As far as diet is concerned there really is nothing you can eat or drink that will actually boost your white blood cell count, although keeping to a normal healthy diet is important. When your white count is very low, however, you might be advised to avoid certain foods and adjust your diet to reduce the risk of infection. Typical advice in this situation is to avoid salads, fruit which does not have to be peeled, live yoghurt and ice cream.
Reheated food should also be avoided and all cooked food should be thoroughly cooked. For the great majority of women having chemotherapy for breast cancer these precautions are not necessary, even if the white count is reduced, so check with your doctors and nurses to see if they feel you need to change your diet in this way.
It might be helpful to understand a bit more about why your white blood count is lowered. Chemotherapy for breast cancer is usually given as courses of treatment with an interval of several weeks between each course. Several different types of chemotherapy are used in breast cancer treatment.
Most types of chemotherapy used to treat breast cancer will cause a fall in the white blood cell count about a week after the drugs are given but usually the white cells will have recovered before the next course is given. Allowing time for recovery of the blood count is one of the main reasons for having a gap of several weeks between the courses of treatment.
The different types of chemotherapy will affect the white cells to different degrees. With some treatments there is very little effect whereas with others the white cells are more likely to be reduced. When the white blood count is very low the main risk is of developing infections, as the white blood cells usually protect the body against infection.
If your doctors expect that your treatment might cause your white blood cell count to go very low, they will usually check regular blood counts, so that if there is a big reduction they can give supportive treatment. This might involve taking antibiotics to prevent infection or having a course of injections to boost the white cell count (or both). This is only very occasionally needed in chemotherapy for breast cancer although it is quite common in the treatment of some other types of cancer like leukaemia or lymphomas.