It's impossible to definitively say which family of food-producing plants is the most important, as it depends on what criteria you are using. Different families provide different crucial nutrients and are essential for diverse populations and regions.

However, some families are incredibly significant for their contribution to human sustenance:

* Grasses (Poaceae): This family is arguably the most important, as it includes staples like wheat, rice, corn, barley, oats, and sorghum. These grains provide the majority of calories for billions of people worldwide.

* Legumes (Fabaceae): This family is vital for its nitrogen-fixing properties and provides essential protein in the form of beans, lentils, peas, chickpeas, and soybeans.

* Nightshades (Solanaceae): This family contains many important food sources like potatoes, tomatoes, peppers, and eggplants. They are rich in vitamins, minerals, and antioxidants.

* Brassicas (Brassicaceae): This family includes vegetables like broccoli, cauliflower, kale, cabbage, and Brussels sprouts, which are excellent sources of vitamins, minerals, and fiber.

* Cucurbits (Cucurbitaceae): This family includes gourds, pumpkins, squash, cucumbers, and melons, providing hydration, vitamins, and fiber.

Ultimately, the "most important" family depends on your perspective. Each family plays a vital role in our food system, and all are crucial for global food security.