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Aspartame – Does it Affect PD?

Aspartame – Does it Affect PD?

By Kathrynne Holden, MS, RD

I’m often asked whether aspartame can affect PD symptoms. There are many, many reports on the Internet about the possible harmful effects on people with various conditions, including Parkinson’s disease. While there are no simple answers to this question, it’s certainly a good idea to examine these concerns.

What is aspartame?

Aspartame (also known by the brand names NutraSweet® and Equal®) is a chemical that is 200 times sweeter than sugar; it’s used to sweeten foods without adding significant calories. It is among a class of chemicals known as excitotoxins — compounds that react with certain receptors in the brain. It’s found in soft drinks, chewing gum, breakfast cereals, candies, desserts, many chewable medicines, and many prepared foods. When digested, it is broken down into amino acids, aspartic acid and phenylalanine, and a small amount of methanol.

Is it dangerous?

This is a question in many minds. The position of the Academy of Nutrition and Dietetics’ is that consumers can safely enjoy a range of nutritive and non-nutritive sweeteners when consumed in moderation and within the context of a diet consistent with the Dietary Guideline for Americans.

At the opposite end, there are a number of Internet hoaxes making unproven claims about the dangers of aspartame. You can distinguish these hoaxes by emotionally-charged, fear-inducing language.These are often accompanied by testimonials from people claiming that their diseases, such as multiple sclerosis, lupus, Parkinson’s disease, and other conditions, have been quickly cured after stopping use of aspartame. On the other hand, there are many anecdotal reports that, although not scientific research, are too numerous and too consistent to be ignored.

To help put the controversy into perspective, here is a quote from a neurosurgeon who has studied aspartame extensively, Dr. Russell L. Blaylock, MD; this is taken from the preface to his book Excitotoxins, the Taste That Kills :

“While there is little evidence that food borne excitotoxins are the cause of these disorders, there is growing evidence that they can aggravate these conditions and that they may even precipitate them in sensitive individuals. Certainly the scientific evidence is far too strong to ignore the possibility that excitotoxic food additives may cause such conditions to appear sooner and to a more serious degree.”1

Still another health professional reports:

“…despite what appears to be a concerted effort on the part of aspartame’s makers to negate the allegations of health problems, adverse reactions from aspartame are real. This was eloquently borne out in 1996, when Ralph G. Walton, MD, professor and chairman of the Department of Psychiatry at Northeastern Ohio Universities College of Medicine conducted an analysis of all the medical studies — 164 of them at the time — dealing with human safety as it relates to the use of aspartame.

“The studies were separated into two categories: 74 were sponsored by the aspartame industry and 90 were non-industry-sponsored studies. Dr. Walton found that of the 74 studies sponsored by the aspartame industry, 100 percent of them claimed there were no health problems associated with aspartame use.

“Of the 90 studies that had no connections to industry, all but seven of them identified one or more problems with aspartame use. Interestingly, of the seven studies that did not find problems, the FDA had conducted six. Critics suggest that since a number of FDA officials eventually went to work for the aspartame industry, these six studies should be considered industry-sponsored research as well.”2 (Reprinted from “Aspartame = Diet-astrous Results” by Rebecca Ephraim, RD, CCN, Conscious Choice Magazine, May 2001,

A few research studies have addressed its use in people with specific conditions, including depression, diabetes/poor blood glucose control and Parkinson’s disease. Let’s examine these studies, as well as individual reports, and see if we can draw any conclusions regarding its use by people with PD.

Aspartame and Depression

In the only study conducted on individuals with depression, 40 people with unipolar depression and 40 people without a history of depression were studied to determine whether people with mood disorders were affected by aspartame use.3 Rarely, a study is halted if it is clear that subjects may be endangered by the study protocol. In this study, 13 out of the 40 subjects with depression suffered severe reactions, while the control group (those without depression) did not. The severity of reactions among those with depressive disorders was so great that the Institutional Review Board, responsible for ensuring that the rights and welfare of study participants are protected, halted the project.

Individuals in both groups received 30 mg aspartame per kilogram body weight per day, about the equivalent of ten 12-ounce cans of diet soda daily. With today’s super-sizing of portions, and the great number of products that contain the chemical, it’s not difficult for an individual to consume this amount in a day.

