The study investigated whether high salt intake is linked to cellular aging by assessing its association with leukocyte telomere length, especially in the context of obesity - finding that high dietary sodium intake was associated with shorter telomere length in overweight and obese adolescents "suggesting that high sodium intake and obesity may act synergistically to accelerate cellular aging."
Led by Dr Haidong Zhu of Georgia Regents University in the USA, the team noted that some studies have suggested the increased early onset of conditions such as high blood pressure (hypertension) and type 2 diabetes may be because the aging process in children and adolescents is accelerated - resulting in the premature development of 'adult' diseases.
Previous research has also found that the protective ends on chromosomes (known as telomeres) naturally shorten with age, but the process is accelerated by smoking, lack of physical activity and high body fat.
The new data, presented at the American Heart Association's Epidemiology & Prevention/Nutrition, Physical Activity & Metabolism Scientific Sessions 2014, is the first to examine the impact of sodium intake on telomere length.
"Lowering sodium intake, especially if you are overweight or obese, may slow down the cellular aging process that plays an important role in the development of heart disease," said Zhu.
As part of the study 766 people aged 14-18 years old were divided into the lowest or highest half of reported sodium intake. Low-intake teens consumed an average 2,388 mg per day, compared with 4,142 mg per day in the high-intake group.
Both groups consumed far more than the 1,500 mg per day maximum recommended by the American Heart Association, said the study.
After adjusting for several factors that influence telomere length, researchers found:
In overweight and obese teens, telomeres were significantly shorter with high-sodium intake, with a T/S ratio of 1.24 vs. 1.32. The T/S ratios is the ratio of the length of the telomere to the length of a single gene.
However, in normal weight teens, telomeres were not significantly different with high-sodium intake (T/S ratio of 1.29 vs. 1.30).
"Even in these relatively healthy young people, we can already see the effect of high sodium intake, suggesting that high sodium intake and obesity may act synergistically to accelerate cellular aging," said Zhu.
The team noted that obesity is associated with high levels of inflammation — which also speeds up telomere shortening — and increases sensitivity to salt, which may help explain why higher sodium intake had a greater effect in that group.
"Lowering sodium intake may be an easier first step than losing weight for overweight young people who want to lower their risk of heart disease," added Zhu.
"The majority of sodium in the diet comes from processed foods, so parents can help by cooking fresh meals more often and by offering fresh fruit rather than potato chips for a snack."