The global market for protein supplements is projected to reach approximately £21 billion this year, with powders dominating sales. These supplements, once primarily used by bodybuilders, are now widely marketed to a broad audience, including professionals and older adults, for muscle growth, hair, skin, nail, and immune system support.
However, experts suggest that the trend towards widespread protein supplementation may be outpacing the scientific evidence for its benefits in the general population. Ro Huntriss, a dietitian, stated that protein is an essential macronutrient crucial for building and repairing muscle, hair, skin, and nails, and for supporting the immune system.
Government guidelines recommend 0.75 grams of protein per kilogram of body weight daily. For an average 75kg man, this is 56g, and for a 60kg woman, it is 45g. Despite these recommendations, most individuals in the UK already exceed these amounts, with men averaging around 85g and women around 67g per day, according to the British Nutrition Foundation.
Stuart Gray, a professor of muscle and metabolic health at Glasgow University, noted that the guideline amounts are intended to prevent muscle tissue loss. He added that the average intake in the UK is already between 1.1g and 1.2g per kilogram, which is generally sufficient. He also emphasized the importance of the source of protein, cautioning against over-reliance on ultra-processed products like bars and powders, which can contain high levels of sugar and fat.
Research indicates that protein supplements do not necessarily enhance athletic performance. A study published in the International Journal of Sport Nutrition and Exercise Metabolism found no difference in performance or perceived exertion between cyclists who consumed a carbohydrate and protein powder and those who received a placebo. Professor Gray explained that protein's primary role in exercise is for recovery and repair post-training, not for endurance energy.
Graeme Close, a professor of human physiology at Liverpool John Moores University, explained that muscle repair and growth depend on amino acids, the building blocks of protein. To build muscle, protein intake must exceed the rate of muscle protein breakdown. He also debunked the idea of a strict 30g protein limit per meal, stressing instead the importance of spacing protein intake evenly throughout the day to prevent the body from breaking down its own muscle tissue.
Experts warn that protein supplements can be a significant expense without proven benefits for those not engaging in resistance training. Professor Gray stated that added protein offers no benefit in the absence of exercise, and the primary driver of muscle growth is resistance training. The body can only effectively utilize protein for muscle building up to about 1.6g per kilogram of body weight, with any excess either excreted or stored as fat. He also pointed out that the body has a limited capacity to process protein in a single sitting, suggesting that large amounts, such as 60g shakes, may not be fully utilized.
Regarding the concept of an "anabolic window" – a supposed 30-minute post-exercise period for optimal protein intake – experts suggest this window is likely much broader, potentially up to 48 hours. Professor Gray noted that the urgency often associated with this window is less critical in real-world scenarios where individuals may have already consumed protein before exercising.
When choosing protein powders, consumers are advised to be aware of ingredients. While whey and plant-based options exist, some products may be high in sugar, salt, and saturated fat. Professor Close also cautioned about potential contamination with prohibited substances, heavy metals like lead and cadmium, and advised checking for manufacturing certifications. He also noted that marketing terms like 'tone' or 'slim' often targeted at women are misleading, as protein needs are based on body weight, not gender.
Dietitian Dr. Emily Leeming highlighted the importance of muscle strength for overall health and longevity, particularly in older adults. She recommends that older adults aim for 1 to 1.2g of protein per kilogram of body weight daily. Beyond protein, a balanced diet rich in vegetables, fruits, whole grains, nuts, and fish supports muscle health by providing essential nutrients like magnesium and vitamin C, and can help reduce inflammation. Studies suggest that diets high in ultra-processed foods are associated with increased fat storage within muscles, indicating poorer muscle quality.