Diet Sodas & Calcium Absorption

When trying to manage weight, women often turn to calorie-free diet sodas. This switch might help your waistline---it saves about 200 calories for a 16-oz. serving---but it does nothing to help your bone health. A woman's body, more than a man's, is less able to absorb calcium when she drinks more than one serving of cola-type soda per day.

Definition

Calcium helps the body build and maintain bones and teeth. It is also helps your muscles function properly, assists with transmitting nerve signals, and plays a role in blood clotting. According to the University of Arizona's Cooperative Extension Office, low calcium can lead to muscle cramps and weak bones. Your calcium needs vary with age, but people from 19 to 50 years old generally need about 1,000 mg of calcium each day.

Absorption

Taking in enough calcium is only half the battle: the other half is getting your body to keep it. Sodas have a complex effect on calcium absorption.

Debate surrounds the issue, but there is a link between drinking large quantities of cola and low calcium absorption. In a 2003 Tufts University study, Katherine Tucker found that women who drank more than 36 oz. of cola per day had 2.3 to 5.1 percent lower bone density than women who consumed less than one serving of cola per day. Tucker's study found no difference between diet and regular sodas.

Caffeine

According to the Surgeon General, excessive amounts of caffeine can temporarily interfere with the body's ability to absorb calcium, but you can overcome this effect by increasing calcium intake. Caffeine can't be the only component of the high-soda/low-calcium connection, because the non-cola sodas with caffeine didn't have the bone-thinning effects of colas in Tucker's study.

Phosphorous

In 2001, Leonard Sax wrote in the "Journal of the American College of Nutrition" that all cola drinks sold in the United States contain phosphate additives. Non-cola sodas use citric acid instead. Phosphorous in general is not a harmful substance. It is a natural component of chicken and beef, and it has important functions in the body. But the phosphorous in food is different from phosphoric acid in sodas. Sax also noted that the ratio of calcium to phosphorous is important---so if you must drink colas, look for ways to boost your calcium intake.

Prevention/Solution

If you're on a diet, it's an easy switch to move from sugary to diet sodas, but this switch won't help your bone health. The NIH recommends that women cut current soda consumption by half while adding in more calcium-rich products. Consider a low-fat smoothie made with fresh fruit and unsweetened yogurt or calcium-fortified orange juice. Smoothies do contain more calories than a diet soda, but they also have plenty of nutrients to fuel your body.