(P18-014-24) Controlled Feeding Trials to Administer Plant-Forward Meal Plans

Objectives: The 2020 Dietary Guidelines for Americans (DGA) emphasize plant-based diets, but adherence to plant-based foods or DGA is low among Americans. We report protocol and preliminary observations from all-food-provided 18-week randomized controlled two-arm crossover feeding trials designed to assess the impact of plant forward meal plans that follow the DGA macronutrient recommendations and are low in added sugar, artificial, and processed ingredients on age related disease biomarkers.

Methods: Healthy upper Midwestern older adults were enrolled after a two-step eligibility screening and randomized to one of the two plant forward meal plans, each for eight weeks separated by a two-week washout. The primary protein sources, lean pork and pulses, contributed at least 45% of the total protein intake. 47 participants completed 24 h dietary recalls, health and study-satisfaction surveys, physical assessments, compliance reporting, blood, stool, and urine sample submissions. Aside from a few store-bought snacks, menu items were prepared from scratch using fewer ingredients. Data reflects descriptive statistics.

Results: The study diets matched for daily total calories, macro and micronutrients, and compared to the habitual diets, provided lower amounts of fats (-10.6%), sodium (-13.9%), ultra-processed food (-35.65%), while doubled the fiber intake due to including a variety of vegetables. Protein Digestibility-Corrected Amino Acid Scoring (0.82 versus 0.98 for red meat) showed that plant-sourced proteins could achieve an adequate essential amino acid score (160% versus 194% for red meat). With comparable satisfaction ratings for both diets (p>0.05), >70% participants acknowledged the intervention diets as healthier than pre-study diets and enjoyed the convenience of portioned, ready-to-eat meals. Recruitment was challenging due to the significant dietary changes and substantial time commitment required by the study. Attrition fell to 20.34% once the intervention began.

Conclusions: Systematic testing of lifestyle recommendations using controlled feeding is logistically challenging but important. Plant-forward study menus, with or without meat, may encourage healthier consumer meal planning. Sharing complex protocols may help promote uniformity across future feeding studies.

Funding Sources: National Pork Board
USDA