Protein powder harms

Short answer

In healthy adults without kidney disease, high protein has not been shown to impair kidney function; for the liver and bone as well, no harm was shown or the evidence is insufficient. The more concrete risks are these: the protein limit in chronic kidney disease, acne case reports in adolescents, and product quality (protein amount on the label not matching, heavy metals, contamination with prohibited substances). ^{[1] [3] [6]}

Does protein powder harm the kidneys?

The meta-analysis by Devries and colleagues compared high-protein diets (≥1.5 g/kg, ≥20% of energy, or ≥100 g/day) with normal or low-protein diets in randomized trials lasting more than 4 days in adults without kidney disease. 28 studies (1,358 people) entered the analysis. Post-intervention GFR was trivially higher in the high-protein group (SMD 0.19; 95% CI 0.07–0.31); the change in GFR did not differ between groups (SMD 0.11; 95% CI −0.05–0.27). The authors summarize the result as “high protein intake does not adversely affect kidney function” and say that the risk of selection bias in the included studies is unclear; in their own GRADE tables the certainty of evidence is “very low” for change in GFR and “low” for post-intervention GFR. One of the authors reported receiving research funding and speaking fees from dairy and beef industry organizations. ^[1]

This result is for healthy adults. The studies look at high-protein diets, not protein powder; durations vary, being longer than 4 days. The EFSA 2012 opinion also states that data are insufficient to set a reference value based on health outcomes that may be associated with protein intake; so “no harm was seen” and “proven that there is no harm” are not the same thing. ^[9]

The situation is different in people with chronic kidney disease

The KDIGO 2024 guideline recommends maintaining a protein intake of 0.8 g/kg/day in adults with chronic kidney disease (CKD) at stages G3–G5 (2C: weak recommendation, low certainty). It also includes, as a practice point, avoiding high protein intake (>1.3 g/kg/day) in adults with CKD at risk of progression. The guideline does not recommend a low-protein diet in metabolically unstable people; not restricting protein in children with CKD because growth may be impaired, and considering higher targets in older adults with CKD if frailty and sarcopenia are present, are also separate practice points. ^[3]

The ISSN also accepts that people with kidney failure benefit from a protein-restricted diet and finds it inappropriate to generalize this pathophysiology to exercising people without kidney disease. ^[2] In those with a diagnosis of kidney disease, elevated creatinine, or protein leakage in the urine, the opinion of a physician and dietitian is needed before starting protein powder; this guide gives no personal target.

Does protein powder harm the liver?

For the liver, the data reported by the ISSN are limited but consistent: in a series of studies by Antonio and colleagues in people doing resistance training, about 3.4–4.4 g/kg/day of protein was prescribed and no harmful effects were reported; in the study where intake up to 3.4 g/kg/day lasted 8 weeks, no changes were seen in blood markers (including kidney and liver function), and in a one-year crossover-design study with 14 men, no harm to kidney and liver function or blood lipids was found at a mean intake of 3.3 g/kg. These are small, healthy, resistance-trained groups; they cannot be generalized to people with liver disease, women, adolescents, or older adults. ^[2]

The main warning regarding the liver concerns the substances added to the powder rather than the powder itself: a product analysis in India reports that some protein formulations contained herbal extracts that, according to the authors, may carry liver toxicity, such as green tea extract, turmeric, Garcinia cambogia, and ashwagandha. ^[6] For this reason, a product labeled “protein powder” cannot be assumed to be pure protein; the ingredient list provides this information.

Does protein powder draw calcium from bone?

The evidence behind this common concern is weak. The umbrella review prepared for the German Nutrition Society guideline examined whether protein intake above the recommended level (0.8 g/kg/day in young adults, 1.0 g/kg/day in older adults) affects bone density and fracture risk. 11 systematic reviews published between 2008 and 2021, covering cohort and randomized studies, were included; the certainty of most results was found to be “low” or “very low,” and the overall certainty of evidence “insufficient.” The only exception was probable evidence for a reduced risk of hip fracture when high and low protein intake were compared. ^[4]

So high protein has not been shown to weaken bone; but there is also no strong evidence of protection for bone outcomes. Calcium itself and its food sources are covered in the calcium guide.

Does protein powder cause digestive problems or lactose problems?

