One Way to Treat Asthma and Autoimmune Diseases with Diet

Cutting two teaspoons of salt’s worth of sodium from one’s daily diet can significantly improve lung function in asthmatics

In the 1960s and 1970s, a mystery was emerging. Why were childhood asthma rates between 2 to 5 percent in the developed world but as low as 0.007 percent in the developing world? For example, in the developing world, instead of 1 in 20 kids affected, or even 1 in 50 kids, it could be more like 1 in 10,000 kids—extremely rare. And, when kids moved from a low-risk area to a high-risk area, their risk went up. What was going on? Were they exposed to something new? Did they leave some protective factor behind?

As I discuss in my video How to Treat Asthma with a Low-Salt Diet, all the way back in 1938, scientists showed they could stop asthma attacks by lowering children’s sodium levels. That was done with a diuretic drug, but subsequent dietary experiments showed that diets high in salt seemed to increase asthmatic symptoms, while “lowering the salt decreased the asthmatic symptoms…” This body of evidence was apparently forgotten…until it was picked up again in the 1980s as a possible explanation for why Western countries had higher asthma rates.

Maybe it was the salt.

As you can see at 1:34 in my video, researchers graphed out childhood death from asthma versus family salt purchases, and it seemed more salt meant more death. Just because a family buys more salt doesn’t necessarily mean the kids are eating more, though. The way to find out how much salt someone is eating is to collect their urine over a 24-hour period and measure the amount of sodium, since how much salt we eat is pretty much how much salt we excrete. The way to test for asthma, called a bronchial challenge test, is to look for an exaggerated response to an inhaled chemical. And, indeed, there was a strong correlation between how their lungs reacted and how much sodium they were taking in. However, there are all sorts of food additives, like preservatives, that can trigger these so-called hypersensitivity reactions, so maybe high sodium intake was just a marker for high processed food intake. Maybe it wasn’t the salt at all.

Or maybe it was other components of the diet. For example, the reason sodium may be a risk factor for another inflammatory disease, rheumatoid arthritis, may be that sodium intake is just a marker for increased fish and other meat intake or decreased fruit and vegetable intake. We needed a study where researchers would take asthmatics, change the amount of salt in their diets, and see what happened—and that’s just what came next.

As you can see at 3:16 in my video, researchers doubled the salt intake of ten asthmatics, and lung sensitivity worsened in nine out of ten. There was no control group, though. Is it possible the subjects would have gotten worse anyway?

In a randomized, double-blind, placebo-controlled trial, researchers put everyone on a low-salt diet, but then gave half of the subjects sustained-release sodium pills to bring their salt intake back up to a more normal level and the other half a placebo. After five weeks, the groups switched regimes for another five weeks. That’s how you can randomize people to a true low-sodium diet without them even realizing it. Genius! So what happened? Asthmatics on the salt got worse. Their lung function got worse, their asthma symptoms got worse, and they had to take more puffs on their inhalers. This study compared asthmatics consuming about three teaspoons’ worth of salt a day to those consuming less than one, so they were effectively able to drop their sodium intake by two teaspoons’ worth of salt, as you can see at 4:04 in my video. If you do a more “pragmatic” trial and only effectively reduce people’s salt intake by a half a teaspoon a day, it doesn’t work.

Even if you are able to cut down your sodium intake enough to get a therapeutic effect, though, it should be considered an adjunct treatment. Do not stop your asthma medications without your doctor’s approval.

Millions suffer from asthma attacks triggered by exercise. Within five minutes of starting to exercise, people can get short of breath and start coughing and wheezing such that lung function significantly drops, as you can see at 0:19 in my video Sodium and Autoimmune Disease: Rubbing Salt in the Wound?. On a high-salt diet, however, the attack is even worse, whereas on a low-salt diet, there’s hardly a significant drop in function at all. To figure out why, researchers had the subjects cough up sputum from their lungs and found that those on the high-salt diet had triple the inflammatory cells and up to double the concentration of inflammatory mediators, as you can see at 0:43 in my video. But why? What does salt intake have to do with inflammation? We didn’t know…until now.

