Minority groups not genetically prone to diabetes

A study by Australian and US researchers is helping dispel the 40-year-old "thrifty genotype theory' " that certain minority groups are genetically prone to diabetes.

The study, co-authored by UC Irvine anthropologist, Michael Montoya and an epidemiologist and population geneticist, analysed existing genetic studies published across a variety of disciplines.

The team found no evidence to support the widely-held thrifty genotype theory, which suggests that cycles of feast and famine early in human history created a gene that helps the body use scarce nutrients " a gene that leads to obesity and diabetes in comfortable, sedentary modern lifestyles.

"Our study challenges the presumption that Native American, Mexican American, African American, Australian Aborigine, or other indigenous groups are genetically prone to diabetes because the evidence demonstrates that higher rates of diabetes across population groups can be explained by non-genetic factors alone," said Montoya.

The study helps explain why more than 250 genes have been studied as possible causes of type-2 diabetes, but together these genes explain less than 1% of diabetes prevalence worldwide.

"When it comes to diabetes, we're finding that genes are no more important for ethnic minorities than for anyone else," said Stephanie Fullerton, a population geneticist and bioethicist at the University of Washington and co-author of the study.

Also, it was found that in most existing studies of the suspected genes that contribute to diabetes in ethnic minorities, researchers failed to control the potential impact of social and environmental factors.

Controls would have enabled researchers to see that other factors " such as poverty, housing segregation or poor diet " were stronger indicators of diabetes than genes.

Montoya argues that in order to gain a better understanding of the causes of type-2 diabetes, future research efforts will require interdisciplinary teams that assess social, historical and environmental factors as carefully as researchers have studied the genetic factors.

The findings are published in the spring issue of the journal Perspectives in Biology and Medicine.