When you are going through chemotherapy, there comes a time when white blood cells, especially neutrophils, drop sharply. It is the period when immunity hits rock bottom, so to speak. When the care team says "be careful with food for a while" at a time like this, you come home and feel lost about what to eat. It is because the raw vegetables, freshly squeezed juice, and fermented foods you usually ate as healthy choices become dangerous instead during this period. "Low-microbial diet" sounds grand, but the core is simple. Avoid foods that may carry a lot of germs and uncooked foods, and eat thoroughly cooked food. That is all there is to it.
The first standard to keep in mind is "raw foods are on pause for now." Sashimi and raw beef go without saying, but vegetables eaten raw like in a salad and fruit eaten with the peel must also be handled carefully during this time. It is safer to cook vegetables well and, for fruit, to peel off thick skins like apples and pears cleanly. Fruits with bumpy surfaces that are hard to wash, like strawberries, grapes, and blueberries, are easier on the mind if you put them off for a while. Nuts surprisingly carry a risk of mold toxins too, so while immunity is low, sealed processed packages are better than a bag opened long ago or nuts still in the shell.
Dairy and fermented foods are the area people get most confused about, since they are foods that have live germs deliberately added. Fresh cheese, spoonable fresh yogurt, unpasteurized milk, and well-fermented kimchi or salted seafood are better kept at a distance until immunity recovers. Instead, sterilized milk, heat-pasteurized processed cheese, and forms heated once more like kimchi stew boiled and cooked are far more reassuring. Even with the same kimchi, it divides on whether you eat it raw or boiled.
Cooking and storage habits matter as much as choosing ingredients. No matter how good the ingredients you choose, it is meaningless if you touch cooked food with the cutting board and knife used as-is for handling raw items. Use separate cutting boards for handling meat and for vegetables and fruit, eat food right after making it, and reheat anything that has cooled thoroughly before eating. Side dishes left at room temperature for two or three hours, delivery or buffet food of unknown origin, and bottled water or ice whose purity is uncertain are best avoided during this period. For water too, water boiled once and cooled is the most reliable if possible.
Written out like this, it may look like there is nothing to eat, but in fact most of the home cooking we usually eat — warm rice and well-cooked soup, thoroughly boiled porridge, braised tofu, steamed egg, cooked seasoned vegetables — is safe food as is. If you think about it too strictly, even your appetite drops, so just hold to the big principle of warm food freshly made by cooking, and choose what you want to eat within that. A low-microbial diet is not a lifelong diet but a temporary measure to get safely through that short, hard period when counts are low. Once immunity recovers, the fresh fruit and well-fermented kimchi you loved come back too. That said, the allowed range can differ depending on your own counts and condition, so I recommend checking your specific diet once with your care team or the hospital nutrition team.