Research shows that people in Japan have an average life expectancy higher than most other countries.
How important is a traditional Japanese diet to life expectancy? Has the introduction of more Western diets affected their health and longevity? How easy is it for us to adopt a Japanese diet if we live outside Japan?
In this article, we try to answer these questions by looking at research-based evidence:
- Japanese longevity
- Lifestyle vs genes
- Diet as a lifestyle factor
- The Japanese diet, Western diets and CVD
- The Japanese diet and happiness
- Should we switch to a Japanese diet?
- How can we adopt a Japanese-style diet if we’re living in the West?
If you were born in Japan, you can expect to live longer than in almost any other developed country, despite there being a slight fall in Japanese longevity in 2021, which was probably due to the Covid pandemic.
This trend in increasing longevity dates back to the 1950s and 1960s, when Japan began reducing deaths from infectious diseases by improvements in public health, by reducing mortality due to strokes with blood pressure drugs, and by cutting down salt in food.
That’s not the whole story though. Already by the 1950s, deaths from cancers and heart attacks (coronaries) were low in Japan compared with other developed countries and, in the case of coronaries, continued to fall. This appears to have given the Japanese a ‘life expectancy advantage’, even though deaths from strokes remain relatively high, probably due to what is still a relatively high level of salt in Japanese food.
Lifestyle vs genes
Lifestyle rather than genes seem to explain this comparative advantage. Studies in the 1970s and 1980s showed that Japanese who were born and were living in Japan were less likely to experience coronaries than Japanese Americans. More recent research appears to confirm that third-generation Japanese Americans display the disease patterns of the American lifestyle they have adopted.
In contrast, according to a paper published by the American College of Cardiology in 2020, those Japanese who were born and were living in Japan continue to be less likely to die from cardiovascular disease than in most other countries.
Diet as a lifestyle factor
Among lifestyle factors, diet is important. That is the verdict of a review published in 2021 which identified a combination of important factors in the modern Japanese diet:
- High intakes of fish, plant foods and non-sweetened drinks
- Reductions in salt intake
- A modest increase in Westernised foods such as meat, milk and dairy products.
The Japanese diet and the Mediterranean diet
Compared with the Mediterranean diet (seen as one of the healthiest diets in the world) the Japanese diet is low in calories and low in fats of any kind. It is well established that eating fruit and vegetables can reduce the risk of heart disease, stomach cancer and colorectal cancer, while high-calorie foods promote obesity and all the problems, such as diabetes, that can result from such a diet.
The Japanese diet and soy
The Japanese diet is said to contain the highest amount of soy in the world. Studies of soy’s effects on health have sometimes produced mixed results. However, the Harvard School of Public Health concludes, ‘recent population studies suggest that soy has either a beneficial or neutral effect on various health conditions. Soy is a nutrient-dense source of protein that can safely be consumed several times a week, and probably more often, and is likely to provide health benefits—especially when eaten as an alternative to red and processed meat.’
A study of 79,594 Japanese people, reported in the British Medical Journal in 2016, concluded that those who followed Japanese dietary guidelines had a lower risk of death from all causes, including cardiovascular disease. This study suggested this was due to a balanced consumption of energy, grains, vegetables, fruits, meat, fish, eggs, soy products, confectionaries and alcoholic beverages.
The Japanese diet and rice
Higher consumption of white rice is a factor in the rest of Japan but, according to study of 21 countries reported in 2020, white rice is associated with an increased risk of type 2 diabetes in South Asia.
This would suggest another reason why the Okinawan diet (see below), which uses sweet potatoes instead of rice, helps people there live longer.
The Center for Science in the Public Interest in the USA, rates sweet potatoes as the most nutritious of all vegetables and high in the anti-oxidants, fibre and vitamins that help protect against heart and other age-related diseases.
Regional differences in diet: Okinawa
Of course, there are a whole host of cultural factors other than diet –hygiene, regular health check-ups etc. – which may account for the Japanese living longer. But regional differences of ‘age at death’ suggest that diet plays some part.
For instance, the Okinawan Japanese, who live on a group of islands about 400 miles south of mainland Japan, traditionally had the longest life expectancy within Japan, although this life expectancy has reduced in recent years as they have adopted more western diets and lifestyles.
