Cancer and its treatment can weaken the immune system by affecting the blood cells that protect us from disease and germs. As a result, your body cannot fight infection and disease as effectively as a healthy person's.

Chemotherapy is usually the main reason why immunity is affected. As a result of chemotherapy, bone marrow produces fewer white blood cells. This reduces your body's defences against infection during and after treatment. The level of white blood cells is at its lowest 7 to 14 days after chemotherapy, so you are more susceptible to infections.

Nadir is the term used by doctors to describe this period. Depending on the drug used, it may vary slightly. But the number of white blood cells will increase steadily and usually returns to normal before your next cycle of chemotherapy. 

What foods should cancer patients avoid? 

Following are examples of foods that may contain bad bacteria that could affect your immunity

1. Egg dishes and cream- and mayonnaise-based foods should not be left unrefrigerated for more than an hour.

2. Do not eat raw vegetable sprouts.

3. Throw away slimy or mouldy fruits and vegetables.

4. Throw away eggs with cracked shells.

5. Throw out foods that look or smell strange. Never taste them! 

6.Do not buy produce that already has been cut at the grocery store (like melon or cabbage).

Food-handling during cancer treatment 

1. Wash your hands with warm, soapy water for 20 seconds before and after preparing food and before eating.

2. Use defrosted foods right away, and do not refreeze them.

3. Keep hot foods hot (warmer than 140° F) and cold foods cold (cooler than 40° F).

4. Thaw meat, fish, or poultry in the refrigerator in a dish to catch drips. Do not thaw at room temperature.

5. Wash fruits and vegetables well under running water before peeling or cutting. 

6. Using a clean vegetable scrubber, scrub produce that has a thick, rough skin or rind (melons, potatoes, bananas, etc.) or any produce that has dirt on it.

7. Rinse leaves off leafy vegetables one at a time under running water.

8. Rinse packaged salads, slaw mixes, and other prepared produce again under running water, even when marked pre-washed. Using a colander can make this easier.

9. Wash tops off canned foods with soap and water before opening.

10. Use different utensils for stirring foods and tasting and do not taste the food (or allow others to taste it) with any utensil that will be put back into the food.

Meat Safety for Cancer Patients: Do not cross-contaminate

1. Cook meat until it’s no longer pink and the juices run clear. The only way to know for sure that meat has been cooked to the right temperature is to use a food thermometer. Meats should be cooked to 160° F and poultry to 180° F. You can test a thermometer’s accuracy by putting it into boiling water. It should read 212° F.

2. Use a clean knife to cut different foods.

3. In the fridge, store raw meat sealed and away from ready-to-eat food and keep foods separated on the countertops. Always remember to use a different cutting board for raw meats.

4. Clean counters and cutting boards with hot, soapy water. Disinfecting wipes may be used if they’re made for use around food.

Food shopping: What every cancer patient needs to know

1. Check “sell-by” and “use-by” dates. Do not buy products that are out of date. Pick only the freshest products!

2. Do not use damaged, swollen, rusted, or deeply dented cans. Be sure that packaged and boxed foods are properly sealed. 

3. Keep away from damaged fruits and vegetables.

4. Do not eat deli foods. In the bakery, avoid unrefrigerated cream- and custard-containing desserts and pastries.

5. Do not eat foods that are bought from self-serve or bulk containers.

6. Do not eat yogurt and ice cream products from soft-serve machines.

7. Do not eat free food samples or use cracked or unrefrigerated eggs.

9. Get your frozen and refrigerated foods just before you go to the check out, especially during the summer months, and refrigerate food right away. Never leave food in a hot car. It is best to do this within 2 hours of buying. 

10. Do not buy produce that already has been cut at the grocery store (like melon or cabbage).

Eating out: How to stay safe 

1. Avoid crowded places or find somewhere with outside seating. 

2. Ask for single-serving condiment packages, and avoid self-serve bulk condiment containers.

3. Do not eat from high-risk food sources, including salad bars, delicatessens, buffets and sidewalk vendors. Plus keep away from raw fruits and vegetables.

4. Ask for pasteurised fruit juices. Avoid “fresh-squeezed” juices.

5. Use food safe disinfection wipes to wipe down the cutlery, table and drinks. 

6. For leftovers, ask for a container, and put the food in it yourself rather than having the server take your food to the kitchen to do this. 

For more safety tips visit our 'safety section'