Rats, by nature, are scavengers. Various species prefer certain types of food, but overall, most rats eat all kinds of things.
The main dietary need of rats is carbohydrates. Foods that are rich in carbohydrates, such as grains and seeds, help rats grow and develop, as well as reproduce healthily. Not all carbohydrates are equal in terms of rat health. Sucrose and fructose can cause birth defects and create abnormal growths in rats. Glucose is the main carbohydrate that rats seek for health and maintenance.
Rats do need some protein, but they aren't dependant on it like other mammals. They get their protein from nuts, oats and other grains, so they have little use for meat or other sources of protein.
Vitamins and minerals come from the various fruits and vegetables that rats consume. Rats will eat watermelon and blueberries to get doses of vitamin C and other nutrients that they need.
Rats are rodents and they need to chew constantly to keep their teeth in good condition. The front two teeth of rats continue to grow and so rats will gnaw on wood, concrete or any other hard substance to maintain their teeth. Hard seeds and nuts do double duty as a sharpening device, as well as a food source for rats.
Keeping rats away from your food can be simple. Make sure all containers in your pantry are sealed, and all spilled food vacuumed up. Any cuttings from fruits or vegetables should be cleaned up immediately. Keep garbage can lids sealed tightly and don't allow any food to be stored in areas where rats can be found. Dry dog food is a favorite for rats, so keeping that in a tightly sealed container can be very beneficial.
If you have a rat problem, make sure you place all baits and traps away from any food sources. Rats carry a number of diseases and can easily contaminate your pantries or cupboards.