(P03-026-24) Effects of Red Meat Consumption on Circulating and Urinary Trimethylamine-N-Oxide (TMAO): A Systematic Review of Randomized Controlled Trials

Objectives: Randomized controlled trials (RCTs) show that intake of unprocessed lean red meat as part of healthy dietary patterns does not adversely affect traditional cardiovascular risk factors. However, cardiovascular concerns remain about the effect of red meat on trimethylamine N-oxide (TMAO), a novel cardiovascular risk factor. Thus, a systematic review of RCTs was conducted to evaluate the effect of higher red meat intake, compared to lower intake of red meat and intake of other animal derived protein sources and/or non-animal derived protein sources, on circulating and urinary concentrations of TMAO in generally healthy adults.

Methods: A systematic literature search was conducted using PubMed, the Cochrane Collaboration Library, and Web of Science on 15 February 2023. Randomized controlled trials examining the effect of a ≥7-day dietary intervention featuring red meat (i.e., beef, pork, lamb) on urinary and/or circulating (plasma or serum) concentration of TMAO in adults (≥18 years) were included. Eligible trials had a comparator group/condition that was exposed to a dietary intervention for ≥ 7 days lower in red meat and featuring white meat (i.e., chicken, turkey, other poultry), fish, eggs, dairy, or plant-based protein sources.

Results: In total, 375 publications were identified by the search strategy and 12 papers reporting the results of 10 RCTs (n=690) were eligible for inclusion. Five RCTs with a duration of 15 - 56 days showed higher TMAO concentrations in plasma/serum and/or urine following red meat intake (~71 - 420 g/day) compared to the comparator conditions. In four RCTs, no significant difference in serum/plasma TMAO concentration was observed with higher red meat diets (~60 - 156 g/day) compared to diets lower in red meat containing non-meat protein sources or poultry. One RCT showed lower TMAO concentrations following a diet containing ~11.4% of total energy from non-seafood sources, including red meat, compared to a seafood-containing diet.

Conclusions: In the limited number of RCTs conducted, inconsistent effects of red meat intake on circulating and urinary TMAO concentrations in generally healthy adults have been observed. Well-controlled trials are needed to elucidate the effect of red meat on TMAO and identify contributors to inter-individual variability.

Funding Sources: National Cattlemen’s Beef Association through the Beef Checkoff