Brent Kearney

The dietary salt boogeyman has resurfaced via a New York Times article citing a study from last July in the Archives of Internal Medicine. The study examined the ratio of salt to potassium in the diets of 12 267 Americans, and concluded that a higher ratio (more salt, less potassium) presented a significantly increased risk of cardio vascular disease (CVD) and overall mortality.

At issue is the effect of sodium on nitric oxide in the body. Nitric oxide relaxes arteries, lowering blood pressure. Sodium generally blocks nitric oxide. When nitric oxide is blocked by sodium, arteries can become stiffer, and it is thought that this contributes to increased risk of CVD.

Potassium has the opposite effect: it activates nitric oxide, thus contributing to more flexible arteries and lower blood pressure, counteracting the action of sodium, and promoting better circulation. Most fruits and vegetables are food sources of potassium.

Given the basic facts of the findings, it seems immediately obvious that the solution is to balance sodium intake by increasing potassium consumption. The recommendation should be to eat more fruits and vegetables, and less fast food.

However, NYT journalist Jane Brody focusses exclusively on the top half of the ratio, sodium. There are a plethora of studies and commentary warning of the ominous danger of excessive salt intake, and this new sodium:potassium study is taken by Brody only to confirm these prior warnings. None of which took into account the mitigating effects of potassium.

This July, Scientific American published an article entitled “It’s Time to End the War on Salt”, which argued that there is insufficient evidence to support a recommendation to curtail the use of salt in food. The largest study, examining the diets of 78 million Americans, compared salt intake to CVD mortality and concluded that the more salt, the less risk of death from heart disease.

Studies that have explored the direct relationship between salt and heart disease have not fared much better. Among them, a 2006 American Journal of Medicine study compared the reported daily sodium intakes of 78 million Americans to their risk of dying from heart disease over the course of 14 years. It found that the more sodium people ate, the less likely they were to die from heart disease. And a 2007 study published in the European Journal of Epidemiology followed 1,500 older people for five years and found no association between urinary sodium levels and the risk of coronary vascular disease or death. For every study that suggests that salt is unhealthy, another does not.

The problem is that population studies do not tell you much about individuals. There are many, many variables from person to person that will influence the results of any single dietary factor, such as salt. For example, how much exercise a person gets, their genetic makeup, and the potassium in their diet.

The Sodium and Potassium study has given us a clearer idea of the association between salt intake and CVD risk: a significant factor is the ratio of sodium to potassium, not sodium alone. If you eat real food instead of processed food, you probably don’t have to worry about too much salt.

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