Research news from Tufts University, Friedman School of Nutrition Science and Policy: February 2004


Extra Pounds Paired with Certain Genes May Increase Heart Disease Risk

As public health experts calculate the number of overweight or obese people in America at 45 million, researchers are delving into the relationship between carrying added weight, genetics and coronary heart disease. Jose Ordovas, PhD, a professor at the Friedman School of Nutrition Science and Policy, and his colleagues found that men carrying a certain gene, called APOE 4, who were also obese or overweight, were in a "double bind." They were more likely to be insulin resistant, a condition that which makes it less likely that their bodies will burn excess fat. Insulin resistance makes active muscle cells unable to take up glucose easily, therefore the blood insulin and glucose levels are higher, inhibiting fat cells from giving up energy stores. Obese individuals have an increased risk for insulin resistance. In simple terms, "their genes were against them once they put on extra weight," explained Ordovas.

In a recent study published in the journal Obesity Research, Ordovas and his colleagues at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, examined both obese and non-obese men who were divided into three groups, each of which had a different form of the gene Apolipoprotein A (APOE). The three forms of the gene are APOE2, APOE3, and APOE4. APOE is known to regulate cholesterol levels in the blood. The researchers found that men who were of a normal weight all had glucose and insulin levels lower than those of the obese men, regardless of what gene they carried.

Interestingly, obese men with the APOE4 had higher levels of insulin and glucose in their blood than those with normal weight and those who were obese and did not carry the gene APOE4. Therefore, Ordovas and his colleagues concluded that men who carry APOE4 and who are obese are at an increased risk for coronary heart disease, while normal weight men with APOE4 are not. The study authors conclude that weight control as a means of reducing insulin and glucose levels is an important component of heart disease prevention for everyone, but it may be especially crucial for men who carry the APOE4 gene form. Such individuals especially, should follow a balanced, low-fat diet and adopt a regular exercise routine, Ordovas recommends.

Losing Weight Helps Reduce Inflammation and Disease Risk

Many people associate inflammation with arthritis, but now emerging research supports the idea that inflammation can also increase the risk of high blood pressure and heart disease. The good news, summarized in the February 2004 edition of the Tufts University Health & Nutrition Letter, is that inflammation can be treated with dietary modifications. One of these is losing excess weight. Ernst Schaefer, MD, professor at the Friedman School of Nutrition Science and Policy, comments that "anti-inflammatory eating is nothing if not calorie-controlled eating." Schaefer specializes in research on nutrition, genetics, lipoproteins, and cardiovascular disease risk and leads the Lipid Metabolism Lab at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts.

Doctors can detect inflammation by measuring the levels of C-reactive protein (CRP) in blood. In one recently published study, researchers measured CRP levels in women 45 years or older. After eight years, they re-examined the women and discovered that those who developed high blood pressure had had high levels of CRP. They also noted that women who were overweight tended to have the highest levels of CRP overall. According to Schaefer, losing weight especially around the middle is the most important way to lower CRP levels, and thereby reduce the risk that comes along with inflammation.

The Tufts University Health & Nutrition Letter suggests eating food that contains omega-3 fatty acids, which lead to the production of substances in the body that inhibit inflammation. Fish, such as salmon and fresh bluefin tuna, are good sources.

Eat Carrots Rather than Supplements: Research Shows High Doses of Beta-carotene Can Be Harmful

Research has shown that beta-carotene and other carotenoids have anti-cancer activity by blocking certain cancer processes and tumor cell growth. Large studies have also shown that people who consume diets rich in carotenoids have a lower risk of cancer, especially lung cancer. But the results of two large-scale studies show reason for concern when taking "mega doses" of the vitamin. They both show that very high doses increase the risk of lung cancer, by 18 percent in one trial and 28 percent in another. The researchers were testing what is considered a "mega dose." While the government has not set a safe standard for beta-carotene, it does recommend a daily allowance for vitamin A, a nutrient that is derived from beta-carotene. The most likely way for people to consume very high doses of beta-carotene is through supplements; it is highly unlikely for a person to consume too much beta-carotene from food.

According to Robert Russell, MD, director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, "Beta-carotene's paradoxical effects on lung cancer appear to be related to dose. I'm concerned that the public perception of something as 'natural' is that it is safe, even at very high doses." In a recent article in the Journal of Nutrition, Dr. Russell explains that laboratory models that simulate human metabolism should be used to thoroughly test nutrient doses that greatly exceed normal dietary levels before embarking on large-scale trials. Without these results, the effect on people may be unexpected and even harmful, as was the case with using unnaturally high doses of beta-carotene.

According to Dr. Russell, also a professor at the Friedman School of Nutrition Science and Policy, "When talking about lung cancer risk as a physician, I'd recommend that the most important action is for people is to stop smoking but those who do continue to smoke put themselves at high risk if using high doses of beta-carotene." Beta-carotene is still promising as an anti-cancer nutrient, but the protective dose seems to be best obtained from dietary sources such as fruits and vegetables at natural levels. "Experiments have taught us that simply taking a natural product at any dose is not wise. Dose does count," says Russell. The lesson: more is not always better. For now, the best way to ensure an adequate intake of antioxidant nutrients, such as beta-carotene, is by eating five to nine servings of fruits and vegetables per day, Russell advises.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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