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How Much of a Risk Factor is Ethnicity?
January 26, 2007
Three recent studies have shed some light on why particular ethnic groups seem to be at a higher risk for chronic health conditions such as heart disease and some types of cancer. It appears that certain modifiable lifestyle factors, often involving diet, may be largely responsible for the variations in disease risk factors between different ethnic groups.
First, a study published in the January 2007 issue of the American Journal of Clinical Nutrition looked at how much carbohydrate members of different ethnic groups usually ate and their cholesterol and triglyceride levels. To do this, researchers analyzed the diets and lipid profiles (or blood fat levels) of 619 Canadians of Native American, South Asian, Chinese, and European descent.
The researchers found that people of South Asian descent, the group that ate the most carbohydrate, had the lowest levels of HDL, or “good,” cholesterol, while people of Chinese descent ate the least amount of carbohydrate and had the highest levels of HDL cholesterol. (Europeans ate the second-highest amount of carbohydrate, followed by Native Americans.) HDL cholesterol helps keep the body’s blood vessels from becoming clogged, and therefore helps protect against cardiovascular disease (heart disease and stroke).
The relationship between increased carbohydrate consumption and decreased HDL cholesterol levels held fast among all of the study’s participants, even when factors such as age, ethnicity, body-mass index, and alcohol consumption were controlled for. Drinking and eating sugar-sweetened soft drinks, juices, and snacks in particular were linked with lower HDL cholesterol levels. Triglyceride levels, which are associated with heart disease risk, were also found to increase as people’s carbohydrate intakes increased.
These findings led the researchers to conclude that it may not be ethnicity itself, but rather patterns of carbohydrate consumption, that help explain differences in cholesterol and triglyceride levels between ethnic groups. While some previous studies have found that differences in blood fat levels between ethnic groups couldn’t be explained by genetics, obesity levels, lifestyle factors, or diet, this new study’s researchers point out that the older studies usually looked at dietary fat intake, rather than carbohydrate intake, when analyzing the diets of the different groups.
Another study, published in the January 17 issue of The Journal of the American Medical Association, sought to discover why people from South Asian countries (India, Pakistan, Bangladesh, Sri Lanka, and Nepal) tend to have more heart attacks at younger ages than people from other countries.
Over a period of four years, the researchers recorded information and took measurements and blood samples from thousands of people who had had a first heart attack and people of the same age and sex who had not had a heart attack from both South Asian countries and other countries around the world.
After analyzing the data, the researchers concluded that the South Asian people had higher levels of several heart disease risk factors at younger ages, such as smoking, high blood pressure levels, and a history of diabetes. They also found that people from South Asian countries had significantly lower rates of exercise and fruit and vegetable intake than people from other countries. Exercise and fruit and vegetable intake were found to offer protection against heart attack by other studies examining both South Asian and other populations.
The researchers concluded that there was probably not a novel risk factor for heart disease in people of South Asian descent. Rather, they stated that “modifying behavior related to known risk factors could lead to a substantial impact” in reducing risk of early heart attack in the South Asian population.
Finally, in a study published in the January 2007 issue of The Journal of Nutrition, researchers tried to determine why African-Americans develop colon cancer at a substantially higher rate than any other ethnic group in the United States (more than 1 in 2,000 are diagnosed) while native Africans have a very low rate of colon cancer (less than 1 in 100,000). To do this, the researchers compared the diets and results of medical tests (including blood tests and colonoscopy) of 17 African-American people, 18 native African people, and 18 white American people aged 50–60 years old. They found that, while all groups had similar body weights, blood pressure levels, and fiber intake, both the African-American and white American groups ate much more red meat and animal fat than the native Africans and also showed more markers of colon cancer risk in their medical tests.
Previous research has shown that, as a group, African-Americans consume more beef and pork than other ethnic groups in the United States.
The study’s authors wrote in their conclusion, “Why do AAs [African-Americans] get more colon cancer than NAs [native Africans]? The answer is that they live in different environments. … Our study confirms the USDA figures that suggest Americans, and particularly AAs, consume excess quantities of animal protein and fat and lead us to the conclusion that a healthier lifestyle that includes less meat and more fruit, vegetables, grains, and exercise should be beneficial not only for the colon but also for general health.”
Further research will hopefully shed more light on the question of whether ethnicity is a true risk factor for certain medical conditions. According to the American Diabetes Association’s Standards of Medical Care in Diabetes—2007, being a member of a certain ethnic group (African-American, Latino, Native American, Asian-American, and Pacific Islander) is a risk factor for developing diabetes.
No matter what ethnic group a person belongs to, having diabetes increases his risk of developing cardiovascular disease, so making healthy lifestyle changes to reduce cardiovascular risk is an important part of diabetes management.
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