The prefix ‘nano’ refers to the number 9, as in 10^-9, usually in the context of nanometers. In other words, a nanometer is 1 x 10^-9, or a billionth of a meter—a scale that is almost unimaginably small. Some nanoparticles are byproducts of industry, or even normal physiologic breakdown of food. Others are manufactured on purpose. These are called nanotechnology.
Because nanotechnology is so small, it can confer certain unique benefits to food and medicine—but like all technological advancements, they are not without potential risk.
Concerns with Nanoparticles
Nanoparticles may enter the body via inhalation, ingestion, or skin penetration. The body has a number of mechanisms to protect its sensitive inner workings from foreign invaders, be they chemical or pathogens—particularly the Blood-Brain Barrier to protect the brain, and the cell membranes to protect the interior of the cells. Unfortunately, nanoparticles are so small that they can slip right past these defenses. Nanoparticles have been shown to cross the Blood-Brain Barrier, as well as freely pass through cell membranes and even make their way into the cell nucleus.
How damaging or benign these particulates might be is a function of their individual properties, including shape, size, charge, hydrophobia or hydrophilia (whether they repel or attract water), and inner structure. These properties will determine how readily the particles are taken up by the cells, and how easily they are either eliminated or bioaccumulate. Once inside, potential damage may be induced by generation of reactive oxygen species (ROS, otherwise known as free radicals, or pro-oxidants), which leads to oxidative stress and inflammation, and potentially even to cancer. Since nanoparticles can also penetrate into the cell nucleus, they can damage the DNA itself, ultimately by triggering programmed cell death. Inhaled nanoparticles can trigger pulmonary allergic inflammatory responses.
Common nano-sized ingredients include silicon dioxide and other synthetic silicas, calcium carbonate, silicate, and tricalcium phosphates, iron compounds, and titanium dioxide. Metal nanoparticles produced as byproducts of industry and manufacturing include silver, copper, and aluminum, though these can be used intentionally in food packaging, too (see below). In some cases, exhaust, and fumes can also produce accidental nano-titanium dioxide and carbon particulates. Presumably these have been an issue since the Industrial Revolution, at least to some degree.
Metal nanoparticulates have been associated with neuronal and glial cell damage, as well as endothelial damage (damage to the blood vessel lining).
Nanoparticulates produced by combustion or otherwise aerosolized in industry likewise have been shown to reach the brain, and are potentially connected to neurodegeneration.
Nanoparticles in Food Packaging
Nanotechnology is used in food packaging to better ensure seals against oxygen (which causes oxidation and thus, more rapid decay), a well as to enhance its water and flame resistance, strength, and other properties.
Unfortunately, whatever the food is in contact with tends to leech into the food itself. I see this often in my practice with hormone-disrupting phthalates from plastics (in plastic water bottles, seran wrap, tupperware storage containers, etc), as well as styrofoam containers. The same thing can happen with nanoparticulates in packaging.
Metal nanoparticles are sometimes used to prevent the breakdown of plastic packaging from sunlight, and also for their antimicrobial properties. Metal nanoparticles can bioaccumulate and cause heavy metal toxicity.
Nanoparticulates in Food Itself
Unfortunately, because nanotechnology is Generally Recognized as Safe (GRAS) by the FDA, companies are not required to mention it on ingredient lists–so they don’t. But it can serve a number of different purposes in the food manufacturing industry.
Nanotechnology can manipulate the structure of food to decrease calories, while maintaining flavor.
They are used as emulsifiers, to keep ingredients from separating.
Silicon dioxide in particular is used as a carrier for flavor and fragrance in food. There is some evidence that nano-sized silicon dioxide can be absorbed through the gut lining, making it a potential cause for leaky gut syndrome.
Like with packaging, edible nano-particulate coatings from gelatin, silica, cellulose, and silicon dioxide are used to help preserve shelf life of foods.
Titanium dioxide nanoparticles in the sugar coating on chewing gum get released into the saliva and slowly bioaccumulate.
There are even experiments to wrap allergenic proteins like gluten in nanotechnology, in an attempt to ‘hide’ it from the immune system to avoid triggering an allergic or autoimmune response.
Nanoparticles in Medicine
Given the ability of nanoparticles to venture into places of the body that were previously heavily guarded (the cells, the cell nucleus, the BBB), they are studied and used to improve drug delivery, as well as in vaccine development, imaging and diagnostic technologies, and implants. Most recently, nano-sized polyethylene glycol was used in COVID vaccines, to stabilize the mRNA that would otherwise rapidly degrade in the body.
For any therapeutics intended for the brain, nanoparticles offer a novel method to deliver the drug right where it’s most needed.
Nano-sized lipids (fats) are also used to encapsulate drugs, enabling better absorption through cell membranes.
Nanoparticles in Cosmetics and Personal Care Products
In some cases, nanoparticles form as a byproduct in some personal care products, but in others they are added intentionally.
There is some debate over whether or not titanium dioxide in cosmetics is nanosized or not. Nanosized silicon dioxide is often used as an anti-caking agent, a thickener, and a carrier for fragrances as it is in foods.
For most normal-sized particles, traditional detoxification protocols will work. For nano-sized particles that can slip right through the gut lining and the cell membranes and the Blood-Brain Barrier, though? These might still work, but we simply don’t know. (Would ordinary binders, for instance, be like trying to pick up sand with a colander? Would the liver be able to process them via its same six phase 2 detox pathways?) It takes years, and in most cases decades, before we can really say whether or not a new innovation has unforeseen health consequences. But, judging by the explosion of chronic disease in the last several decades, it certainly appears likely that some of the things we thought were safe, weren’t.
Since nanotechnology isn’t required to be labeled on packaging, it seems to me that this is another excellent reason to forego prepackaged and processed foods, and to make as many of your personal care products yourself as possible. At least we can limit our exposure to the extent that we are able.