What Negative Effects Does Protein Have on the Body?

December 22, 2025 •

3 min read

According to a 2017 review, consuming a high-protein diet leads to lower gains in fat mass than diets high in carbs or fats. While many associate protein with positive outcomes like muscle growth and weight loss, consuming it in excess can pose several risks. Understanding what negative effects does protein have on the body is crucial for maintaining optimal health, particularly for those on high-protein regimens.

Quick Summary

Excessive protein intake can strain the kidneys, cause dehydration, trigger digestive issues like bloating and constipation, and potentially increase cardiovascular risk, especially with high red meat consumption. Over-relying on protein supplements can lead to nutrient imbalances and unexpected weight gain due to a caloric surplus. This article explores the health risks associated with overconsuming protein and emphasizes the importance of moderation and balance.

Key Points

Kidney Strain: Excessive protein intake forces the kidneys to work harder to filter waste products, which can be particularly damaging for those with pre-existing kidney disease.
Cardiovascular Risk: High intake of animal protein, especially red meat, is linked to an increased risk of atherosclerosis by activating inflammatory pathways in immune cells.
Digestive Issues: Many high-protein diets, especially those low in fiber, can lead to digestive problems such as constipation, bloating, and discomfort.
Dehydration: The process of metabolizing and eliminating excess protein requires more water, which can increase the risk of dehydration if fluid intake is not sufficient.
Weight Gain: Consuming too much protein can contribute to a caloric surplus, and if this excess energy is not used, it can be stored as body fat, leading to weight gain.
Nutrient Imbalance: Over-reliance on protein can displace other essential nutrients like fiber, vitamins, and minerals found in fruits, vegetables, and whole grains, negatively impacting overall health.
Bone Health Concerns: Some studies indicate that high protein intake, especially from animal sources, can lead to higher calcium excretion, potentially affecting long-term bone mineral density.

Potential Health Risks of Excessive Protein Intake

While protein is an essential macronutrient for building muscle, repairing tissue, and producing hormones, overconsumption can lead to a range of negative health outcomes. The risks are often associated with consistently high intake over prolonged periods, especially in individuals with pre-existing health conditions.

Kidney Strain and Long-Term Damage

Excessive protein intake can increase the workload on the kidneys as they filter nitrogen waste products. This process, called glomerular hyperfiltration, can be particularly concerning for individuals with pre-existing chronic kidney disease (CKD), potentially accelerating its progression. While healthy kidneys can generally handle higher protein, long-term high intake may still pose a risk, and some studies suggest a link to rapid renal function decline in women with mild insufficiency. High animal protein can also increase the risk of kidney stones by increasing uric acid and calcium excretion.

Increased Cardiovascular Risk

Studies indicate a link between high protein intake, especially from animal sources, and an increased risk of heart disease. Consuming over 22% of daily calories from protein may increase the risk of atherosclerosis, with the amino acid leucine, abundant in animal protein, playing a role in activating immune cells involved in plaque buildup. High intake of red and processed meats, often high in protein and saturated fats, is associated with increased cholesterol and inflammation, further contributing to heart disease.

Digestive Issues and Dehydration

High-protein diets may displace fiber-rich foods, leading to digestive problems. A lack of fiber, common in diets heavy in animal products, can result in constipation, bloating, and gas. The increased metabolic load from processing excess protein also requires more water, which can lead to dehydration if fluid intake is not sufficient.

Nutrient Imbalance and Weight Gain

Focusing excessively on protein can lead to a deficiency in other vital nutrients found in fruits, vegetables, and whole grains. Additionally, if increased protein intake results in a caloric surplus without increased energy expenditure, the excess can be stored as fat, leading to weight gain. Some protein supplements can also contribute to unexpected calorie and sugar intake.

Bone Health Controversy

The impact of high protein intake on bone health is debated. While earlier concerns suggested high animal protein could lead to calcium loss and increased fracture risk due to its acid-forming nature, newer research indicates it might also increase calcium absorption. Sufficient calcium and Vitamin D are important mitigating factors, but long-term effects, especially in older adults, require further clarification.

Comparing High-Protein Sources: Animal vs. Plant

The source of protein is important in its potential impact on health.


Feature	Animal Protein (e.g., red meat, dairy)	Plant Protein (e.g., legumes, nuts)
Cardiovascular Risk	Higher risk, especially for red and processed meat, due to saturated fats and leucine.	Lower risk due to fiber, antioxidants, and isoflavones.
Kidney Impact	Higher acid load, potential kidney stone risk.	Lower acid load; vegetable protein linked to reduced CKD risk.
Fiber Content	None; can contribute to constipation.	High in fiber; aids digestion.
Nutrient Density	Rich in heme iron, B12, saturated fats; lacks fiber/antioxidants.	High in fiber, vitamins, minerals, antioxidants; may need careful planning for all essential amino acids.

Conclusion: The Importance of Moderation and Balance

While protein is crucial, excessive, unbalanced intake can lead to negative health effects. High protein, particularly from animal sources and supplements, can strain kidneys, increase cardiovascular risk, and cause digestive issues. Overconsumption may displace other nutrients and lead to weight gain if not managed. Healthy adults should generally aim for less than 2 grams per kilogram of body weight, prioritizing a balanced diet rich in fiber from fruits, vegetables, and whole grains. Individuals with pre-existing conditions should consult a healthcare professional for personalized guidance. A balanced diet is key to long-term health.

Frequently Asked Questions

For healthy individuals, moderate increases in protein intake are generally not considered harmful to the kidneys. However, long-term, extremely high consumption can place a significant workload on the kidneys, and those with underlying or undiagnosed kidney issues are at a higher risk of accelerated decline.

High-protein diets, particularly those lacking sufficient fiber from fruits, vegetables, and whole grains, can lead to constipation, bloating, and other forms of gastrointestinal discomfort. Whey protein supplements can also cause these issues in individuals with lactose sensitivity.

Yes, if you consume more protein than your body needs and it results in a caloric surplus, that excess energy can be stored as body fat. This is especially relevant if you are consuming protein supplements without adjusting your overall calorie intake.

Some studies have found that high protein intake, particularly from animal sources, is linked to a higher risk of heart disease. The amino acid leucine, common in animal protein, has been shown to activate inflammatory pathways that promote the formation of atherosclerosis.

Yes, consuming high amounts of protein increases the body's need for water to excrete nitrogen waste products, which can lead to dehydration if fluid intake is not increased accordingly. It is important to drink plenty of water to compensate.

The definition of "excessive" varies based on individual factors like activity level, weight, and overall health. However, many experts suggest that healthy individuals should not consistently exceed 2 grams of protein per kilogram of body weight per day. For those with kidney disease, the safe limit is much lower.

Yes, the source of protein is a significant factor. Diets high in animal protein, like red meat, are more often associated with cardiovascular risks, kidney strain, and potential bone issues. Plant-based proteins, which contain fiber and other protective nutrients, generally pose fewer risks when consumed in balance.