Plasma Amino Acid Appearance and Status of Appetite Following a Single Meal of Red Meat or a Plant-Based Meat Analog: A Randomized Crossover Clinical Trial

Abstract

Background Red meat is a nutrient-dense food and a dietary staple. A new generation of plant-based meat analogs (PBMA) have been designed to mimic the experience of eating meat, but there is limited evidence about their digestive efficacy and nutritional quality. Objectives We compared the postprandial digestive response of a single meal containing meat commercially raised in New Zealand including lamb, on-farm pasture-raised beef (Pasture), or grain-finished beef (Grain) with a PBMA (Beyond Burger) sold through consumer retail. The primary outcome was the appearance of amino acids in plasma. Secondary outcomes included glucose and insulin, appetite assessment, and anthropometry. Design Thirty healthy men (20–34 years) participated in a double-blinded randomized crossover trial. Each consumed one of the four test meals on four occasions separated by a washout period of at least one week, following an overnight fast. The meal was a burrito-style wrap containing meat or PBMA, vegetables, salsa, and seasonings in a flour tortilla. The amount of Pasture, Grain, Lamb, or BB was 220 g raw (∼160 g cooked). Venous blood samples were collected over 4 hrs. Appetite and hunger status was scored with visual analog scales. Results Pre-meal amino acid concentrations in plasma did not differ by group (P > 0.9) although several non-essential amino acids differed strongly according to participant BMI. Postprandial amino acids peaked at 2–3 hours in all groups. The BB meal produced significantly lower plasma concentrations of total-, essential-, branched-chain- and non-proteogenic amino acids, than the Lamb, Pasture, or Grain meals, based on area under the time-course curves (AUC). There were no significant differences between meal groups in scores for hunger, fullness, or cravings. Conclusions Red meat meals exhibited greater bioavailability of amino acids compared to the PBMA (BB). Pasture versus Grain origins of the beef had little influence on participants’ responses. This trial was registered at ClinicalTrials.gov as NCT04545398.

Peripheral Amino Acid Appearance Is Lower Following Plant Protein Fibre Products, Compared to Whey Protein and Fibre Ingestion, in Healthy Older Adults despite Optimised Amino Acid Profile

“…The results of the present study add to those previously reported that the digestion speed of whey protein is higher than that of plant-based proteins [ 18 , 19 , 23 , 48 , 73 , 74 , 76 ], even after adding fibre. However, as previously noted, others have shown similar findings regarding AA appearance when comparing plant and animal proteins matched for net protein content [ 17 ]. One of the factors that could explain the reduced postprandial aminoacidemia concentrations observed after the PPF meals is the greater sequestration of AA in splanchnic tissue [ 45 , 78 , 79 ], which is known to be higher for plant vs. animal proteins [ 45 , 78 , 79 ].…”

“…The lack of increase in their postprandial plasma concentrations would classify them as limiting. Methionine’s low postprandial availability was recently flagged after plant-based protein ingestion in young [ 74 ] and older adults [ 17 , 76 ], miniature pigs [ 69 ], and rainbow trout [ 85 ]. Accordingly, we paid particular attention to methionine in the PPF blend design, yet reduced bioavailability of methionine occurred despite this.…”

“…Additionally, our study provided the extra proteins with fibre, as older adults often also consume sub-optimal amounts of fibre. A recent study by Pham et al [ 17 ] tested postprandial AA availability in young, healthy men after animal meat proteins (beef and lamb) or a meat analogue (pea protein-based) ingestion. All meals had a highly matched overall protein content (117–118 g) and IAA profile, yet meat ingestion resulted in a significantly higher postprandial AA appearance and higher digestion speed.…”

“…We should note that we measured static concentrations of plasma, which cannot determine the dietary protein processes responsible for the AA concentration readouts, for which stable AA isotope-labelled tracing is needed [ 83 ]. Nonetheless, postprandial AA appearance and clearance are accepted as a proxy measure for AA digestion and absorption rates [ 17 , 84 ].…”

“…It is associated with frailty [ 12 ], mobility disability [ 13 ], loss of independence [ 14 ], reduced quality of life [ 15 ], and exacerbated by undernutrition [ 16 ]. Albeit many studies have addressed the impact of animal and plant protein on postprandial AA profiles [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], to our knowledge, none have examined the potential interactions between protein and dietary fibre on AA availability, which is key for understanding how protein from plant sources, naturally higher in fibre, would appear in circulation. Furthermore, fibre is important in preventing constipation and other chronic diseases common in older populations (e.g., chronic inflammation [ 25 ], irritable bowel syndrome [ 26 ], obesity, diabetes [ 27 ], heart disease [ 28 ], and some cancers [ 29 , 30 ] known to challenge negatively muscle mass and function.…”