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In this guest post, American Heart Association president Elliott Antman, MD, explains why the organization's stance on sodium won't be shaken by the negative study published this week in JAMA Internal Medicine.
Helping people get healthier is a responsibility we take very seriously at the American Heart Association. That's why we carefully evaluate the latest scientific evidence before we make recommendations about the healthiest way to eat.
And that's why, as president of this trusted organization, I feel it is my duty to clear up some confusion about a problematic study that's been getting a lot of attention.
The study published Jan. 19 in the journal JAMA Internal Medicine suggested that lower sodium intake did not affect mortality, cardiovascular disease or heart failure for some elderly patients during a 10-year span.
Before getting into the details why this study is problematic, let me first emphasize this very important point: Everyone, except those with specific and rare medical conditions or circumstances, should take in less than 1,500 mg of sodium a day.
More than that increases the risk of high blood pressure – a deadly condition that greatly increases the risk of stroke. A large body of evidence proves less than 1,500 mg is safer for heart health -- why the American Heart Association so strongly recommends this limit.
The new study, called the Health ABC Study, is one of a handful in recent years questioning how much sodium is healthy. In each of these cases, the AHA's scientists have reiterated their concerns about the serious limitations of the research. In fact, we have published a detailed critique of these problems.
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.
Here are the basic facts about the Health ABC Study. It focused on just over 2,400 Medicare patients between the ages of 71 and 79 and studied them in three groups: Those consuming less than 1,500 mg of sodium a day; those consuming between 1,500 and 2,300 mg; and those consuming over 2,300.
The study authors asked the patients to fill out a "food-frequency questionnaire," then followed up during phone interviews every 6 months. The investigators reported that eating more than 2,300 mg of sodium per day was not associated with higher mortality.
After analyzing this study, we found several important limitations, and we feel there is nothing in this report causing us to reconsider the AHA's sodium recommendation. Here are the key limitations we found:
1. The use of a food-frequency questionnaire is an unreliable method for estimating daily sodium intake. The standard method is through a urine specimen.
2. The investigators assigned patients to the three categories of sodium intake based on the questionnaire, assuming that the estimated intake was stable and that it could be applied to the 10 years of follow-up. This assumption couldn't be verified in this study and is unlikely to be correct given the natural variation in dietary habits.
3. The sample size was small. In particular, only 291 subjects were in the less-than-1,500 per day category. This makes the study underpowered with respect to detecting the effects of eating a sodium diet recommended by the AHA.
4. The 291 participants in the less-than-1,500 group were significantly different from the other groups. They appeared to be sicker at the outset of the study, eating a median of only 940 calories a day. These people also were more likely to be on a potassium-sparing diuretic. This suggests they had conditions requiring more medical therapy.
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.
Healthcare providers, government agencies and regulators – not to mention the consumers who like to read the latest in health information – should not be distracted by problematic studies as this one.
That's not to say studies into sodium consumption are not important. The average American eats nearly 3,500 mg a day, which is more than double our recommendation. And nearly 80% of our sodium intake comes from processed or restaurant foods, so that it's very, very difficult for people who want to eat a lower sodium diet to actually do so.
How dangerous is this over-salting of our nation? Here's a powerful illustration: Recent statistics showed deaths from most cardiovascular diseases declined over a 10-year span, yet deaths related to high blood pressure actually increased 13% in that time.
A recent study projects that a national effort that reduces sodium intake by1,200 mg per day should result in fewer heart attacks and strokes and reduce healthcare costs by up to $24 billion per year
So it is urgent that we fix this problem. But we must do it the right way. We have to lower the sodium in our food supply. We have to continue to offer tools and resources so people can lower their sodium intake. And we've got to make sure people understand the seriousness of this problem.
At the AHA, we're committed to working toward these solutions, but only by using scientifically sound data. There's too much at stake to settle for anything less.
Antman is a cardiologist at Brigham and Women's Hospital in Boston. He also serves as associate dean for clinical and translational research at Harvard Medical School and a senior investigator in the TIMI Study Group. He is the immediate past chair of the American College of Cardiology/AHA Task Force on Practice Guidelines.
From the American Heart Association:
- An Effective Approach to High Blood Pressure Control: A Science Advisory From the American Heart Association, the American College of Cardiology, and the Centers for Disease Control and Prevention
- Sodium, Blood Pressure, and Cardiovascular Disease: Further Evidence Supporting the American Heart Association Sodium Reduction Recommendations