Thursday Dec 11, 2008 (foodconsumer.org) -- In patients with moderate chronic kidney disease (CKD), higher levels of phosphorus in the blood may increase calcification of the major arteries and heart valves and raise the risk of cardiovascular disease, a study in the Journal of the American Society of Nephrology (JASN) suggests.

Very high levels of phosphorus in the blood have already been linked to increased risk of cardiovascular disease and vascular calcification in dialysis patients, according to Bryan Kestenbaum, MD, of the University of Washington in Seattle, Washington, coauthor of the study.

"We are now recognizing that even a mild increase in the serum phosphorus level is associated with cardiovascular events in people with CKD who are not on dialysis," said Dr. Kestenbaum.

The study was meant to examine the association between blood phosphorus levels and vascular (blood vessel) calcification in a group of 439 patients with moderate CKD.  

The researchers used a special computed tomography (CT) scan to assess calcification indicative of overall atherosclerosis.   Coronary artery calcification is associated with an increased risk of cardiovascular events, such as myocardial infarction (heart attack).

The researchers found calcifications of the coronary arteries in two-thirds of the CKD patients although 95 percent of the patients had phosphorus levels within the normal range—between 2.5 and 4.5 milligrams per deciliter (mg/dL).

Within the normal range of phosphorus, each 1 mg/dL increase in the phosphorus level raised risk of coronary artery calcification by 21 percent after other factors were considered, the study found.   The association was not influenced by traditional risk factors including vitamin D.

"Higher serum phosphorous levels within the normal range have been associated with cardiovascular events and premature death in people with CKD," said Dr. Kestenbaum. "Experimental work suggests that phosphorous causes toxicity by promoting calcification of blood vessels. We were able to demonstrate that people with higher serum phosphorus levels tended to have more calcification."

In the same issue of JASN, another study showed that high-normal phosphorus levels are linked to increased coronary artery calcium even in healthy adults without kidney disease.

Both studies suggested that reduced intake of dietary phosphorus may lower the risk of cardiovascular disease in CKD patients and even in healthy adults. Those who have high levels of phosphate levels may be better off cutting their dietary intake of this mineral.

Phosphorus is a structural component of bone in the form of a calcium phosphate salt known as hydroxyapatite. Phosphorus in the form of phospholipids is present as major structural components in cell membranes. It is also present in molecules involved in energy production and responsible for the storage and transmission of genetic information.

High levels of phosphorus have been linked to Attention Deficit Disorder and Attention-deficit hyperactivity disorder in children. Reducing intake of phosphorus in diet may help reduce ADD/ADHD risk.

According to phosadd.com, the following processed foods and beverages contain high levels of phosphate, cited in verbatim:

Soft drinks, soda drinks, especially cola or coke and fizzy lemonade

Cordials/fruit syrup beverages

Chocolate, lollies, sweets, candy, sugar

Ice-cream

Skim milk powder (often added to processed foods)

Biscuits, cookies, cakes from the supermarket

Tomato ketchup

Mayonnaise

Fish fingers

Processed cheese, especially soft cheese spread

Frozen pizzas

Hot dogs

Processed meats

Baking powder and self-raising flour often contains phosphate aerator

All foods that list as an ingredient mineral salts, emulsifiers and lecithin

Phosphorus may even show up at high levels in natural foods. Those who want to restrict their intake of this mineral may pay attention to those foods listed as follows, cited in verbatim from phosadd.com:

Egg yolks

Milk

Nuts

Wheat germ

Soybeans and their by-products

Peas

Beans

Lentils

Corn

Mushrooms

Oats

Cocoa beans (chocolate)

Sweet breads - liver, brains, kidneys