“The ‘Western diet,’ high in saturated fatty acids and salt, has long been postulated as one potential…cause for the increasing incidence of autoimmune diseases in developed countries…” The rapidly increasing incidence of autoimmune diseases may be due to an overactivation of immune cells called T helper 17 (Th17) cells. “The development of…multiple sclerosis, psoriasis, type I diabetes, Sjögren’s syndrome, asthma, and rheumatoid arthritis are all shown to involve Th17-driven inflammation,” and one trigger for the activation of those Th17 cells may be elevated levels of salt in our bloodstream. “The sodium content of processed foods and ‘fast foods’…can be more than 100 times higher in comparison to similar homemade meals.”

And, sodium chloride—salt—appears to drive autoimmune disease by the induction of these disease-causing Th17 cells. It turns out there is a salt-sensing enzyme responsible for triggering the formation of these Th17 cells, as you can see at 2:07 in my video.

Organ damage caused by high-salt diets may also activate another type of inflammatory immune cell. A high-salt diet can overwork the kidneys, starving them of oxygen and triggering inflammation, as you can see at 2:17 in my video. The more salt researchers gave people, the more activation of inflammatory monocyte cells, associated with high-salt intake induced kidney oxygen deficiency. But that study only lasted two weeks. What happens over the long term?

One of the difficulties in doing sodium experiments is that it’s hard to get free-living folks to maintain a specific salt intake. You can do so-called metabolic ward studies, where people are essentially locked in a hospital ward for a few days and their food intake is controlled, but you can’t do that long term—unless you can lock people in a space capsule. Mars520 was a 520-day space flight simulation to see how people might do on the way to Mars and back. As you can see at 3:17 in my video, the researchers found that those on a high-salt diet “displayed a markedly higher number of monocytes,” which are a type of immune cell you often see increased in settings of chronic inflammation and autoimmune disorders. This may “reveal one of the consequences of excess salt consumption in our everyday lives,” since that so-called high-salt intake may actually just be the average-salt intake. Furthermore, there was an increase in the levels of pro-inflammatory mediators and a decrease in the level of anti-inflammatory mediators, suggesting that a “high-salt diet had a potential to bring about an excessive immune response,” which may damage the immune balance, “resulting in either difficulties on getting rid of inflammation or even an increased risk of autoimmune disease.”

What if you already have an autoimmune disease? In the study titled “Sodium intake is associated with increased disease activity in multiple sclerosis,” researchers followed MS patients for a few years and found that those patients eating more salt had three to four times the exacerbation rate, were three times more likely to develop new MS lesions in their brains, and, on average, had 8 more lesions in their brain—14 lesions compared to 6 in the low-salt group. The next step is to try treating patients with salt reduction to see if they get better. But, since reducing our salt intake is a healthy thing to do anyway, I don’t see why we have to wait.


What else can we do for asthma? See:

Have you heard that salt reduction was controversial? That’s what the processed food industry wants you to think. Check out the science in:

What are some of the most powerful dietary interventions we have for autoimmune disease? See, for example:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

What About the Sodium in Miso?

According to the second World Cancer Research Fund/American Institute for Cancer Research expert report, “[s]alt is a probable cause of stomach cancer,” one of the world’s leading cancer killers. If the report’s estimate of an 8 percent increase in risk for every extra gram of salt a day is correct, then in a country like the United Kingdom, nearly 1,700 cases of stomach cancer happen every year just because of excess salt intake, as you can see at 0:27 in my video Is Miso Healthy?, and, in a country like the United States, it would be thousands more annually.

The risk of stomach cancer associated with salt intake appears on par with smoking or heavy alcohol use, but may only be half as bad as opium use or increased total meat consumption, as you can see at 0:43 in my video. These findings were based on a study of more than a half million people, which may explain why those eating meatless diets appear to have nearly two-thirds lower risk.

