Japan gives us its secrets for a long and healthy life

Tsuyoshi Tsuduki, associate professor of food and molecular biosciences at Tohoku University, has been studying the exact version of the Japanese diet that may contribute to a long life.

The first step was using national survey data to develop Japanese food recipes from the 1990s and American food recipes from the same time period. They freeze-dried those meals and fed them to rats for three weeks.  Researchers monitored them carefully.

The rats following the japanese diet showed less fat in their abdomens and lower fat levels in their blood, even though both diets contained the same amount of fat, protein and carbohydrates.

These results suggest that the sources of these nutrients – meat or fish, rice or wheat, for example – affect the outcome.
Later on, the researchers decided to see what different versions of the Japanese diet the Japanese population has consumed over the last half-century or so (especially in cosmopolitan cities, the diet has been more Western-influenced).

The researchers developed meal plans that took into account the changing dietary habits of the nation from 1960 to 2005 and then fed the food to mice. Foods were then cooked and freeze-dried before being observed. The trials lasted eight months this time.

Results have shown that not all Japanese diets are equal. Indeed, mice fed the 1975 diet had a lower risk of diabetes and fatty liver disease than others. When scientists examined their livers, they found that genes that prevent the manufacture of fatty acids, among other things, were activated. The diet was particularly rich in seaweed and seafood, legumes, fruits and traditional fermented seasonings, and generally had a wide variety of foods while avoiding excess sugar.

In subsequent experiments, the mice lived longer and had better memory and fewer physical impairments as they aged when they ate this 1975 diet. A Japanese diet is correlated with healthier, more active years as people age. Additionally, the Tsuduki group and colleagues also found that the diet had positive health effects on humans.

The results of a 28-day trial involving overweight participants who were placed on either the contemporary Japanese diet or the 1975 national diet revealed that those on the 1975 diet lost more weight and had better cholesterol levels. While others reported that healthy weight participants on the 1975 diet lost less weight at the end of the study, other studies found that the healthy weight subjects on the 1975 diet were in better shape at the end of the trial.

Tsuzuki and colleagues believe that people’s microbiome may be one of the elements mediating these effects after observing changes in the gut microbiome during one of their studies.

So what’s the secret? According to Tsuduki, if this version of the Japanese diet has positive effects, it could be due to the way the meals are prepared and the specifics of the nutrients. The meals are composed of several small dishes, which allow for a variety of flavours.
Ingredients are steamed or simmered more often than fried. In addition, they favor spices to season over excessive salt or sugar.In summary, the benefits of the Japanese diet may not be due to any magical quality of seaweed or soy sauce, but rather to the emphasis on eating a variety of foods cooked in a healthy manner and moderation, with a focus on vegetables and legumes.