Perhaps you read the article published this week in the online Journal of Human Hypertension (paid subscription required) by Dr. Graham MacGregor claiming dietary salt was responsible for high blood pressure in children. MacGregor and colleagues claim their results support "a reduction in salt intake for children and adolescents."
Not so fast. Though the media carried the author's conclusions from the study, an accompanying editorial (free) by Dr. Michael H. Alderman, immediate past president of the International Society of Hypertension, in the same edition points out that the entire relationship is due to the fact that those who ate more salt ate more food. Adjusting for caloric intake wiped out the significance of the relationship. Nor was there any difference between the high-salt and low-salt groups in terms of preference for adding salt at the table. Alderman pointed out that those consuming more salt and calories may also have had more adequate intakes of other vital, growth-related nutrients, but that the study did not include these data. Thus, Alderman concludes that the data "support the Cochrane Collaboration conclusion that there was not sufficient evidence for a general dietary recommendation to reduce sodium intake."
Alderman cautioned against following MacGregor's prescription of having children reduce dietary salt.
...randomized clinical trials in adults have shown that lowering sodium intake increases sympathetic nerve activity, reduces insulin sensitivity, increases the activity of the renin-angiotensin system and increases aldosterone secretion.
Do these or other changes occur in children? This is critical because, of course, the health impact of any intervention is the sum total of all its consequences. While I remain an agnostic on that score, I continue to believe firmly that solid knowledge based on evidence of benefit and risk must precede any clinical or public health intervention -- particularly when it comes to dependent children. Good observational studies such as this one generate hypotheses. They need to be tested in clinical trials. Absent such evidence, and absent some pressing public health challenge, therapeutic restraint may be the best and safest way to avoid doing harm.
Alderman may be "agnostic" with regard to his pursuit of an evidentiary basis for an intervention. It's too bad too many proponents of salt reduction seem to advance their arguments with strong faith and religious zeal -- and without scientific basis. We've heard no better argument against the establishment of a state religion.
