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Salt, Science And The American Heart Association's Double Standard

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Once again the American Heart Association is sticking by its recommendation that pretty much everyone should consume no more than 1,500 milligrams of sodium each day. This is dramatically lower than the 3,500 mg/d the average American now consumes. In a blog post reprinted on MedPage Today the president of the American Heart Association,  Elliott Antman, assails a study published earlier this week which found no benefits-- and even a hint of harm--  for elderly people with low sodium consumption.

But Antman only tells one side of the story.

On the one side, Antman attacks the study with gusto and precision. His analysis is a model of how to take apart a study. Here's what he concludes:

Given the small sample size of this observational study, the limitations of the methodology and the unreliability of the assumption of a stable dietary pattern over a decade, these findings should not be used to formulate dietary recommendations in the elderly.

Antman is absolutely correct in his analysis of the study and in his conclusions. It is far from a perfect study and by itself should have little or no impact on the salt debate. Antman links the AHA's position on salt to an even greater commitment to the principles of science. The AHA, he writes is "committed to working toward... solutions, but only by using scientifically sound data." Here is his impressive statement of principle:

For a science-based organization dedicated to saving and improving lives, confusion about something as dangerous as excess sodium is unacceptable. We owe it to the public to provide the most scientifically sound dietary advice.

Double Standard

But Antman has a confused notion of what constitutes scientifically sound advice. If you only read Antman's post you would think the study under attack was a lonely island in a sea of overwhelming evidence supporting the AHA guideline. You'd never know that for decades there's been a lively, heated scientific debate over the salt recommendations. Antman doesn't tell you that there is much more additional evidence casting doubt on the AHA recommendation than this week's study. And Antman doesn't tell you that the scientific basis for the AHA recommendation is at least as weak as the scientific basis for opposing views.

I think a "science-based organization" has an obligation to present all the important evidence and to fairly and accurately reflect the diversity and complexity of scientific opinion. There is no broad scientific consensus about salt.

To cite only 2 important recent developments: in 2013 the prestigious Institute of Medicine published a report concluding that there’s no evidence to support current efforts to lower sodium consumption to less than 2,300 mg/day. And then last summer the New England Journal of Medicine published two papers from the PURE study that also did not support the AHA recommendation. PURE-- like all studies in this field-- is far from perfect, but it was much more rigorous than the study assailed this week by Antman.

Just how divided is the field? The NEJM papers were accompanied by an editorial that also expressed disagreement with the AHA low salt recommendations. Unless and until there is better evidence, "the results argue against reduction of dietary sodium as an isolated public health recommendation," wrote the editorialist, Suzanna Oparil.  Here's the kicker: Oparil is, herself, a former president of not only the American Society of Hypertension but also Antman's own American Heart Association. I find it remarkable that the current AHA president doesn't feel it necessary to note an opposing view from his own predecessor.

Finally, it is important to note that the evidence base for the AHA recommendation is itself extremely weak. In fact, there is NO evidence from good clinical trials or even epidemiological studies showing that lowering sodium intake in a large population is beneficial. The AHA logic, instead, is this:  lowering salt reduces blood pressure, lowering blood pressure reduces cardiovascular disease, therefore lowering salt reduces cardiovascular disease. Now that is a reasonable hypothesis but there are a host of reasons why it might not be true. Last year, in a publication that accompanied the PURE papers in the New England Journal of Medicine, a group of top investigators performed a detailed analysis that predicted there would be very large health benefits as a result of the population-wide blood pressure lowering effect of salt reduction. But, wrote Oparil, “given the numerous assumptions necessitated by the lack of high-quality data, caution should be taken in interpreting the findings of the study.”

I've written before that I think guidelines are necessary but that they can also be dangerous. Like war, they should be waged only when there is overwhelming evidence and consensus. The American Heart Association needs to be especially careful in this regard. As I've said before, there's widespread speculation that the AHA's earlier guidelines on cholesterol and diet, which demonized fats starting back in the 1980s,  may have had the catastrophic consequence of pushing people to consume more carbohydrates, including sugar. We will probably never know the full extent of the damage, but many have speculated that this may have contributed to the obesity and diabetes epidemics. Let's make sure this doesn't happen again with salt.