Application of the Total Nutrient Index as a Precision Nutrition Tool to Address Dietary Recommendations Across the Life Course

BACKGROUND: Indexes are a standardized tool for assessing dietary exposures from foods/beverages (F&B) and have recently been extended to include dietary supplements (DS). The Total Nutrient Index (TNI) (F&B + DS) and the Food Nutrient Index (FNI) (F&B only) were developed to assess micronutrient intakes relative to Dietary Reference Intakes for micronutrients and were previously examined for relative validity among US adults. OBJECTIVE: This study examined the micronutrient quality (ie, TNI and FNI) of the diet across all age groups and compared TNI and FNI total and component scores with Healthy Eating Index 2020 scores among the US population. This analysis also sought to demonstrate the flexibility of the TNI and FNI frameworks across the life course. DESIGN: A nationally representative, cross-sectional analysis of the 2015-2020 National Health and Nutrition Examination Survey demographic, dietary, and dietary supplement data (ie, 24-hour dietary recall and DS inventory) was conducted among the US population. PARTICIPANTS AND SETTING: This study included US adults and children (aged 1 year and older; n = 19 903) who participated in the 2015-2020 National Health and Nutrition Examination Survey. MAIN OUTCOMES: The main outcome measures were TNI and FNI total and component scores (range = 0 to 100) overall and by age group, with higher scores indicating greater adherence to the Dietary Reference Intakes. STATISTICAL ANALYSES PERFORMED: TNI and FNI scores were calculated via the simple algorithm method, for 11 age group-dependent micronutrients (calcium, choline, magnesium, phosphorus, potassium, and vitamins A, B12, C, D, E, and K), and compared with Healthy Eating Index 2020 scores. RESULTS: Americans scored 72 out of 100 on TNI, but scores varied by age and were higher for the TNI than FNI (∼3 to 11 points.). Younger children (aged 1 to 3 years, TNI = 87; aged 4 to 8 years, TNI = 82) and older adults (aged 71 years and older, TNI = 77) exhibited higher TNI scores than other ages, due to higher calcium, magnesium, and vitamins A, C, and B12 intake. Healthy Eating Index 2020 total scores were low (52) overall and followed similar scoring trajectories by age group as the TNI and FNI. CONCLUSIONS: Evaluating total dietary exposures is important, considering the differential intake patterns from F&B, vs those with DS. Given low Dietary Reference Intakes adherence for some nutrients across the life span, these findings warrant improved diet quality and micronutrient density for many, to optimize nutrition and reduce diet-related chronic disease risk among Americans.