Salt and Obesity Study Hard to Swallow

By ACSH Staff — Sep 03, 2015
Does high salt consumption cause obesity? A recently published study says so, but sometimes research isn't reliable, or reliably interpreted. After giving this a shake, we've found that the results are fairly hard to swallow.

salt-shaker-1478372-639x852It's clear that obesity is a major health problem in developed countries and also that it's becoming one in the rest of the world. So it should not be surprising that significant research has been devoted to understanding the causes, consequences and efforts to discover effective treatments. But sometimes the research isn't reliable, or reliably interpreted, and that's the case with a study recently published in the Hypertension Journal.

The investigators analyzed dietary data from 458 children (average age: 10 years) and 785 adults (mean age: 49 years), obtained from four-day food intake diaries. They also analyzed 24-hour urine collections for sodium excretion a valid measure of sodium and thus salt intake. The results included the following:

  1. A one-gram increase in salt intake was associated with 28 percent increase in the risk of obesity, and a 26 percent increased risk for adults.
  2. Salt intake was greater in overweight and obese individuals than in normal weight people.

Because this was an observational study that examined the data at only one point in time, it cannot be assumed that any links between the observed association between salt intake and obesity was causal. Further, one might well expect larger people to consume more food, and thus might well consume more salt, depending on their dietary choices.

Although the authors state that their analyses were corrected for myriad of factors including demographic data, physical activity, energy intake and diet misreporting it is hard to believe that the corrections were complete. Food intake, energy intake (calculated from the food diaries) and physical activity are all notoriously hard to assess accurately. So any conclusions drawn from such data must be viewed with caution, although one of the authors of the study, Dr. Graham McGregor, was quoted as saying, "the government and the food industry now need to take much stronger action."

Dr. Ruth Kava, ACSH's senior nutrition fellow, had this reaction to the investigation: "I think this conclusion is way overblown considering the weaknesses inherent in this type of study. It is just as likely that a high calorie diet would contain more salt, and that salt intake itself is not necessarily a causal factor for obesity."

In short, it would be wise to take the results of this study with more than a grain of salt.