A series of N-of-1 dietary intervention studies with whole-grain foods and nuts reveals individual predictors of blood pressure and heart rate.

BACKGROUND/

OBJECTIVES

To determine predictors of systolic and diastolic blood pressure (SBP/DBP), of heart rate, and of whole-grains and nuts consumption, on an individual level, using a series of N-of-1 studies.

METHODS

Participants were enrolled in individual 24-wk N-of-1 studies, consisting of 8-wk observation, intervention, and follow-up periods. Participants completed personalized morning and evening questionnaires and took their own blood pressure daily. During the intervention period, participants received 3-4 portions of whole-grains and a portion of nuts daily. Fasted blood samples were collected every 4 weeks for analysis of lipids and plasma alkylresorcinol concentrations. Dynamic regression modeling was used to determine factors associated with changes in blood pressure, heart rate, and compliance with the intervention.

RESULTS

12 participants completed their study, with 11 collecting enough data to permit analysis. Dynamic regression modeling identified variables significantly affecting individual blood pressure, heart rate, and consumption of whole-grains and nuts, including sleep quality, weekday, motivation to eat well, alcohol consumption, day of menstrual cycle, outside temperature, and physical activity. Consumption of whole-grains and nuts was associated with a significant (p < 0.01) decrease in SBP for one participant, a significant (p < 0.05) decrease in DBP for two participants, and a significant (p < 0.01) lowering in heart rate for five participants.

CONCLUSIONS

The N-of-1 studies uniquely identified individual-level factors that were associated with changes in blood pressure and heart rate, and with compliance to consumption of whole-grains and nuts. N-of-1 studies are imperative to better understand heterogeneity of response and to develop more targeted, personalized and acceptable dietary advice.

TRIAL REGISTRATION: https://clinicaltrials.gov/study/NCT04326686 . First registered 20 March 2020.