The Ukraine crisis means bread prices will skyrocket in some of the world's poorest and most unstable countries, potentially sparking a cycle of instability.

Wheat prices jumped to a record $12.94 a bushel and are up an astounding 70% in the past month.

Throughout history, the rising price of bread—think of the French and Russian Revolutions—has been a major source of instability and violence.

More recently, rising food prices, including wheat, have been cited as a major factor in the wave of instability known as the Arab Spring that has gripped the Middle East since 2011.

Russia and Ukraine are the superpowers of the wheat world. Russia produces 11% of world wheat and is its largest exporter. The two countries together export more than a quarter of the world's supply.

At the same time, Russian and Ukrainian wheat is cheap. They sell it to some of the world's poorest countries in the Middle East and North Africa.

Egypt, the world's largest wheat importer, gets about 60% of its wheat from Russia and 25% from Ukraine.

Ethiopia has also become a major importer in recent years as the war disrupted agriculture. The government bought wheat in bulk to provide the population with subsidized food. But now the government cannot afford to buy enough wheat to meet domestic demand, USDA analysts wrote last month.

Rising prices forced Lebanon to cut subsidies in order to prevent the burning of reserves in the national currency.

This could exacerbate Lebanon's social problems, as the country has only a month's supply of wheat in reserve, according to Fitch Ratings analysts.