The article in the Communist party-controlled newspaper was headlined:
"Condemned to premature death by hunger and thirst more than three billion people of the world."
"This is not an exaggerated figure, it's more likely cautious," Castro wrote.
"I've been meditating quite a bit since President Bush's meeting with North American automobile makers."
Persistent rumours
Castro's condition and his exact ailment are a state secret but he is widely believed to suffer from diverticular disease, which causes a weakening in the walls of the colon.
In his article, Castro quotes extensively from a Washington-datelined story by the Associated Press reporting from a meeting held on Monday between Bush and representatives from US car manufacturers and their comments about using corn to create ethanol as an alternative to fossil fuels.
The Cuban leader noted that Cuba has also experimented with extracting ethanol from sugarcane.
But if rich nations decide to import huge amounts of traditional food crops such as corn from developing countries to help meet their energy needs, it could have disastrous consequences for the world's poor, Castro wrote.
He said: "Apply this recipe to the countries of the Third World and you will see how many people among the hungry masses of our planet will no longer consume corn."