Pour salt on it
A recent Australian article headline caught attention with its “Deadly sprinkles in lunches” and claims that a favorite “cheese stick could be killing your children.”We were told that we are feeding our children things that are going to cause heart attacks and strokes later in life and that the salty foods parents are allowing their children to eat are like feeding them “solid seawater for lunch.” Without a doubt, fear was being used to market something.
The person quoted in the article was Professor Graham MacGregor of
The evidence for these headlining claims was a recent study he co-authored with Feng J. He and published in the journal Hypertension. The media echoed the CASH press release, saying this study proves that a modest reduction in salt intake among children can almost immediately cause significant falls in blood pressure, “which in turn could lead to major reductions in the risk of developing stroke, heart attacks and heart failure later in life.”
This study is also the evidence used by the Center for Science in the Public Interest to supports its recent call on the FDA to revoke salt’s status as “generally recognized as safe” and regulate it as a food additive. Michael Jacobson, executive director of CSPI, stated in Salt the Forgotten Killer (2005): “Reducing sodium consumption by half would save an estimated 150,000 lives per year.”
Such extraordinary claims require extraordinary evidence. Does this study hold up?
This study is said to be the “first ever meta-analysis of salt reduction studies in children.” And it epitomizes every caveat of these types of studies. MacGregor and He “developed a strategy” of their own design to look for words in several databases and through reference lists at the end of articles to find studies of salt reduction in children. They only used studies published in English and of the 33 they found, decided to use 10 on children for this report. The studies all had different designs, with only one being a double-blind trail and only 9 were randomized; the studies varied in length from 2 weeks to 3 years; compliance with salt reductions appeared poor in two of the studies; we have no information on the racial/ethnic mix of the children and if it is representative of the general population; and only 3 measured 24-hour urinary sodium levels — which the researchers admitted is “the only accurate way to assess dietary salt intake.” Simplifying what they did next, they pooled the data on blood pressures and net changes in salt intake, and used statistics to estimate the changes as needed to fill in missing data. Then, they applied two computer models to plot the results and more statistical analyses to reach their findings. What they reported was that cutting salt intake by 42% reduced systolic blood pressures in the children by 1.17 mmHg. Most parents and children would consider such a salt reduction — nearly in half — to be extreme; while most doctors would debate the clinical significance of a mere 1 point reduction in blood pressure. Taking blood pressures in young children is an imprecise task at best and the children in these different studies were also at varying stages of development, with corresponding variable changes in blood pressures over the study durations, according to their growth and size. The researchers stated that the “physiological need for salt intake in children has not been studied,” but concluded anyway that “current salt intake in children is unnecessarily high and is very likely to predispose children to develop hypertension later.” They went on to declare that these results “provide strong support for a reduction in salt intake for children. [And] if continued, may well lessen the subsequent rise in BP with age and prevent the development of hypertension. This would result in major reductions in cardiovascular disease.” Their press release promised possible “massive population health gains.” ·But this study did not examine a single child. ·It conducted no clinical research to learn how much salt is needed or might be harmful for children. ·It offered no clinical evidence to know if a lower blood pressure reading of 1 point means anything for children’s health or is maintained as a child grows. ·It offered no proof that a blood pressure reading during childhood has any bearing on adult blood pressures or heart disease. ·And worse, it didn’t follow a single child to see if there were any health effects from the salt restrictions they are recommending.
In other words, this study offered no clinically meaningful evidence, only speculations. While controversy, debates and politics have surrounded salt recommendations for decades, as Gary Taubes outlined in the magazine Science, the body of evidence has not demonstrated that low-salt diets result in health benefits for the general population, nor that current salt intakes of Americans pose health risks for the general population. Even a recent Cochrane Library review of the evidence found insufficient information to know what effect salt reduction might have on health and mortality. Of greatest concern is evidence suggesting that low-salt diets may actually be harmful for most people; increasing heart attacks, mortality and insulin resistance (a precursor to diabetes). Shouldn’t we have something tenable to go on before experimenting on an entire generation of children? I suspect most parents would think so.
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