- With Mayo Clinic nutritionist
Katherine Zeratsky, R.D., L.D.
read biographyclose windowBiography of
Katherine Zeratsky, R.D., L.D.
Katherine Zeratsky, R.D., L.D.
As a specialty editor for the nutrition and healthy eating guide, Katherine Zeratsky helps you sort through the facts and figures, the fads and the hype to learn more about nutrition and diet.
A Marinette, Wis., native, Katherine is certified in dietetics by the state of Minnesota and the American Dietetic Association. She has been with Mayo Clinic since 1999.
She is active in nutrition-related curriculum and course development in wellness nutrition at Mayo Clinic in Rochester, Minn., and nutrition education related to weight management and practical applications of nutrition-related lifestyle changes.
Other areas of interest include food and nutrition for all life stages, active lifestyles and the culinary arts.
She graduated from the University of Wisconsin-Madison, served a dietetic internship at the University of Iowa Hospitals and Clinics, and worked as a registered dietitian and health risk counselor at ThedaCare of Appleton, Wis., before joining the Mayo Clinic staff.
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Question
Phenylalanine in diet soda: Is it harmful?
My favorite diet soda has a warning about phenylalanine. Is phenylalanine bad for your health?
Answer
from Katherine Zeratsky, R.D., L.D.
Phenylalanine isn't a health concern for most people. But if you have the genetic metabolic disorder phenylketonuria (PKU), or certain other health conditions, phenylalanine can be a serious health concern. If you have PKU, phenylalanine can cause mental retardation, brain damage, seizures and other problems.
Phenylalanine occurs naturally in many protein-rich foods, such as milk, eggs and beef. Phenylalanine also is sold as a dietary supplement. And the artificial sweetener aspartame (Equal, NutraSweet), which is added to many medications, diet foods and diet sodas, contains phenylalanine. Because of this, federal regulations require that any food product that contains aspartame bear a warning stating "Phenylketonurics: Contains phenylalanine." This warning helps people with PKU and other conditions avoid products that are a source of phenylalanine.
If you don't have PKU, you probably don't need to worry about harmful health effects of phenylalanine — with certain important exceptions. Aspartame can cause a rapid increase in the brain levels of phenylalanine. Because of this, use products with aspartame cautiously if you:
- Take medications such as monoamine oxidase inhibitors, neuroleptics or medications that contain levodopa
- Have tardive dyskinesia
- Have a sleep disorder
- Have an anxiety disorder or other mental health condition
If you aren't sure if phenylalanine or aspartame is a concern for you, talk to your doctor.
- Bodamer OA, et al. Overview of phenylketonuria. http://www.uptodate.com/home/index.html. Accessed Jan. 21, 2011.
- PKU (phenylketonuria). March of Dimes. http://www.marchofdimes.com/professionals/14332_1219.asp. Accessed Jan. 25, 2011.
- How is aspartame handled by the body? The NutraSweet company. http://www.nutrasweet.com/articles/article.asp?Id=37. Accessed Jan. 27, 2011.
- Aspartame.Electronic Code of Federal Regulations. http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=e057b68f0345a6d44b25b082c07ffa91&rgn=div8&view=text&node=21:3.0.1.1.3.9.1.3&idno=21. Accessed Jan. 21, 2011.
- Hoecker JL (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 1, 2011.
- Phenylalanine. Lexi-Interact. Lexi-Comp. http://www.uptodate.com/crlsql/interact/frameset.jsp. Accessed Jan. 21, 2011.
- Magnuson BA, et al. Aspartame: A safety evaluation based on current use levels, regulations, and toxicological and epidemiological studies. Critical Reviews in Toxicology. 2007;37:629.
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