African nations with millions of undernourished people continue to refuse US food aid containing genetically modified corn. Their leaders lash out against the giant agricultural biotechnology companies that make it, accusing them of using Africans as guinea pigs in their food experiments. The companies, in turn, state that Europe, which has so far shunned genetically modified, or GM, foods and which imports heavily from Africa, is encouraging the opposition. 

Seldom has a major change in the food supply generated such a mix of controversy and indifference. In the United States, where industry leader Monsanto is based, products such as corn genetically altered to resist pests have entered the market with little public attention. But, in other parts of the world, the acronym ''GM'' triggers alarm bells.

In ''Food, Inc.,'' author Peter Pringle reviews an array of genetically modified food case studies -- stories that bring together science, politics, business, and biotechnology ethics -- in an attempt to shed light on all sides of the debate.

He starts with the basics: What is genetic engineering? What classifies a food as GM? How is traditional plant breeding -- where a farmer breeds from the best plants in each generation --different from genetic manipulation in the laboratory?

Pringle strips connotation-laden terms such as ''gene modification'' and ''genetic engineering'' down to their biological basics, teaching the reader how these technologies actually work. How a microorganism called agrobacterium, for instance, shuttles foreign genes into plant cells to make a ''transgenic'' crop, or how an inverted strip of DNA blocks production of the enzymes that cause fruit to rot.

Simple and engaging explanations of the technical details serve as the bedrock from which we step onto the swampy terrain of experts and special interests. On the pro-GM side of the debate, we encounter the giant ''agbiotech'' companies such as Monsanto and Syngenta, as well as the corporate-friendly US government. On the anti-GM side, we find a collection of environmental groups, nongovernmental organizations, and outspoken individuals such as Vandana Shiva and Jeremy Rifkin. In between the extremes are the scientists, farmers, and consumers who are more often ambivalent or confused about GM than certain of their position.

It may be as difficult to be wholly impartial as it is to grow a weed-free patch of corn. But, in discussing the scientific squabbles and legal wrangling that surround GM crops, Pringle goes to great lengths to give a fair hearing to both sides.

Yes, the proponents of GM foods have oversold their value to the public and have prematurely vouched for their safety. But the naysayers, too, have been rash -- readily twisting scientific data for the sake of propaganda. The result, Pringle states, is that instead of a measured and rational discussion about GM technology, what we have gotten is hotheaded activism from the ''green warriors'' and arrogant manipulation from agribusiness.

Admirably, throughout this book, Pringle avoids championing a particular position, aside from his certainty that GM crops are here to stay. In dealing with GM, he states, it's not a question of whether but how?

For hard-line GM proponents, that he even questions their cost to the environment and their safety for human consumption will be annoying. For anti-GM activists, that Pringle takes GM food as a foregone conclusion will be galling. But, as Pringle makes clear from the outset, this book is not an attempt to convert those who have already made up their minds. It is intended, rather, for those who value scientific rigor, who question hype, and who understand that life always carries risks.