It appears another devil has been found to be not so evil, and that the real devil is once again in the details. Conventional medical wisdom has preached for years that salt is evil and should be avoided at all costs. The US government perpetuated this by making it part of their dietary recommendations to limit salt below 2.3g/day.
It is becoming an all too common occurrence, but was once again we should be shocked to find out how the government based its strong recommendation on extremely suspect data (see the previous blog on fat intake). Their decision to firmly recommend low salt intake for the general population came from a single trial that followed people for only 30 days. It is true that the DASH trial showed a reduction in systolic blood pressure by reducing salt to less than 2.3 g per day (NEJM 2001;344:3-10). However, it turns out that the absolute BP reduction was only 5mmHg/2mmHg. Hardly earth shattering. In addition, since the trial was so short there was no data on clinical outcomes (i.e. reduced heart attacks, strokes etc.). Once again, a government guideline that shaped medical dogma came from very limited data.
We now know that the data was not only limited, but also clinically misleading. Since 2001 there have been no trials showing a correlation with low sodium intake and reduction of heart attack, death or stroke. So although it may mildly reduce BP, it doesn’t help people clinically. Does this sound familiar? To me it sounds awfully similar to some type of fat increasing an LDL level but not having a direct increase on heart attack, stroke, or cardiovascular death. Clearly one measure does not tell the whole story.
Why is this an issue now? There was a recent article in the San Diego Union Tribune talking about a study that showed how salt may be potentially beneficial for wound healing (it was a small study in mice so I am not convinced it will apply to humans yet), and in addition, the WSJ had a recent “point and counterpoint” article about the benefit or risk of a low salt diet. Both articles highlighted the evidence that has come out over the past few years showing salt intake to not be as dangerous as once thought, and that salt restriction may actually be where the danger lies.
What is the evidence? A 2014 paper looked at data from 23 different studies and showed there was a U-shaped outcome for salt intake. U shaped meaning there was an INCREASE in harmful outcomes at both low (less than 3 g per day) and high (greater than 7 g per day) levels of sodium intake. Specifically, they looked at the risks of heart attack, stroke or cardiovascular death (Am J HTN 2014 Apr 26). This confirmed the findings of a 2011 study (JAMA 2011;306(20):2229) showing the same conclusion. In fact, in 2013, a committee at The Institute of Medicine officially said there was no scientific reason to recommend less than 2.3g of daily sodium intake (the AHA has yet to change its position despite the preponderance of evidence).
How can this be? Is there any potential scientific rationale as to why low sodium intake could increase a patient’s risk? The proposed mechanism of low-sodium causing adverse cardiovascular outcomes is that decreased blood flow to the kidneys can trigger a harmful hormonal response with associated downstream clinical effects. This is not a proven mechanism, but it is always nice to know that there is at least a plausible hypothesis for our scientific findings.
Once again we are confronted with the reality that the medical community and population as a whole need to continuously question the rationale for guidelines and official recommendations. We need to rely on outcome-based studies and use those preferentially to frame our recommendations.
(Keep in mind; however, avoiding sodium restriction would not apply to individuals with poorly controlled hypertension, or patients with a weakened heart muscle and congestive heart failure. And on the other side, avoiding high sodium intake would not necessarily apply to high performance athletes at risk for excessive sweat loss.)
We can rest assured that we no longer need to enforce a restrictive low-salt diet in the general population. So if you are so inclined, dust off the old salt shaker with a smile.
However, we also have to remember that medicine, health and wellness is not a one size fits all treatment program. We are each different and unique in our own way, and that applies to our sodium sensitivity as well. At Boundless Health we evaluate every client as an individual. We work closely with you to develop an individualized health and wellness program that works specifically for you. Together, we can start on your path to optimal health and wellness.
Please contact us today to find out more about what Boundless Health has to offer, and how we can help you achieve your health and wellness goals!
Bret Scher MD FACC
President, Boundless Health
Titleist Level 1 Certified
NASM Certified Personal Trainer
Best Evidence Summary
|1- Sodium intake above 2.3g/d can modestly increase BP2- There have been no proven adverse clinical effects of sodium intake between 3-7gm/d|
3- Sodium intake below 3gm/d or above 7gm/d have both been associated with increased risk of heart attack, heart failure or death
4- In the absence of poorly controlled hypertension or heart failure, there is no clinical need for sodium restriction aside from excessive intakes above 7gm/day
5- Previous recommendation for low salt diet was based on a small trial over 30 days showing a modest increase in BP. No clinical outcomes were measured.
Approx. amount of sodium for a given amount of table salt