Friday, May 06, 2011


There is an interesting and controversial paper out in the Journal of the American Medical association on urinary excretion amongst normal individuals, and their blood pressure and their 8 year outcome. An interesting paper that some have chosen to call as a afornt to the theory of reducing salt intake to lessen hypertension and strokes. I did not see it as such. The paper by Dr Katarzyna Stolarz-Skrzypek from the University of Leuven, Belgium, is entitled "Fatal and nonfatal outcomes, incidence of hypertension, and BP changes in relation to urinary sodium excretion".
The experts have chosen to label this paper in their editorial as " New salt paper raises controversies", claiming that the paper does not support the conventional wisdom that too much salt is bad for health.
Dr Skrzypek et al, studied 3681 subjects who were without heart disease. Followed them up for a mean of 7.0 years. reviewed them and assess their 24hrs urinary sodium excretion and blood pressure. After 7.9 years of follow-up, they found that those with lowest urinary sodium excretion in 24 hrs, had an 50% increase incidence of cardiovascular events, including fatal MIs. There were 50deaths in the lowest excretion tertile, 25 deaths in the intermediate group and 10 deaths in the highest urinary sodium excretion group. They also showed that this group, after 7.9 years of follow-up, had their BP mildly elevated.
These conclusions obviously raised much hue and cry, as it is commonly perceived that 24 hr urinary sodium excretion, is one way of assessing salt intake. The experts ( including my friend Dr Graham MacGregor ) concluded that the paper showed that people who ingested less sodium in their diet ( 24hr urinary sodium excretion ), had an increase CVS fatalities, while recording a marginal increase in blood pressure. These conclusions will certainly raise some eyebrows.
I did not see it the same way after going through the paper. I thought that the paper simply said that in their European population, low 24 hr urinary sodium excretion, was associated with increase CVS fatalities. There could be many reasons for a low 24 hr urinary sodium count, not excluding poor compliance, low 24 hr urine volume ( giving false positives ), or simply "not collecting properly". I think that all the fuss over this paper, is much ado about nothing.
It is undoubtedly true, that increase salt intake in our diet, is associated with an increase rise in BP ( logically, by pure physics, and also supported by a large body of evidence and epidermiological data ). An increase in blood pressure, will see an increase in strokes and CVS events.
It is good, in an academic community, to have some controversies and debates. That always allows us to re-examine of first principles and recheck our understanding, less we take them for granted. Controversies and debates are healthy and should be encourage. I suppose, in an academic discussion, there is unlikely to be violence. Innovations and a high income economy must also come with its fair share or controversies and debates, so that we can get new ideas, from which innovations comes. Sterile boring mono types, only breed complacency and the " continue with the same" mentality., otherwise called " lack of ideas". How then to have innovations??

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