Sodium intake linked to obesity

A new US study has drawn a link between high sodium intake and obesity in teenagers. Dr Haidong Zhu, a molecular geneticist, found a correlation between salt and fatness, and also inflammation.

In a study of 766 healthy adolescents, 97% self-reported exceeding the American Heart Association’s recommendation to consume less than 1500 mg of sodium daily.

“The majority of studies in humans show the more food you eat, the more salt you consume, the fatter you are,” said Dr Zhu, who researches at the Medical College of Georgia and the Institute of Public and Preventive Health at Georgia Regents University (GRU).

“Our study adjusted for what these young people ate and drank and there was still a correlation between salt intake and obesity.”

Study participants who had a high sodium intake also had high levels of tumour necrosis factor alpha, which is secreted by immune cells. It contributes to chronic inflammation and is implicated in autoimmune diseases like lupus and arthritis.

The teenagers also had high levels of leptin, a hormone produced by fat cells that normally suppresses appetite and burns fat. However, at chronically high levels, leptin can have the opposite effect.

“Losing weight is difficult, but hopefully more people can be successful at reducing their sodium intake,” Dr Zhu said.

“We hope these findings will reinforce for parents and paediatricians alike that daily decisions about how much salt children consume can set the stage for fatness, chronic inflammation and a host of associated diseases like hypertension and diabetes,” said Dr Gregory Harshfield, Director of the Georgia Prevention Center at GRU and study co-author.

While this study does not claim to prove a causal effect, the authors say it contributes to mounting evidence that high sodium could be a direct cause of obesity and inflammation.

“Obesity has a lot of contributing factors, including physical inactivity,” said Dr Zhu. “We think that high sodium intake could be one of those factors.”

The researchers say longitudinal or randomised clinical trials are needed to clarify the relationships.