Phosphates added to dairy and cereal products have been found to cause bigger spikes in blood phosphorus levels than naturally occurring phosphates, potentially putting harmful stress on kidneys.

Too much dietary phosphate stiffens blood vessels, enlarges the heart, and is bad for bones, but the new study by Houston Methodist researchers suggests it matters where the phosphates come from.

The findings, reported online in the American Journal of Clinical Nutrition, are based on an analysis of patient medical records from the National Health and Nutrition Examination Survey, a U.S. Centers for Disease Control and Prevention project that combines survey and laboratory reports.

The researchers tracked what foods people were eating and how these foods affected blood phosphorus levels. The results showed the most significant increases in blood phosphate levels occurred in people who ate dairy foods and cereal/grain-based foods that contain artificially added phosphates.

"The study suggests people should be more aware of what they eat," said Linda Moore, director of clinical research programs for Houston Methodist Hospital's Department of Surgery and the report's lead author.

"The Institute of Medicine recommends 700 milligrams of phosphate per day and we think that's a good number. What we were seeing in this study was twice the consumption of that amount for a lot of people. Too much phosphate is concerning to people who are healthy -- but it is of special concern to people who already have kidney damage or chronic renal disease."

She added that pancake and quick-bread mixes often contain a lot of inorganic phosphate, “so those should be consumed less frequently," said Moore.

Currently, the Food and Drug Administration does not require food producers to distinguish between naturally occurring and artificially added phosphates on labels.

The researchers said the findings of the new study suggest the FDA should modify its regulations to require such labeling.