We know dietary salt intake is directly associated with the risk of stomach cancer, and the higher the intake, the higher the risk. A meta-analysis went one step further and looked at specific salt-rich foods: pickled foods, salted fish, processed meat, and miso soup. Habitual consumption of pickled foods, salted fish, and processed meat were each associated with about a 25 percent greater risk of stomach cancer. The pickled foods may explain why Korea, where the pickled cabbage dish kimchi is a staple, appears to have the highest stomach cancer rates in the world, as you can see at 1:39 in my video. But researchers found there was no significant association with the consumption of miso soup. This may be because the carcinogenic effects of the salt in miso soup are counteracted by the anti-carcinogenic effects of the soy, effectively canceling out the risk. And, if we made garlicky soup with some scallions thrown in, our cancer risk may drop even lower, as you can see at 2:06 in my video.

Cancer isn’t the primary reason people are told to avoid salt, though. What about miso soup and high blood pressure? Similar to the relationship between miso and cancer, the salt in miso pushes up our blood pressures, but miso’s soy protein may be relaxing them down. If we compare the effects of soy milk to cow’s milk, for example, and, to make it even more fair, compare soy milk to skim cow’s milk to avoid the saturated butter fat, soy milk can much more dramatically improve blood pressure among women with hypertension, as you can see at 2:43 in my video. But would the effect be dramatic enough to counter all the salt in miso? Japanese researchers decided to put it to the test.

For four years, they followed men and women in their 60s, who, at the start of the study, had normal blood pressure, to see who was more likely to be diagnosed with hypertension in that time: those who had two or more bowls of miso soup a day or those who had one or less. Two bowls a day may add a half teaspoon of salt to one’s daily diet, yet those who had two or more bowls of miso soup every day appeared to have five times lower risk of becoming hypertensive. So, maybe the anti-hypertensive effects of the soy in the miso exceed the hypertensive effects of the salt.


Indeed, miso paste, a whole soy food, can be used as a “green light” source of saltiness when cooking. That’s why I used it in my pesto recipe in How Not to Die and in my How Not to Die Cookbook. It can help you in Shaking the Salt Habit.

Not convinced that salt is bad for you? Check out these videos:

Not convinced that soy is good for you? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Should We Tax Meat and Dairy Like We Do Cigarettes?

One of the most effective ways to decrease the harms of smoking is by increasing the cost of cigarettes through tobacco taxes. Indeed, an increase in the cost of cigarettes by only 10 percent could prevent millions of tobacco-related deaths. What about taxing unhealthy food? In general, public health decision makers have had three main options: inform through labeling, nudge with incentives, or directly intervene in markets using more heavy-handed approaches like instituting regulations or taxes.

“Policy approaches have proven crucial for other public health priorities, such as reducing tobacco use, alcohol abuse, and deaths from motor vehicle crashes.” In fact, installing air bags, for example, helped more than either “driver education alone or by labeling cars with information on crash risk.” Given that heart disease kills more than ten times more people than injuries on the road, maybe the “current epidemic of nutrition-related disease requires a similar multifaceted approach…[E]ven modest resulting dietary improvements could help reduce the burden of chronic disease significantly.” Perhaps a national system of subsidies for good foods, as well as taxes for bad ones, could “facilitate more sensible dietary choices.” Would they work? I discuss this in my video Would Taxing Unhealthy Foods Improve Public Health?.

A systematic review of the available evidence suggests such taxes and subsidies would in fact work. As I show in my video at 1:30, it seems the more unhealthy foods are taxed, the more consumption drops. Likewise, the more healthy foods like fruits and vegetables are subsidized and their prices drop, the more consumption increases. A small price difference between leaded and unleaded gasoline, for example, succeeded in decreasing our exposure to lead. What about a tax to decrease our exposure to saturated fat? As you can see from the data at 1:52 in my video, such a tax could potentially save thousands of lives.

