What are the effects of eating too much protein?

December 15, 2025 •

3 min read

According to a review published in the journal ISRN Nutrition, consuming excessive protein, especially from red meat and supplements, can lead to negative health outcomes. So, what are the effects of eating too much protein?

Quick Summary

Excessive protein intake can strain the kidneys, cause dehydration, lead to digestive issues like constipation and bloating, and contribute to weight gain from excess calories. Over-reliance on animal protein can also lead to nutrient imbalances and increase the risk of heart disease.

Key Points

Kidney Strain: Excessive protein forces kidneys to work harder to filter metabolic waste, potentially leading to long-term issues, especially for those with pre-existing kidney conditions.
Digestive Problems: High-protein, low-fiber diets can cause constipation, while an over-reliance on dairy and processed meats may lead to bloating and diarrhea.
Dehydration Risk: Metabolizing excess protein increases the body's need for water, raising the risk of dehydration if fluid intake is not increased.
Nutrient Imbalance: Over-prioritizing protein can crowd out other essential foods like fruits, vegetables, and whole grains, leading to deficiencies in fiber, vitamins, and minerals.
Heart Disease Risk: Diets high in animal protein, especially red and processed meats, are linked to higher cholesterol and an increased risk of heart disease.
Bad Breath: A low-carb, high-protein diet can lead to a metabolic state called ketosis, which produces compounds that cause bad breath.
Potential for Weight Gain: Consuming too much protein can contribute to weight gain, as excess calories from any macronutrient are stored as body fat.

The Risks of Protein Overconsumption

While protein is an essential macronutrient, consuming too much can be harmful. Many people, seeking muscle gain or weight loss, often exceed their protein needs, leading to potential health issues.

Impact on Kidney Health

Excessive protein intake is linked to potential kidney strain because kidneys must work harder to filter nitrogen waste from protein metabolism. This can be particularly concerning for individuals with pre-existing kidney conditions. High protein can also increase urinary calcium, potentially leading to kidney stones.

Digestive Problems and Gut Health

High-protein diets, especially those low in fiber, can disrupt digestive health. Animal proteins, lacking fiber, can lead to constipation. Conversely, dairy or processed proteins might cause diarrhea, bloating, and gas in some individuals.

Potential for Weight Gain

Eating too much protein can result in weight gain if it leads to consuming more calories than you burn, as the excess calories are stored as fat. High-protein diets can sometimes be high in overall calories.

Nutrient Deficiencies and Imbalances

Overemphasis on protein can displace other nutrient-rich foods, leading to deficiencies in essential vitamins, minerals, and antioxidants found in fruits, vegetables, and whole grains.

Other Notable Side Effects

Dehydration: Increased protein processing requires more water, potentially causing dehydration if fluid intake isn't sufficient.
Bad Breath: Low-carb, high-protein diets can lead to ketosis, producing chemicals that cause bad breath.
Increased Risk of Certain Cancers: Diets high in red and processed meats have been associated with an increased risk of certain cancers.
Increased Risk of Heart Disease: High-protein diets rich in saturated fats from sources like red meat can elevate cholesterol and heart disease risk.

Comparison of High vs. Moderate Protein Intake


Feature	Moderate Protein Intake (0.8-1.6g/kg)	High Protein Intake (>2.0g/kg)
Energy & Metabolism	Supports satiety and metabolism without overstressing organs.	Can cause fatigue due to low carbohydrate intake and digestive issues.
Digestive Health	Promotes healthy digestion when balanced with fiber-rich foods.	Increases risk of constipation, bloating, and other GI discomforts.
Kidney Strain	Safe for healthy kidneys, with manageable waste processing.	Places a heavier workload on the kidneys, potentially risking long-term damage, especially with pre-existing conditions.
Nutrient Balance	Part of a well-rounded diet that includes fruits, vegetables, and whole grains.	Can crowd out other nutrient-dense foods, leading to deficiencies.
Heart Health	Often includes lean and plant-based sources, promoting cardiovascular health.	Associated with increased risk of heart disease, especially from high red meat consumption.

How to Find Your Protein Balance

Finding the right protein balance is crucial. Needs vary based on age, activity, and health. The recommended daily intake for most healthy adults is around 0.8 grams per kilogram of body weight. Active individuals may need slightly more. Focus on quality protein sources like lean meats, fish, eggs, beans, and lentils. Balance protein with fiber-rich carbs and stay hydrated. Consult a healthcare provider or dietitian for personalized advice.

Note: A helpful resource for understanding dietary guidelines and how to calculate your needs is the USDA's website. For an overview of nutrient requirements, visit the USDA's Dietary Reference Intakes page.

Conclusion

While essential, excessive protein intake can have negative consequences. Risks include kidney strain, digestive issues, dehydration, and nutrient imbalances. Prioritizing moderation, diverse quality sources, and a balanced diet with other nutrients is key to benefiting from protein without health risks.

Frequently Asked Questions

For most healthy adults, consuming more than 2.0 grams of protein per kilogram of body weight per day is often considered excessive and may lead to health risks.

Yes, excessive protein can increase calcium excretion in the urine, raising the risk of forming kidney stones, particularly in susceptible individuals.

Yes, when following a high-protein, low-carb diet, your body can enter ketosis, producing chemicals that cause an unpleasant odor, often called 'keto breath'.

Yes, excess protein intake contributes to extra calories. If you consume more calories than you burn, regardless of the source, your body will store the excess as fat, potentially causing weight gain.

High protein intake increases the amount of nitrogen waste your body must excrete. The kidneys use more water to perform this function, which can lead to dehydration if fluid intake is not increased.

No, the source of protein matters. High intake of red and processed meats is linked to a higher risk of heart disease and certain cancers, whereas plant-based proteins are generally considered safer.

Focus on moderation, and include a variety of protein sources, especially plant-based and lean options. Ensure your diet includes plenty of fiber from fruits, vegetables, and whole grains, and drink plenty of water throughout the day.