Scientists generally accept that 24-hour urine samples are the most accurate means of measuring sodium intake -- the "gold standard" for dietary sodium just as randomized controlled trials are the "gold standard" in the hierarchy of levels of evidence.

With that as background, how should we understand the claim by the Heart and Stroke Foundation (Canada) which "revealed" today that "500,000 kilograms of salt have been removed from the food supply in the last four years by companies participating in the Health Check program." HSF's health policy director equated the amount to "20 dump trucks of salt."

On its surface, the claim is that the total food sold over the past four years bearing a Health Check logo contains a half million kilos less salt (that figures to 550 tons of salt). Every year, Canadians consume about 130,000 tons of salt. So over four years, Canadians consumed a half billion tons of salt (520,000). In other words, this effort is claimed to reduce Canadians' salt intake by 0.1%.

But is it true? The claim can only be evaluated if we also know the answers to these questions:

1. Compared to the baseline four years ago, what was the composition of the foods bearing the HSF label? If the quantities and/or configuration of the sales differed, what can be said about the 500,000 gram number? If people, for example, are eating less of these foods (because they don't taste good or cost more) the number is invalid. But even more:
2. Compared to baseline, what other foods are Canadians eating and in what quantities? If they are eating less salt in Health Check foods, are they simply eating that salt in other foods?

No, the entire exercise is entirely bogus.

What we need to test the proposition (and we're all for the test!) is to track the total sodium consumption for a representative sample of Canadians randomized to consume a diet including as much as possible all the Heart Check foods and compare that over a year or two, with those randomized into a control group which eats whatever they want. The outcome would be ascertained by frequent collection of 24-hour urine specimens and the analysis done in blinded fashion.

Evidence suggests that physiology determines sodium consumption, not package labels. If an individual consumes "low salt" foods, they may simply eat additional quantities of food (and extra calories) to satisfy this innate "salt craving" automatically determined by the body to reflect that individual's varying need. That's why research shows such a consistent pattern of salt intake between populations and over time .