Are there any negative effects of protein?

December 25, 2025 •

4 min read

According to the American Heart Association, the recommended daily allowance for protein is 0.8 grams per kilogram of body weight for adults, but many people exceed this amount, prompting questions about potential negative effects. While protein is vital for health, overconsumption can lead to various issues, particularly impacting kidney and digestive function.

Quick Summary

Excessive protein intake can strain the kidneys, cause digestive problems like constipation or bloating, and potentially lead to dehydration and nutrient imbalances. Risks are higher for individuals with pre-existing conditions or those relying heavily on unhealthy protein sources. Moderation and a balanced diet are key to mitigating these adverse effects.

Key Points

Kidney Strain: Excessive protein forces kidneys to work harder to filter waste products, a risk factor particularly for those with pre-existing kidney conditions.
Digestive Issues: Diets too high in protein and low in fiber can cause gastrointestinal discomfort, including constipation, bloating, and gas.
Dehydration Risk: Processing high amounts of protein increases the body's need for water, potentially leading to dehydration if fluid intake is not increased.
Nutrient Imbalance: Over-emphasizing protein can displace other vital food groups, potentially leading to deficiencies in fiber, vitamins, and minerals.
Source Matters: The health risks of a high-protein diet are amplified when the protein comes primarily from red and processed meats, which can increase risks for heart disease and certain cancers.
Consideration for High-Risk Groups: Individuals with conditions like chronic kidney disease or gout should be especially mindful of their protein intake and seek professional medical advice.

Understanding the Effects of Excess Protein

Protein is an essential macronutrient, playing a crucial role in building and repairing tissues, producing hormones, and supporting immune function. However, the notion that more is always better for protein consumption is a common misconception, especially given the popularity of high-protein diets. When protein intake significantly exceeds the body's needs, particularly over an extended period, it can trigger adverse effects. A typical recommended daily intake for adults is 0.8 grams per kilogram of body weight, although athletes and older adults may need slightly more. Chronic high intake, generally considered above 2.0 g/kg, is where concerns for healthy individuals often arise.

Potential Strain on Kidneys

One of the most frequently discussed risks of excessive protein intake is the potential strain on the kidneys. The kidneys are responsible for filtering the byproducts of protein metabolism, such as nitrogenous waste. When a person consumes significantly more protein than the body can efficiently use, the kidneys must work harder to excrete this waste. This can cause hyperfiltration, an increased workload on the filtering units of the kidney.

While this is an adaptive response in healthy individuals, and short-term studies often show no significant long-term harm, this extra stress is a concern for people with pre-existing kidney disease.
For those with chronic kidney disease, a high-protein diet can accelerate the decline in kidney function.
Excessive consumption of animal protein, rich in purines, can also increase the risk of kidney stones by raising uric acid levels and lowering urine pH.

Digestive Issues and Gut Health

Excess protein can also wreak havoc on your digestive system, especially when not balanced with sufficient fiber. Many high-protein diets, particularly those emphasizing animal products like meat and cheese, are naturally low in fiber-rich fruits, vegetables, and whole grains. This nutritional imbalance can lead to several gastrointestinal problems.

Constipation and bloating: A low-fiber diet, often a consequence of focusing heavily on protein, can lead to sluggish bowel movements and feelings of fullness or bloating.
Diarrhea: Some individuals may experience the opposite effect. Certain protein supplements, particularly those high in lactose like standard whey powder, can cause diarrhea in lactose-intolerant individuals. Artificial sweeteners used in some supplements can also have a laxative effect.
Gut microbiome imbalance: Relying heavily on animal-based protein sources might decrease the diversity of beneficial gut bacteria, which thrive on dietary fiber.

Dehydration and Nutrient Imbalances

High protein intake can affect the body's fluid balance, potentially leading to dehydration. As the kidneys process more nitrogen from protein metabolism, they require more water to flush out the waste products, increasing urine output. If fluid intake doesn't increase to compensate, dehydration can occur, causing symptoms like fatigue, headache, and dizziness. Furthermore, prioritizing protein can lead to displacing other essential nutrients.

A diet focused almost exclusively on protein may lack important vitamins, minerals, antioxidants, and healthy fats found in a diverse range of foods, leading to deficiencies over time.
This imbalance can impact overall health, including energy levels, immune function, and metabolism.

Comparison of High vs. Balanced Protein Diets


Feature	High-Protein Diet (e.g., >2.0 g/kg/day)	Balanced Diet (following RDA/DRI)
Kidney Impact	Increased workload for filtering nitrogenous waste. Potential for hyperfiltration.	Manages workload efficiently for healthy individuals.
Digestive Health	Higher risk of constipation or diarrhea due to low fiber or certain supplements.	Promotes healthy bowel movements and diverse gut microbiome with adequate fiber intake.
Satiety and Weight	Strong satiating effect can help with weight loss in the short term. Excess calories can lead to weight gain.	Satiety is balanced with other macronutrients. Weight management depends on overall calorie balance.
Nutrient Balance	Risk of nutrient deficiencies from neglecting fruits, vegetables, and whole grains.	Ensures a diverse range of vitamins, minerals, and antioxidants.
Heart Health	Increased risk if protein comes mainly from red/processed meat high in saturated fat.	Lower risk by emphasizing lean protein and plant-based sources.

Conclusion: Finding the Right Balance for Your Health

While protein is indisputably critical for bodily function, the notion of unlimited consumption without consequence is a myth. For most healthy individuals, moderate protein intake is well-tolerated and beneficial, but consistently consuming significantly more than is necessary can lead to potential health issues, including increased strain on the kidneys and digestive system. The source of protein also matters significantly, with plant-based proteins generally favored over excessive amounts of red and processed meats due to heart and cancer risk associations. The optimal approach is to meet your individual protein needs—considering factors like age, activity level, and overall health—without relying solely on protein or neglecting other essential food groups. Consult a healthcare provider or a registered dietitian for personalized guidance, especially if you have pre-existing health conditions or are considering a substantial change in your diet. A balanced diet, adequate hydration, and moderation are the pillars of safely incorporating protein into your nutritional plan.

Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults

Frequently Asked Questions

Yes, if your protein intake provides more calories than your body needs, the excess calories can be stored as fat, leading to weight gain. This often occurs when people rely heavily on protein shakes or bars in addition to their regular diet without balancing their total energy intake.

For healthy individuals, moderate protein intake does not typically harm the kidneys. However, in those with pre-existing kidney disease, high protein intake can accelerate the decline in kidney function. It's always best to consult a doctor, especially if you have a family history of kidney problems.

When the body processes large amounts of protein, particularly in low-carbohydrate diets, it can enter a metabolic state called ketosis. This can produce chemicals that cause an unpleasant odor in the breath.

Early theories suggested high protein intake could cause calcium loss from bones, but more recent studies suggest this is largely a myth for healthy individuals. Some research indicates that higher protein intake, especially when combined with adequate calcium, may even be beneficial for bone health.

The standard recommendation is 0.8 grams of protein per kilogram of body weight for healthy adults. However, individual needs vary based on age, activity level, and health status, so some individuals may require slightly more.

To prevent digestive issues, ensure your diet includes plenty of fiber from sources like fruits, vegetables, and whole grains. If using supplements, choose low-lactose or non-dairy options and increase fluid intake.

When it comes to certain risks like heart disease and kidney stone formation, plant-based proteins are often considered healthier than excessive amounts of red and processed meat. Plant-based sources typically contain less saturated fat and may promote a healthier gut microbiome.