WHO SAYS A TEASPOONFUL WILL DO?

Such studies are re-drawing the battle lines around salt. Foodmakers are starting to fight back against the low-salters. Campbell’s is now putting more salt back into all 31 of its Select Harvest soups after consumers voted with their taste buds and stopped buying the reduced-salt version.

“One size doesn’t fit all,” says Juli Mandel Sloves, Campbell’s senior manager for nutrition and wellness communications. “And what this research debate shows is exactly that. You can’t make a recommendation based on the needs of only one part of the population. It’s really important that we offer a variety of choices.”

Other major food industry groups and manufacturers approached by Reuters, including Kellogg’s and Pepsico, as well as the U.S. Grocery Manufacturers’ Association, either declined to be interviewed or sent statements reiterating their commitment to reducing sodium levels in their foods, in line with government dietary recommendations.

But the powerful U.S. National Restaurant Association is questioning the accepted wisdom. “The science is very clear in showing that reducing sodium reduces blood pressure. There’s no question about that. The controversy is around reducing cardiovascular disease and ... basically the risk of death. That’s where the evidence is completely weak,” says Joy Dubost, the NRA’s Director of Nutrition and Healthy Living. In other words, cutting back on salt does reduce blood pressure, but it may not reduce the risk of dying early.

Michael Alderman, a blood pressure expert at Albert Einstein College of Medicine in the United States and editor of the American Journal of Hypertension, believes there’s a sense that some scientists - and most policymakers - may have moved too early to target salt as the cause of the problem. “If we’re doing something so dramatic to the diets of whole populations, there should be no argument. The evidence should be overwhelming, but it’s not overwhelming at all,” he said.

Of around a dozen scientists interviewed by Reuters for this story, about half shared this point of view; but since they included salt-reduction campaigners and salt industry representatives, that is not necessarily an indicator of the balance of opinions across the scientific community.

Alderman argues that in addition to changing blood pressure, cutting sodium can cause other physiological changes such as increased resistance to insulin - which can set the stage for diabetes and increase the risk of death from heart disease. Too little sodium can also increase sympathetic nerve activity which raises the risk of heart attacks, and boost the secretion of aldosterone, a hormone produced by the adrenal gland that is bad for the cardiovascular system.

“What we have - like almost all interventions in health and medicine - is something that produces a multitude of different effects,” said Alderman, who disclosed having taken one $750 payment more than a decade ago from the Salt Institute, but who said he has since had no financial help from the industry. Besides Alderman and Heagerty, none of the other academic scientists interviewed for this article have disclosed financial interests.

In a letter to the British government seen by Reuters, the UK’s Salt Association - which along with the Salt Institute has a vested interest in defending the salt industry - cites the Cochrane and JAMA papers and demands an urgent review of the salt reduction strategy. It goes as far as to say: “People may actually be dying as a result of poorly founded advice.”