The study aimed to examine the impact individualized dietary advice and a food supplement of 30 grams of walnuts per day had on BP in the intensive phase of a weight-loss trial.
The study serves as a secondary analysis to the three-month baseline data from the 12-month HealthTrack randomized controlled trial that began in May 2014.
Participants (n=377) were randomly assigned to one of three dietary groups: general dietary advice (the control group), individualized advice (intervention group, I), or intervention group supplemented with 30 grams of walnuts per day (IW).
Dietary intake was assessed through self-reported diet history interviews conducted by accredited practicing dietitians.
“Previously, dietary trials for BP-lowering have primarily focused on interventions that result in reductions in sodium intake, either with or without a concomitant increase in potassium intake,” the researchers wrote.
“However, the urinary sodium-to-potassium (Na:K) ratio may be more strongly associated with BP than urinary sodium or potassium alone, and may be more indicative of total diet.”
Urinary sodium and potassium excretion were used as biomarkers for estimation of dietary sodium and potassium intake.
Relationship between weight loss and BP
Weight loss is recommended as a way to lower BP in overweight individuals and past randomized clinical trials and observational studies have been limited to the effects of single foods on BP.
However, research that focuses on individual nutrients or single foods may not consider the complexity of the interdependence between nutrients and foods and their relationship with disease outcomes, according to the researchers.
“In nutritional epidemiology, research on dietary patterns may present a broader view of the impact of nutrient and food intakes and enable a better understanding of the association between diet and chronic disease risk,” they wrote.
Study methods and results
Participants’ weight reduced significantly in all three groups over the course of three months, but SBP (systolic blood pressure) and DBP (diastolic blood pressure) reductions were greatest in the third intervention group given a personalized dietary advice along with a daily supplement of walnuts (SBP -3.7mmHg, P=0.06; DBP -2.8mmHg, P=0.057).
The third intervention group had consumed greater amounts of seed and nut products and dishes compared to the other two cohorts starting at 3-month baseline mark when the secondary analysis began and increased their intake of these foods more across the intervention period, according to the study.
“Dietary patterns, key foods such as nuts and dietary levels of nutrients such as sodium and potassium can all affect BP, but these effects are also inter-related,” researchers wrote.
“The present analysis showed that individualized dietary advice, strengthened by a daily supplement of a healthy food, 30 grams walnuts, resulted in greater decrease in urinary Na:K ratio, a parameter associated with lower BP.”
Source: European Journal of Clinical Nutrition
“Effect of individualised dietary advice for weight loss supplemented with walnuts on blood pressure: the HealthTrack study”
Authors: Rhoda N. Ndanuko, Linda C. Tapsell, Karen E. Charlton, Elizabeth P. Neale, Marijka J. Batterham