This is a tough question to answer. Each country's culinary tradition is diverse and enriched with different food choices and preparation. It is almost impossible to make any solid conclusion without drawing protest.
In general, being an island nation, Japanese food is known for its rich seafood content. Fish has been known for decades to provide good source of omega-3 fatty acid among other good nutrition. Traditional Chinese food has high portion of complex carbohydrates and good variety of vegetables. Interestingly style and ingredients aside, macro-nutrient composition for both Chinese and Japanese TRADITIONAL diet came very close. Here we are talking about % carbohydrates, fat and proteins. Both traditional diets were high in complex carbohydrates, low in fat and the proteins came from mostly plant source.
Consumption of traditional, not the modern Americanized Asian food, in our study has shown to improve glucose metabolism in both Asians and Caucasians. Modern versions of both culinary traditions are likely to include more fat, meat and rich sauces.
Answer by: William Hsu, M.D.