How to spread your protein across the day after 40.

The macro calculator on this site gives you a total daily protein target. That number is important. But a growing body of research suggests that, particularly for adults over 40, how protein is distributed across the day may be as significant as the total amount consumed.

This article covers what the peer-reviewed literature shows about per-meal protein thresholds, muscle protein synthesis in older adults, and how the ageing process changes the way the body responds to dietary protein at each meal.

Why distribution matters: the per-meal threshold

Muscle protein synthesis is the process by which the body builds new muscle tissue. It requires both a stimulus, such as resistance exercise, and a supply of amino acids from dietary protein. Research has established that muscle protein synthesis does not respond in a purely linear way to the amount of protein consumed at a single meal. Instead, the response plateaus once sufficient amino acids are available, particularly the amino acid leucine, which acts as a key trigger for the cellular signalling pathway that initiates muscle protein synthesis.[1]

A 2024 review published in Frontiers in Nutrition synthesised this research: older adults over 60 years require meals with at least 2.8g of leucine, equivalent to approximately 30g of protein from a mixed protein source, to stimulate muscle protein synthesis. This meal-level threshold is not observed in younger adults under 30, who produce a nearly linear muscle protein synthesis response across a wider range of protein intakes.[1]

The practical implication is that consuming a large amount of protein in a single meal does not proportionally increase muscle protein synthesis across the full day. Amino acids consumed beyond the saturable dose are predominantly oxidised rather than directed toward muscle protein synthesis.[2]

The research on even protein distribution

A 2014 study published in the Journal of Nutrition by Mamerow and colleagues used a randomised crossover design to compare 24-hour muscle protein synthesis in healthy adults consuming the same total daily protein in either an even distribution across meals or a skewed distribution weighted toward the evening meal, as is common in Western eating patterns. The study found that an even protein distribution produced 25% greater whole-body protein synthesis over 24 hours than the skewed distribution, despite identical total daily intake.[3]

A 2016 study published in Clinical Nutrition analysed data from 1,081 adults aged 50 to 85 from the US National Health and Nutrition Examination Survey. It found that the frequency with which individuals consumed meals providing at least 30g of protein was positively associated with leg lean mass and knee extensor strength, independent of total daily protein intake.[4]

Why older adults are specifically affected

The phenomenon of anabolic resistance, described in more detail in the protein needs article on this site, means that the muscle protein synthesis response to a given amount of dietary protein is blunted in older adults compared to younger adults. This is well documented in the research literature and forms the basis for higher protein recommendations in adults over 40.[5]

The 2024 Frontiers in Nutrition review notes that while the efficiency of dietary protein to stimulate muscle protein synthesis declines with ageing, the capacity for that response to occur is maintained if a meal provides adequate protein. In other words, the threshold rises with age, but the ceiling does not necessarily fall.[1]

Research by Moore and colleagues published in the Journal of Gerontology in 2015 found that older men required a greater relative protein intake per meal than younger men to achieve the same myofibrillar protein synthesis response.[6]

The role of leucine

Leucine is one of the nine essential amino acids and is the primary trigger for the mTORC1 signalling pathway that initiates muscle protein synthesis. The per-meal threshold of approximately 30g of protein in older adults is largely defined by the need to provide at least 2.8g of leucine.[1]

The leucine content of different protein foods varies. Animal-based proteins including chicken, beef, fish, eggs and dairy generally provide higher leucine concentrations per gram of protein than most plant-based sources. Soy protein is an exception, with leucine content closer to animal proteins than most other legume-based proteins.[7]

This does not mean plant protein is insufficient, but it does mean that adults relying primarily on plant protein sources may need to consume somewhat larger quantities to achieve the equivalent leucine threshold per meal.[7]

What this means for a typical day's eating

Research by Paddon-Jones and colleagues, summarised in a 2023 tribute review in The Journal of Nutrition, proposed a protein threshold of approximately 30g per meal to optimise muscle protein synthesis in older adults. This implies three or four meals, each providing at least 30g of protein, rather than one large protein meal and two smaller ones, as the most effective distribution pattern from a muscle preservation standpoint.[8]

As a reference point, 30g of protein is found in approximately 120g of cooked chicken breast, 150g of cooked fish, 4 to 5 large eggs, a combination of 200g of Greek yogurt with a protein-rich accompaniment, or 200g of firm tofu. These are reference amounts only, not recommendations for any individual's specific intake.