An Argument for Not Reducing Salt Intake

Canadians across the country found out that the salt levels in popular processed foods were significantly higher in our country than in the same foods in other countries, thanks to a survey conducted by World Action on Salt and Health (WASH). In a Globe and Mail article by Carly Weeks, we’re told that a serving of All-Bran cereal in the U.S. contains 160 milligrams of sodium while the All-Bran sold in Canada contains a whopping 620 milligrams; one third of the Daily Recommended Intake (DRI).

The salt issue is one that is fraught with controversy. This Globe article, and indeed many health experts in the field, maintain that high salt intake causes high blood pressure and in turn causes cardiovascular disease, a proposition that is far from settled in the scientific literature.

Since the late 1970s, the the Canadian public have been told to eat less salt. In 2003, guidelines were set out by the Institute of Medicine Electrolyte DRI Committee saying 2300mg of salt should be the upper limit per day and in 2005 added that 1500mg should be the target upper limit for those with hypertension (high blood pressure). But what if how much salt we eat has less to do with how much is unknowingly included in our meals and more a result of complex Central Nervous System controls?

This is the position put forward in a recent study published in the Clinical Journal of the American Society of Nephrology (CJASN). The study maintains that we are, in fact, hardwired to consume a certain amount of salt.

The study reviewed surveys done in the UK over the past two or three decades that found sodium intake has varied little in that time. UK populations surveyed fell within a very specific range of salt intake (117 mmol/d to 212 mmol/d as measured by urinalysis). They also looked at a US study that found those who were blindly given excess salt in the form of a tablet naturally regulated their salt intake through diet, maintaining a constant rate and, surprise surprise – subjects innately maintained sodium levels of about 176 mmol/d on average; smack dab in the middle of the range of salt levels observed in the UK study.

So what does this mean? This study’s authors argue that humans maintain a pretty constant level of salt intake – between 2,700 and 4,900 mg per day – despite increases from unknown sources.

In light of this information, the idea that public policy can control the physiological human need for sodium is questionable. As Dr. McCarron, lead author of the study puts it “we’ve been wired in our brains to consume salt within a very narrow range, to maintain our bodies’ functions. That range, at its very lowest limit, is 20 percent higher than what the government is telling us is the upper limit for the normal population. The average around the world … is over 60 percent higher than what the government is telling us that we should consume.” How relevant are sodium target numbers if your body is telling you something different? Given the body’s inherent control mechanisms, how relevant are those numbers period?

So this brings us back to Canadian processed foods and their significantly higher levels of sodium. Unless Canadians differ drastically in the physiological makeup of those in the US and UK, which I would argue they don’t, it can be assumed that we’re innately regulating our salt intake just like the rest of the world. Are Canadians actually consuming more salt? Sure our processed foods have more salt, but at the end of the day, are we failing to self-regulate our salt intake through other foods in our diet? Or could there be an unseen factor leading to Canadians desiring higher salt content in their foods?

Dr. Ed Stricker, a professor of neurology at the University of Pittsburgh and an expert in salt appetite was quoted in the Post-Gazzette, expressing concern that people who are following low sodium recommendations could be consuming too little sodium. Too little sodium could possibly be just as dangerous as too high sodium. “Your blood pressure is going to be too low, your kidney function isn’t going to be what it should be, there are a host of secondary problems.”

And in the outrage over salt content of processed foods, did anyone check to see if Canadian hypertension rates are higher than those in the US and UK? Or the rest of the world? Admittedly, I was unable to find this information, but it seems an important question to ask in the interest of testing our assumptions about high salt intake, if there is indeed such a thing.

The Healthy Foodie is Doug DiPasquale