Diet-Affected Genetic Metabolic Disorders

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Determining Body Fat Content: Reliable Options & Optimal Weight

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Metabolic Disorders
  • 1:52 Phenylketonuria
  • 3:14 Maple Syrup Urine Disease
  • 4:27 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed
Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

This lesson covers diet-affected metabolic disorders, which are genetic diseases that interfere with the body's ability to break down substances and require a special diet that avoids these substances. Learn about two disorders: PKU and MSUD.

Metabolic Disorders

Parents give their children many wonderful gifts. They provide all of the basic necessities of life, such as food and shelter, as well as some extras, like hugs and kisses. However, sometimes parents pass along things that children would rather not receive, such as a faulty gene that results in a metabolic disorder.

Metabolic disorders are inherited diseases that interfere with the body's ability to break down certain substances. For example, the body might be missing an enzyme that is needed to break down certain amino acids. Because they cannot be processed, these substances accumulate in the body and cause damage. Many people who are born with a metabolic disorder need to follow a special diet that limits or avoids the substances they cannot metabolize.

There are different types of metabolic disorders that affect different nutrients. For example, sugar metabolism is affected by diabetes, which is a metabolic disorder characterized by problems with glucose metabolism, and galactosemia, which is a metabolic disorder that affects the way galactose is metabolized. Fats can be a problem for some people affected by a metabolic disorder. For example, Gaucher's disease is a metabolic disorder characterized by problems with fat metabolism.

In this lesson, we will take a close look at two diet-affected genetic metabolic disorders that involve the metabolism of amino acids: phenylketonuria and maple syrup urine disease. Both of these metabolic disorders are inherited recessive genetic diseases, which means two copies of the bad gene, one from mom and one from dad, must be passed on to the child for the disease to develop.


Phenylketonuria, or PKU for short, is a genetic disorder in which the enzyme phenylalanine hydroxylase (PAH) is missing. PAH is needed to break down the amino acid phenylalanine. The result is an accumulation of phenylalanine in the blood and brain. If left untreated, this toxic buildup can damage nerve cells and cause brain damage.

Problems with PKU start at birth. Individuals born with PKU must avoid ingesting food and food components that contain phenylalanine. This is a challenge because the amino acid is part of most protein-containing foods. To complicate matters further, we see that phenylalanine is an essential amino acid, so it is required in small amounts. Therefore, people with this condition must drink special medical formulas that are synthetically made to provide the vital nutrients.

Interestingly, a person with PKU must also avoid low-calorie foods and diet beverages that contain the artificial sweetener aspartame. Phenylalanine is a component of aspartame, making it off limits for anyone suffering from PKU. In fact, you can find warnings on aspartame-containing food items that alert consumers of the presence of this ingredient.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account