Insects' nutritional content, small size and fast reproduction rates have also made them appealing solutions to problems traditional agriculture can't solve. 

There is a rational, even persuasive, argument for voluntarily eating insects: Bugs are high in protein, require less space to grow and offer a more environmentally friendly alternative to the vertebrates we Westerners prefer, advocates of the bug fare say.

On Valentine's Day, express your love with a giant hissing cockroach Plants search high and low in response to global warming Extreme rain and snow events linked to global warming, study finds However, this topic is not a hotbed of research, so while some data exist — in particular on the protein content of insects — there are some assumptions built into the latter part of this argument.

"The suggestion that insects would be more efficient has been around for quite some time," said Dennis Oonincx, an entomologist at Wageningen University in the Netherlands. He and other researchers decided to test it, by comparing the greenhouse gas emissions from five species of insects with those of cattle and pigs.

Untapped potential

For much of the world, eating insects — officially called entomophagy — is neither strange nor disgusting nor exotic. In southern Africa, Mopani worms — the caterpillars of Emperor moths — are popular snacks. The Japanese have enjoyed aquatic insect larvae since ancient times, and chapulines, otherwise known as grasshoppers, are eaten in Mexico. But these traditions are noticeably absent in Europe and European-derived cultures, like the United States.

Insects' nutritional content, small size and fast reproduction rates have also made them appealing solutions to problems traditional agriculture can't solve. For instance, a task force affiliated with the Japanese space agency has looked to insects like silkworms and termites as a self-replenishing supply of fats and amino acids for astronauts on extended missions.

For children from 6 months to 3 years of age, low calories and low protein are the main causes of death, about 5 million a year, according to Frank Franklin, a professor and director of pediatric nutrition at the University of Alabama at Birmingham. Protein from insects could offer a less expensive solution if processed into a form similar to Plumpy'Nut, a peanut-based food for those suffering from malnutrition, he said.

Franklin embraced the arguments for entomophagy after learning about it roughly a year ago.

"The more I looked at it, the more it made incredible sense that this would be an important nutritional advance that is only going to bring back what has probably been there since the primitive man," he told LiveScience.

The comparison

A 2006 report by the U.N.'s Food and Agriculture Organization blamed the livestock sector for a sizable portion of humans' greenhouse gas emissions – 9 percent of our carbon dioxide emissions (much of this originates in changes in land use), 37 percent of our methane and 65 percent of our nitrous oxide emissions.

Oonincx and his colleagues used two important livestock animals, pigs and cattle, and compared existing data on their emissions of these greenhouse gases, plus ammonia, with data they collected from five species of insects: mealworms, house crickets, migratory locusts, sun beetles and Argentine cockroaches. The latter two species are not considered edible, at least not directly. Their taste is just not good, Oonincx said, however, protein extracted from them could be added to foods.

To quantify the animals' greenhouse gas footprints, the team measured the five insects' growth rates and their production of the greenhouse gases and ammonia — also a pollutant but not a greenhouse gas. They compared these to data already available on the cattle and pigs' growth rate and the rates at which they emitted the same pollutants.

Cattle produced the least carbon dioxide per unit of body mass. However, the picture changed once growth rate was considered. The data indicated that insects grow more rapidly, and they emit less carbon dioxide per unit of weight gained than do cattle and pigs. The cockroach was the clear winner in this latter category; meanwhile, cattle produced the most carbon dioxide per pound (or kilogram) gained. [The Truth about Cockroaches]

The insects generally produced less methane, nitrous oxide and ammonia both per unit of body mass and per unit of mass gained than pigs or cattle.

"It proves the hypothesis that insects can be a more efficient source [of protein], and I definitely believe there is a future for edible insects," Oonincx said. "It may not be as the animal as such but regarding protein extraction there is a lot to be learned and a lot to be gained."

Solving the livestock problem

There are strategies that can reduce greenhouse gas emissions associated with raising livestock but these improvements can't bring about reductions necessary to meet emissions targets intended to curb global warming, write the authors of a paper published in the medical journal the Lancet in November 2009.

Their solution: a 30 percent reduction in livestock production, and therefore, a drop in meat consumption. This would mean diets with less saturated fat and fewer premature deaths caused by heart disease, they write. (The researchers note that not everyone needs to reduce meat consumption; agriculture produces enough fat, protein and other nutrients to feed all of us, but food isn't distributed equally, resulting in malnutrition and starvation in some places.)

A policy that reduces our hamburgers and barbeque is likely to encounter resistance, one of the authors, Alan Dangour, of the London School of Hygiene & Tropical Medicine, acknowledged. However, so will a push to switch to insects, he told LiveScience in an e-mail.

"It is clearly worthwhile investigating alternative sources of high-quality protein," Dangourwrote. "However, the practical barriers to eating insects (in Westernized societies) are extremely large and perhaps currently even likely to be insurmountable."

David Gracer, an American advocate for entomophagy who co-organized a conference on the subject in December, welcomed the findings.

"It is wonderful to see science showing the world that what is instinctively apparent is actually factually correct," Gracer said. "The point is that most scientists in Western nations are too busy ignoring this subject to go ahead and take it seriously, and as soon as people do so, the experiments simply reinforce what we already assumed was true."