You probably know that consuming too much saturated fat, trans fat and sodium increases the risk of cardiovascular disease. But what about phosphorus, which is found in a wide variety of foods, both whole and processed? In recent months, several papers have raised concerns that this often-overlooked mineral may also be bad for your heart (and overall health) when consumed in excess.
Phosphorus is naturally found in meat, poultry, seafood, dairy foods, nuts, seeds, beans and whole grains. These are organic sources of phosphorus. Some food additives are sources of inorganic phosphorus (in the form of phosphates); researchers are generally more concerned about inorganic phosphorus because this form is more easily absorbed by the body. Phosphate additives are used as leavening and anti-caking agents, stabilizers, flavor enhancers, emulsifiers and moisture binders, and are found in a variety of processed foods—from packaged meats and chicken nuggets to processed cheeses and dry cereals. Colas, both regular and diet, are also notable sources of phosphorus, but other sodas and beverages, such as some powdered drink mixes, may contain them too.
Not surprisingly, Western diets tend to be high in phosphorus because they typically contain lots of animal protein and processed foods.
Phosphorus: a double-edged sword
Phosphorus performs essential roles in the body—it is needed for energy metabolism, translating genetic information, maintaining cell membranes and regulating calcium, among other functions. Usually, the only people who have had to worry about phosphorus are those with chronic kidney disease—especially those with kidney failure—since they have trouble removing it from their blood, and excess amounts can be harmful. Now, though, there may be reason for healthy people also to be wary of getting too much phosphorus.
Animal studies have linked high phosphorus intake to a spectrum of health problems, including cardiovascular events, kidney impairment and bone loss. So, too, have some observational studies in people. For example, in a paper published in the American Journal of Clinical Nutrition last November, high dietary phosphorus intake (more than 1,400 milligrams a day, which is double the daily recommendation) was associated with increased mortality in healthy people without kidney disease.
The mechanism isn’t clear, since phosphorus metabolism is complex. One theory is that excess phosphorus increases FGF-23, a hormone that plays a role in regulating phosphorus in the body and is a marker for phosphorus balance. At high levels, FGF-23 may cause cardiovascular changes, including increased calcification and stiffening of blood vessels. Some scientists speculate that a high blood concentration of phosphorus might also directly cause adverse changes in cell functions. One complication is that the new study did not differentiate between organic and inorganic forms of phosphorus. It’s also hard to accurately assess phosphorus intake because food databases may underestimate its presence.
A scientific symposium on dietary phosphorus was held in Boston last spring. According to one of the symposium papers, published in Advances in Nutrition, an abundance of research has linked high amounts of FGF-23 to cardiovascular disease and death, leading the author to conclude that “restriction of phosphorus consumption may represent an effective intervention for mitigating adverse cardiovascular outcomes in the general population.”
As for bone health concerns, “there is accumulating evidence that phosphorus added to the food supply may be contributing to the burden of osteoporosis in the population,” according to another paper from the symposium, published in the Annals of the New York Academy of Sciences. Several studies have noted a link, for example, between cola consumption and low bone density and fractures, possibly due to the cola’s high phosphorus content (though other factors—such as colas displacing milk and other healthier beverages—cannot be ruled out). The mineral is needed for healthy bones, but excess amounts may disrupt calcium absorption as well as hormonal regulation of phosphorus, calcium and vitamin D.
Additional studies suggest that excess phosphorus may contribute to other chronic diseases as well, including type 2 diabetes, some cancers and even obesity.
Colas versus beans
More research is needed to determine how much of a health risk a high phosphorus intake poses—and whether certain food sources are more harmful. It’s possible that inorganic phosphorus (the kind found in additives and thus in processed foods and some beverages) is a greater health risk because it is more easily absorbed, as is the organic phosphorus in meat, compared to that in plant foods (such as beans).
The calcium content of phosphorus-containing foods may also matter, and may mitigate potential problems. In fact, dairy foods (high in both phosphorus and calcium) lower blood pressure, which is why they are an integral part of the DASH (Dietary Approaches to Stop Hypertension) diet. Of course, a high phosphorus intake may simply be a marker for a less-healthful diet in general—that is, one rich in processed foods, soda and meat.
Bottom line: Many Americans greatly exceed the daily recommendation for phosphorus. As scientists continue to tease apart its possible adverse effects, one thing is certain: Following a predominantly whole-foods, plant-based diet and cutting back on processed foods, sodas and meat is the most healthful way to eat—and, as a result, will naturally lower your phosphorus intake, particularly of the inorganic form.
If you have chronic kidney disease, it’s particularly important to watch your phosphorus intake, with the guidance of your health care provider or a registered dietitian. Food manufacturers do not have to list the amount of phosphorus on labels. To avoid phosphorus-containing additives, check the ingredients lists of packaged foods for anything with “phosph-” or “phosphate” in the name—such as phosphoric acid, pyrophosphate, dipotassium phosphate, hexametaphosphate or diammonium phosphate. A 2013 study from Case Western Reserve University, published in the Journal of Renal Nutrition, found that 44 percent of top-selling grocery items in northeast Ohio contained such additives, especially frozen foods, dry food mixes and processed meats.