Does Diet Soda Get the Blame for Joint Pain?

Various studies around aspartame consumption have correlated the sugar substitute with various health issues, but causation is not known at this time.
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Diet soda is the artificially sweetened zero-calorie version of regular soda, and aspartame is a commonly used artificial sweetener in carbonated beverages. But if you drink in this sugar substitute, are you more likely to have joint pain and inflammation?

Aspartame and Inflammation

Aspartame was approved by the Food and Drug Administration (FDA) in 1983 for use in carbonated beverages. Your acceptable daily intake of aspartame, as set by the FDA, is 50 milligrams per kilogram of your body weight, according to the University of Alabama at Birmingham (UAB). If you weigh 150 pounds, for example, your daily intake limit would be 3,409 milligrams (mg) a day. For reference, according to UAB, one 12-ounce can of diet soda sweetened with aspartame contains about 200 mg.

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Aspartame is a chemical compound made up of phenylalanine, aspartic acid and methanol, according to a September 2015 study in The Journal of Biomedical Research. The study was conducted on rats that consumed aspartame to determine the brain effects of oxidative stress (cell damage). While more research needs to be completed — especially on humans — to confirm this finding, the results showed that the methanol from the breakdown of aspartame can, in fact, induce oxidative stress.

As described in research published in Life Sciences in March 2016, oxidative stress is an imbalance of oxidative and antioxidative systems of the cells and tissues, which creates free radicals in your body that, in excess, can result in cellular dysfunction, genetic mutations and inflammation.

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"There are many studies that suggest aspartame can trigger an oxidative reaction in the body leading to inflammation," says Adrienne Dowd, RD, a dietitian based in Idaho Falls, Idaho. "Generally speaking, inflammation can exacerbate some types of arthritis and, therefore, could cause pain in associated joints."

Read more: A List of Foods Containing Aspartame

Aspartame Sensitivity

It's not clear why some people are sensitive to aspartame and others are not. According to the Arthritis Foundation, studies on aspartame's effects have been mixed, but if you're sensitive to it, your immune system may be responding to aspartame as a foreign body and attacking it, causing an inflammatory response.

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On the other hand, a small study published in PLoS One in May 2015 compared 48 people who reported aspartame sensitivity with 48 people of similar age and gender who said they were not sensitive to aspartame. All participants randomly received either an aspartame-containing snack bar or a snack bar without aspartame at least seven days apart. The researchers found that the participants, regardless of their self-reported sensitivity, had no adverse responses to the aspartame-containing bar.

Read more: What Really Happens to Your Body When You Give Up Soda?

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Sodas and Bone Health

Beyond aspartame, concerns about adverse effects of soda on bone health have also been raised. One concern is that its phosphorus content could have a negative effect on calcium metabolism. According to the International Osteoporosis Foundation, evidence doesn't uphold this theory, but the caffeine content may decrease the amount of calcium that's stored in your body.

Another concern — whether soda consumption had any effect on hip fracture — was examined in a large study published in The American Journal of Clinical Nutrition in September 2014.

The participants, nearly 74,000 postmenopausal women who were tracked for up to 30 years, identified how much and what kind of soda they drank on a regular basis (regular, diet, caffeinated or decaf, for instance). Results showed that, among both regular and diet soda drinkers, their risk for hip fracture increased as their soda consumption increased.

Read more: What Are the Dangers of Splenda, Sucralose and Aspartame?

Although the exact reasoning behind why soda affects bone density is unknown, the Cleveland Clinic notes that drinking more soda drink might correlate to a lower consumption of calcium-rich beverages, such as milk.

The bottom line? The FDA recommends that if you feel you're having an adverse reaction to an artificial sweetener, it's best to discontinue ingesting it and reach out to your doctor.

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