A randomized crossover trial on the effect of plant-based compared with animal-based meat on trimethylamine-N-oxide and cardiovascular disease risk factors in generally healthy adults: Study With Appetizing Plantfood-Meat Eating Alternative Trial (SWAP-MEAT)

Abstract

Background: Despite the rising popularity of plant-based alternative meats, there is limited evidence of the health effects of these products.

Objectives: We aimed to compare the effect of consuming plant-based alternative meat (Plant) as opposed to animal meat (Animal) on health factors. The primary outcome was fasting serum trimethylamine-N-oxide (TMAO). Secondary outcomes included fasting insulin-like growth factor 1, lipids, glucose, insulin, blood pressure, and weight.

Methods: SWAP-MEAT (The Study With Appetizing Plantfood-Meat Eating Alternatives Trial) was a single-site, randomized crossover trial with no washout period. Participants received Plant and Animal products, dietary counseling, lab assessments, microbiome assessments (16S), and anthropometric measurements. Participants were instructed to consume ≥2 servings/d of Plant compared with Animal for 8 wk each, while keeping all other foods and beverages as similar as possible between the 2 phases.

Results: The 36 participants who provided complete data for both crossover phases included 67% women, were 69% Caucasian, had a mean ± SD age 50 ± 14 y, and BMI 28 ± 5 kg/m2. Mean ± SD servings per day were not different by intervention sequence: 2.5 ± 0.6 compared with 2.6 ± 0.7 for Plant and Animal, respectively (P = 0.76). Mean ± SEM TMAO concentrations were significantly lower overall for Plant (2.7 ± 0.3) than for Animal (4.7 ± 0.9) (P = 0.012), but a significant order effect was observed (P = 0.023). TMAO concentrations were significantly lower for Plant among the n = 18 who received Plant second (2.9 ± 0.4 compared with 6.4 ± 1.5, Plant compared with Animal, P = 0.007), but not for the n = 18 who received Plant first (2.5 ± 0.4 compared with 3.0 ± 0.6, Plant compared with Animal, P = 0.23). Exploratory analyses of the microbiome failed to reveal possible responder compared with nonresponder factors. Mean ± SEM LDL-cholesterol concentrations (109.9 ± 4.5 compared with 120.7 ± 4.5 mg/dL, P = 0.002) and weight (78.7 ± 3.0 compared with 79.6 ± 3.0 kg, P < 0.001) were lower during the Plant phase.

Conclusions: Among generally healthy adults, contrasting Plant with Animal intake, while keeping all other dietary components similar, the Plant products improved several cardiovascular disease risk factors, including TMAO; there were no adverse effects on risk factors from the Plant products.This trial was registered at clinicaltrials.gov as NCT03718988.

Keywords: cardiovascular disease risk factors; diet; meat; plant-based alternative meat; randomized controlled trial; trimethylamine-N-oxide.

Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.

Figures

FIGURE 1

Participant flowchart. Animal, animal meat; Plant, plant-based alternative meat.

FIGURE 2

Nutrient data for means of sodium (A), saturated fat (B), fiber (C), and protein (D) consumed daily between the 2 diet phases (n = 36). Product indicates the nutrients from only Plant or Animal, whereas Nonproduct indicates the nutrients from all other sources. Together they add up to the overall amounts of nutrients. Paired t tests were conducted for energy intake and each nutrient to assess for any differences between the Plant and Animal phases. Data are based on estimates determined using NDS-R. Animal, animal meat; NDS-R, Nutrition Data System for Research; Plant, plant-based alternative meat.

FIGURE 3

TMAO concentrations at 7 time points (baseline and biweekly during the 16-wk protocol) by randomization order: Plant→Animal (n = 18) and Animal→Plant (n = 18). (A) Boxplots with medians, IQRs, 5th and 95th percentiles, and extreme values. (B) Spaghetti plots of each participant's data across the full protocol; means are represented by filled squares. Significant differences in TMAO concentrations after 8 wk of Plant compared with Animal were observed (P = 0.01). However, a significant order effect was observed (P = 0.02). For participants assigned to the Plant group first, TMAO concentrations were not significantly different at weeks 8 and 16 (mean ± SEM: 2.5 ± 0.4 and 3.0 ± 0.6 µM, respectively, P = 0.28, Wilcoxon test). For participants assigned to the Animal group first, TMAO concentrations were significantly lower during the Plant than during the Animal phase (mean ± SEM: 2.9 ± 0.4 and 6.4 ± 1.5 µM, respectively, P = 0.007). Animal, animal meat; Plant, plant-based alternative meat; TMAO, trimethylamine-N-oxide.