Association between the naturally nutrient rich score and type 2 diabetes mellitus risk: a case-control study

The Naturally Nutrient Rich (NNR) score is a validated nutrient-density metric that quantifies micronutrient adequacy relative to energy intake, yet its association with type 2 diabetes mellitus (T2DM) risk remains uninvestigated. This study aimed to examine the association between the NNR score and T2DM risk among Saudi adults.

A hospital-based case-control study was conducted at Prince Abdulaziz bin Musaed Hospital, Saudi Arabia between November 2024 and August 2025, enrolling 140 confirmed T2DM cases and 280 non-diabetic controls (same healthcare facility) matched 1:2 by age and sex. Dietary intake was assessed using a validated 152-item semi-quantitative food frequency questionnaire. The NNR score was calculated as the mean percentage daily value (%DV) of 14 key nutrients per 2,000 kcal (protein, vitamins A, C, D, E, B1, B2, and B12, calcium, zinc, iron, folate, potassium, and unsaturated fatty acids). Logistic regression models were applied to evaluate the association between the NNR score and T2DM risk, with progressive adjustment for age, sex, smoking, physical activity, BMI, and total caloric intake.

Cases had significantly higher BMI (28.32 ± 2.64 vs. 26.85 ± 2.15 kg/m²; p = 0.039), caloric intake, carbohydrate, and cholesterol consumption, alongside significantly lower intakes of dietary fibre, PUFA, magnesium, selenium, folate, vitamins A, E, and B₁, beta-carotene, and biotin compared to controls. Participants with higher NNR scores demonstrated significantly greater intakes of fibre, zinc, potassium, magnesium, and multiple B vitamins, without significant differences in total energy or macronutrient intake. Across all logistic regression models, higher NNR scores were independently and inversely associated with T2DM risk, with the fully adjusted model yielding an odds ratio of 0.90 (95% CI: 0.82-0.93; p < 0.001).

Higher dietary nutrient density, as measured by the NNR score, is significantly and independently associated with reduced odds of T2DM in Saudi adults. These findings underscore the relevance of micronutrient adequacy, beyond total energy intake, in relation to lower odds of T2DM and support the integration of nutrient density metrics into dietary guidance and public health strategies.