Whey and casein are milk-derived. In the production process described by the ISSN, proteins are first separated from lactose and fat in milk and then purified by filtration steps; those with 29–80% of dry weight as protein are counted as concentrate, and those above 90% as isolate. ^[2] According to the ISSN, the purity of the product increases as filtration steps increase; the tolerance of concentrate versus isolate in people with lactose intolerance is not compared in the ISSN text. In those diagnosed with milk allergy, the suitability of milk-derived products is assessed with an allergy physician.

How often bloating, gas, or diarrhea occur in people using protein powder was not measured as an outcome in any of the studies on this page; the question “in what percentage do side effects occur” therefore remains unanswered. The same applies to digestive complaints related to plant proteins and additives.

Does protein powder cause acne?

The only source for acne is a small case series reported from Türkiye: 6 healthy adolescent boys using whey protein supplements for bodybuilding who developed acne only on the trunk. The authors state that it is known from previous studies that milk and dairy products can trigger acne and that there is increasing evidence for whey as well; these sentences are background information in the introduction of the article, not a finding of the series. The series’ own finding is that trunk acne appeared in these 6 youths after whey use. There is no control group and causality is not shown. ^[5]

Therefore neither “whey causes acne” nor “does not” can be concluded. Protein powder use in adolescents with acne is handled with the opinion of a physician or dermatologist.

Do protein powders have problems with heavy metals and incorrect labels?

Two separate laboratory studies report problems in product quality; both are from different markets and cannot be generalized to products in Türkiye.

• Indian market (2024): The “Citizens Protein Project” is a self-funded analysis published in a peer-reviewed journal; most of the popular protein supplements did not meet the protein amount on the label, while some showed more protein than declared, which raised suspicion of “protein/amino acid spiking.” The authors also reported detectable mycotoxins and pesticide residues in major brands and heavy metals such as lead and arsenic in many formulations. ^[6] Amino acid spiking is the addition of cheap amino acids that artificially raise the measured protein amount.
• European market (2023): Spanish researchers checked the protein content on the label by the Kjeldahl method in 47 isolate and concentrate whey supplements, obtained from different points of sale in 2021–2022 and described as representing the European market. The mean declared content was 74.3% and the measured mean 70.9% (range 18–92.3%); the difference was statistically significant, and 17% of samples contained slightly more protein than declared. The authors state that non-conformity to label declarations is high and that product quality should be monitored; the study received no external funding. ^[7]

These findings do not mean “all products are bad”; but they show that the grams of protein seen on the label are not a reliable measure on their own. Details of label reading are described on the whey protein page and the how to use page.

Can protein powder cause problems in doping tests?

For athletes subject to doping control, the main risk is not the powder’s natural content but contamination. The review by Walpurgis and colleagues reports that anabolic androgenic steroids and stimulants are frequently found in supplements as undeclared content, either from cross-contamination under poor manufacturing conditions or from deliberate addition; even small trace amounts can make a doping test positive. The review reports that in an analysis examining 48 supplements (29 protein concentrates, 15 creatine products, 4 citrus extracts), prohibited steroids were found in two samples, one of which was a whey “gainer” product. The review also reports that a study that screened 634 supplements not containing hormones and found undeclared anabolic steroids in 14.8% was repeated a few years later and this time found them in 4 of 597 products (0.7%), meaning that the proportion of contaminated products has decreased since 2004. ^[8]

The same review recommends that, if supplement use is deemed necessary, they be obtained from sources with low contamination risk, and notes that independent product test results are published in databases such as the Cologne List, the Informed Sport list in the United Kingdom, and the NZVT list in the Netherlands. ^[8] This guide does not recommend products or brands.

Who needs a physician’s assessment regarding protein powder?

• People with chronic kidney disease: KDIGO recommends a protein limit. ^[3]
• Children and adolescents: The acne case series is above; data on the benefit and safety of protein powder at these ages are limited.
• Pregnancy and breastfeeding: Safety data specific to protein powder are limited; the decision to use is made with a physician.
• People diagnosed with milk allergy: Whey and casein are milk proteins.
• Athletes subject to doping control: Because of contamination risk.

This guide does not recommend a personal dose; if there is a concerning complaint or laboratory result (such as elevated creatinine or elevated liver enzymes), interpretation is the physician’s job.

Detailed guideProtein powder: types, daily need, and evidence→ Detailed guideWhey protein: concentrate, isolate, hydrolysate, and label reading→ Detailed guideWhen to take protein powder?→ Detailed guideHow to use protein powder?→