Curious whether cutting out meat undermines muscle growth? In a nine-day controlled feeding trial, healthy young adults followed either a vegan or omnivorous diet while completing resistance training and myofibrillar protein synthesis measurements. Contrary to expectations, daily synthesis rates were virtually identical across omnivorous and vegan groups, indicating plant-based whole-food diets may be able to match animal-based diets in supporting short-term anabolic responses.
Overview
- What did they test? This study employed a nine-day, fully controlled feeding + resistance-training trial in 40 healthy young adults. Participants were divided into four separate groups which involved either an omnivorous (OMN) or vegan (VGN) dietary pattern along with a balanced (B) or unbalanced protein (UB) distribution. Each group was provided meals resulting in 1.1-1.2 grams of protein per kilogram body mass per day (g/kg/day) of protein. In the balanced groups, five meals were provided containing ~20% of the daily target protein in each meal. In the unbalanced groups three meals per day were provided where ~10% of target daily protein was consumed at meal one, 30% at meal two, and 60% at meal three. Myofibrillar protein synthesis rate was measured over a nine-day period and three full-body resistance training sessions were completed on non-consecutive days. Psychological well-being questionnaires were also used to assess perceived energy, fatigue, and pleasantness during the trial.
- What did they find? Integrated myofibrillar protein synthesis rates over the nine-day period did not significantly differ between omnivorous and vegan diets, nor between balanced (5 meals/day) and unbalanced (3 meals/day) protein distributions. The omnivorous groups reported greater pleasantness, while vegan groups reported higher energy and lower tiredness post-exercise and post-meal.
- What does it mean for you? Hitting ~1.1–1.2 g/kg/day of protein from whole-food vegan sources yielded muscle protein synthesis rates equivalent to omnivorous diets, regardless of meal distribution. Improvements in energy and reduced fatigue on a vegan diet might enhance adherence in some individuals but long-term effects warrant further investigation.
What’s the Problem?
Prior research comparing plant- and animal-based proteins' effects on muscle protein synthesis has primarily relied on acute, single-meal tracer studies—often using isolated supplements 1. Research has consistently reported a blunted postprandial muscle protein synthesis response to plant proteins as compared to animal proteins 2. This may be due to “anti-nutritional” factors (e.g., phytates, lectins) which can reduce digestibility and essential amino acid availability when plant proteins are consumed in isolation. However, "real-world" diets often consist of mixed whole-food meals eaten habitually, and only one prior integrated feeding trial has compared vegan versus omnivorous patterns 3 and used relatively high protein intakes (~1.8 g·kg⁻¹·d⁻¹) that exceed typical intake recommendations. Additionally, although even versus skewed protein distribution is often promoted as an important regulator of anabolism, public health guidelines do not address meal-to-meal metabolic fates, and evidence from whole-diet interventions is scarce. Traditional methods of measuring muscle protein synthesis capture only short windows of synthesis, whereas heavy-water (D₂O) labeling can track integrated myofibrillar protein synthesis over days. This method helps to capture the combined effects of daily living and resistance exercise in free-living conditions. This new study from Askow and colleagues provides the first controlled test of plant-based versus omnivorous diets on short-term anabolic remodeling alongside resistance training and was designed to help address these gaps in the research using more ecologically valid (e.g., "real world") daily protein intakes, whole-diet patterns, meal distribution, and cumulative protein synthesis measures.
Purpose
The primary purpose of this study was to determine whether, under a fully controlled 9-day resistance-training protocol, a whole-food vegan diet providing 1.1–1.2 g·kg⁻¹·d⁻¹ of protein elicits myofibrillar protein synthesis rates comparable to an omnivorous diet in healthy young adults. A secondary aim was to assess whether protein distribution—balanced (5 meals/day) versus unbalanced (3 meals/day)—modulates these anabolic responses.
