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Aspartame vs. Phenylalanine: What's the Difference?

Edited by Janet White || By Harlon Moss || Updated on November 16, 2023
Aspartame is an artificial sweetener, while phenylalanine is an amino acid and one of the components of aspartame.

Key Differences

Aspartame is a low-calorie artificial sweetener used as a sugar substitute in many foods and beverages. It is made synthetically by combining the amino acids aspartic acid and phenylalanine. Phenylalanine, on the other hand, is a naturally occurring essential amino acid found in various foods and is also used by the body to produce proteins and other important molecules.
Phenylalanine is one of the building blocks of proteins and is important for the production of other amino acids and neurochemicals in the body. Aspartame, after ingestion, is broken down in the body into its constituent amino acids, including phenylalanine, which can be problematic for individuals with phenylketonuria (PKU), a metabolic disorder.
Aspartame is often used by individuals looking to reduce their caloric intake or manage diabetes because it is about 200 times sweeter than sugar and does not raise blood sugar levels. Conversely, phenylalanine is used by the body in a wide range of physiological processes, including the synthesis of tyrosine, another amino acid, and neurotransmitters like dopamine and norepinephrine.
While aspartame is subject to regulatory scrutiny and debate regarding its health effects, phenylalanine is a well-understood component of the human diet, necessary for normal growth and maintenance of life. Aspartame consumption needs to be monitored by those with PKU due to the presence of phenylalanine, which they cannot metabolize effectively.
Aspartame’s inclusion in food can often be identified by a warning label indicating its presence, primarily for the benefit of those with PKU who must limit their intake of phenylalanine. While phenylalanine is essential and safe for the general population, aspartame's safety has been a topic of discussion, although approved by many health authorities.

Comparison Chart


Artificial sweetener made from two amino acids
An essential amino acid

Use in Foods

Used as a sugar substitute
Found naturally in protein-containing foods


Sweetens foods without adding calories
Building block for proteins

Health Considerations

Controversial due to potential health effects
Must be monitored by individuals with PKU

Nutritional Contribution

No nutritional value, used for sweetness
Contributes to protein synthesis and neurotransmitter production

Aspartame and Phenylalanine Definitions


A low-calorie artificial sweetener.
She chose diet soda because it contained aspartame instead of sugar.


Found in protein-rich foods.
Meat, dairy, and beans are good sources of phenylalanine.


Controversial food additive.
There is ongoing debate about the safety of aspartame in food and drinks.


Precursor to neurotransmitters.
Phenylalanine is important for the production of dopamine.


Composed of two amino acids.
Aspartame breaks down into aspartic acid and phenylalanine in the body.


An essential amino acid.
Phenylalanine must be obtained through diet as the body cannot produce it.


Sugar substitute.
Aspartame is often found in sugar-free chewing gum.


Must be restricted in individuals with PKU.
People with PKU have to monitor their intake of phenylalanine.


Approximately 200 times sweeter than sugar.
Due to its intense sweetness, only a small amount of aspartame is needed.


Non-synthetic dietary component.
Unlike aspartame, phenylalanine is not artificially created.


An artificial sweetener, C14H18N2O5, whose metabolic breakdown products include aspartic acid and phenylalanine. It must be avoided by people with phenylketonuria.


An essential amino acid, C9H11NO2, that occurs as a constituent of many proteins and is converted to tyrosine in the body.


(organic compound) An artificial sweetener, the methyl ester of a dipeptide formed from aspartic acid and phenylalanine, used in many processed foods and beverages.


(amino acid) An essential amino acid C9H11NO2 found in most animal proteins; it is essential for growth; the inability to metabolize it leads to phenylketonuria; it is a constituent of aspartame.


An artificial sweetener containing an aspartic acid peptide, (C14H18N2O5); it is 160 times sweeter than sucrose (cane sugar) and is used as a calorie-free sweetener. Chemically it is N-L-


An essential amino acid found in proteins and needed for growth of children and for protein metabolism in children and adults; abundant in milk and eggs; it is normally converted to tyrosine in the human body


An artificial sweetener made from aspartic acid; used as a calorie-free sweetener


What is phenylalanine?

Phenylalanine is an essential amino acid found in various foods.

Why is aspartame used in food?

Aspartame is used to sweeten foods without adding calories.

Does aspartame affect blood sugar levels?

No, aspartame does not affect blood sugar levels, making it suitable for diabetics.

Can everyone consume phenylalanine?

Most people can, except those with phenylketonuria (PKU).

What is aspartame?

Aspartame is an artificial sweetener used as a sugar substitute.

What is PKU?

PKU is a metabolic disorder where the body cannot break down phenylalanine.

Is phenylalanine artificial?

No, it is a natural amino acid, while aspartame is an artificial compound.

Do all artificial sweeteners contain phenylalanine?

No, only some artificial sweeteners like aspartame contain phenylalanine.

Can phenylalanine be synthesized in the body?

No, it must be obtained through the diet as it is an essential amino acid.

Is aspartame safe for consumption?

Aspartame is approved by health authorities, but its safety is sometimes debated.

What foods contain phenylalanine?

Phenylalanine is found in protein-rich foods like meat, dairy, and beans.

Are there any calories in aspartame?

Aspartame has very few calories and is considered non-caloric.

How sweet is aspartame compared to sugar?

Aspartame is about 200 times sweeter than sugar.

What does phenylalanine do in the body?

It is used to make proteins and other important molecules like neurotransmitters.

Can aspartame cause allergies?

Aspartame can cause allergic reactions in some people, although it is rare.

How can phenylalanine intake be controlled?

By managing diet and avoiding high-protein foods and aspartame for those with PKU.

Is phenylalanine only found in artificial products?

No, it is naturally occurring in many foods.

Why does aspartame have a warning label?

The warning is for people with PKU who need to avoid excess phenylalanine.

What are the symptoms of PKU?

Symptoms can include intellectual disability and behavioral issues if not managed.

Has aspartame been banned in any countries?

Aspartame is widely approved, but some countries have considered restrictions based on health concerns.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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