Japan boasts one of the highest life expectancies globally, a phenomenon often attributed to its unique dietary habits. Recognizing the crucial role of diet in public health, the Japanese government introduced dietary guidelines in 2000. These guidelines, emphasizing a balanced intake of various food groups, have been suggested to play a vital role in promoting the health and longevity of the Japanese population.
The Japanese Dietary Guidelines: A Balanced Approach
The Japanese government's dietary guidelines, visually represented by the "Spinning Top" (a food pyramid), advocate for a balanced consumption of energy, grains, vegetables, fruits, meat, fish, eggs, soy products, dairy products, confectionaries, and alcoholic beverages. The "Spinning Top" also emphasizes the importance of water or tea consumption and regular physical exercise. Serving sizes are relatively small, with vegetables capped at around 70 grams per serving.
Investigating the Effectiveness of Dietary Guidelines
A study by researchers from the National Centre for Global Health and Medicine (NCGHM) in Japan sought to evaluate the effectiveness of these dietary recommendations. The study involved 36,624 men and 42,920 women aged 45 to 75, with no prior history of cancer, stroke, heart disease, or chronic liver disease. Participants completed food and lifestyle questionnaires and were monitored for 15 years.
The study revealed that individuals who adhered more closely to the guidelines experienced a 15 percent lower total mortality rate over the 15-year period. This suggests a strong correlation between adherence to the Japanese government's dietary guidelines and a reduced risk of death, particularly from cardiovascular disease.
Washoku: The Foundation of Japanese Dietary Culture
Japanese people take great pride in their traditional cuisine, "Washoku," which was recognized by the United Nations Educational, Scientific, and Cultural Organization (UNESCO) as an intangible cultural heritage in 2013. The Japanese government has actively promoted Washoku, emphasizing its health benefits. Authentic Washoku relies on Japan's favorable climate, high-quality water sources, and abundant seafood.
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Health Benefits of the Japanese Diet: An Overview
The European Journal of Clinical Nutrition published a special issue dedicated to the health benefits of the Japanese diet. The issue provides an overview of how Japan achieved its world-leading life expectancy through diet. It also includes review articles focusing on the health effects of foods that characterize the Japanese diet, such as fish and omega-3 polyunsaturated fatty acids, seaweed, soy, and green tea.
Specific Findings from Prospective Studies
Several prospective studies have yielded intriguing findings. For instance, the Japan Public Health Center-based Prospective Study found that fermented soy foods, like natto, were inversely associated with cardiovascular disease incidence, particularly in women. Another study suggested that frequent green tea intake might enhance resistance against influenza.
Dietary Diversity and Cognitive Health
Dietary diversity, a hallmark of the Japanese diet, has been linked to slower hippocampal atrophy, potentially offering protection against Alzheimer's disease. This finding emerged from a 2-year follow-up study of the National Institute for Longevity Sciences-Longitudinal Study of Aging.
Social Epidemiology: The Role of School Lunch Programs
From a social epidemiological perspective, school lunch programs in Japan play a crucial role in preserving Washoku culture and reducing socioeconomic disparities in diet quality.
Evaluating the Impact of Nutrient-Based Dietary Guidelines
To assess the impact of Japan's national nutrient-based dietary guideline on lifestyle-related disease outcomes, a retrospective observational cross-sectional study was conducted using data from the 2016 National Health and Nutrition Survey of Japan. The study included 3,861 participants aged 20 years or older with low health risks of diabetes, hypertension, hyperlipidemia, and obesity.
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Methodology and Analysis
The study employed five health outcome indicators: hemoglobin A1c (HbA1c), systolic blood pressure, diastolic blood pressure, high-density lipoprotein cholesterol, and body mass index. A summary score was developed to reflect adherence to the recommended intake of seven nutrients defined by the guideline: proteins, fat, saturated fatty acid, carbohydrate, dietary fiber, sodium, and potassium.
Findings and Implications
The study revealed that only 0.3% of participants adhered to the guideline for all seven nutrients. Significant variation existed in adherence rates between different nutrients, ranging from 24.2% to 61.8%. The results indicated no clear association between the adherence score and the health outcome indicators considered in the study.
Interestingly, systolic blood pressure among participants aged 20-59 years, demonstrated significant results with positive regression coefficients for every quantile. Importantly, a positive coefficient means that the higher the adherence score, the greater the systolic blood pressure, while better (lower) systolic blood pressure levels indicate better overall control and a lesser risk of hypertension.
Japan's Progress Toward Global Nutrition Targets
Japan is 'on course' to meet two of the global nutrition targets for which there was sufficient data to assess progress. Japan is 'on course' to meet one target for maternal, infant and young child nutrition (MIYCN). No progress has been made towards achieving the target of reducing anaemia among women of reproductive age, with 19.0% of women aged 15 to 49 years now affected. Meanwhile, there has also been no progress towards achieving the low birth weight target, with 9.5% of infants having a low weight at birth.
Japan is 'on course' to meet the target for stunting, with 7.1% of children under 5 years of age affected, which is lower than the average for the Asia region (21.8%). The prevalence of overweight children under 5 years of age is 1.5% and Japan is 'off course' to prevent the figure from increasing.
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Japan has shown limited progress towards achieving the diet-related non-communicable disease (NCD) targets. 4.3% of adult (aged 18 years and over) women and 6.0% of adult men are living with obesity. The country is 'on course' to meet the target for diabetes when looking at adult women (5.0% affected), but they are 'off course' to meet the target for diabetes when looking at adult men (9.1% affected).
Dietary Reference Intakes (DRIs): A Closer Look
The Japanese government publishes Dietary Reference Intakes (DRIs) for its citizens, specifying the recommended daily amounts of nutrient consumption. These guidelines are regularly updated based on new studies and cover a wide range of targets, including healthy people and the prevention of lifestyle-related diseases.
Key Components of the Japanese DRI
The Japanese DRI includes guidelines for recommended nutrient intake ranges for each age group. It covers essential nutrients such as energy, protein, lipids, carbohydrates, fiber, vitamins, and minerals. The DRI also establishes sex-stratified estimated energy requirements (EERs) for three physical activity levels.
Unique Aspects of the Japanese DRI
Unlike some other countries' DRIs, the Japanese DRI does not specify recommended amounts of docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA). Additionally, no standard has been established for choline. The DRI sets an adequate intake (AI) and upper limit (UL) for vitamin E, with no discussion of deficiency limits.
Salt Intake and Potassium
The latest version of the Japanese DRI sets a salt intake limit of less than 7.5 grams per day for adult men and less than 6.5 grams per day for adult women. It also emphasizes the importance of consuming 3510 mg (90 mmol) of potassium per day, based on WHO guidelines and meta-analysis.
Food Balance Guides: Visualizing a Balanced Diet
Recognizing the challenges of translating nutrient quantities into real-life applications, the Ministry of Agriculture, Forestry, and Fisheries (MAFF) of Japan designed a food balance guide. This guide uses easy-to-understand visual diagrams to recommend the daily consumption of vegetables, meat, fish, dairy products, and fruits.
The Japanese Food Guide Spinning Top
The Japanese Food Guide Spinning Top visually represents the recommended daily servings of grains, vegetables, fish and meat dishes, milk, and fruits. It provides a clear and accessible way for individuals to assess whether their meals are well-balanced.
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