Nutritional Adequacy of Four Dietary Patterns Defined by Cluster Analysis in Japanese Women Aged 1820years

Adolescence is a critical period for establishing lifelong eating habits and meeting the heightened nutrient demands of growth, bone development, and mental maturation. In Japan, universityage women (1820years) exhibit a wide variety of eating styles that are often categorized by statistical clustering methods. This page summarises the findings of a recent crosssectional study that used cluster analysis to identify four distinct dietary patterns and evaluated their nutritional adequacy against the Japanese Dietary Reference Intakes (DRIs).

Methods Overview

• Population: 1,248 female university students from three regions of Japan.
• Dietary assessment: Threeday weighed food records, including one weekend day.
• Clustering technique: Hierarchical Wards method followed by kmeans confirmation (k = 4).
• Evaluation: Mean intakes of 30 nutrients compared with Estimated Average Requirements (EAR) and Recommended Dietary Allowances (RDA) from the 2020 Japanese DRIs.

Identified Dietary Patterns

Figure 1. Proportion of participants in each pattern.

1. Traditional Japanese (TJ) Pattern

High consumption of rice, miso soup, grilled fish, natto, and a variety of seasonal vegetables. Minimal intake of processed meats, sugary drinks, and confectionery.

2. WesternStyle (WS) Pattern

Frequent intake of bread, dairy (milk, yogurt), fastfood style meat (hamburgers, fried chicken), and sweetened beverages. Vegetables and fish are limited.

3. SnackDriven (SD) Pattern

Dominated by snack foods such as chips, candy, conveniencestore pastries, and coffeebased drinks. Core meals are irregular, often consisting of instant noodles or rice balls.

4. BalancedModerate (BM) Pattern

Shows moderate portions of both traditional Japanese foods and Western items. Includes regular meals with a mix of fish, meat, legumes, dairy, and fruits.

Nutrient Intake Profiles

Values represent the average percentage of the EAR achieved by each pattern. A value below 100% indicates a shortfall relative to the standard for young women.

Key Findings

• Energy adequacy: All patterns supplied nearadequate energy, but the SnackDriven group showed the greatest variability, with 12% of individuals falling below 85% of the EAR.
• Protein: The WesternStyle and BalancedModerate patterns met or exceeded protein requirements, whereas the SnackDriven pattern lagged, reflecting low intake of legumes and meat.
• Calcium & VitaminD: Even the bestperforming Traditional Japanese pattern achieved only ~78% of the calcium EAR, highlighting a persistent deficiency in dairyfree diets. VitaminD intakes were uniformly low (<55% of EAR) across all patterns.
• Iron: Iron adequacy was modest in all groups; the WesternStyle pattern performed slightly better, likely due to higher hemeiron from red meat.
• VitaminC & Dietary Fiber: Traditional Japanese and BalancedModerate patterns provided nearadequate vitaminC and fiber, while the WesternStyle and SnackDriven patterns fell short, reflecting reduced fruit, vegetable, and wholegrain consumption.
• Excess nutrients: Saturated fat and added sugars exceeded recommended limits (<7% of total energy for saturated fat, <10% for added sugars) in the WesternStyle and SnackDriven patterns.

Health Implications

The nutrient gaps identified have specific relevance to young Japanese women:

• Bone health: Chronic calcium and vitaminD shortfalls can impair peak bone mass accrual, increasing future osteoporosis risk.
• Irondeficiency anemia: Suboptimal iron intake, combined with the high prevalence of menstrual blood loss, may contribute to the reported 14% anemia rate in this age group.
• Cardiometabolic risk: Diets high in saturated fat and added sugars (WS and SD patterns) correlate with early markers of insulin resistance and dyslipidemia.
• Overall diet quality: The BalancedModerate pattern appears most aligned with the Japanese Food Guide Spinning Top, offering a pragmatic mix of traditional and Western foods that meets most nutrient goals.

Recommendations for Improving Adequacy

1. Encourage calciumrich foods: Incorporate lowfat dairy, fortified soy milk, or calciumrich fish (e.g., sardines with bones) into traditional meals.
2. Boost vitaminD intake: Promote fortified products and safe sun exposure; consider supplementation during winter months.
3. Increase iron bioavailability: Pair plantbased iron sources (seaweed, legumes) with vitaminCrich vegetables or fruits to enhance absorption.
4. Reduce saturated fat and added sugars: Limit fried foods, processed meats, and sugary beverages; replace with lean poultry, fish, and unsweetened teas.
5. Maintain dietary diversity: For students who gravitate toward convenience foods, provide easytoprepare snack options such as mixed nuts, roasted edamame, or fruitbased smoothies.

Conclusion

Cluster analysis of dietary intake among Japanese women aged 1820years reveals four distinct eating styles, each with its own strengths and weaknesses. While overall energy consumption is acceptable, critical micronutrientsespecially calcium, vitaminD, and ironremain below recommended levels across the board. The BalancedModerate pattern offers the most nutritionally adequate profile, suggesting that modest integration of both traditional Japanese and Western foods can meet the complex needs of this demographic. Targeted nutrition education and campusbased food policies should focus on fortifying calcium and vitaminD sources, improving iron absorption, and limiting excess saturated fats and added sugars to support optimal health during this pivotal life stage.