Personal & Professional Encounters with Salt

 

At about the time I entered medical school it was discovered that a low salt diet was very good treatment for dropsy, now known as congestive heart failure.  A few years later during my wife’s first pregnancy, I gave up salt in the spirit of an ornery kid brother.  Her obstetrician ordered the diet, and she said it wasn’t fair because it was our baby and she had to give up salt.  From my point of view not eating salt was no big deal and I have never resumed eating it.  An unexpected benefit has been that I have seldom had to get up at night to urinate. Incidentally my wife stopped adding salt after her (our) second pregnancy.  We have salt shakers only for guests (but not ash trays).

 

Several times during my career otherwise healthy patients complaining of nocturia have been relieved of getting up at night by cutting down on salt.  A partial exception was a young farmer with this complaint whom I met one summer.  Initially, cutting down on salt did not help his nocturia very much until I found that he drank mostly milk instead of water.  In hot weather, this might add up to two gallons each day.  The knowledge that milk is the saltiest natural food (1/2 teaspoon per quart) finally stopped his excess urine production at night.  Salt is retained in the body longer than plain water and it hangs on to the water, or induces thirst, until the salt is eliminated.  There is evidence from controlled experiments that salty snacks increase soft drink consumption in some modern Americans, especially those of us who almost never drink plain water (1).  Cultural biases definitely influence health.

 

When my grandchildren’s parents were babies, salt appeared on the list of ingredients of commercially prepared jars of baby food.  I tried to imagine how salt got into baby food because obviously the babies couldn’t care less.  However, mothers taste baby food in order to mutter something like, “mm, mm, good.”  Market research must have shown that the mothers say it with more enthusiasm if the baby food is salted.  I am pleased to report that there are some saner heads out there than market researchers, pediatricians for example—added salt is disappearing from infant food.

 

Through the years there were a number of reports of studies showing small increments of increased blood pressure in proportion to salt intake.  Salt intake can be easily and accurately averaged as 24 hour urine excretion of salt because over time, what goes in comes out.  Then a report came along with much appearance of authority, like many references to peer reviewed literature (2), purporting to show that salt intake had no influence on health in people without heart disease.  This report was widely mentioned in sources available to the general public as reported to me by my patients.

 

A report of the Council on Science and Public Health of the American Medical Association to their House of Delegates on June 13, 2006 as report #10 of this council was summarized in the Archives of Internal Medicine for July 23, 2007 (84 references) (3). Here is a quotation from their conclusions.

“Substantial public health benefits accrue from small reductions in the population blood pressure distribution, achievable with long term modest reduction in sodium.   A 1265 mg/d lower lifetime intake translates into an approximately 5 mm Hg smaller rise in SBP [systolic blood pressure] as individuals age from 25 to 55 years.  This corresponds to a 20% lower prevalence of hypertension and a reduction in mortality rates of 9% for CHD [coronary heart disease], 14% for stroke, and 7% for death from all causes and would save 150,000 lives annually……

 

“An appropriate target is a stepwise, minimum 50% reduction in sodium in processed foods, fast-foods, and restaurant meals to be achieved in the next decade.  In addition, physicians and other clinicians should educate patients about the benefits of  long term, moderate reductions in sodium intake.  Substantial cooperation among the government, the food industry, physicians, and the public will be required to accomplish meaningful change and enable a larger proportion of the population to experience the long term benefits of reductions in dietary sodium intake.  However, with an appropriate food industry response, public education, and knowledgeable use of food labels, consumers will be able to choose a lower sodium diet without inconvenience or loss of food enjoyment.  In the absence of substantive voluntary actions, regulatory measures to limit sodium in processed and restaurant foods and/or to require warnings or recognizable symbols on the labels of high sodium products will be required.”

 

These rather definitive conclusions and recommendations suggest to me that some agnotology was at work in postponing action on reducing unnecessary salt intake by the general public.  Agnotology is the science of promoting ignorance.  It was honed to a near-perfect edge for about 40 years by the tobacco industry in delaying the public’s appreciation of the proven harm of smoking.  Did the salt industry use some similar “spin doctors” to those used in behalf of tobacco?

 

I can offer some personal testimony to the harmlessness of giving up added salt ever since my early adult life.  In spite of a lifestyle of accepting heavy exertion – up to 100 miles bicycling or climbing up to 9000 feet in a day (multiple mountains in one day is called “peak bagging”) – none in our family have needed salt beyond that naturally present in food.  We have carried salt in our emergency kit when backpacking and never used it or felt any ill effects from not using it. The primary problem is dehydration.  Normal kidneys, if required to do so, can excrete urine virtually free of salt and sweat glands can acclimatize to heat by reducing the salt content of sweat to 1/10 that of blood and other extracellular fluids (where most body sodium is located).  So up to 2 gallons of sweat per day can be accommodated by the amount of salt naturally present in food.  An early experience illustrates this point.  I noticed that the Swiss chard tasted salty. After being reassured that none had been added, I looked up the natural salt content of various foods.  Swiss chard and celery were  the record holders.  These quantities of salt are minor compared to the salt added in commercially processed food.  So don’t cut out Swiss chard if you are on a low salt diet.  Incidentally, my success in getting along without any added salt even with heavy exertion in hot weather might have been aided by involuntary salt consumption for convenience.

 

At one point I asked the manufacturer of canned and dried soup, “Why is salt-free soup more expensive than salted soup?”  The answer was that salt-free soup requires better quality control because salt covers up minor off tastes.  I confirmed this with some tainted unsalted home canned tomato juice (one bad spot must have crept in).  On blind testing of this juice salted and salted “perfect” juice were indistinguishable to all participating friends and relatives.  In plain English, salt may be a cover-up for defects in taste. Obviously, this is less pertinent to modern requirements with canning, freezing and dehydration available for food preservation.

 

Summary:  even a moderate decrease in dietary sodium of the total population will result in a significant reduction in not only high blood pressure but also stroke, heart attacks, and (surprise!) obesity because of less spurious thirst and resulting soft drink consumption.

 

John A. Frantz, MD

September 3, 2007

                                                             References

1)  He, FJ et al. Effect of Salt Intake on Renal Excretion of Water in Humans. Hypertension.  2001. 38 (3): 317-20

      2)  Porter GA. Chronology of the Sodium Hypothesis and Hypertension. Ann Intern Med. 1983. 98 (5pt2): 720-3

3)  Dickinson, Barry D. and Hovar, Stephen. Reducing the Population Burden of Cardiovascular  Disease by Reducing Salt Intake.  Arch Intern Med. 21 July 2007. 167 (14): 1460-68

 

 

 

              Never fight evil as if it were something that arose totally outside yourself.

                                                                       Saint Augustine