disease of increasing affluence. People eat three meals a day and risk developing diabetic symptoms when they have more money,' said Diamond, a professor of geography and environmental health sciences at the University of California at Los Angeles.

Among the more susceptible populations, he said, are U.S. Latinos and African-Americans, Pacific Islanders, Arizona's Pima Indians, westernized Australian aborigines and urban Asians and East Indians.

Diamond's research supports the long-standing 'thrifty gene' theory, which assumes an evolutionary advantage for people whose genes promote metabolism and storage of fat, thus allowing carriers to better survive periodic famines.

In times of plenty, however, those same genes contribute to insulin resistance, obesity and diabetes.

Asset becomes liability
'Much like the gene that protects against malaria but also predisposes so many people of African-American ancestry to sickle cell anemia, the thrifty gene is an asset that becomes a liability when circumstances change,' Diamond said.

Diamond hopes his findings will sound the alarm for what he sees as an exploding global problem that can be confronted through improved awareness, diet and exercise. Although the disease was largely unrecognized as recently as 30 years ago, there are now an estimated 160 million cases worldwide.

'At its present rate of increase, within a few decades adult-onset diabetes will become one of the world's commonest diseases and biggest public health problems with an estimated half a billion cases,' Diamond wrote in Nature.

Diamond's previous studies and popular books have challenged long-held theories of human development, winning him a Pulitzer Prize and the National Medal of Science. Other scientists seemed startled by his latest conclusions.

'Jared Diamond is always interesting and comes up with wonderful stories,' said population geneticist Chung-I Wu, chairman of the department of ecology and evolution at the University of Chicago. '[But] such hypotheses remain to be tested. Any genetic disease, cystic fibrosis, lactose intolerance, diabetes, has a hypothetical history that has yet to proved.'

The populations with the highest rates of adult-onset diabetes tend to be very small and isolated, Wu pointed out.

'Every such population has its own private disease. It's not that Darwinian natural selection favors these disease-causing genes. It could be due to chance alone. Small populations, by definition, tend to be very inbred.

'For example, color-blindness, like diabetes, is also on the rise. But what evolutionary advantage could it give us to be color blind?'

Adult-onset (or Type 2) diabetes, the most common form, is characterized by high blood-sugar levels caused by altered insulin secretion and resistance. People with Type 2 diabetes produce the hormone, but their bodies are unable to respond effectively to it.

If left unchecked, elevated blood sugar levels can result in heart attacks and strokes, blindness, kidney damage and nerve destruction leading to loss of limbs.

Diamond's research also offers a novel theory about why only 2 percent of native Europeans are diabetic, compared with 13 percent of African-Americans, 17 percent of U.S. Latinos and up to 50 percent of Native Americans.

He speculates that a diabetes epidemic occurred in Europe from about 1600 to 1800 as food became more plentiful.

'European states got more efficient about transporting food to places where there were famines,' he said. 'New World crops like corn, potatoes and tomatoes came into Europe during that period, so there was a greater variety of crops and less risk of crop failure.'

Because no treatment existed for diabetes, it could have wiped out many of the people who carried predisposing genes, he said.

Bach among victims?

Diamond suggests composer Johann Sebastian Bach might have been among the victims, noting his sedentary lifestyle. At one point in Leipzig, Bach composed a cantata a week for five years.

'The corpulence of his face and hands in the sole authenticated portrait of him, the accounts of his deteriorating vision in his later years and the evident deterioration of his handwriting, possibly due to his failing vision, are all consistent with Type 2 diabetes,' he said.

Europeans who immigrated to the U.S. and Australia, however, were a mostly poor population whose thrifty genes would not have been wiped out.

'The upper classes had already been enjoying good food for centuries and been dying of diabetes and losing their thrifty genes,' Diamond said. 'The people who came here to better themselves brought the genes with them. That could account for the difference in rates.'

The research merits a warning, Diamond said. 'If I'm correct, Type 2 diabetes is going to get a lot worse in countries that never had very much of it before. It pays to warn the Chinese about diabetes before millions of them come down with it.'
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