Do you need protein powder to build muscle?

Not necessarily. Protein supplements added modest gains to weight training, and total daily protein may matter more than the product.

Published October 2026

Short answer

Not necessarily. Extra protein gave modest muscle gains alongside resistance training, and two reviews suggest total daily protein matters more than the powder itself. Evidence grade B (Moderate). Several meta-analyses of randomised trials; downgraded once for inconsistency, because the older-adult and timing results disagree and the gains are small.

Key takeaways

Across 49 trials with 1,863 people, protein supplements added about 0.30 kg of fat-free mass and 2.49 kg of one-rep-max strength during resistance training [1].
In that same review, protein supplements gave no further gain in fat-free mass once total protein intake passed about 1.62 g per kg of body weight a day [1].
In one meta-analysis of 16 trials, protein source did not change absolute lean mass or strength gains, though animal protein favoured percent lean mass [2].
In older adults the evidence is mixed: a review of nonfrail adults found no significant effect on lean mass, while protein with resistance exercise gave small gains in another review [3] [4].
Changes in kidney filtration rate did not differ between higher-protein and normal-protein diets in healthy adults [5].

The short version

Not necessarily. In trials of people doing resistance training, protein supplements added modest gains in muscle and strength [1]. Taken together, two reviews suggest total daily protein may matter more than the product: in one meta-analysis of 16 trials, protein source did not change absolute lean mass or strength gains [2][1]. The evidence is mixed for older adults. The full evidence is on the protein powder topic page.

What the studies show

A 2018 meta-analysis pooled 49 randomised trials with 1,863 adults doing resistance training for at least six weeks. Protein supplements added about 0.30 kg of fat-free mass and 2.49 kg to one-rep-max strength, more than in control groups [1]. Author SMP (Phillips SM) has received grant support, travel expenses and honoraria from the US National Dairy Council, which supported trials in this review [1].

A 2020 review of 65 trials found that protein improved lean body mass by 0.62 kg in adults and 0.46 kg in older adults, but strength changes were not statistically significant [6].

Total intake may matter more than any single product. The 2018 meta-analysis found no further gain in fat-free mass once total protein intake went beyond about 1.62 g per kg of body weight a day [1]. Read together with the protein-source review, this suggests total intake matters more than the product. That is our reading of the two studies, not a finding of either [1][2].

In one meta-analysis of 16 trials, animal and plant protein did not differ in absolute lean mass or strength changes. Animal protein did favour percent lean mass, with a larger advantage in adults under 50 [2]. A 2018 meta-analysis of nine trials with 266 people found that soy and whey gave similar strength and lean mass gains during resistance training [7].

A 2026 network meta-analysis of 36 trials ranked whey first for lean mass gains alongside training [8].

Timing is less clear. A 2025 meta-analysis of five trials that compared protein before and after exercise found no effect on lean mass [9]. A 2024 network meta-analysis of 116 trials found that protein after exercise gave the largest gain in fat-free mass compared with placebo, about 0.54 kg; the authors rated the certainty as moderate [10].

The nuances

Older adults. Results disagree. A 2018 meta-analysis limited to community-dwelling older adults without frailty found no significant effect of protein supplements on lean body mass, strength or physical performance, and no extra benefit when resistance exercise was added [3]. A 2022 meta-analysis found small gains in appendicular lean mass and handgrip strength, but only in trials that also included resistance exercise; without it, protein added no benefit [4]. In the 2018 review of all adults, the benefit to fat-free mass shrank with age [1]. In people with sarcopenia or physical frailty, a 2025 review found that protein with exercise improved skeletal muscle index and handgrip strength more than exercise alone, but rated the evidence as very low [11].

Kidneys in people without kidney disease. A 2018 meta-analysis of 28 trials with 1,358 people found that changes in kidney filtration rate did not differ between higher-protein and normal-protein diets [5]. The review looked at higher-protein intakes, not protein powders specifically, and its main limit was unclear risk of selection bias [5]. It only included trials lasting more than four days, so it does not show effects over years [5].

Kidney disease. Low-protein diets have been proposed for chronic kidney disease to slow its progression [12]. In adults with non-diabetic kidney disease, stages 3 to 5, not on dialysis, a 2020 Cochrane review found that very low protein diets (0.3 to 0.4 g per kg a day) probably reduced the number reaching kidney failure compared with low protein diets. Low protein compared with normal protein may make little or no difference [12]. That review did not test protein powders, so it says nothing about supplements in kidney disease [12].

Heavy metals. In a 2025 test of 22 protein powders sold in Hungary, none had heavy metal levels above the regulatory limits [13]. The authors argue that heavy metal testing should be a routine, mandatory part of quality control [13]. A 2020 risk assessment used previously reported concentrations of arsenic, cadmium, mercury and lead; it estimated that typical use would not cause adverse effects, with a hazard index below 1 [14]. Mass-gain powders came closest to that threshold, approaching 1, while whey powders had the lowest values [14].

What the evidence does not cover. The reviews mainly measure muscle size and strength, not illness or long-term health [1]. This article does not cover pregnancy, children or medicine interactions; ask a doctor about those.

What this means for you

Protein supplements added to resistance training gave modest gains in these trials [1]. Taken together, these two reviews suggest the total amount of protein you eat each day may matter more than any particular product [1][2].

If you are older, the results are mixed, so a doctor or dietitian can help you judge your protein needs [3][4].

If you have kidney disease, check with your kidney doctor before adding protein powder, since low-protein diets are used in that condition [12].

Go deeper

Protein Powder — Protein supplements added to resistance training give modest gains in muscle and strength.