Soda, Phosphorus, and Your Bones

There has been confusion about phosphorus in sodas and calcium absorption.  Because there’s widespread misinformation about soda and phosphorus, I want to address this confusion more completely.

Phosphorus is an essential mineral, one of the body’s building blocks for bone. The Dietary Reference Intake (DRI) for phosphorus is 700 mg per day for adult women. Though many women don’t get enough calcium in their diet, insufficient phosphorus is seldom a problem because phosphorus is abundant in many common foods. But calcium metabolism can suffer when you consume considerably more phosphorus than calcium. This is because both calcium and phosphorus require vitamin D for proper metabolism. If there’s an excess of phosphorus, less vitamin D is available for processing calcium, so calcium absorption is reduced.

Could soda consumption cause a phosphorus excess? Very unlikely. Many sodas have no phosphorus at all – and even those that do contain phosphorus have modest amounts compared to other common foods.

There’s no phosphorus at all in club soda or seltzer, according to the USDA Nutrient Database for Standard Reference (1998). Sodas that do have phosphorus contain well less than 100 milligrams per 8-ounce serving. Here are a few typical examples:

Coca-Cola (8 oz)
Diet Coke (8 oz)
Tab (8 oz)
Sprite (8 oz)
Minute Maid orange (8 oz)
Source: Coca-Cola USA

To put these quantities in perspective, let’s look at some other foods. Among the most significant sources of phosphorus in the typical American diet are whole grains (including cereal), meat, poultry and dairy foods. Some examples:

Whole wheat bread (1 slice)
Kellogg’s All Bran (1/2 cup)
Cheerios (1 cup)
Ground beef, lean, grilled (3 oz)
Chicken breast, no skin, roasted (3 oz)
Cottage cheese, low fat (4 oz)
Skim milk, 1% (8 oz)
Source: Online USDA Nutrient Database

In other words, you’d have to drink more than two six-packs of Diet Coke to ingest as much phosphorous as you’d get from a modest serving of All Bran and skim milk.

Reducing soda consumption to avoid phosphorus is like cutting back on carrots to save calories: Yes, carrots provide calories – but they’re very unlikely to be a significant source of excess calories in your diet.

Finally, there are two legitimate bone-related concerns involving soda. One is that some people – especially teenagers – may drink soda instead of milk and consequently they don’t get enough calcium.

The other possible issue is caffeine, an ingredient in many colas and other sodas. Caffeine has a diuretic effect and can interfere with calcium absorption if you consume more than 400 milligrams per day (the equivalent of about four cups of coffee). If you’re already close to that limit with coffee, and also drink several glasses of caffeine-containing soda daily, you might want to cut back or switch to decaffeinated. Typically, sodas that contain caffeine have about as much as teas that contain caffeine – considerably less than coffee. But check the label for exact amounts. For example, an 8-ounce glass of regular Coca-Cola contains 31 milligrams of caffeine; there’s none in the caffeine-free version.

by Miriam Nelson, PhD