For a healthy adult, a simple protein powder taken to fill a dietary gap has not shown any inherent toxicity. The danger lies elsewhere: in what else the powder contains, what it contains without saying so, and the underlying health of the person drinking it.
Protein is the least suspicious ingredient in the tub. Lead in a plant-based powder, a “matrix” packed with stimulants or a hidden steroid in a product bought from a shady website are far more suspect.
The following table summarises the main risk by profile, with details below:
| Profile | Main risk | Default decision |
|---|---|---|
| Healthy adult who trains | contaminants and blended products | simple, traceable powder, without stacking servings |
| Kidney disease, albuminuria | total protein intake | amount agreed with your nephrologist |
| Liver disease, hepatotoxic medication | added ingredients, green tea extracts | short ingredient list, medical advice |
| Milk, soy or peanut allergy | allergic reaction, sometimes severe | no self-experimentation |
| Acne-prone skin | possible flare-up with whey | stop-and-restart trial, dermatological advice |
| Pregnancy, planning a pregnancy | lead, excess protein | food first, advice from your midwife |
| Teenager | contaminated products, body image | rarely useful, adult supervision |
| Levodopa treatment | reduced medication effectiveness | protein distribution planned with your neurologist |
Protein is rarely the problem
Once digested, a serving of whey or pea protein becomes amino acids, just like a plate of chicken or lentils. Your body has no special “shaker” pathway. The physiological question is therefore primarily about the total amount of protein per day and the health of the person consuming it.
EFSA sets the adult reference intake at 0.83 g/kg/day. The agency states that intakes up to twice this amount are commonly consumed by healthy, active adults in Europe and are considered safe. No upper limit could be established because of insufficient data: three times the reference intake has not been validated; it simply has not been studied.
The nature of the risk changes as soon as the powder stops being just protein powder. A “mass gain” tub adds sugars and sometimes creatine. A “cutting” tub may contain caffeine, green tea extract or so-called fat-burning herbs. This is the Pill Cupboard: a pile-up of supplements taken without knowing what each one does, here concentrated in a single tub.
To estimate your target before judging a product, the guide how much protein per day for your weight and goal does the maths. If your meals are enough, the easiest risk to eliminate is the powder you do not buy.
Heavy metals: the real issue with plant-based powders
In October 2025, Consumer Reports published an analysis of 23 protein powders and drinks sold in the United States, testing two or three batches per product. More than two-thirds exceeded, in a single serving, the lead level the organisation considers acceptable for an entire day. This threshold uses California’s Proposition 65 value, which is deliberately highly protective.
The detail that matters for your choice: plant-based powders contained, on average, about nine times more lead than dairy-based powders, and about twice as much as beef-based powders. Mercury was not detected at a concerning level in any product.
To put these figures in perspective, the FDA has set interim reference levels for total dietary lead: 2.2 µg/day for children and 8.8 µg/day for women of childbearing age. A product classified by Consumer Reports as “once a week maximum” contained 6.3 µg of lead per serving. A single daily serving would therefore use up most of that reference level, before the rest of your diet is counted.
There is also a contrasting analysis. A risk assessment published in 2020 in Toxicology Reports, conducted by three consultants from Cardno ChemRisk using earlier Consumer Reports and Clean Label Project data, concluded that there was no increased non-cancer risk from arsenic, cadmium, mercury and lead at one or three servings per day. However, it noted that one product exceeded the United States Pharmacopeia’s arsenic limit and another, with a very high cadmium content, exceeded the risk threshold at three servings per day. Mass-gain products had the highest indices; whey had the lowest.
The two interpretations converge: one serving will not poison anyone, but a heavily contaminated product consumed every day for years adds avoidable exposure to a metal that accumulates and for which no safe threshold is known. “Clean” and “natural” marketing tells you nothing about the soil where the peas or rice grew.
In the European Union, food supplements are subject to maximum levels for lead, cadmium and mercury under Regulation (EU) 2023/915. A powder sold as an ordinary food for athletes does not necessarily fall into this category. Either way, a legal limit is not a test result: only a batch-specific certificate of analysis tells you what is in your tub.
Adulterated products and blends: the risk that claims victims
In July 2024, ANSES reviewed sports supplements and fortified foods, a category that includes products rich in protein, amino acids or plant extracts. Between 2016 and February 2024, its nutrivigilance system received 154 new reports, including 18 deemed very serious, two deaths and four life-threatening cases. Cardiovascular effects predominated: tachycardia, palpitations and cardiac arrest.
These reports do not prove that pure whey was responsible, and ANSES mainly targets blends. But it highlights a stark fact: some products fraudulently contain banned substances such as anabolic steroids, clenbuterol or ephedrine. Its recommendations are clear: avoid combining several products with each other or with medications, seek professional advice, favour products compliant with the European standard EN 17444:2021 and avoid buying online.
The historical scale of the problem was measured by an international study funded by the International Olympic Committee. Of 634 “non-hormonal” supplements purchased in 13 countries between 2000 and 2001, 94, or 14.8%, contained undeclared anabolic steroids. The data are old, but there is no basis for assuming the fraud has disappeared.
The same reasoning applies to the liver. EFSA concluded that supplemental doses of at least 800 mg of EGCG per day, the main compound in green tea extracts, significantly increase transaminase levels in clinical trials. A “cutting” powder containing concentrated green tea extract therefore changes its risk profile, whatever the quality of its protein.
The risks, profile by profile
You have kidney disease or albuminuria
In adults without kidney disease, trials of high-protein diets do not show a consistent decline in kidney function. Details of the tests to consider are in our analysis whey and kidneys in weight training.
