Member - Academy Of Nutrition & Dietetics. USA.

​Metabolic Disorders Nutrition

Metabolism is the process by which our body converts anything we eat or drink into energy. The food we eat constitutes proteins, carbohydrates and fats. Sugars and acids, fuel for our body, are present in the food we eat. Our digestive system breaks the food into these fuels which can be used by our body immediately for some activity or store it in our tissues, such as the liver, muscle and body fat, for later use.
Metabolic disorder happens when any abnormal chemical reaction in our body disturbs this process.

Types of Disorders

There are various classes of disorders. Many of the disorders affect the breakdown of carbohydrates, lipids and amino acids while some affect the cells that produce energy resulting in mitochondrial disorders. Also common are metabolic disorders that occur due to the improper functioning of the liver or pancreas. Diabetes is a classic example for such a disorder. Genetic metabolic disorders are also popular.

Liver/Pancreas Disorder

Our pancreas secretes insulin, a hormone, which converts glucose into energy from the foods we consume. But sometimes the glucose is not completely converted and stays back in the blood leading to increased sugar levels and thus causing diabetes, a common pancreatic metabolic disorder. Diabetes is classified into type 1 and type 2. Type 1 diabetes is common in children with rare occurrence while type 2 is prevalent among adults and very common.

Type 2 Diabetes
Genetic, environmental factors, lifestyle and eating habits are common causes of type 2 diabetes. Symptoms are very mild that generally people fail to notice them initially. Wounds that take long time to heal, frequent urination, excess thirst and blurry vision are some common symptoms. You doctor may recommend you for a blood test to diagnose the presence of the disorder. It is recommended to go for an early diagnosis as high blood sugar levels can lead to heart ailments, kidney problems, nerve impairments and eye problems over time. Treatment involves consuming healthy foods, involving in some physical activity and keeping your mind stress-free. Medications are recommended when all these options fail to work out.

Mitochondrial Disorder
Mitochondria are generally known as the power house of the cells as they supply the cells with energy for their functioning. These cells contain hundreds of mitochondria and a disorder can result in many of these mitochondrial cells to be shut down resulting in energy deficiency. Mitochondrial disorder can affect one organ, tissue or cell type but mostly it affects many parts of the body as nearly all the cells depend on mitochondria for their energy supply. Muscle and nerve cells have high energy needs and hence muscular and neurological problems are common.
Genetic mutations are the primary cause for a mitochondrial disease. A mitochondrial disease causing muscular problems is termed as mitochondrial myopathy while a mitochondrial disease causing both muscular and neurological problems is termed as mitochondrial encephalomyopathy.  Symptoms of myopathy include muscle weakness and exercise intolerance. Along with myopathy symptoms, encephalomyopathy includes symptoms like hearing impairment, migraine-like headache and seizures. Rarely these diseases attack the muscles that aid in breathing causing respiratory problems or the heart disturbing the rhythmic heart beat.
Though total cure is not available treatment options include special diets, physical therapy, vitamin and mineral supplementation and medicines. The disease manifestations can be mild or severe and hence complete care is required during treatment.

Genetic Metabolic Disorder
Genetic metabolic disorders are inherited and result in the absence or reduced activity of an enzyme or cofactor. Initially genetic metabolic disorders were mainly classified into disorders of carbohydrate metabolism, amino acid metabolism, organic acid metabolism or urea cycle metabolism. But off late, hundreds of metabolic disorders have been discovered and many more are still being identified.

Amino Acid Metabolism Disorders
Amino acids are the building blocks of protein. If your body lacks the ability to get enough of these amino acids or if there is any trouble in using the amino acids present to build new proteins required by your body it results in amino acid metabolism disorders. Most common are phenylketonuria (PKU) and maple syrup urine disease.

Phenylketonuria (PKU)
Phenylketonuria increases the level of an amino acid called phenylalanine (Phe) in the blood. If the levels increased drastically mental retardation may result. Newborns must be screened soon after birth for PKU. Diets with low-protein content are the best treatment prescribed for PKU. Phe-free formula must be supplemented along with breast milk and regular infant formula during infancy.

