Polymer microparticles release vitamins and minerals when they encounter the stomach’s acidic environment.
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Every year, 2 million children die because they don’t get enough vitamins and minerals. Billions more face blindness, debilitating disease, and birth defects for the same reason. Now, researchers have fortified corn grain and other staple foods with these essential micronutrients by encapsulating them in a biocompatible polymer made of a well-known food additive. The coating prevents the nutrients from degrading during storage or cooking and it may help people better absorb them. If the new coating proves effective in large trials, it could offer public health officials a new tool for saving countless lives.
“It’s an encouraging result and a very interesting technology,” says Howard Sesso, an epidemiologist and micronutrient expert at Harvard Medical School in Boston who was not involved with the work.
Micronutrient deficiency isn’t a common problem in developed countries, where most people have access to a well-rounded diet and vitamin supplements. Yet, in many low-income nations, poor agriculture, bad roads, and a host of other challenges can stymie efforts to get food where it’s needed most. What’s more, some people distrust medical personnel, which hampers efforts to distribute vitamin pills.
Public health officials have long combatted this problem by adding essential nutrients, such as iodine, iron, and folate, to common food staples. But this approach doesn’t always work. Iron supplements, for example, can change foods’ taste and color, making people less likely to use them, says Ana Jaklenec, a biomedical engineer at the Massachusetts Institute of Technology (MIT) in Cambridge. And light, heat, and moisture can break down vitamin A.
Researchers and food companies have tried to shield micronutrients by encapsulating them in food additives, such as proteins and sugars. But these coatings typically fall apart in boiling water or other cooking conditions.
Frustrated by such failures, health policy experts at the Bill & Melinda Gates Foundation in Seattle, Washington, sought the help of Jaklenec and her supervisor, Robert Langer, an MIT chemical engineer who has pioneered numerous dissolvable coatings for protecting and delivering fragile medicines.
Jaklenec, Langer, and their colleagues initially considered more than 50 different polymer coatings that were stable in boiling water but would dissolve in the stomach’s acidic environment. After narrowing the list to 10 candidates and studying each closely, they settled on a polymer known as BMC. A protective coating in dietary supplements, BMC is already approved by the Food and Drug Administration (and therefore considered safe). The MIT team coated 11 micronutrient powders in BMC, including iron, zinc, folate, vitamin A, and vitamin D. They also coated microparticles containing up to four different vitamins and minerals. Lab testing showed that all stood up well to heat, ultraviolet light, and even 2 hours straight of being cooked in boiling water. The particles also readily dissolved in a low pH solution meant to mimic stomach acid.
In tests in mice, the researchers showed that the particles broke down in the stomach, after which the cargo traveled to the intestines and was absorbed. The researchers then teamed up with Michael Zimmermann, a food fortification expert at ETH Zurich in Switzerland, to do human tests of BMC-coated micronutrients. In their first trial, the researchers incorporated encapsulated iron sulfate into salt that was added to maize porridge, a common staple in low-income countries. The researchers were disappointed to find that people who ate the fortified maize absorbed less than half the iron of subjects who ate the salted porridge with unencapsulated iron sulfate. The polymer coatings likely delayed the release of the iron too long for it to get absorbed in the upper intestinal tract, Jaklenec says. So she and her colleagues reformulated their coating, decreasing the amount of BMC. A subsequent test with 24 people who ate bread made with fortified flour showed that they absorbed nearly an identical amount of iron as people who ate unencapsulated iron particles in their food, the researchers report today in Science Translational Medicine.
If the microparticle powders could be incorporated into commonly used food items, Langer says the process could easily be scaled up. Right now, he and his colleagues are in talks with food companies that produce bouillon cubes for soup, for example, to see whether they can conduct larger human trials in the places they are needed most.