Protein powders and shakes: evidence, safety and who might need them

The best single piece of evidence is a systematic review and meta-analysis in the British Journal of Sports Medicine that pooled randomised trials of at least six weeks of resistance training. Adding protein produced a small average gain in fat-free mass of about 0.3 kg and in one-repetition-maximum strength of about 2.5 kg over the training period. The authors stressed that doing the training matters far more than the supplement.

The review found the benefit was larger in people who were already resistance-trained and weaker in older or untrained people. It also found that timing, the dose after exercise and the protein source (whey, soy and so on) played a minor role at most. What mattered was total daily intake, with no further gain once it passed roughly 1.6 g per kilogram of body weight per day.

The NHS eating guidance points to fish, as a good source of protein, vitamins and minerals, alongside a mixed pattern of meals. Meat, eggs, dairy products, pulses and tofu all provide complete or complementary protein. A powder is a convenient way of topping up when appetite is poor, schedules are tight or a vegetarian pattern makes reaching a target harder, not a requirement.

The site guide on daily protein targets covers how much most adults need. If that figure is already met from meals, an extra scoop is likely to add calories rather than a measurable benefit.

Loss of muscle with age (sarcopenia) is often cited as a reason for protein shakes. A systematic review of fifteen controlled trials in older adults, with an average age of about 77, found that protein or essential amino acid supplements did not significantly improve the effects of resistance training on strength, muscle size, function or body composition, apart from a few individual measures. Results were limited by differences between studies and called inconclusive.

That does not mean protein is unimportant for older people; it means a supplement is not a proven shortcut and exercise remains the main intervention. Where weight and appetite are falling, a GP or dietitian can check whether the cause needs attention and whether a prescribed nutritional supplement is appropriate.

A 2024 narrative review of whey protein safety found that the main concerns relate to chronic high-dose use in sedentary people and to those with existing liver or kidney problems, and that evidence of harm in healthy exercisers is limited. It also described a consistent association between whey supplementation and acne, especially in male bodybuilders and adolescents, although evidence comes mostly from small studies. People who form kidney stones may be advised by their clinicians to limit protein, since high protein intake is linked with changes in urinary calcium.

NICE guidance on chronic kidney disease does not advise low-protein diets for adults and recommends dietetic supervision for any dietary restriction, and it notes that eGFR estimated from creatinine may be less reliable in adults who use protein supplements. Anyone with kidney disease, liver disease or diabetes should therefore discuss powders with their care team first.

• Kidney disease, kidney stones or a family history of kidney failure.

• Liver disease or abnormal liver blood tests.

• Milk allergy or lactose intolerance if the product is milk-based.

• Pregnancy and breastfeeding, where the FSA advises checking with a GP or midwife first.

• Under-18s, where training advice and dietary needs differ.

Sports supplements are a known route to accidental exposure to banned or unlisted ingredients. A survey-based paper on high school athletes in the United States found that many of the protein and pre-workout products they used contained banned, regulated elsewhere or unknown substances. That study is from another country and cannot be generalised to every UK product, but it shows why batch-tested products and reputable sellers are sensible choices, especially for people who are subject to anti-doping rules.

The FSA advises caution when buying supplements from online marketplaces, checking that any health claim is an authorised one, and reporting problems to the local authority.

• Check your usual daily intake before adding any powder, so you are not exceeding the useful range.

• Follow the serving on the label and do not exceed it; the FSA warns high doses can cause nausea and headaches.

• Read the full ingredient list for added sugars, sweeteners, caffeine and herbal extracts, which are common in shakes and pre-workout blends.

• Drink enough fluid and keep to a varied diet with vegetables and fibre.

• Tell your GP, pharmacist or dietitian that you use protein products if you have a long-term condition or blood and urine tests are planned.