Why sushi, soft cheese and the deli counter are off limits

The restrictions handed out at the start of chemotherapy get mistaken for nutrition advice. They are not. Nobody is claiming sushi is unhealthy.

The FDA sets out the reasoning. Cancer therapy such as radiation, chemotherapy and other medicines may weaken the immune system. That makes patients more open to infections like foodborne illnesses. Cancer that spreads to bone marrow weakens immune function directly.

So the foods on the avoid list are the ones most likely to carry live germs. Normally your immune system deals with them quietly. During treatment, it may not.

MedlinePlus guidance on safe eating during cancer treatment names specific items.

Raw proteins

• Do not eat raw fish, such as sushi or sashimi, raw oysters, or any other raw shellfish
• Avoid runny eggs — yolks and whites should be cooked solid
• Do not eat uncooked tofu

Dairy

• Avoid soft cheeses such as Brie, Camembert and blue-veined varieties
• Avoid Mexican-style fresh cheeses including queso blanco fresco and cotija
• Consume only pasteurised dairy products

Other items

• Raw vegetable sprouts such as alfalfa and mung bean
• Raw honey, and sweets with creamy fillings
• Refrigerated salsa and salad dressings from deli cases
• Unpasteurised juices

The deli counter shows up twice on this list for a reason. Those foods are ready to eat. Many hands have touched them. And they sit at fridge temperature. That is exactly the situation the guidance is built around.

MedlinePlus gives figures worth writing on a card. Stick the card inside a cupboard door.

• Poultry and casseroles: 165 °F (74 °C)
• Beef, lamb, pork and venison: 160 °F (71 °C)
• Tofu: cook for at least 5 minutes

For fresh produce, the instruction is simple. Wash all raw fruits, vegetables and fresh herbs under cold running water.

A cheap food thermometer removes the guesswork from the first two. Judging doneness by eye is the sort of rough guess this guidance is meant to replace.

Cooked properly is the theme. Most of what is banned raw is fine once heat has done its job.

MedlinePlus does not ask you to stop going out. It asks you to choose differently.

Its advice is to avoid salad bars, buffets, potlucks and delis. Request food prepared fresh. Use single-serving condiments rather than shared containers.

The common thread is food that has been sitting out, handled again and again, or shared. A dish cooked to order and brought straight to the table is a very different thing from a tray under a heat lamp for an hour.

That depends on you. It is the question to take to your clinic. Different treatments carry different levels of risk. Immune recovery also varies a lot between people and regimens.

Ask directly how strict your team wants you to be. Ask whether the rules tighten during certain parts of your cycle. And ask when they can be relaxed. Guidelines written for everyone have to be cautious. Your team can tell you where you sit within them.

Eating something from the avoid list happens. A slice of cake with a soft cheese filling. A sandwich made by someone who did not know. Panicking helps nobody.

Watch for signs of infection and report them promptly. CDC says infections during cancer treatment can be life threatening and require urgent medical attention. It lists a fever of 100.4 °F (38 °C) or higher among the signs to call about. Chills, diarrhoea and other symptoms are on that list too. CDC also advises against taking medicine to lower a fever before speaking to your doctor.

Ring your team. Do not wait to see how the night goes.