Salt: How Bad Is It, Really?

Much like cell phones and eggs, salt is one of those things that studies say is bad for you one day, but O.K. the next.

Just last year, an article in the New England Journal of Medicine estimated (using previous studies' numbers) that the U.S. could prevent 44,000 deaths annually if Americans reduced their salt intake by 3 grams per day.

Then, early this month, a review of seven real-life interventions to reduce salt consumption found nothing of the sort. The review, from the Cochrane Collaboration, found only ambiguity, with no evidence to suggest that salt reduction did the trial participants any good or any harm.

"It's Time to End the War on Salt," a headline in Scientific American proclaimed last week. "For every study that suggests that salt is unhealthy, another does not," the article said. As if to prove that point, a new paper this week in the journal Archives of Internal Medicine now argues, again, that too much salt is bad.

The latest study used national U.S. survey data linked to mortality files to show that the more salt people ate, the higher their death rates from all causes combined. The study looked further at salt intake in relation to potassium intake, and found that the lower people's potassium and the higher their sodium, the more likely they were to develop heart disease or die of a heart-related cause.

So just how bad is salt for us exactly — and why is there so much disagreement on the issue?