Process evaluation of a clinical preventive nutrition intervention

We report process data on the feasibility of delivering a clinical preventive nutrition intervention that was effective in increasing participants' consumption of fruits and vegetables. We also examine relationships between process variables and study outcomes.

We randomly assigned six practice sites in a managed care organization to a dietary intervention or control condition. We invited adults 18 years of age or older scheduled for routine health visits within the subsequent 2 months to participate. Of the 566 patients we contacted from the intervention sites, 230 (41%) enrolled. From the control sites, we contacted 617, and 274 (44%) enrolled. Intervention participants received a tailored letter providing feedback on their consumption of target foods together with recommendations for improvement, stage-matched nutrition education booklets, a diet-health endorsement from their primary care providers (PCPs), and two motivational counseling telephone calls. Of enrollees, 195 (85%) in the intervention group and 252 (92%) in the control group returned the final survey 3 months later.

Seventy-one percent of both participants and PCPs reported that the PCPs had discussed the relationship between diet and health at their visit. Fifty-seven percent of participants and 62% of PCPs reported that they discussed the complete diet-health endorsement, which included: (1) acknowledgment of the relationship between diet and health and (2) tailored study recommendations. The inclusion of both parts of the diet-health endorsement, but not the length of time spent, appeared to correlate with healthful outcomes.

These process data suggest that the brief PCP diet-health endorsement contributed to the intervention effect on fruits and vegetables.