Salt intake, obesity go hand in hand

A study published in the journal “Progress in Cardiovascular Diseases” refutes the frequently repeated claims that a comprehensive salt reduction would not produce any overall health benefits, or would even increase diseases and shorten the life-span.

Professors, Dr. Heikki Karppanen of the University of Helsinki and Dr. Eero Mervaala of the University of Kuopio report that an average 30-35 % reduction in salt intake during 30 years in Finland was associated with a dramatic 75 % to 80 % decrease in both stroke and coronary heart disease mortality in the population under 65 years. During the same period the life expectancy of both male and female Finns increased by 6 to 7 years.

The most powerful explaining factor for the favorable changes was the more than 10 mmHg (“point”) decrease in the average blood pressure of the population. A marked decrease in the average cholesterol levels of the population also remarkably contributed to the decrease of heart diseases. The extensive use of drugs contributed less than 10 % of the observed decreases in blood pressure, cholesterol, and cardiovascular diseases.

“To our surprise, the sales figures of the American Salt Institute divulged that salt intake increased more than 50 % in USA during 15 years from mid-1980s to the late 1990s”, says Professor Karppanen. The study reports that the prevalence of high blood pressure, which had long shown a decreasing trend, turned to a marked increase concomitantly with the increase in salt intake.

Perhaps the most interesting finding of the study is the close link between salt intake and obesity. The study reports that increasing intakes of sodium (salt) obligatorily produce a progressive increase in thirst. The progressive increase in the average intake of salt explains the observed concomitant increase in the intake of beverages which, in turn, has caused a marked net increase in the intake of calories during the same period in the United States.

Between 1977 and 2001, energy intake from sweetened beverages increased on the average by 135 % in the United States. During the same period, the energy intake from milk was reduced by 38 %. The net effect on energy intake was a 278 kcal increase per person a day. The American Heart Association has estimated that, to burn the average increase of 278 kcal a day and avoid the development or worsening of obesity, each American should now walk or vacuum 1 hour 10 minutes more every day than in 1977. Unfortunately, this has not been the case.

In a decade from 1976-1980 to 1988-1994 the prevalence of obesity increased 61 % among men and 52 % among women. During 1999 to 2002, the prevalence of obesity was 120 % higher among men and 99 % higher among women as compared with the 1976 to 1980 figures. The increased intake of salt, through induction of thirst with increased intake of high-energy beverages has obviously remarkably contributed to the increase of obesity in the United States.

It is noteworthy that, until 1983 the use of salt did not change or even showed a continuous decreasing trend in the United States. The prevalence of obesity was relatively low and remained essentially unchanged from early 1960s to early 1980s. The study suggests that a comprehensive reduction in salt intake, which would reduce the intake of high-energy beverages, would be a potentially powerful means in the so far failed attempts to combat obesity in industrialized societies.

The authors conclude that there now is conclusive population-wide evidence, which indicates powerful beneficial health effects of comprehensive salt reduction. Decrease of obesity is now added to the previous list of recognized benefits. The population-wide long-term experience from Finland indicates that a remarkable decrease in the salt intake has not caused any adverse effects. Professor Karppanen states that “the repeated warnings of various industries on possible harmful effects of comprehensive salt reduction are unjustified and even unethical”.

From University of Helsinki

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5 thoughts on “Salt intake, obesity go hand in hand”

  1. Is the “silly season” of US elections spilling over into anti-salt advocacy? Drs. Heikki Karppanen and Eero Mervaala assert that their study “refutes the frequently repeated claims that a comprehensive salt reduction would not produce any overall health benefits, or would even increase diseases and shorten the life span.” It does no such thing.

    As president of the Salt Institute, I should point out that we have made the argument frequently (and, apparently, someone is listening!) that observational studies of health outcomes fail to identify population health benefits at levels common in the North American diet — and advocating a controlled trial of reduced salt diets to determine whether they decrease heart attacks and cardiovascular mortality.

    That is the right question, but this claim that low-salt diets “would be a powerful means against obesity” is just over the top. Of course, if we made foods so unpalatable as to stop people from eating as much (as has been done with less-than-happy results in geriatric institutions) we might be able to link salt and body mass, but to assert “The increased intake of salt, through induction of thirst with increased intake of high-energy beverages has obviously remarkably contributed to the increase of obesity in the United States” with no evidence adduced to support the allegation is irresponsible.

    The authors specifically cited Salt Institute statistics of U.S. salt sales saying that salt intake had increased “more than 50%” over a recent 15 year period. That’s wrong. In response, I wrote Dr. Karppanen:

    “Your concern with increased salt intakes is obviously misplaced. While salt intakes in the U.S. have increased in the past 15 years, they track population increases. The U.S. population is 300 million today. We’ve added 50 million in population in those years. I know population growth is something a bit foreign to your part of the world, but we’ve experienced a lot of immigration and natural population growth. Even so, our latest figures show food salt sales growth up 41%, not “over 50%” and while greater than the population growth, this does not account for US food salt which is exported in US processed foods, salt used in food processing and wastage. The better metric, as I’m sure you agree, is 24-hour urines and those in study after study show that baseline salt intakes per capita are unchanging generation after generation.

    “Of course, correlation is not causation, but to correlate salt intake with the rise in obesity ignores evidence that those on higher salt diets are actually leaner than other Americans. Just as obviously, the longest-lived national population in the world, the Japanese, have much higher salt intakes than Americans. Your “obvious” correlation of salt intake and thirst and obesity makes interesting headlines, but sorry science.”

    The Finns claim salt reduction is responsible for increasing the life span of their compatriots by 7-8 years over the past one-third century. Let’s keep in mind, Romans lived to an average age of 28. The Yanomamo people of the Brazilian jungles who are touted as low-salt-consuming models for our diet live only into their 30s. A century ago, Americans lived only 48 years on average while a century later we live 77 years on average. If Finland’s medical and nutrition improvements parallel Americans, 7-8 years additional longevity over the past 30 years is just average, nothing to crow about — nor to try to assign causation when none can be adduced from ecologic data.

    Unfortunately, while preposterous charges amongst American politicians will likely abate after November 7th, there is no apparent reprieve from the anti-salt crowd.

    Dick Hanneman
    Salt Institute

    See our blog on salt and health —

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