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Genetic Metabolic Disorders Diet

Genetic metabolic disorders are inherited characteristics due to the reduction or lack of particular enzyme activity and its co-factor. Most of the metabolic disorders have severe clinical complications such as mental retardations and neurological disorders. Medical nutrition therapy in metabolic diseases is the maintenance of biochemical balance for injured patients, supplying adequate nutrients for growth and development, and improving emotional and social growth. There are many various genetic metabolic disorders that their symptoms and treatments are not related to the others. Still, the most effective way of treating them is going on a modified and special diet.

How to Diagnose Genetic Metabolic Disorders and What Are the Causes for a Diet?


Most of the inherited metabolic disorders occur because of a particular enzyme that does not work correctly due to its deficiency or lack of the body's enzyme. The enzyme may not be produced, or even if it is produced, it has dysfunctions. Genes are responsible for creating the enzyme, and any defects in them can change the product or its function. The screening can help people, especially those who want to get pregnant because a significant risk factor of inherited metabolic disorders is in people with a family history of those disorders. Gene defects, gene changes, and the mutation can be inherited from parents to the next generation. The best way to prevent these disorders is consoling a genetic counselor before the choice of having children.


There are different ways of determining and diagnosis of genetic metabolic disorders, such as:
♦ Metabolic testing
♦ Amniocentesis before the baby is born
♦ Signs and physical symptoms after birth
♦ Blood test
♦ Abnormality in the size of inner body organs

Types of Genetic Metabolic Disorders in Need for a Diet

Metabolic genetic disorders have various categories that depend on the substances, hormones, and enzymes participating in the body's normal function. Therefore, they can build an unreasonable amount of other specific substances that may be harmful, or the body suffers from a lack of them due to the inadequate amount of them needed.
Many genetic metabolic disorders can be diagnosed at birth. At the same time, the other number of them need more time to be determined.
Here are some common metabolic disorders:
♦ Hurler syndrome
♦ Niemann-Pick disease
♦ Tay-Sachs disease
♦ Gaucher disease
♦ Fabry disease
♦ Krabbe disease
♦ Zellweger syndrome
♦ Adrenoleukodystrophy
♦ Metal metabolism disorder:
♦ Wilson disease
♦ Hemochromatosis
♦ Phenylketonuria (PKU)
♦ Maple Syrup urine disorder(MSUD)
♦ Galactosemia
♦ Glycogen storage disorder
♦ Propionic academia (PA)
♦ methylmalonic academia
♦ Friedreich ataxia
♦ Hunter syndrome
♦ Metachromatic leukodystrophia(MLD)
♦ Urea cycle disorders

Metabolic Disorder Diet

There are categories of disorders connected to the nutrients we gain from the foods we eat and our intakes. Diet and nutrition have a crucial role in the treatment and help way of having a better life for patients with genetic metabolic disorders. The modified diet in the nutrients and the substances can affect the patients' body metabolism and the making dysfunction in the normal cycles. Therefore, dietitians can help in this way.

Diet of Disorders Related to Amino Acids:

PKU diet

PKU or phenylketonuria is a disease related to the reduction in or lack of phenylalanine hydroxylase enzyme, converting phenylalanine to tyrosine.
The medical nutrition therapy for this metabolic disease restricts phenylalanine intake and supplement therapy with tyrosine.
Blood phenylalanine concentration should be controlled. The foods containing phenylalanine should be consumed so that the blood phenylalanine stays in a normal range.
The increase in blood phenylalanine due to excess intake and tissue catabolism can be harmful.
In the energy deficit or infection, proteins of the body will be catalyzed, and the amount of phenylalanine in the blood will increase. Stress and illnesses can lead to a short intake of energy, and in this situation, we need a refined liquid diet. Observing and following a diet restricted in phenylalanine in children with PKU is essential.

