A patient with multiple joint pains comes into the office for evaluation.  He asks about aspartame poisoning as a potential cause of his complaints.   I was not familiar with this as a cause of joint pain and I did some research.  His reference was a website that you can find here. 
After some additional research, I found a reference summarizing current medical opinion on the Mayo Clinic website. 
More than ever, people are consuming large amounts of sugar as part of their daily diet. But in excess, sugar can take its toll. Eating large amounts of sugar adds extra calories, which can cause weight gain. So many people opt for artificial sweeteners — also referred to as sugar substitutes or low-calorie sweeteners — as a way to enjoy their favorite foods without as many calories.

What are artificial sweeteners?

Artificial sweeteners are chemicals or natural compounds that offer the sweetness of sugar without as many calories. Because the substitutes are much sweeter than sugar, it takes a much smaller quantity to create the same sweetness. Products made with artificial sweeteners have a much lower calorie count than do those made with sugar. Artificial sweeteners are often used as part of a weight-loss plan or as a means to control weight gain. 
People with diabetes may use artificial sweeteners because they make food taste sweet without raising blood sugar levels. But keep in mind that if you do have diabetes, some foods containing artificial sweeteners, such as sugar-free yogurt, can still affect your blood sugar level due to other carbohydrates or proteins in the food. Some foods labeled “sugar-free” — such as sugar-free cookies and chocolates — may contain sweeteners, such as sorbitol or mannitol, which contain calories and can affect your blood sugar level. Some sugar-free products may also contain flour, which will raise blood sugar levels. Also, remember that foods containing sugar substitutes may also contain calories that may undermine your ability to lose weight and control blood sugar.

Sweet choices

The Food and Drug Administration (FDA) has approved the following low-calorie sweeteners for use in a variety of foods. The FDA has established an “acceptable daily intake” (ADI) for each sweetener. This is the maximum amount considered safe to eat each day during your lifetime. ADIs are intended to be about 100 times less than the smallest amount that might cause health concerns.
Artificial sweetener ADI* Estimated ADI equivalent** OK for cooking?
Aspartame (NutraSweet, Equal) 50 milligrams (mg) per kilogram (kg) 18 to 19 cans of diet cola No
Saccharin (Sweet’N Low, SugarTwin) 5 mg per kg 9 to 12 packets of sweetener Yes
Acesulfame K (Sunett, Sweet One) 15 mg per kg 30 to 32 cans of diet lemon-lime soda*** Yes
Sucralose (Splenda) 5 mg per kg 6 cans of diet cola*** Yes

*FDA-established acceptable daily intake (ADI) limit per kilogram (2.2 pounds) of body weight.
**Product-consumption equivalent for a person weighing 150 pounds (68 kilograms).
***These products usually contain more than one type of sweetener.

Safety of artificial sweeteners

Artificial sweeteners are often the subject of stories, presented in the popular press and on the Internet, claiming that they cause a variety of health problems, including cancer. According to the National Cancer Institute, however, there’s no scientific evidence that any of the artificial sweeteners approved for use in the United States cause cancer. And numerous studies confirm that artificial sweeteners are safe for the general population. 

Aspartame does carry a cautionary note, however. It isn’t safe for people who have the rare hereditary disease phenylketonuria (PKU). Products that contain aspartame must carry a PKU warning on the label.

Still empty calories

Just removing sugar from cookies and chocolates doesn’t make them low-calorie, low-fat foods. If you eat too many, you’ll still get more calories than you may need, and you may not get enough nutritious foods. Unlike fruits, vegetables and whole grains, sugar-free soft drinks, candy and desserts often provide few — if any — beneficial nutrients.
Use artificial sweeteners sensibly. It’s OK to substitute a diet soda for a regular soda, for example, but diet soda shouldn’t be the only beverage you drink.

My thoughts:

When something like aspartame, seems to cause every disease known to mankind, one has to look carefully at the supporting data.  While too much of anything is not good for you, I cannot find anything that scientifically supports aspartame as a cause of joint pain.  We cannot know everything and additional research is important.

Just because the FDA says it is OK does not mean much.  Think about how may medications have been on the market only to be recalled after people develop side effects. 

In addition, just because people says they have problems related to a compound or implant, does not mean that it is really the culprit.  Think about silicone breast implants. 

For this patient, however, the best test is to stop all use of aspartame, and see what happens to the joint pain.

I am not sure this proves anything about aspartame, but it does suggest that patients should be wary of what they read on the Internet.  If you don’t believe me, just check your email SPAM folder.

Thanks,

JTM, MD