How Salt Got Its Bad Reputation: A Brief History of the “Salt = High Blood Pressure” Myth - PART 2
The idea that salt is inherently bad for your heart has been repeated so often that it’s taken as gospel. But where did this salt-phobia originate? It turns out the evidence was shaky from the start, relying on extreme experiments and misinterpreted data that became entrenched in policy before the science was settled.
Understanding this history will reveal how we ended up vilifying salt in the first place.
Early 20th Century Suspicions: Doctors observed over a century ago that some patients with high blood pressure appeared to eat a lot of salt, hinting at a connection [1].
In 1904, French doctors reported a handful of hypertension patients who were “salt fiends,” planting the seed of suspicion that salt could drive up blood pressure [1]. However, these were just small case observations, hardly proof, and even then some experts questioned the idea that salt was the lone culprit [2].
Extreme Rat Experiments:
The true crusade against salt began in the 1950s–60s with the work of Dr. Lewis Dahl, who performed infamous experiments on rats. Dahl fed rats astronomically high amounts of salt, the equivalent of a human eating 500 grams of sodium a day (that’s *1¼ pounds* of salt daily!), and observed some of the rats eventually developed hypertension[3][4].
This was considered “unequivocal” evidence by Dahl that salt causes high blood pressure. But think about that dose: no human consumes anywhere near 500 g of sodium per day (the average American eats about 3.4g sodium, or 8.5 g of salt per day)[5].
Dahl’s rat studies were done under extreme conditions that don’t reflect normal human diets[4]. Essentially, he had to nearly poison the rats with salt to get that effect, a fact often glossed over when his work was cited later.
Population Studies and Outliers:
Dahl also pointed to international data: countries with very high salt intakes (like post-war Japan, where diets high in salty pickles and soy sauce were common) seemed to have more hypertension and strokes[6].
Indeed, 1950s Japan had high rates of stroke, and salt was thought to be a factor. However, this early analysis ignored other differences (genetics, other dietary factors) and treated correlation as causation.
Later, when scientists looked more carefully within populations, the salt–blood pressure link largely evaporated[7].
For example, a landmark global study in 1988 (the INTERSALT study) collected blood pressure and sodium excretion data from 52 populations worldwide. The results were surprising: across most populations, there was no clear relationship between sodium intake and hypertension prevalence[8].
In fact, the population that ate the most salt (about 14grams of salt per day) had lower median blood pressure than the population that ate the least (about 7.2 grams per day)[9]!
How could that be?
It turned out INTERSALT’s slight overall correlation between salt and BP was driven mainly by a few extreme outlier groups, four very isolated, primitive tribes (e.g. the Yanomami Amazonian tribe) who consumed almost no salt and had low blood pressure[10].
When those outliers were removed from the analysis, even the modest correlation vanished[11]. In other words, apart from communities nearly salt-free (which also had many other lifestyle differences), the world’s populations tended to consume moderate salt (most fell in a narrow band of ~5–10 grams of salt per day) and showed no consistent blood pressure differences attributable to salt intake alone[12].
The 1977 Guidelines – Policy Jumps Ahead of Science:
Despite the weak and conflicting evidence, public health bodies forged ahead with salt reduction advice. In 1977, the U.S. Senate’s Select Committee on Nutrition (led by Senator George McGovern) released the first dietary goals for Americans.
Based largely on Dahl’s work and the prevailing fears, the guidelines urged Americans to cut their salt intake by 50–85%[13]. This was a dramatic recommendation, essentially telling people to halve the salt they were accustomed to eating, and it wasn’t based on any long-term human trials, just the assumption that less salt should improve health.
Other countries followed suit with similar conservative targets (for instance, the UK recommends no more than ~6 grams of salt per day, and Australia set a “suggested target” of 2000 mg sodium, ~5 g salt[14][15]).
Thus, by the 1980s, “salt is bad” became institutionalised in dietary advice, even as many scientists remained unconvinced.
Continued Controversy:
Over the ensuing decades, the salt hypothesis remained highly controversial. For every study that suggested high salt might be harmful, another study found no effect or even an opposite trend[16].
Small trials did show that extremely low-salt diets can drop blood pressure slightly, but the effect was minimal for most people. A 2004 Cochrane review of 11 trials found that intensive salt restriction reduced systolic BP by only ~1.1 mmHg in people with normal blood pressure (and ~5 mmHg in hypertensives), a tiny change that would barely move someone from, say, 120/80 to 119/79[17].
Such a minor reduction in a risk factor might not translate into any meaningful reduction in heart attacks or strokes for an individual[18][17].
In 2011, a meta-analysis of 7 studies (6,250 people) found no strong evidence that cutting salt intake reduced risks of heart attack, stroke, or death in people with normal or high blood pressure[18].
Even more striking, some observational studies hinted that people who ate the least salt were more likely to die of heart disease than those who ate more salt, suggesting a potential unintended harm in over-zealous sodium restriction[18][16].
For example, a 2006 American Journal of Medicine study tracking 78 million Americans found that the ones who consumed more sodium actually had lower rates of cardiac death over 14 years[16].
Another study in 2007 (European Journal of Epidemiology) followed older adults for 5 years and saw no link between urinary sodium levels and cardiovascular disease or mortality[16].
Scientists Sound the Alarm – “The War on Salt is Misguided”:
By the 2010s, some leading researchers and clinicians were openly questioning the dogma. In 2010, an editorial in The Journal of the American Medical Association pointed out that the evidence for population-wide sodium reduction was weak, and noted paradoxes like the lack of association in INTERSALT and the possibility that genetics and diet quality confound the issue[6][19].
In 2011, Scientific American ran a piece titled “It’sTime to End the War on Salt”, arguing that the crusade to force salt intake ever lower had little scientific basis and could even be doing harm[20][18].
Experts like Dr. Michael Alderman (an epidemiologist and former president of the International Society of Hypertension) pointed out that individuals vary greatly in their response to salt: some people are salt-sensitive (their BP goes up on high salt), but many are “salt-resistant” or even experience drops in BP when increasing salt[19].
One 1987 study found that the number of people whose BP fell on a high-salt diet was roughly equal to the number whose BP rose; the rest saw no change[21].
In other words, a blanket recommendation ignores the reality of biochemical individuality. Our kidneys are designed to handle varying salt intakes by excreting what we don’t need; for most healthy people, the body maintains balance whether you eat a bit more or less salt on a given day[22].
In summary, the vilification of salt originated from questionable science, extreme animal studies and simplistic population comparisons, which snowballed into public policy before more rigorous evidence was available.
Once the low-salt guidelines became “conventional wisdom,” they gained a life of their own, even as numerous studies failed to confirm that eating below some very low sodium target improved health outcomes. It’s a case of policy leaping ahead of proof.
The result is decades of salt being treated as a dietary villain, with mainstream medicine repeating the mantra “less salt, less salt” while under the surface, scientific debate continued to brew
Next, we’re going to look at what the Latest Research Really Says About Salt, Blood Pressure, and Heart Health.
