You open a can of Bumble Bee tuna for a light summer lunch, thinking you’ll do your body good. But wait — is that glass in there? That’s been the reaction of many people upon encountering struvite — naturally occurring crystals that, despite looking scary, won’t do you any harm. Your body will digest the crystals just fine.
Known by the chemical name magnesium ammonium phosphate, struvite is a soft mineral that dissolves in acid. The FDA allows the addition of sodium acid pyrophosphate to be added in a quantity “not in excess of 0.5 percent by weight of the finished food” to prevent the formation of struvite in tuna and salmon. But eaters concerned about struvite’s health effects will prefer a few harmless shards to the additive meant to prevent it.