Protein intake is a widely debated topic among nutritional scientists and cancer researchers. Many individuals adopt high-protein diets to support weight loss, muscle gain, or general health, but questions persist about whether prolonged and excessive protein intake could contribute to cancer development. At the same time, since most cancer patients undergoing treatment experience malnutrition, weight loss, muscle wasting, and immune suppression, many physicians recommend increasing protein consumption. But should they?
How much protein is too much for cancer patients? How about healthy individuals? How much can they eat without exposing themselves to long-term harm? Let’s answer these questions and more below.
Protein and Its Sources
Protein benefits the body in many ways. It supports tissue growth [1], repairs damaged cells [2], strengthens the immune response [3], and forms the building blocks of enzymes and hormones [4]. All of these processes require a healthy intake of dietary protein.
The Mayo Clinic Health System recommends protein to account for 10% to 35% of daily calories. For a 2,000-calorie diet, that translates to 200 to 700 calories from protein, or about 50 to 175 grams. To prevent deficiency, the dietary guideline for a generally inactive adult is 0.8 grams per kilogram of body weight [5].
There are animal- and plant-based protein sources. Animal proteins include poultry, beef, pork, eggs, milk, cheese, and fish. Plant proteins come from soy, legumes, nuts, seeds, whole grains, and vegetables. Many people also consume protein powders from whey, casein, soy, or peas.
While both animal and plant proteins supply the necessary amino acids, their composition and effects on health differ. In fact, one is more likely to increase cancer risk than the other.
High-Protein Diets and Cancer Risk: What Does the Research Say?
Several studies have investigated how long-term protein intake relates to cancer incidence. Many findings suggest that protein quantity alone does not determine cancer risk. Instead, the type of protein and preparation method show stronger ties to cancer risk.
Specifically, processed meats such as bacon, sausage, and deli cuts contain nitrates and other preservatives. These substances may contribute to malignant tumor growth in the stomach and bowel [6]. Frequent consumption of grilled or charred red meat may also raise cancer risk due to the formation of carcinogenic compounds like acrylamide during high-temperature cooking.
The World Health Organization classifies processed meats as carcinogenic (cancerous) and red meat as likely carcinogenic. These statements are a result of consistent correlations found in large population-based studies. However, researchers do not see the same connection with lean poultry, fish, and plant-based proteins.
IGF-1 and Tumor Growth
Insulin-like growth factor 1 (IGF-1) is a protein, a peptide with 70 amino acids, that supports cell growth and repair, as well as regulates protein synthesis in skeletal muscle. The liver produces most of the body’s IGF-1, though other tissues such as skeletal muscle produce smaller amounts. Despite its vital functions, elevated levels may lead to the growth of certain tumors.
Some researchers argue that increased IGF-1 activity could increase cancer risk under certain conditions, especially in middle-aged individuals. One longitudinal study observed higher cancer mortality in people aged 50 to 65 who consumed large amounts of animal protein. Interestingly, this association disappeared or reversed in people over 65, possibly due to different metabolic demands later in life [7].
These findings suggest that protein source, cooking method, and age are factors in how protein consumption affects long-term cancer risk.
Protein Intake During Cancer Treatment
Nutritional needs change almost immediately after a cancer diagnosis. Many patients struggle with metabolic stress due to the disease, treatment side effects, or both. These stressors increase protein turnover and muscle breakdown.
Treatments like radiation, chemotherapy, immunotherapy, and surgery all increase the need for protein. Without adequate intake, the body pulls protein from muscle tissue [8], leading to fatigue, reduced immune defense, and slower healing.
For these reasons, oncologists and dietitians often recommend increasing protein consumption during treatment. Unfortunately, many patients have a difficult time eating normally due to chemotherapy-related nausea, appetite loss, taste changes, or trouble swallowing. Maintaining muscle mass and weight becomes more challenging when these symptoms persist for weeks or months.
Malnutrition and cachexia (involuntary weight loss with muscle wasting) are common among cancer patients. These conditions reduce tolerance to treatment and raise the risk of infections and hospital readmissions. To minimize complications, patients must consume enough protein to meet their needs despite reduced appetite.
How Much Protein Do Cancer Patients Need During Treatment?
General dietary guidelines for healthy adults suggest 0.8 grams of protein per kilogram of body weight per day. However, people undergoing cancer treatment may need more than that. Clinical nutrition guidelines suggest 1.0 to 1.5 grams per kilogram of body weight daily for most cancer patients.
This range varies by individual and treatment type. Those receiving surgery may require higher intake to support tissue repair. Patients with gastrointestinal cancers may struggle with nutrient absorption, raising the need further. Those undergoing chemotherapy or immunotherapy may need additional protein to compensate for immune system demands.
