How Genetically Modified Foods Could Affect Our Health in Unexpected Ways

Chinese researchers have found small pieces of rice ribonucleic acid (RNA) in the blood and organs of humans who eat rice. The Nanjing University-based team showed that this genetic material will bind to receptors in human liver cells and influence the uptake of cholesterol from the blood.

The type of RNA in question is called microRNA (abbreviated to miRNA) due to its small size. MiRNAs have been studied extensively since their discovery ten years ago, and have been implicated as players in several human diseases including cancer, Alzheimer's, and diabetes. They usually function by turning down or shutting down certain genes. The Chinese research provides the first in vivo example of ingested plant miRNA surviving digestion and influencing human cell function in this way.

Should the research survive scientific scrutiny -- a serious hurdle -- it could prove a game changer in many fields. It would mean that we're eating not just vitamins, protein, and fuel, but gene regulators as well.

That knowledge could deepen our understanding of many fields, including cross-species communication, co-evolution, and predator-prey relationships. It could illuminate new mechanisms for some metabolic disorders and perhaps explain how some herbal and modern medicines function.

This study had nothing to do with genetically modified (GM) food, but it could have implications on that front. The work shows a pathway by which new food products, such as GM foods, could influence human health in previously unanticipated ways.

Monsanto's website states, "There is no need for, or value in testing the safety of GM foods in humans." This viewpoint, while good for business, is built on an understanding of genetics circa 1960. It follows what's called the "Central Dogma" of genetics, which postulates a one-way chain of command between DNA and the cells DNA governs.

The Central Dogma resembles the process of ordering a pizza. The DNA codes for the kind of pizza it wants, and orders it. The RNA is the order slip, which communicates the specifics of that pizza to the cook. The finished and delivered pizza is analogous to the protein that DNA codes for.

We've known for decades that the Central Dogma, though basically correct, is overly simplistic. For example: miRNAs that don't code for anything, pizza or otherwise, travel within cells silencing genes that are being expressed. So while one piece of DNA is ordering a pizza, it could also be bombarding the pizzeria with RNA signals that can cancel the delivery of other pizzas ordered by other bits of DNA.

Researchers have been using this phenomena to their advantage in the form of small, engineered RNA strands that are virtually identical to miRNA. In a technique called RNA interference, or RNA knockdown, these small bits of RNA are used to turn off, or "knock down," certain genes.

RNA knockdown was first used commercially in 1994 to create the Flavor Savr, a tomato with increased shelf life. In 2007, several research teams began reporting success at engineering plant RNA to kill insect predators, by knocking down certain genes. As reported in MIT's Technology Review on November 5, 2007, researchers in China used RNA knockdown to make:

...cotton plants that silence a gene that allows cotton bollworms to process the toxin gossypol, which occurs naturally in cotton. Bollworms that eat the genetically engineered cotton can't make their toxin-processing proteins, and they die.

And,

Researchers at Monsanto and Devgen, a Belgian company, made corn plants that silence a gene essential for energy production in corn rootworms; ingestion wipes out the worms within 12 days.

Humans and insects have a lot in common, genetically. If miRNA can in fact survive the gut then it's entirely possible that miRNA intended to influence insect gene regulation could also affect humans.