Okinawans are affected by the same cultural factors, and some aspects of their diet are similar to other parts of Japan. For instance, they eat a lot of vegetables and moderate amounts of fish. However, their traditional diet differs in some significant respects:
- The staple carbohydrate in Okinawa is not rice; it is sweet potato.
- Okinawan tofu contains more isoflavone, which may be connected to the low rates of breast and prostate cancer in Okinawa.
- Salt intake, which can cause strokes and stomach cancer if too high, is lower in Okinawa than elsewhere in Japan.
- Okinawans traditionally have a lower-than-average intake of calories, even by Japanese standards.
The Japanese diet, Western diets and CVD
At the same time, the Japanese diet has also changed in recent years, with a study published in 2018 reporting a ‘continuous Westernisation of the Japanese diet’.
This change in diet may help explain a continuous and marked rise in total cholesterol intake, which is usually seen as a risk factor for CVD.
However, other factors appear to be at work here, as deaths from coronary heart disease (CHD) have actually fallen in Japan. A 2015 study reported that this decline in CHD mortality, despite a continuous rise in total cholesterol, was unique to Japan. It concluded, ‘This may suggest some protective factors unique to Japan’.
Why have deaths from coronaries fallen in Japan?
If diet is important for living longer, and the Japanese diet has become more Westernised, why have deaths from coronaries fallen in Japan? There are aspects of the modern Japanese diet that may explain this:
- The Japanese still eat more fish than most people elsewhere, although this consumption has been falling and has led the Japanese government to introduce a ‘Fast Fish’ campaign to promote consumption.
- High fish consumption means that the intake of omega-3 fatty acids is also high. Omega-3 can reduce the risk of coronaries as long as it is combined with traditional Japanese (i.e., low) levels of saturated and monounsaturated fats.
- Many Japanese have now adopted a diet typical of a Westernised breakfast: high in bread, confectionaries, and milk and yogurt. This diet may actually help reduce the risk of heart disease, because it involves less salt (a factor in high blood pressure) and less alcohol. It can also reduce the risk of type 2 diabetes, not just because of the lower salt intake but because bread substitutes for white rice.
- A moderate amount of meat (less than 100g a day) does not increase the risk of heart disease and may provide some protection against strokes.
The Japanese diet and happiness
Not only can you expect to live longer if you are born in Japan, you may also be happier.
According to a study published in 2021, women who eat the traditional Japanese diet showed fewer symptoms of depression.
Should we switch to a Japanese diet?
The traditional Japanese diet, or even the Okinawan diet, won't guarantee a longer, or happier, life. For one thing, it is difficult to isolate diet from other aspects of Japanese life which may also play a part. For another, the high salt content of Japanese food, soy sauce in particular, can lead to high blood pressure and diabetes.
Although there are indications as to which particular foods may be more beneficial – sweet potato, vegetables, fruit, soy, and fish for example – nothing has been conclusively identified as the magic bullet. However, this tends to be true of most regional diets, including the Mediterranean diet.
It is usually the combination of a number of different types of healthy foods that seems to have a beneficial effect.
What the studies do suggest, however, is that more vegetables, fish and fruit in our diet and less fat and fewer calories is likely to be good for our health here in the West.
How can we adopt a Japanese-style diet if we’re living in the West?
Although some of the more specific local ingredients – such as bitter melon or konbu seaweed – may not be easily available outside Japan, we can still adopt a Japanese-style diet.
- Many of the ingredients of a Japanese or Okinawan diet are now fairly readily available, including vegetables, fruit, tofu, sweet potatoes, miso soup, green tea, and fish.
- There are now ranges of products like soya milk available in supermarkets for those who want to follow a low dairy diet.
- Japanese approaches to cooking and eating – from stir fry to preparing raw fish (for instance for sushi) – are now also options in the West.
- If we exercise a degree of self-control over what we eat, we can limit both our intake of meat and our intake of calories.
So it is possible to adopt many aspects of the Japanese diet. Combining these aspects with, for instance, Western style breakfasts (with bread rather than rice) may help give us the best of both worlds when it comes to health benefits.
Judith Barnes and Emma Juhasz, November 2022. Next review date October 2026.
Other relevant articles on the Age Watch website:
Living longer: Why do people live longer in Japan?