Does Drinking Protein Cause Any Side Effects? What You Need to Know

January 12, 2026 •

4 min read

A 2022 report from Harvard Health highlighted that some protein powders, particularly from less reputable manufacturers, contained detectable levels of heavy metals. This raises valid concerns, leading many to ask: does drinking protein cause any side effects, and are they really as harmful as some believe?

Quick Summary

Potential side effects of protein supplements include digestive distress, acne, and weight gain if overconsumed, though major health risks like kidney damage are rare for healthy individuals.

Key Points

Digestive Issues: Bloating, gas, and cramping are common side effects, often caused by lactose in whey protein or artificial sweeteners.
Kidney Health: High protein intake does not harm healthy kidneys but can exacerbate pre-existing kidney disease.
Acne: Whey protein, due to its effect on insulin-like growth factor 1 (IGF-1), can trigger or worsen acne in some susceptible individuals.
Weight Gain: Protein powders contain calories, and overconsumption without adequate exercise can lead to unwanted weight gain.
Contaminants: Some low-quality protein powders may contain heavy metals and other contaminants, highlighting the importance of choosing third-party tested brands.
Nutrient Imbalance: Relying too heavily on supplements can displace whole foods, leading to a deficiency in other essential nutrients like fiber.

The Most Common Side Effects: Digestive Issues

For many individuals, the most immediate and noticeable side effects of drinking protein come in the form of digestive discomfort. Bloating, gas, cramping, and even diarrhea or constipation are frequent complaints, often linked to the type of protein being consumed, its quality, or the user's personal tolerances.

Lactose Intolerance and Whey Protein

Whey protein, a derivative of milk, is one of the most popular and rapidly absorbed protein supplements. However, it contains lactose, a milk sugar that many people have trouble digesting. For those who are lactose intolerant, consuming whey concentrate can lead to significant gastrointestinal issues. Choosing a whey protein isolate, which contains much less lactose, or switching to a plant-based protein source can help alleviate these symptoms.

Additives and Artificial Sweeteners

Beyond the protein source itself, many commercial protein powders contain artificial sweeteners and other additives to enhance flavor. Sugar alcohols, often used as low-calorie sweeteners, are a known cause of bloating and digestive distress in sensitive individuals. Reading the label carefully and choosing products with natural sweeteners like stevia or monk fruit, or opting for an unflavored version, can be a simple solution.

The Kidney and Liver Health Debate

For years, a persistent myth claimed that high protein intake could damage healthy kidneys. This has been largely debunked by modern research, which has shown that moderate to high protein diets do not adversely affect kidney function in healthy individuals. However, this is not true for everyone.

Pre-existing Kidney Conditions

Individuals with pre-existing kidney disease or compromised kidney function must manage their protein intake carefully and under a doctor's supervision. The kidneys are responsible for filtering waste products from protein metabolism, and excessive protein can add a significant burden to already strained kidneys. The National Kidney Foundation recommends that people with chronic kidney disease (CKD) should work with a healthcare professional to determine their appropriate protein intake. Similarly, the liver's role in processing protein can be stressed by long-term overconsumption, particularly in individuals with pre-existing liver issues.

Unwanted Consequences: Weight Gain and Acne

While many people use protein supplements for weight management or muscle building, they are not immune to side effects like unwanted weight gain or skin problems.

Accidental Weight Gain

Protein powders contain calories, and adding them to your diet without adjusting your overall caloric intake can lead to a caloric surplus and subsequent weight gain. This is especially true for powders high in added sugars or when mixed with high-calorie liquids like full-fat milk. For those aiming to lose weight, focusing on whole food protein sources and using supplements sparingly can be more effective. If gaining weight is the goal, pairing protein shakes with resistance training is essential to ensure the extra calories contribute to muscle mass rather than fat storage.

The Link Between Whey Protein and Acne

Some individuals, particularly those prone to hormonal acne, may experience breakouts after consuming whey protein supplements. The hormonal cascade triggered by whey protein, specifically the increase in insulin-like growth factor 1 (IGF-1), can stimulate sebum production and inflammation, contributing to acne. Research on this link has yielded mixed results, but if you notice an increase in breakouts, switching to a different protein type or consulting a dermatologist is a wise step.