The situation reverses in chronic kidney disease. The KDIGO 2024 guidelines suggest maintaining an intake of around 0.8 g/kg/day and avoiding more than 1.3 g/kg/day in adults at risk of progression. Adding a powder without doing the maths can push you over this threshold. Some formulas also contain potassium, phosphorus or creatine, which should be mentioned during check-ups.
You have liver disease or take medication requiring monitoring
Liver injuries attributed to whey alone remain isolated cases. The most frequently cited involves a 27-year-old man who had been taking creatine for eight months and whey for four weeks, and developed severe cholestatic jaundice that resolved after stopping the products. One case does not establish causality, and the combination with creatine prevents blaming a single ingredient.
The more credible risk comes from added plant extracts, fraudulent steroids and combinations with medications that already put a strain on the liver. If you have a known liver condition, review the ingredient list and protein amount with the doctor treating you.
You are allergic to milk, soy or peanuts
Whey and casein are milk proteins. “Lactose-free” does not mean “milk-free”: an isolate may be suitable for lactose intolerance while remaining dangerous for someone with a milk protein allergy. Our comparison lactose-free whey and reading labels · FR explains this distinction.
Going plant-based does not solve everything. Soy is a major allergen. Peas are not among the 14 allergens requiring mandatory declaration in the European Union, yet a 2024 review reports severe reactions to peas and lupin, as well as cross-reactions with peanuts. It also reports anaphylaxis linked to the combination of a legume and exercise. If you are allergic to peanuts, discuss pea or lupin powder with your allergist before your first shake.
Your skin is acne-prone
There is a signal, but it is weak. Case series describe teenagers and young men developing acne, often on the trunk, after starting whey, with improvement after stopping and sometimes a relapse on restarting. A 2024 Jordanian case-control study of 201 young men attending gyms found whey use in 47% of those with acne versus 27.7% of controls.
The main double-blind randomised trial tempers this picture. In 49 men who already had mild to moderate acne, 30 g of whey per day for six months did not worsen acne compared with a whey-free supplement. A small sample, male participants and limited duration: it does not rule out individual sensitivity.
Sudden, severe acne in someone who trains should also raise the possibility of anabolic steroids, sometimes present without their knowledge in a contaminated product: a 2020 dermatological review describes these two causes separately.
You are pregnant or planning to be
Protein needs increase only slightly at first. EFSA adds 1 g/day in the first trimester, 9 g in the second and 28 g in the third, which an extra serving of dairy, eggs or legumes often covers.
WHO does not recommend high-protein supplementation during pregnancy. In the 2015 Cochrane review, one trial involving 505 women associated this type of supplementation with an increased risk of a baby being small for gestational age, with a relative risk of 1.58. These data come from populations where undernutrition was common and cannot be directly applied to a shake in France. They are enough to reject the idea that adding more “cannot hurt”.
Lead matters even more here: the FDA defined a specific reference level for women of childbearing age. If a powder is genuinely useful, favour a dairy-based option or a product with published batch-specific metal analyses, and decide on the amount with your midwife or doctor.
You are under 18
The American Academy of Pediatrics sums it up: for most young athletes, performance-enhancing products offer no significant gains beyond puberty, an appropriate diet and proper training. Its concerns include high product contamination rates and an association with later steroid use.
A Canadian survey published in 2025 involving 2,731 adolescents and young adults associates use of each of the six supplements studied, including whey, with more symptoms of muscle dysmorphia. This is an association, not proof that powder causes the disorder. But a teenager piling up tubs to “get bigger” may be talking less about nutrition than about body image.
You take levodopa or a medication sensitive to interactions
Amino acids from dietary protein compete with levodopa for intestinal absorption and transport into the brain. A 2023 review describes this mechanism and the protein redistribution diets proposed for motor fluctuations. Whey taken at the same time as the medication may therefore reduce its effectiveness. Work out the timing with your neurologist, rather than cutting out protein on your own.
More broadly, tell your pharmacist about your powder if you take long-term medication. ANSES specifically advises against combining these products with medications without professional advice.
Choosing a powder that limits the risks
Before buying, check these criteria in order:
- a short ingredient list: protein, flavouring, possibly an emulsifier and sweetener, with no stimulants or plant extracts
- an identifiable manufacturer, a batch number and an accessible batch-specific certificate of analysis for heavy metals
- compliance with EN 17444:2021 if you are an athlete subject to doping tests or want to limit the risk of contamination with doping substances
- a dairy base if you tolerate milk and use it daily, or a plant-based product with published lead analyses
- allergens and trace warnings relevant to your profile
- a serving providing 20–30 g of protein, without pushing you to take three a day
Our comparison of whey products by composition and traceability applies these criteria to products sold in France. For plant-based options, the guide to choosing a vegan protein powder · FR helps you compare pea, soy and rice.
As for digestion, bloating often comes from residual lactose in whey concentrate or polyols such as maltitol, rather than the protein. Uncomfortable, not dangerous.
Signs that mean you should stop
Stop the product and consult a doctor in these situations:
- jaundice, dark urine, pale stools or unusual fatigue
- palpitations, chest pain or feeling unwell, especially with a product containing stimulants
- hives, itching in the mouth, swelling of the lips or face after taking it
- a clear acne flare-up after starting the product
- swelling, very foamy urine or an unusual decrease in urine output
Difficulty breathing, throat swelling, loss of consciousness or severe chest pain require a call to 15 or 112. Keep the tub and note the batch number: an adverse effect linked to a supplement should be reported to ANSES’s nutrivigilance system, and that report helps other consumers.
