It's surprising how much water it takes to produce a serving of certain foods, when added up throughout the growing and production cycle of the food.
For example:
• Lettuce: 3 gallons
• White Bread: 11 gallons
• Tomato Paste: 12 gallons
• Brown Rice: 16 gallons
• White Rice: 25 gallons
• Pasta (2 oz.): 36 gallons
• Milk: 48 gallons
• Orange Juice: 49 gallons
• Tofu (1/2 cup): 61 gallons
• Chicken (8 oz.): 330 gallons
• Steak (8 oz.): 1,232 gallons
Source: Water Education Foundation, American Water Works Association and US Dept. of Agriculture