Protein supplements are one of the most commercially successful and most misunderstood categories in consumer health. They are simultaneously oversold to people who do not need them and dismissed by people who genuinely would benefit from them. The evidence sits in neither extreme. For some people in some contexts, protein shakes are a practical and effective tool for meeting daily protein targets that support muscle health, satiety and long term metabolic function. For others, whole food sources are sufficient and preferred. Understanding where you sit requires knowing what the evidence actually shows not what the supplement industry or its critics would have you believe.
Why Protein Intake Matters for Healthspan
Muscle mass is one of the strongest physiological predictors of healthy ageing. It underpins metabolic rate, physical function, fall prevention, glucose regulation, and recovery from illness. Skeletal muscle is also the primary site of post-meal glucose disposal making adequate muscle mass a key determinant of metabolic health across the lifespan.
Muscle protein synthesis the process by which muscle is built and maintained is directly stimulated by dietary protein. Without adequate protein intake, muscle is gradually lost through a process called sarcopenia, which accelerates significantly after age 50 and is strongly associated with reduced healthspan, increased all cause mortality, and loss of independence in later life. Meeting daily protein targets is not a performance goal it is a maintenance strategy for the tissue that keeps you functional across decades.
The Australian Recommended Dietary Intake (RDI) of 0.8g per kilogram of body weight per day represents the minimum to prevent deficiency not the optimal intake for muscle maintenance or healthspan. Current evidence from protein research consistently supports higher targets. For generally healthy adults under 65: 1.2 to 1.6g per kilogram per day. For adults over 65, or those engaged in regular resistance training: 1.6 to 2.0g per kilogram per day. For a 70kg adult, this translates to 84 to 140g of protein daily — a range most Australians fall short of, particularly at breakfast and lunch.
Do Protein Shakes Actually Work?
Yes — when used to close a genuine gap between dietary protein intake and protein targets. A 2017 systematic review and meta-analysis in the British Journal of Sports Medicine, analysing 49 randomised controlled trials with over 1,800 participants, found that protein supplementation significantly increased muscle mass and strength gains from resistance training compared to training without supplementation. Critically, the effect was strongest in people who were not already meeting protein targets through diet. In those who were, supplementation produced no additional benefit.
A 2024 update to this evidence base, incorporating newer trials including older adult populations, confirmed the muscle preserving benefit of protein supplementation in those over 60 a group where dietary protein intake is often lowest and the consequences of muscle loss are greatest. The leucine content of the protein source is particularly important for older adults, as the leucine threshold required to stimulate muscle protein synthesis increases with age. Whey protein has the highest leucine content of any commercially available protein supplement, which is one reason it remains the most studied and most recommended for muscle maintenance purposes.
Protein shakes do not build muscle on their own. They are a delivery mechanism for protein and the evidence supports them when they help you reach a daily target that whole food alone is not covering.
Types of Protein Supplements: What the Evidence Shows
Derived from milk during cheese production, whey is the most extensively researched protein supplement and the gold standard for muscle protein synthesis. It is a complete protein containing all essential amino acids, is rapidly absorbed, and has the highest leucine content of any protein source approximately 10 to 11g of leucine per 100g of protein. Whey concentrate (typically 70 to 80% protein by weight) is cost-effective; whey isolate (90%+ protein) has the lactose largely removed and is better tolerated by those with lactose sensitivity. The evidence for whey's superiority over other protein types for muscle protein synthesis is consistent across the literature.
The most evidence-backed plant-based alternative. A 2015 randomised controlled trial in the Journal of the International Society of Sports Nutrition found pea protein produced equivalent gains in muscle thickness to whey over 12 weeks of resistance training. Pea protein is a complete protein, is highly digestible, and is well tolerated. Its leucine content is lower than whey (approximately 8g per 100g of protein), but this gap can be addressed by slightly increasing the dose. For vegans, those with dairy allergies, or anyone who prefers a plant-based option, pea protein is the most robustly supported choice.