Wouldn’t such a tax disproportionally affect the poor, though? Yes, it would benefit them the most—just like cigarette taxes. The classic tobacco industry argument is that cigarette taxes are “unfair” and “regressive,” burdening the poor the most. The public health community’s response? “Cancer is unfair” and “[c]ancer is regressive,” disproportionately burdening the poor such that a cigarette tax could result in the greatest health gains for the least well-off. The so-called Committee Against Unfair Taxes was actually just a front, “organised and funded by the tobacco industry,” one front group among many, as you can see at 2:42 in my video. This is a common tactic used by the industry to hide its role in fighting tobacco taxes, in addition to trying to overtly buy off politicians. The fact that the industry fights tooth and nail suggests that tobacco taxes can indeed affect consumption. Much of the data on food taxes and subsidies, however, have been based on models or “stated preferences” to hypothetical scenarios where people merely say they’d change consumption patterns based on prices. There hasn’t been as much real world data.

Researchers have put people through high-tech, 3D supermarket simulators, which you can see depicted at 3:15 in my video, and found that a 25 percent discount on fruits and vegetables appears to boost produce purchases by 25 percent. That’s nearly two pounds a week, but virtual fruits and veggies don’t do you any good. Does this work out in the real world? Yes. In fact, South Africa’s largest health insurance company started offering up to 25 percent cash back on healthy food purchases to hundreds of thousands of households—up to $500 USD a month. Why would the insurance company do that? Why give money away? Because it works. The healthy food cash-back program was associated with an increase in the consumption of fruits, vegetables, and whole grains, as well as a decrease in  foods high in added sugar, salt, and fat, including processed meats and fast food.

Subsidies are more common than taxes, though, in Europe, where a number of countries have instituted taxes on foods that are sugary or salty. Denmark was the first to introduce a tax on saturated fat, such as meat, dairy, and eggs, but it only took the food industry about a year to squash it, demonstrating that “public health advocates are weak in tackling the issues of corporate power.”

There’s “an enormous imbalance” between the influence exerted by public health professionals compared to the political might of the food industry. It brings to mind the fight over proposed “traffic light labelling” on food in the European Union. Apparently, it was much too easy to understand, simple and straightforward, so the industry lost its mind and spent more than $1.4 billion USD killing it in favor of the confusing “daily amount” labeling guidelines that require a “bring-your-calculator-to-the-grocery-store” approach to make grocery shopping as confusing as possible, as you can see at 4:51 in my video.

Denmark ended up canceling the fat tax and shelving their sugar tax because the farming and food company interests claimed too many jobs would be lost if people ate healthier. Apparently, a healthy economy was more important than a healthy population. Ironically, it was abolished just when evidence of its effects started to appear. Researchers “conclude[d] that the introduction of the saturated fat tax contributed to reducing the intake of saturated fat among Danish consumers” from some meat and dairy products—but not from sour cream, though. The public ate so much more low-fat sour cream that it outweighed the smaller reduction in consumption of high-fat sour cream.

Indeed, we always have to think about the unintended consequences. Swapping out sugary cookies for salty chips, for example, might not do the public’s health many favors. One field study of a tax on soda found that it may drop soft drink purchases, at least in the short term, but households may just end up buying more beer.


This idea is the flip side of sorts to my video Taxpayer Subsidies for Unhealthy Foods.

For more on how the food industry has borrowed from the tobacco industry playbook, see

What about those who insist that sodium really isn’t bad for you? Check out:

And those who insist that saturated fat really isn’t bad for you? See The Saturated Fat Studies: Buttering Up the Public and The Saturated Fat Studies: Set Up to Fail.

What about those who insist that sugar really isn’t bad for you? Watch Big Sugar Takes on the World Health Organization and Does Diet Soda Increase Stroke Risk as Much as Regular Soda?.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: