Study rules out the effect of one genetic variation
FRIDAY, Aug. 8 (HealthDay News) -- A British study adds more evidence for the link between dietary salt intake and high blood pressure.
The study, which included researchers at the University of Cambridge, looked at one possible genetic factor that might make people more or less vulnerable to the effects of salt intake on blood pressure -- variants of a gene for angiotensinogen, a molecule that can raise blood pressure by tightening arteries.
But the study of more than 11,000 European men and women found no relationship between variant forms of the gene and the effect of salt on blood pressure. The people who took in and excreted more salt had higher blood pressure, regardless of genetics, according to the report in the August issue of the American Journal of Clinical Nutrition.
"It is a carefully done study that strongly confirms the relationship between salt and hypertension [high blood pressure]," said Dr. Mordecai P. Blaustein, a professor of physiology and medicine at the University of Maryland School of Medicine who has done research on the mechanism by which too much salt causes high blood pressure.
"The power of this study is that it includes a very large cohort," said Blaustein, who is also director of the Maryland Center for Heart, Hypertension and Kidney Disease. "Also, they directly measured salt excretion."
Dr. Paul R. Conlin, an associate professor of medicine at Harvard Medical School, who wrote an accompanying editorial in the journal, added: "The study clearly showed that people who had elevated salt intake were the ones who had high blood pressure. That was independent of the genotype for this specific gene."
But, Conlin added, it would be an "oversimplification" to say that the angiotensinogen gene is the only gene that might influence blood pressure through salt intake. "It is clear that this is the tip of the iceberg," he said. "The hypothesis they tested was reasonable, but they only tested one gene."
Other researchers have identified genes that predispose people to high blood pressure, but they are "very uncommon," Conlin said. "The vast majority of the people we know who have high blood pressure do not carry a gene that we know of."
People shouldn't think about their genes when they salt their food, Conlin said. "You can't worry about your genotype because you can't do anything about it," he said. "This study reaffirms that salt intake has a significant effect on blood pressure, and that is clearly something that you can control."
Left untreated, high blood pressure increases the risk of coronary heart disease, heart attack and stroke.
Learn about high blood pressure, why it is bad for you and how to control it from the American Heart Association.
SOURCES: Mordecai P. Blaustein, professor, physiology and medicine, University of Maryland School of Medicine, Baltimore; Paul R. Conlin, M.D., associate professor, medicine, Harvard Medical School, Boston; August 2008 American Journal of Clinical Nutrition
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