- With Mayo Clinic nutritionist
Katherine Zeratsky, R.D., L.D.
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Katherine Zeratsky, R.D., L.D.
Katherine Zeratsky, R.D., L.D.
As a specialty editor for the Food & Nutrition Center, 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, she 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 pediatrics at Mayo Clinic Rochester and nutrition education related to the physiology and recommended intakes for premature infants.
Other areas of interest include breast milk and formula safety, neonatal feeding, and nutrition for breast-feeding mothers.
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.
Nutrition basics (20)
- Water softeners: How much sodium do they add?
- Caffeine: Is it dehydrating or not?
- Coffee and health: What does the research say?
- see all in Nutrition basics
Healthy diets (8)
- Diverticulitis diet: Can certain foods trigger an attack?
- Butter vs. margarine: Which is better for my heart?
- Canola oil: Does it contain toxins?
- see all in Healthy diets
Healthy cooking (10)
- Lentils: How do I cook with them?
- Food poisoning: How long can you safely keep leftovers?
- Canned pumpkin: Better than fresh?
- see all in Healthy cooking
Healthy menus and shopping strategies (6)
- Calories in sushi: What are the low-cal options?
- Vegetable juice: As good as whole vegetables?
- Buying beef? A guide to choosing the leanest cuts
- see all in Healthy menus and shopping strategies
Nutritional supplements (15)
- Vitamin water: Better than plain water?
- Ground flaxseed: Better than whole?
- Vitamin C: Can too much be harmful?
- see all in Nutritional supplements
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Question
Phenylalanine in diet soda: Is it harmful?
The label on my favorite diet soda says it contains phenylalanine. I thought I read somewhere that phenylalanine is bad for your health. Can you clarify?
Answer
from Katherine Zeratsky, R.D., L.D.
Phenylalanine is an essential amino acid, so you need it in your diet. Amino acids are the building blocks of protein.
Phenylalanine is found in protein-rich foods, such as milk, cheese, nuts, seeds, poultry and fish. It's also found in diet foods, such as diet soda, which contains aspartame.
Phenylalanine isn't a problem for most people. Diet sodas contain a warning about phenylalanine because it can pose a risk to people who have phenylketonuria (PKU). PKU is a rare condition in which the body cannot process phenylalanine. If you don't have PKU, don't worry about phenylalanine in your diet soda.
For infants and children with this disorder, consuming phenylalanine is dangerous. If you're an adult with this disorder, consult your doctor regarding whether phenylalanine is a concern.
Next questionFat grams, calories or percentages: Which are more important?
- Artificial sweeteners. U.S. Food and Drug Administration. http://www.fda.gov/fdac/features/2006/406_sweeteners.html%20Accessed%20Nov.%2019, 2008.
