Salt Consumption: Less Is Not Always Better

After a week of trying to track my salt consumption I have learned two things
1. Tracking salt consumption (unless you make  all your meals at home from scratch or buy from fast food restaurants) is very tedious.
2. My salt consumption is low: less than the 1.5 grams per day recommended by the American Heart Association (AHA) every day (unless I attend a Cardinals game)
After reviewing the latest scientific publications on salt, however, I have to think that for most people, it is not worth the effort to  track daily salt consumption.
Yes , this is nutritional heresy and goes against what my patients have been reading from authoritative nutritional sources for decades.
The AHA 1.5 gram/day limit for all Americans comes from a small, short term (4 weeks) study (Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. N Engl J Med2001;344:3-10.)
The findings are not applicable to all Americans because more than 50% of participants in the DASH study had hypertension or prehypertension, more than 50% of participants were of African ancestry, potassium intake was markedly lower than in the general U.S. population, the trial involved only 412 persons, and a limited range of sodium intake was studied (1.5 to 3.3 g per day).
I asked most  of my patients this week about their salt consumption. None of them could tell me what their average daily salt consumption was. However, almost to a man (or woman) they told me they had been consciously limiting their consumption of salt because they knew that this was healthy.
Thus, the 35 year old white woman with a blood pressure of 110/50 , palpitations and periodic dizzy spells is following the same recommendations to limit salt consumption as the 70 year old African-American with poorly controlled hypertension.
In the last few years this focus on lower salt consumption has been questioned after close analysis by the Institute of Medicine and the Cochrane Analysis.
Two articles in the prestigious New England journal of Medicine published a few weeks ago have convinced me that most individuals who are following a Mediterranean diet do not need to be concerned about their salt consumption.

Salt and Blood Pressure

In the first PURE study paper,(a prospective cohort study that included 101,945 people from five continents)

very few participants had an estimated sodium intake of less than 2.3 g per day, and almost none had an intake of less than 1.5 g per day. This suggests that, at present, human consumption of extremely low amounts of sodium for prolonged periods is rare.

The PURE Study looked at sodium excretion versus blood pressure and

 found a steep slope for this association among study participants with sodium excretion of more than 5 g per day, a modest association among those with sodium excretion of 3 to 5 g per day, and no significant association among those with sodium excretion of less than 3 g per day.

Salt and Death

The second PURE study paper examined the relationship between sodium excretion (a measure of sodium consumption) and death and cardiovascular events

 

This graph of data from the PURE study  shows that lower levels of sodium excretion , below about 3 grams per day were associated with a higher risk of death.
Starting above about 5 grams per day  the risk of death increased with increasing amounts of sodium excretion.
 
This is quite a shocker for those of us who have assumed for the last 20  years that the less salt we consumed the longer we would live.
 

Potassium Consumption

Drawing less controversy were the findings from these two studies on potassium consumption. Higher levels of potassium consumption were associated with lower blood pressures and lower risk of death. The authors point out that high potassium intake may simply be a marker of healthy dietary patterns that are rich in potassium (e.g., high consumption of fruit and vegetables).
You can read more about these papers, including critical and positive comments at the heart.org here.

My Recommendations on Salt Consumption

Here is what I will be telling my patients about salt after a week of tracking my consumption and reading the relevant scientific literature.

• Spend a day or two accurately tracking your consumption of salt to educate yourself. I found this app to be really helpful. I’ll expand on this in a future post.
• Recognize that not everybody needs to follow a low salt diet. If your blood pressure is not elevated and you have no heart failure you don’t need to change your salt consumption.
• If your blood pressure is on the low side and especially if you get periodic dizzy spells, often associated with standing quickly liberalize your salt intake, you will feel better.
• If you have high blood pressure, you are the best judge of how salt effects your blood pressure. In the example I gave in a previous post, my patient realized that all the salt he was sprinkling on his tomatoes was the major factor causing his blood pressure to spike.
• The kidneys do a great job of balancing sodium intake and sodium excretion if they are working normally. If you have kidney dysfunction you will  be more sensitive to the effects of salt consumption on your blood pressure and fluid retention.
• If you are following a Mediterranean diet with plenty of fresh fruits and vegetables you are going to be in the ideal range for both potassium and sodium consumption.

Public health experts are always seeking a “one size fits all” message to give the public. In the case of salt consumption, however, the message of less is better does not apply to all.