by Marion Nestle
Oct 22 2010

The latest salvos in the sodium debates

Scientific debates about the role of sodium in high blood pressure go on and on.  Committees of scientists reviewing the research invariably conclude that people would be healthier if they ate less salt (salt is sodium chloride).  The 2010 Dietary Guidelines Advisory Committee is only the most recent group to urge population-wide reductions in sodium intake.

The Institute of Medicine has just issued a new report on reducing sodium.  Its Report in Brief gives a quick summary

As its primary strategy for sodium reduction, the committee recommends that the FDA set mandatory national standards for the sodium content in foods…beginning the process of reducing excess sodium in processed foods and menu items to a safer level. It is important that the reduction in sodium content of foods be carried out gradually…Evidence shows that a decrease in sodium can be accomplished successfully without affecting consumer enjoyment of food products if it is done in a stepwise process that systematically and gradually lowers sodium levels across the food supply.

But wait!  Hypertension rates have been increasing for years without any change in sodium excretion, says a report in FoodNavigator.com.  The report refers to new study in this month’s American Journal of Clinical Nutrition reviewing trends in sodium excretion from 1957 to 2003.

Sodium excretion, a precise reflection of intake, say Adam Bernstein and Walter Willett of the Harvard School of Public Health, has not changed in the last half century, despite rising rates of high blood pressure.   Instead, they suggest that rising rates of obesity might be the cause.

The accompanying editorial, by David McCarron and his colleagues, takes the argument even further as can be seen just from its title: “Science trumps politics: urinary sodium data challenge US dietary sodium guideline.

The editorial says that this new study provides:

plausible, scientific evidence of a “normal” range of dietary sodium intake in humans that is consistent with our understanding of the established physiology of sodium regulation in humans. This scientific evidence, not political expediency, should be the foundation of future government policies….Guidance for sodium intake should target specific populations for whom a lower sodium intake is possibly beneficial. Such an approach would avoid broad proscriptive guidelines for the general population for whom the safety and efficacy are not yet defined.

Is this review likely to change the Dietary Guidelines due out later this year?  The Advisory Committee was convinced that the preponderance of evidence favors the importance of sodium as a causative agent in high blood pressure.

Because so much is at stake for the processed food industry, this argument is not likely to be resolved quickly.  Stay tuned.

  • Cathy Richards

    Okay, so the food industry blames inactivity as a culprit for obesity so they don’t have to change their methods. Then they blame obesity as a culprit for high blood pressure so they don’t have to change their methods.

    It’s the whole team working together that helps to win a hockey game, not just the goalie. Everybody and every system needs to contribute to this battle against obesity and hypertension.

  • Emily

    I’ve often wondered about this. I consider my sodium intake to be fairly high but my blood pressure is quite low. That said, I don’t eat processed food, so I guess I probably truly take in less than many folks. I just tend to have a fairly liberal hand when I salt my pasta, can my tomatoes, and whip up my stir fry, but when I go to give blood, I usually spend a minute or two in front of the buiding with my arms raised over my head so my BP will be high enough that they’ll take me.

  • Michael Bulger

    @Emily This is from the DGAC report: “On average, the natural sodium content of food accounts for only 10 percent of total intake, while discretionary salt use (i.e., table and cooking salt) provides another 5 to 10 percent of total intake. The remaining 75 percent is derived from salt added in food processing by manufacturers”

  • Brad F

    Marion
    What is your take however. While I know the analysis was retrospective, it is rigorous and biologically plausible.

    Could the IOM panel have it wrong, or at least premature in their decision rendering?
    Thanks,
    Brad

  • Renee

    I’ll echo Brad’s comment. What’s the truth?

  • Anthro

    A certain PhD (biology) I know does not keep salt in his house (he doesn’t cook much) because “salt is bad for you”, yet he eats loads of frozen and other processed food without a care for its sodium content.

    Go figure.

    I’m with Emily on this. That is, limit processed sources but use salt at home. I have cut back on this, though to the bare minimum to enhance taste in some foods.

    My BP went down when I lost 45 lbs, but I still take a minimum dose of a generic med. I almost never eat processed food and am careful with restaurant food as well–stick pretty much to salad. I wish we could sort out who is salt sensitive or find out why someone who has low sodium intake still has elevated BP. My guess is that for me, it’s a genetic thing that benefits from my vigilance but will not entirely go away.