Maple Syrup Urine Disease
Maple syrup urine disease occurs when the body is unable to break down certain protein blocks. The urine of the affected person smells like maple syrup and hence the distinctive naming of the disease. If not diagnosed and treated properly this disease can be life threatening leading to coma, neurological problems or death. Treatment includes consuming a diet devoid of proteins. It is essential to continue a diet low in amino acids throughout the life of people with this disease.

Carbohydrate Metabolism Disorder
Enzymes break down carbohydrates into glucose. At times your body may not have enough enzymes to break down the carbohydrates or there might be insufficient levels of enzymes present resulting in a disorder.

Galactosemia
Galactosemia occurs when our body is unable to break down the simple sugar galactose, found mainly in lactose (another sugar present in dairy products). Galactosemia simply means too much of galactose in the blood. This accumulation can result in kidney problems, liver failure and cataract problems. Treatment includes consuming a galactose-free diet throughout life. Infants diagnosed with this disease should be fed on formula without galactose.

Glycogen Storage Diseases
Glycogen storage diseases (GSDs) demonstrate an inability to convert glycogen to glucose. Type I and type III are the most common of the disorders and their symptoms include poor physical growth, hypoglycemia, hepatomegaly and abnormal biochemical parameters, specifically for cholesterol and triglycerides. Treatment mainly involves maintaining plasma glucose levels in normal range and preventing hypoglycemia through exogenous glucose supply. Hypoglycemia can be prevented by encouraging high-complex carbohydrate and low-fat dietary patterns. Young infants can be administered pancreatic enzyme before ingesting uncooked cornstarch to increase its efficacy. Main motive is to administer various kinds of carbohydrates at various doses during the day and night. Method of carbohydrate administration depends on an individual’s tolerance, body weight, state of health and physical activity.

Organic Acid Metabolism Disorder
Organic acid disorders are due to the accumulation of nonamino acid organic acids. Propionic acidemia and methylmalonic acidemia are common organic acid disorders.
Propionic acidemia is characterized by deficiency of propionyl CoA carboxylase in the pathway of propionyl-CoA to methylmalonyl-CoA. This disorder can be identified within a few days after birth and includes symptoms such as vomiting, poor feeding, lethargy, dehydration and coma. Liver damage, cognitive delay, cardiomyopathy and hypotonia may be the outcome of propionic acidemia.
Methylmalonic acidemia or aciduria is the result of five separate enzyme deficiencies. Though babies may seem to be normal at birth, symptoms occur once they start to consume protein diets. Symptoms are similar to propionic acidemia along with hypoglycemia, ketonuria and elevated plasma ammonia and lactase levels. Kidney failure, coma and death are complications of this disease.

Treatment Recommendations
Treatment primarily involves a low-protein diet to treat organic acid disorders. A daily intake of 1 to 1.5 g/kg of body weight is often effective for infants with the mildest form of disorder. Energy levels and fluid intake should be balanced to prevent dehydration and tissue catabolism. Growth rate, state of health, residual enzyme activity and overall protein and energy intakes must be monitored carefully and correlated with plasma amino acid levels. The patient should be hydrated sufficiently to maintain metabolic equilibrium.

Urea Cycle Metabolism Disorder
Urea cycle disorders are due to the accumulation of ammonia in the body. Signs of increased ammonia levels in the body include vomiting and lethargy which can progress to coma, seizures and death ultimately. Argininosuccinic aciduria, carbamyl-phosphate synthetase (CPS) deficiency, citrullinemia and ornithine transcarbamylase (OTC) deficiency are common urea cycle defects. OTC is the most common among these which affects boys predominantly. Common symptoms of these disorders include confusion, decreased food intake, vomiting, nausea and increased sleepiness.
A balanced protein intake is essential to reduce the amount of ammonia the body produces. The diet should be planned such that the baby gets to consume enough protein for growth but not good enough to cause symptoms. Most people get themselves admitted to the hospital for urea cycle disorders at some point. Treatment at this stage mainly involves dialysis to remove the excess ammonia from the body. Stress can cause further complications in people with these disorders and care must be taken to avoid it.

​Role of Nutritionist in Medical Nutrition Therapy for Metabolic Disorders
The role of a nutritionist is quite complex in treating these disorders. A family-centered counseling approach, knowledge of feeding-skill development and understanding of behavior modification techniques with the support of health care providers are essential.