My son, who works in Belgium, sent me the recent Journal of the American Medical Association (JAMA) salt study, knowing that I had served on the Institute of Medicine’s (IOM) sodium committee. I asked him what he thought and here’s his answer, verbatim: “Salt is bad! I think the fact that they try to claim that decreasing salt can actually hurt you in the long run is just an attempt at sensationalism.”
For the confirmed “non scientist” in the family, I think he hit the nail on the head.
I’m not a medical doctor, never mind a cardiologist, but I recalled my final biochemistry degree paper (many years ago) on cell wall transport mechanisms as we started our deliberations at the IOM. The critical role of sodium potassium channels came back to me, and I recognized that most of us consume less potassium than sodium, despite a need for at least 2–3 times more potassium. The IOM’s committee’s goal was to develop strategies to reduce sodium consumption in the United States, not to evaluate the science supporting this need. However, given past failures to reduce consumption, we concluded that aggressive strategies were required and to justify these we did spend significant time reviewing the basis of that science. I will not take up space here to review that, rather refer those interested to the IOM report appendix which summarizes 40 years of reports and recommendations from the United States and around the world.
Statisticians teach us that one or two data points will often lie outside the “line” so we should expect to see the occasional study that appears to contradict the need for the vast majority of us to reduce sodium consumption. Some of these may be better designed and more representative than this study. Again, there have been several excellent reviews over the past week pointing out the shortcomings of this study, but to me the most obvious relate to the sample.
Although the study quotes a sample size of 3,681, the conclusions about cardiovascular disease (CVD) are based solely on the 84 who died during the study. The low number is probably due to the good health and the young average age of the sample. The inference that only a small percentage of people should be concerned about sodium consumption is misleading, since here in the United States those aged 50 or older have a 90% probability of developing hypertension.
Another weakness is that sodium intake was only determined for a single day over the course of the study and no calorie or other nutritional data was collected. There is an 80% correlation between caloric intake and sodium consumption so the high sodium group would almost certainly have higher caloric intake. Hence, there are many other factors not tracked in this study which would lead to the reported weak inverse correlation between sodium consumption and CVD.
Sodium is safe and necessary, but only up to a point … and most of us are way past that point!