Also derived from milk, casein is digested and absorbed much more slowly than whey releasing amino acids steadily over 5 to 7 hours. This makes it well suited to a pre-sleep dose. A 2012 study in Medicine and Science in Sports and Exercise demonstrated that 40g of casein consumed before sleep significantly increased overnight muscle protein synthesis compared to placebo. For those focused on muscle maintenance or recovery, particularly older adults, a pre-sleep protein strategy using casein or cottage cheese (naturally high in casein) is supported by evidence.
Collagen supplements have grown significantly in popularity, but the evidence for muscle protein synthesis is weak. Collagen is not a complete protein it lacks adequate tryptophan and has a low leucine content making it a poor choice as a primary protein source for muscle maintenance. Where collagen does have emerging evidence is in connective tissue support: a 2019 randomised controlled trial found that collagen peptide supplementation combined with exercise improved tendon and ligament recovery. Collagen is a reasonable addition to a varied supplement strategy but should not replace complete protein sources.
Soy is a complete plant protein with a leucine content intermediate between whey and pea. The evidence for soy protein and muscle protein synthesis is generally positive, though slightly inferior to whey in head-to-head comparisons. Concerns about phytoestrogens have not been substantiated in clinical research at normal dietary doses soy protein consumed in the context of a varied diet does not produce clinically meaningful hormonal effects in men or women based on current evidence.
Timing: Does It Matter?
The "anabolic window" the idea that protein must be consumed within 30 to 45 minutes of exercise to be effective was a dominant concept in sports nutrition for many years. More recent and rigorous research has substantially revised this. A 2013 meta-analysis by Schoenfeld and colleagues found that total daily protein intake and distribution across meals were far more important predictors of muscle protein synthesis outcomes than precise post-exercise timing. Consuming protein within a few hours of training is sensible, but the strict urgency of the anabolic window is not supported by current evidence.
What does have stronger support is protein distribution across the day. Muscle protein synthesis is most effectively stimulated by spreading protein intake across three to four meals, each providing 25 to 40 grams of protein, rather than concentrating the majority in one meal. Most Australians consume protein in a pattern that is back-loaded toward dinner a pattern that leaves muscle protein synthesis suboptimally stimulated across the morning and afternoon. Breakfast is typically the most significant gap.
What to Look For on the Label
The Australian protein supplement market is largely unregulated compared to pharmaceutical products, and label accuracy has historically been variable. Key things to check when selecting a product include the protein content per serve (aim for 20 to 30g), the amino acid profile (complete proteins are preferable), the total ingredient list (minimal additives, no proprietary blends that obscure individual ingredient doses), and whether the product carries third-party testing certification. Informed Sport, NSF Certified for Sport and Labdoor certification all indicate independent testing for label accuracy and banned substance status relevant for competitive athletes and useful for anyone wanting confidence in what they are purchasing.
Proprietary blends that do not disclose individual ingredient quantities · Artificial sweeteners in large quantities if you are sensitive to them · Excessive added sugars (check total sugars per serve aim for under 5g in a plain protein powder) · Amino acid spiking the practice of adding cheap amino acids like glycine or taurine to inflate the nitrogen content and make the protein appear higher than it is on testing. A full amino acid profile on the label or third-party testing reduces this risk.
Who Benefits Most and Who Does Not Need Them
Protein shakes are most useful for people who struggle to meet daily protein targets through whole food alone. This includes older adults with reduced appetite, people following plant based diets where protein sources require more planning, those with very high protein needs due to training volume, people recovering from illness or surgery, and anyone whose schedule makes whole food protein difficult to access consistently at breakfast or mid-morning.
They are less necessary for people who already eat three meals a day with meaningful protein sources at each e.g. eggs, meat, fish, dairy, legumes, or tofu and who are meeting their daily target through food. In this case, an additional protein shake provides no meaningful additional benefit and adds cost without purpose.
Protein shakes are not a substitute for a dietary pattern built around whole foods. They are a supplement in the literal sense something added to address a specific gap. The evidence supports them in that role. It does not support them as a foundation or a replacement for the food quality and dietary variety that broader healthspan depends on.
This article is general information only and not personal medical advice. If you have kidney disease, liver conditions, or specific metabolic health concerns, discuss protein intake targets and supplementation with your GP or an Accredited Practising Dietitian before making significant changes to your diet.