High sodium intake and obesity may act synergistically to accelerate cellular aging in adolescents, according to new research presented Thursday afternoon at the American Heart Association's EPI/NPAM Scientific Sessions 2014.
The study examined the effect of a high salt diet on telomere length in normal weight and overweight/obese teens.
After controlling for factors known to shorten telomeres, researchers observed a statistically significant interaction between weight and sodium intake. Telomere length was significantly shorter in overweight or obese adolescents who had a high sodium intake than in those with low sodium intake (telomere to single gene (TS) ratio, 1.24 ±0.22 versus 1.32 ± 0.21; P=0.02). The same was not true among the normal-weight teens (TS, 1.29 ± 0.24 versus 1.30 ± 0.24; P=0.69).
Telomeres are the protective end-caps on chromosomes that shorten with each round of cell division. When they reach a certain critical length they signal the cell to stop dividing.
Previous studies have suggested that telomere shortening influences cellular aging, and smoking, emotional stress, advancing age, and lack of physical exercise have all been shown to reduce telomere size.
Researcher Haidong Zhu, MD, an assistant professor of pediatrics at the Medical College of Georgia in Augusta, said the new study is among the first to suggest that increased salt intake may also shorten telomere size.
"It is well known that a high salt diet is an important risk factor for hypertension and cardiovascular disease, but the impact of a high salt diet on cardiovascular aging has not been well understood," she told MedPage Today. "This is early research, and it needs to be replicated. But it does suggest that high sodium intake impacts the telomere shortening process."
The study included 766 adolescents between the ages of 14 and 18 who were divided into two salt-intake groups based on self-reported 7-day, 24-hour food-frequency questionnaires. From these assessments it was determined that the low-intake teens consumed, on average, 2,388 mg/day of sodium, while high-intake teens consumed 4,142 mg/day of sodium.
The American Heart Association recommends consuming no more than 1,500 mg of sodium a day -- or about 2/3 of a teaspoon.
After adjusting for age, sex, race, energy intake, Tanner stage, and vigorous physical activity, multiple linear regression analysis revealed that higher dietary sodium intake was associated with shorter leukocyte telomere length in the overweight and obese teens, (beta=-0.37, P=0.045), but not in the teens whose weight was normal.
Zhu said lowering sodium intake in the diets of overweight and obese adolescents by encouraging them to limit processed foods and eat more meals cooked at home may be a more effective strategy for lowering their future heart disease risk than simply telling them to lose weight.
The study was funded by the National Heart, Lung and Blood Institute.
Primary source: American Heart Association Epidemiology & Prevention/Nutrition, Physical Activity & Metabolism Scientific Sessions 2014
Source reference: Zhu H, et al "High sodium intake is associated with short leukocyte telomere length in overweight and obese adolescents" AHA EPI/NPAM 2014; Abstract #MP64.
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