Salt it up, baby!
An article in yesterday’s Science Times explained that limiting the salt in your diet doesn’t actually improve health, and could in fact be bad for you. That’s a huge turn-around for a public health rule that has run very deep.
How can this kind of thing happen?
Well, first of all epidemiologists use crazy models to make predictions on things, and in this case what happened was they saw a correlation between high blood pressure and high salt intake, and they saw a separate correlation between high blood pressure and death, and so they linked the two.
Trouble is, while very low salt intake might lower blood pressure a little bit, it also for what ever reason makes people die a wee bit more often.
As this Scientific American article explains, that “little bit” is actually really small:
Over the long-term, low-salt diets, compared to normal diets, decreased systolic blood pressure (the top number in the blood pressure ratio) in healthy people by 1.1 millimeters of mercury (mmHg) and diastolic blood pressure (the bottom number) by 0.6 mmHg. That is like going from 120/80 to 119/79. The review concluded that “intensive interventions, unsuited to primary care or population prevention programs, provide only minimal reductions in blood pressure during long-term trials.” A 2003 Cochrane review of 57 shorter-term trials similarly concluded that “there is little evidence for long-term benefit from reducing salt intake.”
Moreover, some people react to changing their salt intake with higher, and some with lower blood pressure. Turns out it’s complicated.
I’m a skeptic, especially when it comes to epidemiology. None of this surprises me, and I don’t think it’s the last bombshell we’ll be hearing. But this meta-analysis also might have flaws, so hold your breath for the next pronouncement.
One last thing – they keep saying that it’s too expensive to do this kind of study right, but I’m thinking that by now they might realize the real cost of not doing it right is a loss of the public’s trust in medical research.