Finally, there is ethanol: As more corn has been used for fuel, there is less available for food. Also, with corn at high prices, many farmers this year decided to plant corn instead of wheat or soybeans, reducing supply and subsequently pushing up prices of the latter two.
And that ripples through all food prices.
Think about that slice of pizza that you had last week. Because demand for wheat is high, flour costs are higher and the local pizza shop now must spend more to make a slice for you.
Professor Mike Dicks, an agriculture economist at Oklahoma State University, said that such rises in food prices come in cycles. He said this spike is "almost identical" to one seen from 1973 to 1983.
He said that the country used to have excess farm capacity to deal with shortfalls like we are going through now. But in 1995, many farm subsidies were eliminated, which he said caused many farmers to get rid of their excess land.
Dicks said it could take two to three years for supply to increase enough to lower prices.
So what can you do in the meantime to trim your grocery bill?
Buy dried instead of canned grains and beans because they're generally cheaper. With cans, you're paying for water.
Eat seasonally. It's healthy, supports local growers and vegetables and fruits in season are far less expensive.
Supplement your fresh produce with inexpensive frozen vegetables.
Buy generic store brands whenever they're cheaper but just as tasty.
Check unit prices. Giant packages are not necessarily cheaper than many smaller ones.
On weeks that you buy less expensive proteins, or have protein left over from the week before, stock up on staples.
Try making breakfast out of leftover grains or make muffins from scratch rather than buying boxed cereal, which is expensive.
Other cheap proteins: Edamame soy beans, canned fish, peanut butter.
Use every bit of the item. For example: Make chicken stock out of chicken bones or sauté the greens from turnips.
Clip and use paper and online coupons. Find stores that offer double coupon credit.
If you are a tea drinker, try buying just bulk black and green teas, then adding your own spices to them for variety.