We know that people in Japan live longer. How important is their traditional diet? Has the introduction of more Western diets affected their health and longevity? How easy is it to adopt a Japanese Diet if we live in the UK or the US?
If you’re born in Japan you can expect to live longer than in any other major country in the world. This started back in the 1950s and 1960s when Japan began reducing deaths from infectious diseases by improvements in public health and then began to reduce strokes by using blood pressure drugs and cutting down salt in their food. That’s not the whole story though. Already by the 1950s, deaths from cancers and coronaries (heart attacks) 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 the edge, even though deaths from strokes remain relatively high, probably due to what is still a relatively high level of salt in Japanese food.
Lifestyle seems to explain this comparative advantage, not genes - studies back in the 1970s and 1980s showed that Japanese, born and living in Japan, were less likely to develop coronaries and more likely to suffer strokes than Japanese Americans, who displayed the disease patterns of the lifestyle they had adopted. Japanese, born and living in Japan, continue to be less likely to die from heart attack and more likely to die from stroke than their Western counterparts, according to an overview article published in 2011.
Among lifestyle factors, diet is potentially important. The Japanese have traditionally eaten a lot of fish, vegetables, mushrooms, fruit and soy products, but not much in the way of meat or dairy products such as milk and butter. Compared even to the Mediterranean diet (seen as one of the healthiest diets in the world) the Japanese diet is low in calories and 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 follow.
Soy may be a two edged sword. On the one hand, according to a 2014 analysis of a large scale, long term Japanes study, it is associated with a reduced risk of post menopausal breast cancer, localized prostate cancer, diabetes among overweight women and heart attack among women generally - but an increased risk of liver cancer in women. Meanwhile a 2014 analysis of population studies suggested that soy was associated with a reduced risk of breast cancer in Asian women but only a marginally significant protective effect for post menopausal women in Western countries. While a 2015 study of 29,079 Japanese people identified glutamic acid and glycine as associated with an increased risk of stroke - and soy contains an above average amount of glutamic acid as well as containing glycine (along with other aspects of the Japanese diet, such as seafood).
A study of 79,594 Japanese people, reported in the BMJ in 2016, concluded that those who followed Japanese dietary guidelines had a lower risk of death from all causes, including cardiovascular disease. They suggested this was due to a balanced consumption of energy, grains, vegetables, fruits, meat, fish, eggs, soy products, confectionaries and alcoholic beverages.
Of course, there are a whole host of cultural factors other than diet – emphasis on hygiene, regular health check-ups etc. – which may account for the Japanese living longer. But regional differences in age at death suggest that diet plays some part.
The Okinawans, who live in the southernmost islands, traditionally had the longest life expectancy within Japan – although this has reduced as more western diets have been adopted. They were affected by the same cultural factors and some aspects of their diet were similar to elsewhere in Japan. For instance they ate a lot of vegetables and moderate amounts of fish. However, their traditional diet differs in some significant respects:
- The staple carbohydrate is not rice, it is sweet potato – rated by the Center for Science in the Public Interest 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.
- Okinawan tofu contains more isoflavone, which may be connected to low Okinawan rates of breast and prostate cancer.
- Salt intake, which can cause strokes and stomach cancer if too high, is lower than elsewhere in Japan.
- Lower than average number of calories, even by Japanese standards.
As higher consumption of white rice is a factor in the rest of Japan but is associated with an increased risk of type 2 diabetes, according to an analysis of the evidence reported in the BMJ in 2012, this would suggest another reason why the Okinawan diet, which uses sweet potatoes instead, helped people there live longer.
At the same time the Japanese diet has also become more westernised in recent years – to the point that Japanese men have the same lifetime cholesterol and blood pressure levels as white Americans.
If diet is important for living longer but the Japanese diet has become more Westernised, why are deaths from coronaries less than half those in the US?
There are aspects of the modern Japanese diet that may explain this:
- The Japanese still eat more fish than most people elsewhere which means their intake of omega-3 fatty acids is high; these can reduce the risk of coronaries as long as they are combined with 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 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.
Not only can you expect to live longer if born in Japan, you may also be happier - people who eat the traditional Japanese diet showed fewer symptoms of depression.
So should we switch to eating the Japanese way? The traditional Japanese, or even 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 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. It is usually the combination of a number of different types of healthy food which seems to have a beneficial effect.
What the studies do, however, suggest 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.
So how do we adopt a Japanese style diet if we’re living in the West?
Some of the more specific local ingredients, like bitter melon or konbu seaweed may not be easily available. However:
So it is possible to adopt many aspects of the Japanese Diet – and combining this with, for instance, Western style breakfasts (with bread rather than rice) may help provide the best of both worlds when it comes to health benefits.
Judith Barnes August 2014. Reviewed and updated by Emma Juhasz, March 2017. Next review date February 2020.
The Okinawan Diet
The Japanese Diet