Unbeknownst to us, much of the food we consume contains nanoparticles that are much smaller than most viruses and thousands of times smaller than cells. A variety of nano-size substances added to food or packaging enhance color, flavor and freshness.
Food manufacturers add white titanium dioxide to processed food such as candy, gum, cookies, powdered doughnuts, icing, cheese and yogurt to whiten or brighten color. A tiny amount of a nanomaterial can smooth or thicken liquids, or add to shelf life. Nano-size capsules can enclose nutrients such as omega-3 to add fish oil to juice or mayonnaise without adding fishy taste.
The substances themselves were extensively tested decades ago before nanoparticles had been developed. Titanium dioxide tests in the 1960s using particles larger than 100 nanometers (a nanometer is one-billionth of a meter, or one-millionth of a millimeter) exposed human cells to see how much of the white powder it was safe to consume.
Because of the size of nanoparticles, those safety tests might not apply to all nanosubstances since their small size might interact with cells or behave differently from the larger particles.
So far, laboratory studies have given contradictory results, and researchers say they need more studies to gauge the potential impacts. Current studies, which are limited to mice or lab dishes, analyze megadoses of nanoparticles far beyond what any normal diet might include and thus are inconclusive.
People have been consuming nano-size materials from the beginning of time in natural foods such as milk, which contains casein micelles that help calves digest their mother’s milk. Other environmental sources introduce nanoparticles of carbon, silica or metals into the atmosphere and food chain from burning wood and coal, wildfires, volcanic activity and crashing ocean waves.
In the past two decades a wide range of products — including clothing, electronics and cosmetics, as well as food — have incorporated nano-size particles. What makes them different from those that were tested in macro size or those present in the natural environment is their specificity.
The amino acids and proteins that coat a nanoparticle determine its shape and surface properties, which enhance or reduce how the particles bind to certain molecules. Scientists can fine-tune these surface features to control where or how quickly nanoparticles release their contents.
The most common nanoproducts added to food or packaging are titanium dioxide, silicon dioxide and zinc oxide.
Larger particles of these ingredients have been used in food and medicine for decades and are considered “generally recognized as safe” by the FDA, but how they might react in nanoparticles is unknown.
Food manufacturers are experimenting with loading nanoparticles with nutrients and customizing where and how they release the contents by fine-tuning the surfaces. For example, vitamin E wrapped in nanospheres travels through the acid environment of the stomach and into the small intestine to be absorbed there. Capsules of nanospheres that dissolve in the mouth can latch onto taste receptors on the tongue to deliver bursts of flavor to make food tasty with less salt or sugar.
The era of nanotechnology and food additives is in its infancy. Expect to hear more about this in coming years.
Richard Brill is a professor of science at Honolulu Community College. His column runs of the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.
