Diana Kwon writes:

Walk down the cold-remedy aisle of almost any pharmacy and you’ll see a shelf full of zinc supplements. Clearly, people must be worried that they’re not getting enough zinc, a nutrient often touted for its ability to quash the common cold and other respiratory illnesses. But do many of us really need more zinc? And if so, what good does it do?

As researchers learn more about how our bodies use zinc, they’re finding that the element plays a surprisingly key role, particularly within the immune system. “We think zinc is a gatekeeper of immune function,” says Lothar Rink, an immunologist at RWTH Aachen University in Germany who recently coauthored an overview of zinc’s roles in the immune system in the 2021 Annual Review of Nutrition. And, although scientists still struggle to find good ways to measure zinc levels in the body, it looks as though many people may indeed not have enough zinc in their diet for full immune function.

Too little zinc is clearly bad news for your health. A severe shortage — often the result of a genetic defect or an extremely restricted diet — can cause myriad problems, such as stunted growth in infants and children, hair loss, roughened skin, delayed wound healing and weakened defenses against infections.

But the extent and consequences of more subtle zinc deficiencies have proven harder to pin down. That’s largely because it’s extremely difficult to measure zinc levels accurately in people. Zinc is often on the move both inside and outside our cells. During an infection, for example, blood levels drop as zinc is siphoned out of the bloodstream into cells that help launch an immune response. Zinc levels can also be perturbed by diet, certain drugs and hormones, and health status.

For these reasons, although it is possible to detect zinc levels in blood, these measurements are often imprecise. And unlike iron, which is easily assessed by measuring levels of iron-containing blood proteins like hemoglobin and ferritin, there is no biomarker that can be used as an indicator of zinc levels. “There’s still no 100 percent accurate way to measure zinc in a human being, especially if they have an illness of some kind,” says Daren Knoell, a zinc biologist at the University of Nebraska. Currently, the best way to determine a potential zinc deficit is to look at someone’s dietary intake, he adds. [Continue reading…]