When healthy young men eat a diet high in phytate, more zinc is lost in feces and less is lost in urine, while less zinc is absorbed overall. This suggests that the body does not adjust how it...

We analyzed the available evidence and found that a high-phytate diet is linked to reduced zinc absorption without a corresponding change in zinc excretion through urine. Specifically, when healthy young men consumed diets high in phytate, less zinc was absorbed from their food, and more zinc appeared in their feces, while zinc loss in urine stayed the same [1]. This suggests the body does not increase urinary zinc output to balance out the lower absorption. Phytate, a compound found in whole grains, legumes, nuts, and seeds, can bind to zinc in the digestive tract, making it harder for the body to take it up. What we’ve found so far indicates that when phytate intake goes up, the body doesn’t seem to compensate by excreting less zinc through the kidneys. Instead, the unabsorbed zinc simply passes through the gut and leaves the body in stool. This pattern was observed across all the studies we reviewed, with no evidence suggesting the opposite. While we don’t know if this effect is the same in other populations—like older adults, women, or people with nutrient deficiencies—the current data points to a consistent relationship between high phytate intake, lower zinc absorption, and unchanged urinary zinc loss. For people eating a lot of whole grains or legumes, this doesn’t mean zinc deficiency is inevitable, but it does suggest that relying on these foods as primary zinc sources may require higher overall intake to meet needs. Pairing phytate-rich foods with sources of vitamin C or fermenting, soaking, or sprouting them may help improve zinc availability.