AMHERST, Mass. – In a recent review of the scientific literature, award-winning food scientist David Julian McClements and his colleague Hang Xiao at the University of Massachusetts Amherst conclude that nanoparticle safety in food should be judged on a case-by-case basis, for example, depending on whether the particles are organic or inorganic, natural or engineered, as well as on the properties of the foods they are eaten with.
The researchers point out, “Different mechanisms of action are likely to be more or less important for different types of nanoparticles,” and “at present there is a relatively poor understanding of the gastrointestinal (GI) fate and toxicity of most types of food-grade nanoparticles.” Further, “it is not possible to make a single general recommendation about the safety of all nanoparticle types.”
McClements adds, “There are hundreds, probably thousands of these studies, but most have been carried out on unrealistic systems. One of the things we need is more realistic models of the GI tract, and models that take into account that nanoparticles are eaten in the presence of food, which can make them more or less toxic. Thus, studies need to be better designed to take into account things such as nanoparticle size, charge, surface properties and aggregation state, whether they clump together or not, as well as food matrix composition and structure.”
While nanotechnology offers the food industry new approaches for improving the quality, shelf life, safety and healthiness of foods, consumers, regulatory agencies and the food industry have concerns about potential adverse effects associated with using engineered nanoparticles in foods as delivery systems for colors, flavors, preservatives, nutrients and nutraceuticals, or others used to modify the look, feel or flow properties of food, for example.
The authors summarize the research on engineered silver, iron oxide, titanium dioxide, silicon dioxide and zinc oxide nanoparticles and organic lipid, protein and carbohydrate nanoparticles in foods, the size of which ranges between about 10 and 1,000 nanometers. Details of this research appear in a recent issue of Nature Partner Journals’ Science of Food.
McClements and Xiao note that organic nanoparticles occur naturally such as casein in milk, oil bodies in plants and seeds, and organelles in meats, fruits, vegetables and spices. Engineered nanoparticles are used in a variety of ways such as in nutraceutical delivery systems, antimicrobial coatings and packaging, in dried mixes, powders and baked goods.
McClements adds, “Most organic nanoparticles will be fully digested in the GI tract, and so eventually behave similarly to more conventional organic particles.” For engineered nanoparticles, on the other hand, the authors point out that “their ability to be absorbed by the body, accumulate in certain tissues and produce cytotoxicity are likely to be the most important mechanisms.”
Further, he says, “Naturally, people are more concerned about engineered nanoparticles, which are added to encapsulate bioactive compounds such as vitamins or nutraceuticals. Incorporating them into food can substantially increase their bioavailability, which is desirable for certain applications. However, an unintentional side effect is that you can increase the bioavailability of certain vitamins so much that they may reach toxic levels. Another unintended consequence is that lipid nanoparticles eaten with fruits and vegetables can boost the amount of pesticide absorbed. So there is certainly some reason for caution when using this new technology in foods.”
The authors say that more research is needed to establish the potential magnitude and importance of these effects. McClements’ research group at UMass Amherst is now working with Philip Demokritou’s laboratory at Harvard University’s T.H. Chan School of Public Health to advance the science in this area.
This work was supported by the USDA’s National Institute of Food and Agriculture, its Agriculture and Food Research Initiative and the Massachusetts Agricultural Experiment Station.