Is Miso Healthy?

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Miso is packed with sodium, which is linked to both stomach cancer and high blood pressure, so is it safe to consume?

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Salt is considered “a probable cause of stomach cancer,” one of the world’s leading cancer killers. If the estimate from the Second World Cancer Research Fund / American Institute for Cancer Research expert report, of an 8% increase in risk for every extra gram of salt a day, is correct, then, in a country like the UK, nearly 1,700 cases of stomach cancer happen every year just because of excess salt intake. And, in a country like the U.S., it would be thousands more every year.

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, based on this 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 “[d]ietary salt intake [is] directly associated with [the] risk of [stomach] cancer.” And, the higher the intake, the higher the risks. But, this meta-analysis went further, looking 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% greater risk of stomach cancer. The pickled foods may explain why Korea appears to have the highest stomach cancer rates in the world.

But, there was no significant association with the consumption of miso soup. This may be because the carcinogenic effects of the salt 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, it may drop our cancer risk even lower.

But, cancer isn’t the primary reason people are told to avoid salt. What about miso soup and high blood pressure? Well, it may be the same kind of thing. The salt in miso is squeezing our blood pressures up, but the soy protein in miso may be relaxing our blood pressures down. So, for example, if you compare the effects of soy milk to cow’s milk—and, to make it fairer, compare soy milk to skim milk, to avoid the saturated butterfat—soy milk can much more dramatically improve blood pressure among women with hypertension. But, would the effect be dramatic enough to counter all the salt in miso? Japanese researchers decided to put it to the test.

They followed men and women in their 60s who started out with normal blood pressure, and followed them for four years 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 that had one or less. Two bowls a day would be like adding a half-teaspoon of salt to one’s daily diet, yet those who ate two bowls or more 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.

Please consider volunteering to help out on the site.

Image credit: Kristina DeMuth. Image has been modified.

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Salt is considered “a probable cause of stomach cancer,” one of the world’s leading cancer killers. If the estimate from the Second World Cancer Research Fund / American Institute for Cancer Research expert report, of an 8% increase in risk for every extra gram of salt a day, is correct, then, in a country like the UK, nearly 1,700 cases of stomach cancer happen every year just because of excess salt intake. And, in a country like the U.S., it would be thousands more every year.

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, based on this 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 “[d]ietary salt intake [is] directly associated with [the] risk of [stomach] cancer.” And, the higher the intake, the higher the risks. But, this meta-analysis went further, looking 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% greater risk of stomach cancer. The pickled foods may explain why Korea appears to have the highest stomach cancer rates in the world.

But, there was no significant association with the consumption of miso soup. This may be because the carcinogenic effects of the salt 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, it may drop our cancer risk even lower.

But, cancer isn’t the primary reason people are told to avoid salt. What about miso soup and high blood pressure? Well, it may be the same kind of thing. The salt in miso is squeezing our blood pressures up, but the soy protein in miso may be relaxing our blood pressures down. So, for example, if you compare the effects of soy milk to cow’s milk—and, to make it fairer, compare soy milk to skim milk, to avoid the saturated butterfat—soy milk can much more dramatically improve blood pressure among women with hypertension. But, would the effect be dramatic enough to counter all the salt in miso? Japanese researchers decided to put it to the test.

They followed men and women in their 60s who started out with normal blood pressure, and followed them for four years 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 that had one or less. Two bowls a day would be like adding a half-teaspoon of salt to one’s daily diet, yet those who ate two bowls or more 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.

Please consider volunteering to help out on the site.

Image credit: Kristina DeMuth. Image has been modified.

Doctor's Note

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

For delicious miso-containing recipes, check out:

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

Not convinced that soy is good for you? See:

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