Objective: Examine the relationship between dietary self-monitoring and change in blood pressure in adolescents with pre-/hypertension following a clinic-based nutrition intervention to lower blood pressure.
Subjects: Adolescents 11 to 18 years of age with a clinical diagnosis of pre-hypertension or primary stage 1 hypertension who participated in a 3-month behavioral, nutrition intervention emphasizing the DASH diet.
Methods: Adolescents were asked to monitor their dietary intake for 5 of 7 days each week for the duration of the nutrition intervention. Food trackers were reviewed be research personnel. Adolescents who went 2 weeks without mailing in a food tracker were offered a simpler goal tracking form to record their goals met. Food and goal trackers were independently coded to assess compliance to the skill of dietary self-monitoring. Basic compliance was assessed by determining actual days of food recording, recording sufficiency, complete recording of food descriptions, and complete recording of food amounts. Category compliance was determined based on a participant's ability to categorize foods correctly into DASH food groups. Serving compliance was determined based on a participant's ability to calculate the number of DASH food servings from foods recorded. Baseline and 3-month blood pressures were assessed at the Cincinnati Children's Hypertension Center using standard protocol. Relative blood pressure change was calculated as 3-month blood pressure minus baseline blood pressure.
Results: Over 85% of participants demonstrated excellent compliance to recording sufficiency, recording complete food descriptions and recording food amounts. Forty-six percent of participants were able to correctly classify fruits and vegetables, 21% were able to correctly classify low-fat dairy foods, and 5% were able to correctly classify DASH unfriendly foods (e.g., high fat/high sodium). Approximately half of participants (51%) demonstrated at least good proficiency in correctly calculating DASH serving amounts for low-fat dairy foods. Most demonstrated difficulty in correctly calculating DASH serving amounts for fruit and vegetables (70%) and DASH unfriendly foods (98%).
Poor versus good compliance to food tracking predicted a trend for an increase in systolic blood pressure z-score (p=0.08), as did poor versus excellent proficiency at determining the number of DASH low-fat dairy servings from foods eaten (p=0.10). Being an under-classifier versus an accurate-classifier of DASH unfriendly foods predicted an increase in systolic blood pressure z-score (p=0.04). Poor versus fair compliance to dietary self-monitoring using any form of tracking predicted a significant increase in diastolic blood pressure z-score (p=0.04), while fair versus excellent compliance predicted a significant decrease in diastolic blood pressure z-score (p=0.03). Being an under- versus accurate classifier of DASH unfriendly foods predicted a trend toward an increase in diastolic blood pressure z-score (p=0.08).
Conclusion: Good to excellent compliance to dietary self-monitoring and related skills can be a valuable adjunct to a behaviorally-based, nutrition intervention to help hypertensive adolescents lower their blood pressure.