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And that's a real problem, says Janeen Leon, MS, RD, LD, a researcher at the Center for Reducing Health Disparities at MetroHealth Medical Center in Cleveland, who has spent much of her recent career researching sodium phosphate food additives. "We're finding that, even among healthy adults, people with sodium phosphate levels at the higher end of what's considered normal have higher mortality rates," she says. What's more, rates of chronic kidney disease, a slow loss of kidney function that requires dialysis treatments and even organ transplants, have been on the rise, increasing 16 percent since the 1980s. "The rising rates of hypertension and diabetes likely play a role," she says, but physicians are starting to focus more of their attention on diet. "Though there's no hard evidence that high sodium phosphate diets cause kidney disease, there is sufficient data showing that phosphorus does cause a more rapid progression of the disease," she says.
In addition to chronic kidney disease and increased mortality rates, sodium phosphate additives have been linked to an increased risk of heart disease, they're thought to accelerate the aging process, and they interfere with the way your body activates Vitamin D—which is trouble if you're trying to boost the immune system . Too much sodium phosphate can also lead to weakened bones. In much of the professional research on heart disease, Leon says, "Doctors are making comments like, Is this the next trans fat? Is this the next cholesterol?"
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Leon's concerns were echoed in a recent issue of the European medical journal, Deutsches Ärzteblatt International. In a paper analyzing the available literature on sodium phosphate food additives and human health, the authors concluded that government officials need to institute stronger labeling laws for sodium phosphate content in processed foods because some of that Food Isn't Actually Food, and that food companies should be required to limit the amount of sodium phosphate they add to products.
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Where It's Hiding
Our bodies need phosphorus to survive; it's used to build and maintain strong bones and teeth, and cells use it to transport waste out of our systems. But our bodies only absorb 40 to 60 percent of the naturally occurring phosphorus found in whole grains, non-processed meats, poultry, fish, eggs, dairy products, nuts, and legumes is organic phosphorus.
However, Leon says, the forms of sodium phosphate added to foods are inorganic. They aren't chemically bound to fats and carbohydrates the way naturally occurring phosphorus is, and are much more easily absorbed by the body, leading to excessive levels of phosphate in the blood.
The recommended daily allowance for either form of phosphorus is 700 milligrams per day, yet most of us unknowingly eat about 1,500 mg. A few years ago, Leon did her own analysis of processed foods to determine which had the highest levels, and frozen dinners were at the top of her list. According to Leon, they have varying levels of sodium phosphate, all of which are "extremely high." She was also concerned about baked goods because the baking powder used in muffins, cakes, and other processed baked goods is very phosphate rich, as well as processed meats due to the sodium phosphate that is added to sausage, lunchmeat, ham, canned fish, and other processed meats. The sodium phosphate is used to keep them moist and tender during storage and the levels can range from 50 mg to as much as 400 mg per serving. The next time you're tempted to buy a self-basting turkey or other poultry advertised as containing added broth, put it down. The broth in enhanced meats is added to help the meat retain moisture during the cooking process and is mostly sodium phosphate—which can exist at levels as high as 400 mg, a nearly 30 percenet increase in the amount of phosphorus that exists naturally in meat.
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"Kraft Macaroni and Cheese, flavored noodle mixes—those types of foods are very high in phosphorus," says Leon, and sodas and fruit juice that contain 100 mg of phosphorus per serving "pale in comparison" to other foods. Leon did a separate study on restaurant foods and found that a single chicken and fried rice dinner at one Chinese food chain contained 900 mg of phosphorus. "A lot of that has to do with the enhanced meats," she says. "It's getting difficult to get chicken that's not enhanced at the commercial level." Although Leon is reluctant to condemn all calcium-fortified foods, she says many are fortified with calcium phosphate, which can cause the fortified version to contain 2 to 3 times the phosphorus of its non-fortified equivalent.
Her final advice? We all need to eat less phosphorus, and the best way to avoid it is to read labels. "Read your labels for any words containing 'phos-,' and limit your fast-food consumption," she says.