Maple syrup urine disorder (MSUD) diet

The enzymatic defects in metabolizing branched-chain amino acids(BCAAs) include leucine, isoleucine, and valine. The infants are normal at birth, but 4 to 5 days after, they show malnutrition due to poor feeding, vomiting, weakness, and lethargy.
In the first week of their life, the smell of maple syrup (or burnt sugar) in the urine. The delay in cure can lead to acidosis, nervous disorders, seizures, coma, and death. BCAAs can be put in the diet when the leucine concentration in plasma was low enough. This leucine concentration depends on the infection, too, and it can show the clinical symptoms again.
When the number of leucine increases in the plasma, the BCAAs should be omitted from the diet, and Intravenous nutrition should be taken measures.
Recording the exact concentration of blood amino acids, especially leucine, isoleucine, and valine, and the amount of special powdered milk for maple syrup urine disease is the first nutritional and diet therapy approach for MSUD.

Diet of Metabolic Disorders of Organic Acidemia:

Propionic acidemia (PA) diet

Propionic acidemia (PA) the autosomal inherited metabolic disorder due to the deficit of enzyme propionyl coenzyme A (COA) carboxylase that patients show vomiting, lethargy, and encephalopathy. They may need biotin.

Methylmalonic acidemia diet

Methylmalonic acidemia is a metabolic disorder with these clinical symptoms: hypoglycemia, ketone urea, the increase in plasma ammonia, and the increase in blood lactate. One of the signs of this disease is the incidence of progressive kidney failure. There is a severe deficiency in the B12 vitamin that is needed in converting the substances.
The energy balance and fluid intakes are essential to prevent tissue catabolism and water loss. Metabolic acidosis can occur due to the high intake of protein, infection, or unknown and idiopathic factors.

Ketone consumption disorders diet

The isoleucine metabolism disorders and ketone bodies occur due to the 2-methylacetoacetyl-Coa thiolase deficiency. The restriction in protein, supplement therapy with carnitine, avoiding starvation using small frequent meals mostly containing carbohydrates, and using Bicitra for curing ketoacidosis.

Urea cycle disorders (UCD) diet

Urea cycle metabolism disorders (UCD) are a group of inherited diseases that lead to the accumulation of ammonia in the blood.
♦ The deficiency of ornithine transcarbamylase
♦ Citrullinemia that the children induced to this disease may have malnutrition due to the continuous vomit.
♦ argininosuccinic aciduria
♦ carbamoyl phosphate synthetase deficiency
There are special medical nutrition therapies, restricted protein diets, and supplementation for each one of them.

Diet for Carbohydrate Metabolism Disorders

Galactosemia diet

Galactosemia or the accumulation of galactose in the blood can be dangerous in birth with seizures and infections. It happens because of the lack of a particular enzyme in the first two weeks of life. It can lead to cataracts, growth failure, enlarged liver, and jaundice. They can experience hypoglycemia and become disposed to some infections. If the galactosemia does not be under threat, it can lead to growth retardation, and the IQ decreases in those children. They may have some problems in speaking afterward. Ovarian disorders are a common problem in 95% of women with galactosemia. Galactosemia patients should be on a diet restricted in galactose for their whole lifetime. They should avoid using dairy products containing lactose such as cream butter and some of the margarine, cheese and cheese derivatives, creamy cheese, yogurt, ice-cream, breast milk.

Glycogen storage disease(GSD) diet

The glycogen storage disease is arising from converting the glycogen to glucose. It has different types due to the dysfunctions in other enzymes and their deficiencies.
Using the raw corn starch infrequent meals with a high complex carbohydrate and low-fat diet is useful for preventing hypoglycemia. Still, the amount of consumption differs from person to person and at different ages.
Iron supplements are also recommended, but you should note that it can prevent iron absorption.

Diet for congenital errors in fructose metabolism

These disorders occur due to the lack of B aldolase hepatic enzyme. The patients should restrict the fructose sources and their intakes, such as sucrose and even alcoholic sweeteners like sorbitol.
Intolerance of fructose occurs in the mid-term of infancy due to consuming foods containing carbohydrates.

Fat oxidation disorders diet

The fat oxidation disorders are due to the lack of enzymes that shows clinical symptoms like hypoglycemia, liver dysfunction, decreased or no urinary ketones, secondary lack of carnitine.
The treatment is to prevent starvation, consuming a low-fat diet (less than 30% fat of total energy) and high carbohydrate, and using carnitine supplementations.

Let us know if you have any questions or comments.