Overall health is important in all aspects of any disease. However, when one suffers from memory loss there are several components that come into play. Some folks with memory loss forget to eat, don't eat the right things to maintain good health, and may be suffering from something secondary that hasn't yet been identified.
The Alzheimer's Association provides good information for alternative options that may slow the disease process down at : http://www.alz.org/alzheimers_disease_alternative_treatments.asp
Eating a well-balanced diet, that you help her with, would be your best bet for overall health and maintaining a good balance in her life. Many caregivers want to be sure their loved one is still particapatory in meal time and has 'choices.' Limiting those choices, or presenting them in such a way when they are looking at a menu, allows them to participate, you to control a bit of what they are eating to ensure it's healthy as well as minimizing their feeling of being 'overwhelmed' by too many choices. I encourage caregivers to start with something like "Would you like chicken or beef?" Staring there (and hopefully you being somewhat aware of their past eating likes and habits) you can quickly narrow down their choices and/or choose for them.
Your mother is very lucky to have you as an advocate in her life.