The Food Additive Phosphate Could Harm Your Health

Many processed foods now contain the food additive phosphate, as a preservative and thickening and leavening agent. Too much consumption could harm your kidneys.

If you are a health-savvy consumer you may read labels at the grocery store, or maybe you simply stay away from processed foods. Another reason to skip them is an additive called phosphates, which could harm your health, specifically your kidneys.

Phosphates, comprised of phosphorus and oxygen molecules, occur naturally in many foods, including chocolate, beans, chicken liver, beef liver, carp, cheeses, and oysters.

Food manufacturers add phosphates to processed foods (in the form of salts) as preservatives and thickening and leavening agents. You’ll find them in cake mixes, dairy products, cereals, deli meats, bacon, soda and sports drinks, and many other products.

Phosphorus isn’t normally a villain in your body, at least in reasonable amounts.  It’s an important mineral for many physiological processes and helps regulate muscle and nerve function. Along with calcium, phosphorus builds strong bones, too.

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Normal working kidneys remove extra phosphorus from your blood. So, unless you have chronic kidney disease, eating foods naturally rich in phosphorus shouldn’t pose a serious health problem.

But inorganic phosphates are a different story. They may increase phosphorus to potentially dangerous levels in your body, causing kidney problems, according to research led by Wadi Suki, MD, director of Houston Methodist Hospital's nephrology fellowship program and the report's lead investigator.

"High phosphorus in blood is associated with increased patient mortality, increased blood vessel stiffening, as well as increasing the rate of calcium deposition in heart valves,” he said. “This calcium comes out of bones and, therefore, weakens bones as well as damaging kidneys.”

His research team zeroed in specifically on phosphates artificially added to food to see if they have the same impact on blood levels as similar amounts of naturally occurring phosphates.

"We are seeing an increase in the proportion of Americans who have kidney disease, but we have no good explanations why. We thought that it might matter how the phosphates exist in different foods, and how we absorb them," explained Linda Moore, PhD, director of clinical research programs for Houston Methodist Hospital’s Department of Surgery and the report's lead author.

The investigators looked at data on nearly 8,000 people who participated in the National Health and Nutrition Examination Survey, a U.S. Centers for Disease Control and Prevention project, to see what foods the research subjects ate over three years and how their diets affected blood phosphorus levels. The researchers also studied results from lab tests that measured participants’ blood phosphate levels and kidney function.

The results showed that people who ate dairy products, cereal, and grain-based foods that contained artificially added phosphates had the most significant increases in blood phosphate levels. Although eating a lot of dairy foods that didn’t contain added phosphates also raised blood phosphate levels, it was a less significant increase.

"The study suggests people should be more aware of what they eat," said Moore. "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."

The U.S. Food and Drug Administration (FDA) doesn’t require food producers to list on labels whether phosphate is naturally occurring or artificially added. In fact, reading labels won’t guarantee you’ll know how much phosphate a product contains. The FDA doesn’t require food producers to quantify the phosphate amounts.

"We believe the FDA can reconsider how it requires food producers to describe phosphorus and phosphate additives," said Suki, former president of the American Society of Nephrology. "An educated consumer can make better dietary choices."

For now, if you aren't sure which foods contain added phosphates, concentrate on the outside aisles at grocery stores, where there is usually fresh food. Middle aisles typically contain more processed convenience foods.

"Pancake and 'quick bread' mixes and processed cheeses often contain a lot of inorganic phosphate, so those should be consumed less frequently," advised Moore. 

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