What the Church's website says

Here is what the church's website has to say about a three-month supply of food.

https://www.lds.org/family/family-well-being/emergency-preparedness?lang=eng

Emergency Preparedness and Response

Members of the Church have been counseled for many years to be prepared for adversity. Preparation, both spiritual and temporal, can dispel fear. With the guidance of Church leaders, individual members and families should prepare to be self-reliant in times of personal or widespread emergency.

Family Emergency Planning

Church members are encouraged to prepare a simple emergency plan. Items to consider may include:

• Three-month supply of food that is part of your normal daily diet.
• Drinking water.
• Financial reserves.
• Longer-term supply of basic food items.
• Medication and first aid supplies.
• Clothing and bedding.
• Important documents.
• Ways to communicate with family following a disaster.