Researchers estimate that up to 25% of people with PD experience depression, which should give us pause. It may be that aspartame can further raise the likelihood of depression in those with PD.

Aspartame and diabetes

A number of my colleagues who are certified diabetes educators report an apparent anomaly among some of their clients. Several diabetic patients who carefully followed their diet and took medications at the proper time, nevertheless had high blood glucose. Upon close questioning, they all reported regular use of aspartame, mainly in the form of diet soft drinks. When these patients stopped using aspartame, their blood sugar dropped to a normal range. One dietitian reports that a patient with high blood sugar and a history of migraine headaches stopped using diet sodas and switched to regular soft drinks. His headaches stopped within three weeks; and,
despite the use of sugary soft drinks, his blood sugars returned to normal. While this is not true for all people with diabetes who use aspartame, it’s a good idea to be aware of the possibility. This is especially true because there is a high rate of diabetes among people with PD.

Aspartame and Parkinson’s disease

To the best of my knowledge, only a single study has been conducted on aspartame and PD. In the study of 18 people with PD, researchers examined its effects on motor fluctuations and concluded: “Aspartame consumption in amounts well in excess of what would be consumed by heavy users of aspartame-sweetened products has no adverse effect on PD patients.”4 However, aspartame was administered only for one day, and in capsule form — a form that is not absorbed in the same way as it is via food. Therefore, the study results are not necessarily applicable to people with PD who consume artificially-sweetened foods.

Anecdotally, people with PD who use aspartame have reported short-term memory loss; fatigue; muscle aches; increased tremors and/or rigidity; bloating; headaches; aggressive behavior; shorter “on times,” and edema. Within a few weeks of discontinued use, these patients reported longer “on times,” and a decrease in PD symptoms, including a lower need for levodopa. Such anecdotal reports cannot be taken as proof that aspartame has adverse effects for those with PD; but they should be taken seriously. It may well be that a subgroup of individuals are unfavorably affected by aspartame and cannot use it without harmful results.

Finally, aspartame contains phenylalanine, one of the large neutral amino acids that competes with levodopa for absorption. This may, potentially, be of concern for those using one of the several forms of levodopa medication.


A few people are born with phenylketonuria (PKU), a rare inherited disease that prevents phenylalanine, a component of aspartame, from being properly metabolized. Phenylalanine can then build up in the body and cause health problems. Since aspartame is a source of phenylalanine, aspartame-containing foods must be labeled with a warning — Phenylketonurics: Contains Phenylalanine.


In great part, what we are told about the safety of aspartame is based on studies funded by its makers. This has contributed to the lingering questions many consumers have about it’s safety. I believe that at the very least, there are some people who are affected adversely by aspartame; and I think this can be true at many different levels of intake — from as little as a few sticks of sugar-free chewing gum daily to those who consume six liters of diet cola, as well as aspartame-sweetened Jell-O, yogurt, cocoa mix, powdered soft drinks, tea, breakfast cereal, puddings, breath mints, vitamins, and ice cream daily; and put Equal in their coffee or tea. It is further likely that some people with PD are among this group, and that aspartame may increase PD and other symptoms,
possibly including depression.

If you have PD and use aspartame in any form, I recommend you eliminate these products for at least one month, and note whether there is any change in the way you feel. If not, then resume use of the products, again noting whether there is any change in physical or mental state. If you feel better or symptoms improve after discontinuing use, I would report this to your neurologist, and ask that it be further reported to the FDA.

If you have diabetes, you should be aware that the old belief that people with diabetes should avoid all sugar is no longer valid. People with diabetes can include sugar in their diets; ask your doctor for a referral to a registered dietitian who is a Certified Diabetes Educator (CDE) for counseling.
Here’s to your good health!

1. Blaylock, Russell L., 1994. “Excitotoxins: The Taste That Kills,” Health Press, Santa Fe, New Mexico, c1994.

2. Ephraim R. Aspartame – Diet-astrous Results. Health Conscious; May 2001.

3. Walton RG, Hudak R, and Green-Waite RJ. Adverse reactions to aspartame: double-blind challenge in patients from a vulnerable population. Biol Psychiatry 1993 Jul 1-15; 34(1-2): 13-7.

4. Karstaedt PJ, Pincus JH. Aspartame use in Parkinson’s disease. Neurology. 1993 Mar; 43(3 Pt 1): 611-3.

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