Mary Beth Genter served as a roving reporter at the SOT 2013 Annual Meeting and submitted the article below.
We all thought that it was pretty straightforward—too much salt is a risk factor for developing high blood pressure, right? And reducing salt intake is good for everyone, right?
Depending on who you ask, and how you ask the question, you might be surprised by the answers!
A basic problem is that we all consume too much salt. Without going into excruciating detail, guidelines for desirable levels of daily salt intake range from 1500 to 2300 mg/day. Most of us are well out of that range, averaging 3800 to nearly 5000 mg/day.
In reviewing the findings of a systematic review of the issue of sodium intake and health effects, Niels Graudal set up the question as follows: there is positive evidence for a relationship between salt and blood pressure, and also a positive relationship between high blood pressure and mortality; can we then assume that there is some link between salt intake and mortality?? In order to demonstrate that we might not get the answer that we expect, Dr, Graudal presented data showing that while beta blockers certainly do lower blood pressure, they do not, unfortunately, improve survival. In examining the effect of sodium reduction, people with normal blood pressure showed no further improvement in either systolic or diastolic blood pressure readings. However, sodium reduction did improve blood pressure in people with high blood pressure—so does decreased sodium intake in these people also decrease mortality? Sorry—no direct evidence, he says.
In fact, data presented by Dr. Graudal showed that dramatic reduction of sodium intake can actually increase the secretion of the hormone renin, which is a major regulator of blood pressure. More renin, higher blood pressure. Very low blood levels of sodium were also associated with increased aldosterone, noradrenaline, and adrenaline—again, without going into details, these are all normal physiological responses, but not necessarily desirable at all times. A representative of the salt industry, Mr. Satin, also pointed out that there are associations between very low blood sodium levels and morbidities such as Type 1 and Type 2 diabetes, as well as loss of cognition. Data from Dr. Graudal’s systematic review also showed some evidence for increased cholesterol, and stronger evidence for increase in blood triglycerides with decreased blood sodium levels.
So what are we to think?? Another investigation, provided by Dr. Paul Whelton, might help put all of this into perspective. The studies reviewed in Dr. Graudal’s Cochrane review included studies of very sick individuals, and many of the studies, while well conducted and credible, had actually been designed to answer another question and were then re-analyzed to assess relationships between sodium intake/blood levels and various health outcomes. Dr. Whelton presented from the perspective of observational studies. These are cross-sectional studies specifically designed to study the relationship between sodium and blood pressure. The bottom line of his evaluation was quite black and white: first, high quality observational studies have demonstrated a strong positive relationship between sodium intake and blood pressure. Second: we ALL eat too much salt! Sodium intake is roughly broken down as follows: ~75% from processed foods, ~5% each for salt added during cooking and at the table, and 12% naturally occurring. He urged the processed food industry to continue its efforts to gradually lower the sodium content of processed foods. During the panel discussion, we learned that if salt intake is gradually reduced, individuals don’t miss it, and when re-introduced to their previous level of consumption, they find that level of salt “too salty”.
I’ll skip the salt on my next margarita glass, please!