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:

How to Lower Your Sodium Intake

Reduction of salt consumption by just 15 percent could save the lives of millions. If we cut our salt intake by half a teaspoon a day, which is achievable simply by avoiding salty foods and not adding salt to our food, we might prevent 22 percent of stroke deaths and 16 percent of fatal heart attacks—potentially helping more than if we were able to successfully treat people with blood pressure pills. As I discuss in my video Salt of the Earth: Sodium and Plant-Based Diets, an intervention in our kitchens may be more powerful than interventions in our pharmacies. One little dietary tweak could help more than billions of dollars worth of drugs.

What would that mean in the United States? Tens of thousands of lives saved every year. On a public-health scale, this simple step “could be as beneficial as interventions aimed at smoking cessation, weight reduction, and the use of drug therapy for people with hypertension or hypercholesterolemia,” that is, giving people medications to lower blood pressure and cholesterol. And, that’s not even getting people down to the target. 

A study I profile in my video shows 3.8 grams per day as the recommended upper limit of salt intake for African-Americans, those with hypertension, and adults over 40. For all other adults the maximum is 5.8 daily grams, an upper limit that is exceeded by most Americans over the age of 3. Processed foods have so much added salt that even if we avoid the saltiest foods and don’t add our own salt, salt levels would go down yet still exceed the recommended upper limit. Even that change, however, might save up to nearly a hundred thousand American lives every year.

“Given that approximately 75% of dietary salt comes from processed foods, the individual approach is probably impractical.” So what is our best course of action? We need to get food companies to stop killing so many people. The good news is “several U.S. manufacturers are reducing the salt content of certain foods,” but the bad news is that “other manufacturers are increasing the salt levels in their products. For example, the addition of salt to poultry, meats, and fish appears to be occurring on a massive scale.”

The number-one source of sodium for kids and teens is pizza and, for adults over 51, bread. Between the ages of 20 and 50, however, the greatest contribution of sodium to the diet is not canned soups, pretzels, or potato chips, but chicken, due to all the salt and other additives that are injected into the meat.

This is one of the reasons that, in general, animal foods contain higher amounts of sodium than plant foods. Given the sources of sodium, complying with recommendations for salt reduction would in part “require large deviations from current eating behaviors.” More specifically, we’re talking about a sharp increase in vegetables, fruits, beans, and whole grains, and lower intakes of meats and refined grain products. Indeed, “[a]s might be expected, reducing the allowed amount of sodium led to a precipitous drop” in meat consumption for men and women of all ages. It’s no wonder why there’s so much industry pressure to confuse people about sodium.

The U.S. Dietary Guidelines recommend getting under 2,300 milligrams of sodium a day, while the American Heart Association recommends no more than 1,500 mg/day. How do vegetarians do compared with nonvegetarians? Well, nonvegetarians get nearly 3,500 mg/day, the equivalent of about a teaspoon and a half of table salt. Vegetarians did better, but, at around 3,000 mg/day, came in at double the American Heart Association limit.

In Europe, it looks like vegetarians do even better, slipping under the U.S. Dietary Guidelines’ 2,300 mg cut-off, but it appears the only dietary group that nails the American Heart Association recommendation are vegans—that is, those eating the most plant-based of diets.


This is part of my extended series on sodium, which includes:

If you’re already cutting out processed foods and still not reaching your blood pressure goals, 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, year-in-review presentations:

The Benefits of Wakame Seaweed Salad on Blood Pressure

I used to think of seaweed as just a beneficial whole-food source of minerals like iodine, for which it is the most concentrated dietary source. Indeed, just a daily half-teaspoon of mild seaweeds, like arame or dulse, or two sheets of nori should net you all the iodine you need for the day. But, the intake of seaweeds is advised not only as a whole-food source of iodine, but also, evidently, “for the prevention of lifestyle-related diseases, including cancer, cardiovascular and cerebrovascular disease….” Based on what?

As I discuss in my video Wakame Seaweed Salad May Lower Blood Pressure, the reasoning is that the Japanese live long and eat seaweed, so there is speculation that seaweed might have “influence on life expectancy,” based on suggestive reports. But when we see long lists of the supposed benefits a particular food is purported to have, such as “compounds found in [seaweed] have various biological activities including anticoagulant, anti-viral, antioxidant, anti-allergic, anti-cancer, anti-inflammatory, anti-obesity, and neuroprotective properties,” we need to know if they are based on clinical data, meaning studies with actual people, or so-called preclinical data, that is, from test tubes and lab animals. I mean, what are we supposed to do with a study talking about the effects of “seaweed-restructured pork diets” on rats? Those researchers tried to use seaweed, as well as other ingredients, to “improv[e] the ‘image’ of meat product.” Researchers also tried to add grape seeds to meat, they tried flaxseeds, they tried walnuts, they tried purple rice, and they even tried “thong-weed.”

When you look at epidemiological studies, where you compare the diets and disease rates within a population, you see that Japanese pre-schoolers who eat seaweed tend to have lower blood pressures, suggesting “seaweed might have beneficial effects on blood pressure among children.” That could make sense given all the minerals and fiber in seaweed, but cause and effect can’t be proven with this kind of study. Perhaps other components of the diet that went along with seaweed eating that made the difference.

It’s even harder to do these kinds of studies on adults, since so many people are on high blood pressure medications. University of Tokyo researchers took an innovative approach by comparing the diets of people on different intensities of medication: low-dose of a single blood pressure drug, high-dose of a single drug, and multiple drugs. And, although they all had artificially normalized blood pressure “as a result of effective medication,” those who ate the most fruits and sea vegetables tended to be the ones on the lower dose of a single drug, supporting a dietary role for seaweed. An interesting finding, but why not just put it to the test?

A double-blind, crossover trial found that seaweed fiber lowered blood pressure, apparently by pulling sodium out of the system. Real seaweed couldn’t be used in the study, because the subjects wouldn’t be able to be fooled with a placebo, but why not just put whole powdered seaweed into pills? That was finally attempted ten years later. Compared to doing nothing, subjects receiving a daily dose of dried wakame powder in capsules had beautiful drops in blood pressure. The researchers, however, desalinized the seaweed, taking out about two-thirds of the sodium naturally found in it. So, we still don’t know if eating seaweed salad is actually going to help with blood pressure. What we need is a randomized, controlled trial with plain, straight seaweed. No one had ever done that research, until…they did!

Six grams of wakame, with all of its natural sodium, led to a significant drop in blood pressure, especially in those who started out with high pressure. The subjects experienced only minor side effects and ones that could be expected with increasing fiber intake. A nice thing about whole-food, plant-based interventions is that we sometimes get good side effects, such as the resolution of gastritis (stomach inflammation) some subject had been having, as well as the disappearance of chronic headaches. 


What other foods might help with high blood pressure? See:

For more on preventing and treating hypertension, one of our leading killers, see:

Want more on seaweed and iodine? Check out:

My video Salt of the Earth: Sodium and Plant-Based Diets further addresses the sodium question.

In health,
Michael Greger, M.D.

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