Dietitians calculate targets based on lean body mass, treatment goals, and disease severity. The goal is to maintain strength, prevent excessive weight loss, and support recovery from treatment. In patients with extensive inflammation or advanced disease, targets may rise to 2.0 grams per kilogram or more.
A 70-kilogram patient receiving active treatment may, therefore, need 70 to 105 grams of protein each day. This target increases if the patient has lost weight or muscle.
Safer Protein Sources for Cancer Patients
While protein needs increase during treatment, as mentioned, not all sources have the same long-term risks. Many nutritional scientists recommend adjusting the diet to favor sources with lower links to cancer.
- Poultry, fish, dairy, soy, eggs, legumes, and nuts are rich in protein with fewer associated health concerns. Other plant-based proteins, such as tofu, lentils, quinoa, and chickpeas, also contain fiber, antioxidants, and other beneficial compounds. Related article: How a Plant-Based Diet May Help Fight Cancer
- Red meat may still be included in small amounts, but most doctors recommend avoiding grilled, smoked, or processed versions. As discussed, high-temperature cooking and chemical preservatives introduce compounds that raise cancer risk over time. When preparing animal proteins, boiling, steaming, or baking are safer methods.
- Protein shakes and meal replacement products can help patients with poor appetites meet their nutritional goals. A physician should review these products beforehand, especially if the patient has co-existing kidney or liver conditions.
- Hydration also supports protein metabolism. Patients should drink enough water to help their bodies process amino acids and maintain normal organ function.
Talking to a Doctor or Dietitian About High-Protein Diets and Cancer Risk
Every patient’s nutritional needs differ. A diet that supports healing in one person may cause strain in another. Medical teams use several factors to determine the best approach, including:
- Type and stage of cancer
- Weight history and current body composition
- Kidney or liver function
- Treatment regimen and side effects
Patients should bring nutrition-related questions to their oncology visits. A registered dietitian can develop a tailored eating plan based on bloodwork, weight trends, and physical symptoms. In some clinics, nutrition support teams monitor patients throughout treatment and recommend changes as needed.
Some patients attempt to restrict protein due to concern about feeding cancer cells. However, low protein intake may harm healthy tissue far more than tumors. The goal is to strengthen the body during treatment, not to starve it.
Patients with diabetes or heart disease may need further adjustments. Excess protein can worsen kidney strain in some people, but in most cancer patients, the benefits outweigh these risks. Monitoring kidney function through routine labs helps detect any concerns early.
The Bottom Line on High-Protein Diets
Research does not claim that high-protein diets directly cause cancer. However, frequent intake of processed or charred red meat may heighten risk over time. In contrast, plant-based proteins and lean animal sources appear safer. Cancer patients undergoing treatment need more protein than the general population to maintain weight and support healing.
Meeting this need requires careful attention to food quality and symptom management. A patient undergoing chemotherapy cannot rely on standard dietary advice, as appetite, digestion, and energy levels often fluctuate. Doctor-approved protein shakes, soft foods, and small meals throughout the day may help maintain adequate intake.
Nutrition must remain a daily consideration during cancer treatment. Choosing safer protein sources for cancer patients and meeting appropriate targets can support recovery and preserve strength throughout the process.
For cancer patients seeking nutritional guidance and integrative treatment options, contact New Hope Unlimited today to speak with a team member about available care.
Sources
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[2] Kreider RB, Campbell B. Protein for exercise and recovery. Phys Sportsmed. 2009 Jun;37(2):13-21. doi: 10.3810/psm.2009.06.1705. PMID: 20048505.
[3] Li P, Yin YL, Li D, Kim SW, Wu G. Amino acids and immune function. Br J Nutr. 2007 Aug;98(2):237-52. doi: 10.1017/S000711450769936X. Epub 2007 Apr 3. PMID: 17403271.
[4] What are proteins and what do they do?: MedlinePlus Genetics. (n.d.).
[5] RDN, K. W. (2024, November 27). Are you getting enough protein? Mayo Clinic Health System.
[6] Cancer Council NSW. (2025, March 6). Red meat, processed meat and cancer | Cancer Council NSW.
[7] Sebastian Brandhorst, Valter D Longo. Protein Quantity and Source, Fasting-Mimicking Diets, and Longevity. Advances in Nutrition, Volume 10, Supplement 4, 2019, Pages S340-S350, ISSN 2161-8313.
[8] Carbone JW, Pasiakos SM. Dietary Protein and Muscle Mass: Translating Science to Application and Health Benefit. Nutrients. 2019 May 22;11(5):1136. doi: 10.3390/nu11051136. PMID: 31121843; PMCID: PMC6566799.