Protein Supplement Side Effect Comparison


Feature	Whey Protein Concentrate	Whey Protein Isolate	Plant-Based Protein (e.g., Pea, Hemp)
Digestibility	Can be problematic for lactose-sensitive individuals.	Generally easier to digest due to lower lactose content.	Often gentler on the digestive system, suitable for those with dairy sensitivities.
Lactose Content	Higher levels of lactose.	Minimal lactose, suitable for most lactose-intolerant people.	Lactose-free.
Risk of Acne	Linked to hormonal acne in some susceptible individuals due to IGF-1 levels.	Reduced risk compared to concentrate due to lower lactose and fat, but still possible.	Lower risk of causing acne, as it doesn't have the same hormonal effect as dairy protein.
Cost	Typically less expensive.	More expensive due to extra processing.	Varies depending on the source and processing.

Recommendations for Safe Protein Consumption

To avoid potential side effects and maximize the benefits of protein supplements, consider these guidelines:

Prioritize whole foods: Use protein powders to supplement a balanced diet, not replace whole food sources of protein, which also provide essential vitamins, minerals, and fiber.
Read labels carefully: Check for third-party certifications like NSF International or Informed-Sport to ensure the product has been tested for contaminants like heavy metals. Look for clean formulas without excessive added sugars or artificial ingredients.
Stay hydrated: When consuming more protein, especially via supplements, drink plenty of water. This helps the kidneys process waste products and prevents dehydration.
Listen to your body: If you experience consistent digestive issues, try a different type of protein. If skin problems arise, consider switching from whey to a plant-based alternative.
Consult a professional: If you have pre-existing health conditions or significant concerns, speak with a doctor or registered dietitian before incorporating protein supplements. They can provide personalized guidance based on your specific needs, as advised by organizations like the National Kidney Foundation.

Conclusion

While protein supplements offer a convenient way to meet daily protein needs, it's crucial to understand that drinking protein can cause side effects if not consumed mindfully. Many common issues, such as digestive problems, are often related to lactose intolerance, additives, or excessive intake, and can be mitigated by choosing the right type of protein and brand. Serious health risks to the kidneys and liver are predominantly a concern for individuals with pre-existing conditions, not healthy people consuming protein in moderation. By prioritizing a balanced diet, staying hydrated, choosing high-quality, third-party tested products, and listening to your body, you can safely enjoy the benefits of protein supplementation without unwanted side effects.

Frequently Asked Questions

Yes, drinking protein can cause bloating, especially if you are lactose intolerant and consuming dairy-based proteins like whey concentrate. Artificial sweeteners and other additives found in some protein powders can also cause digestive discomfort.

For healthy individuals, consuming protein powder generally does not cause kidney damage. However, those with pre-existing kidney disease or compromised kidney function must manage their intake under medical supervision, as excess protein can place a strain on their kidneys.

There is evidence suggesting a link between whey protein and acne in some individuals. The increase in insulin and IGF-1 levels associated with whey can stimulate sebum production and contribute to breakouts. If you notice a correlation, try a plant-based alternative.

Protein shakes contain calories, and if they are added to your diet without adjusting your overall calorie consumption, they can contribute to weight gain. This is more likely with high-calorie powders or shakes with added sugars.

To avoid digestive issues, consider switching from whey concentrate to a whey isolate or a plant-based protein. Also, choose products with minimal artificial sweeteners, and ensure you stay well-hydrated and consume adequate fiber.

Some reports have found trace amounts of heavy metals like lead, arsenic, and mercury in certain protein powders, primarily from lesser-regulated or lower-quality brands. To minimize risk, look for products that are independently tested and certified by third-party organizations.

While protein is essential for muscle repair and growth, it's not always necessary to get it from supplements. Many people can meet their protein needs through whole foods like lean meats, fish, eggs, dairy, and legumes. Protein powder is a convenient supplement, not a replacement for a balanced diet.