Can people with cancer eat fish? Safety and effects

Yes most people undergoing cancer treatment can safely eat fish when it is fully cooked, and it can be a nutritious part of the diet. Avoiding raw or undercooked seafood is important because treatment can weaken the immune system and increase the risk of foodborne infections. ^[1] Choosing and preparing fish safely helps protect against illness while allowing you to benefit from its protein and omega‑3 fats. ^[2]

Food safety: what to avoid and how to prepare

• Avoid raw or undercooked fish and shellfish (sushi, sashimi, ceviche, cold‑smoked fish like lox, caviar). These carry higher risks of bacteria and parasites for people with lowered immunity. ^{[1] [3]}
• Cook fish and shellfish thoroughly until steaming hot; home cooking should reach safe internal temperatures (generally similar to other animal proteins). ^[1]
• Be careful with clams, mussels, and oysters in the shell; these are best avoided during treatment due to contamination risk. ^[4]
• Use clean food handling: separate cutting boards for raw fish and produce, and never place cooked fish back on a plate that held raw fish. ^[5]
• When eating out, order seafood that’s well‑cooked and served hot; send back undercooked items and refrigerate leftovers within 2 hours. ^[6]

Potential benefits of eating fish

• High‑quality protein: Supports muscle maintenance and recovery, which can be challenging during chemo or radiation.
• Omega‑3 fats (EPA, DHA): These may help with weight maintenance and moderating inflammation in some people receiving treatment. [PM17] Some trials show improved weight and reduced inflammatory markers (like C‑reactive protein and TNF‑α) with omega‑3 supplementation. [PM19]
• Possible supportive effects during therapy: Reviews suggest omega‑3s can aid nutritional status and immune modulation, though results vary and may not apply to every cancer type or individual. [PM7] Meta‑analyses in people on chemo/radiation report modest improvements in weight and fewer adverse events with omega‑3‑enriched supplements. [PM17]

What the evidence says

• Omega‑3 supplementation during treatment has been associated with small increases in body weight/BMI and reductions in inflammation markers in pooled randomized trials. [PM17]
• In specific cancers (e.g., lung cancer), omega‑3s have shown improved weight and lower inflammation compared with placebo in a randomized trial. [PM19]
• Prevention vs. treatment: Large prevention trials in generally healthy adults found omega‑3s may offer modest risk reduction when combined with other measures, but this does not replace standard cancer care and may not translate directly to treatment settings. [PM16] Broader trials show mixed results and highlight that benefits can differ by individual factors. [PM18]

Practical tips for choosing fish during cancer treatment

• Prefer cooked options: baked, broiled, grilled, or poached fish served hot. ^[1]
• Skip raw bars and cold‑smoked seafood: these are riskier when immunity is low. ^[4]
• Handle safely at home: bag fish separately at the store, keep cold, and cook promptly; use clean utensils and plates for cooked food. ^[5]
• Deli seafood salads and refrigerated pâtés/meat spreads are best avoided due to contamination risk. ^[4]

Mercury and fish choice

• General approach: Many commonly consumed fish (salmon, trout, sardines) are lower in mercury and provide omega‑3s. While mercury guidance is often emphasized in pregnancy, it is reasonable for people with cancer to choose lower‑mercury fish and vary species. This complements standard food safety steps. ^{[2] [4]}

Who should be more cautious?

• Those with severely low white blood cells (neutropenia), recent transplant, or intensive chemo may need stricter food safety rules avoid all raw animal products and ensure all seafood is thoroughly cooked. ^[3] If you are unsure about your immune status, ask your care team before eating restaurant seafood. ^[6]

Omega‑3 supplements: should you take them?

• They can be considered, but individual needs vary. Some evidence supports omega‑3‑enriched oral nutrition during chemo/radiation for weight and inflammation, yet dosing, duration, and benefits differ among studies. [PM17]
• Discuss with your oncology team before starting supplements to avoid interactions, especially if you have surgery scheduled or take blood‑thinning medicines. Clinical nutrition support can help tailor choices. [PM17]

Bottom line

• Cooked fish is generally safe and can be beneficial during cancer treatment, offering protein and omega‑3 fats that may support weight and help with inflammation. ^[1] [PM17]
• Strictly avoid raw or undercooked seafood and follow careful food handling to minimize infection risk while your immune system is compromised. ^{[3] [5]}
• Omega‑3s show promising supportive effects in some studies, but they are not a stand‑alone therapy; decisions about supplements should be individualized. [PM19] [PM7]