By James Beckerman, MD, FACC
Doctors don’t like to be told they may be wrong.
During my medical training and subsequent experience as a cardiologist in clinical practice, I find it striking how despite our track record of innovation and research, we as a profession are not too crazy about the threat of paradigm shifts, particularly when it comes to the definition of a “heart-healthy” diet.
Low in cholesterol. Low in saturated fat. Low in trans fats. Low in refined carbohydrates. Low in processed meats. And the list of lows goes on. When we look back upon the evolution of heart-healthy recommendations, some of our guiding principles are based more on common sense than on long-term research data, and more recent approaches — though sometimes more scientific — sometimes arise from the popular press as well as from scientists breaking from the “party line.”
How do we continue to advance our recommendations in accordance with science, yet avoid providing mixed messages to the public, let alone our physicians?
By now, you have probably heard about the American Journal of Hypertension meta-analysis of 167 studies that was published today. Its purpose was to estimate the effects of various levels of salt in our diets on various markers of cardiovascular risk, like high blood pressure, lipids, and some stress hormones. The conclusion was that despite a small reduction in blood pressure, a lower-salt diet was associated with a worsened lipid profile and higher levels of stress markers of future heart disease.
So what’s a salt-shaker to do?
I probably wouldn’t invest in a salt mine quite yet. While this study does ask some interesting questions, it is a meta-analysis as compared to a placebo controlled prospective study. This means that researchers combined the results of many very differently constructed research studies to form their results. The downside of this design is that some conclusions can occur as the result of chance. In general, we try to avoid making medical recommendations based upon this approach.
The other concern is that we still don’t have very good evidence for or against sodium with respect to its actual impact on heart attacks or other hard endpoints. We tend to measure its impact on risk factors instead, as they are easier to study.
However, I believe that it would be a mistake to ignore this research. I think that this study presents an opportunity for other scientists to create new proposals to readdress the low-salt diet question — and hopefully be able to draw additional conclusions. This report reignites the issue. Sometimes we forget, but that’s a good thing in science. Even if it does sometimes make us feel uncomfortable.