Today the Japanese have one of the longest average lifespans of all nationalities. But it was not always so. A leading cause of death in the 1950s was stroke. At that time they had a high prevalence of high blood pressure. Since then, stroke reduction from lower blood pressure became one of the biggest contributors to their present long lifespan.
How Did Japan Do It?
Like Finland, they reduced their stroke rate mostly by dietary changes. They did this by reducing their salt intake from an incredibly high amount (giving them among the highest stroke rates in the world at the time). As a result, this salt reduction improved their potassium to sodium ratio twofold.
It is estimated that in 1950 the average Northern Japan resident consumed 20 to 30 gm of salt a day. That is equivalent to 7800 mg to 11,800 mg of sodium. In contrast, the desirable amount is 1500 to 2300 mg.
How Japan Cut Their Stroke Deaths By 85%
After peaking in the 1960s, the Japanese began to see a reduction in stroke deaths and high blood pressure (1). Although the Japanese government started a campaign to reduce strokes, hypertension and salt intake in the 1960s, other social factors had a major influence on salt reduction. Food preservation shifted from the use of salt to refrigeration. And the Japanese reduced their use of soy sauce (over 1000 mg sodium in a tbsp) and miso (fermented soybean paste) (over 3600 mg sodium in a half cup).
By 2008, the deaths from strokes had fallen from over 350 per 100,000 population at its peak in the 1960s to 50 per 100,000 (see graph above). And the use of anti-hypertensive medications is not the sole cause of this reduction. Only 40% of hypertensive Japanese men use the medications.
Salt Intake Was Cut By More Than 50%
The biggest contributor to the reduction in stroke deaths is the Japanese reduction of salt intake to less than half of what it was in the 1950s. A study from 2011 (1) looked at multiple other nutrients in the Japanese diet. It felt the only other possible nutrient favorably affecting blood pressure was the high omega-3 intake. Specifically, the study authors felt multiple other nutrients had no effect or had a negative effect.
In addition to nutrients, other lifestyle changes influenced Japanese blood pressure. However, these changes mostly would have had a negative effect on blood pressure. There were increases in several factors that increase blood pressure, such as alcohol, obesity and physical inactivity.
This reduction in sodium affected even the young, so that as they aged they had fewer of the cellular changes that come from a chronic high sodium and low potassium intake. Consequently, all age groups showed a reduction in blood pressure between 1971 and 2000.
Presently, the Japanese population has one of the longest average national life expectancies of any nation. Their life expectancy is 83. A big part of this achievement comes from reducing their number of deaths from strokes to about 14% of what it was in the 1960s. Over a 40 year span they cut their salt intake in half. Thus they doubled their dietary potassium to sodium ratio, assuming potassium intake did not change.
We might say it is just coincidence. Except, it has been repeated by multiple other population groups. And there is a huge body of basic science to support how the potassium to sodium ratio affects our health. Strokes, blood pressure and heart attacks are just the tip of the iceberg.
Find Tables Of Potassium And Sodium Values Of Foods
For tables of foods with potassium, sodium and potassium sodium ratios, see the “Links to Food Potassium Tables” tab above to locate a food group you might be interested in.
1. Epidemiology and prevention of hypertension in Japanese: how could Japan get longevity? Miura K., EPMA J. 2011 Mar;2(1):59-64. doi: 10.1007/s13167-011-0069-y. Epub 2011 Mar 18.