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PaperclipPerfector  1d ago (text post)   508 thread views

Wellness Wednesday for November 26, 2025

The Wednesday Wellness threads are meant to encourage users to ask for and provide advice and motivation to improve their lives. It isn't intended as a 'containment thread' and any content which could go here could instead be posted in its own thread. You could post:

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Via David Friedman:

In 1972, when the National Institutes of Health introduced the National High Blood Pressure Education Program to help prevent hypertension, no meaningful experiments had yet been done. The best evidence on the connection between salt and hypertension came from two pieces of research. One was the observation that populations that ate little salt had virtually no hypertension. But those populations didn’t eat a lot of things—sugar, for instance—and any one of those could have been the causal factor. The second was a strain of “salt-sensitive” rats that reliably developed hypertension on a high-salt diet. The catch was that “high salt” to these rats was 60 times more than what the average American consumes.

Still, the program was founded to help prevent hypertension, and prevention programs require preventive measures to recommend. Eating less salt seemed to be the only available option at the time, short of losing weight. Although researchers quietly acknowledged that the data were “inconclusive and contradictory” or “inconsistent and contradictory”—two quotes from the cardiologist Jeremiah Stamler, a leading proponent of the eat-less-salt campaign, in 1967 and 1981—publicly, the link between salt and blood pressure was upgraded from hypothesis to fact.

In the years since, the NIH has spent enormous sums of money on studies to test the hypothesis, and those studies have singularly failed to make the evidence any more conclusive. Instead, the organizations advocating salt restriction today—the USDA, the Institute of Medicine, the CDC and the NIH—all essentially rely on the results from a 30-day trial of salt, the 2001 DASH-Sodium study. It suggested that eating significantly less salt would modestly lower blood pressure; it said nothing about whether this would reduce hypertension, prevent heart disease or lengthen life.

While influential, that trial was just one of many. When researchers have looked at all the relevant trials and tried to make sense of them, they’ve continued to support Dr. Stamler’s “inconsistent and contradictory” assessment. Last year, two such “meta-analyses” were published by the Cochrane Collaboration, an international nonprofit organization founded to conduct unbiased reviews of medical evidence. The first of the two reviews concluded that cutting back “the amount of salt eaten reduces blood pressure, but there is insufficient evidence to confirm the predicted reductions in people dying prematurely or suffering cardiovascular disease.” The second concluded that “we do not know if low salt diets improve or worsen health outcomes.”

The idea that eating less salt can worsen health outcomes may sound bizarre, but it also has biological plausibility and is celebrating its 40th anniversary this year, too. A 1972 paper in The New England Journal of Medicine reported that the less salt people ate, the higher their levels of a substance secreted by the kidneys, called renin, which set off a physiological cascade of events that seemed to end with an increased risk of heart disease. In this scenario: eat less salt, secrete more renin, get heart disease, die prematurely.

With nearly everyone focused on the supposed benefits of salt restriction, little research was done to look at the potential dangers. But four years ago, Italian researchers began publishing the results from a series of clinical trials, all of which reported that, among patients with heart failure, reducing salt consumption increased the risk of death.

The articles quoted seem dated. There have been various interventional trials into sodium intake.

Meta-analysis from 2013: Effect of longer‐term modest salt reduction on blood pressure

From 2020: Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and meta-analysis of randomised trials

*From 2021: Blood Pressure Effects of Sodium Reduction

*From 2022: Impact of different dietary sodium reduction strategies on blood pressure: a systematic review

Obviously you can attack one or all of those sources as illegitimate or ideologically captive. But there is evidence out there. Taubes himself reminds me to a degree of Robert Lustig, also a dude who tries to fight mainstream scientific consensus (in Lustig's case he is also convinced sugar is the ultimate baddie and calls it poison.)

It's not clear that the results are even contradictory. The argument seems to be that there is a clear dose response relationship with urinary sodium and short term blood pressure but the relationship with premature death and other negative effects of cardiovascular disease and what constitutes a "modest" reduction are not as well established.

In particular, of the three obvious interventions weight loss, blood pressure medication, and sodium restriction; sodium reduction seems to have the smallest impact and at the cost of potentially making your food significantly less palatable. There is a pretty substantial part of the population where, in quality of life adjusted terms it would not be worth it. Reducing sodium intake from something like 12 g/day to the recommended 2.3 g/day would take most of the joy they get out of eating. The expected reduction in blood pressure might be as much as 5 mmHg, but they likely would still need medication and the difference would still be entirely controllable with medication dose.

The best controlled long-term study I've seen is from the Mars500 people. They did find the expected dose response relationship. But, for normal people the reductions in intake would not feel "modest" as the He et.al. title implies. They also show that the 24 hour sodium urine measures used in most of those meta-analyses are, at best, an imperfect proxy for long term sodium intake.

All of this not medical advice. That being said, high blood pressure is very likely supper bad for you. If you have high blood pressure the modern pharmaceutical interventions are nearly perfect. Drastic sodium reduction might be marginally beneficial, or not. The aggregate evidence seems to indicate that it will produce a reduction in blood pressure, but the effect size (even in those pro reduction review papers) is likely too small small to fully resolve chronic significantly elevated blood pressure, for most people.

I didn't know the Mars500 project had been so rigorous. Is there anything interesting that came out of it?

Mostly that they didn't have to rely on urine samples or food log proxies, and they observed for long enough to avoid the transient effects on body water. I assume the transient change in plasma volume has very little benifial impact on long term health. Since it was pretty long term, they made enough samples on each individual to clearly see the effects on the longitudinal axis, which is much more what you care about at an individual intervention level.

If you look at the plots in the supplemental materials, you can very clearly see the step change in blood pressure with sodium in each individual. You can also see seasonality in urine sodium excretion that is independent of sodium intake.

The part I don't like about just using urine samples is, why isn't you null that the body reestablishes homeostasis when it increases/decreases excretion? Like obviously since your body excreats less sodium if you consume less sodium the net is smaller than the raw magnitude of adjustment you make. Why isn't the net zero over the long term? What is the proposed mechanism by which reducing sodium is improving health? A naive model of less sodium leads to less plasma leads to lower blood pressure leads to better health doesn't work, because plasma volumes return to close to normal once you body has a chance to decrease excreation and restore osmotic balance.

Helpfully they observe in highly controlled conditions over a long enough period you can see that there are indeed appreciable hormonal contributions beyond pure osmotic arguments. It is assumed that the mechical effect of lower pressure and the hormonal effects are beneficial. You can lower the mechical pressure with medication though, so the residual question is what the health effects of sodium are beyond blood pressure. That I don't know. The mainstream consensus seems to be more sodium is bad independent of blood pressure. Hard to say for sure though, since high sodium food is correlated with other things that are bad for us when they try to disentangle it in population level studies.

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