Taranis
Living well with the diet.
Inherited disorders of amino acid catabolism and chronic kidney disease mean learning to eat differently, with protein carefully counted. This page brings together practical guidance for you and your loved ones. It does not replace the advice of your medical team, who alone decide your diet.
Living well with the diet
Protein and amino acids
To understand the diet properly, it helps to know what happens to protein in a healthy body.
What food gives us
Our bodies are made of water, protein, fats (lipids), sugars (carbohydrates) and minerals, not forgetting vitamins. All of these are essential to life and come mainly from what we eat. Digestion gradually breaks food down into nutrients, substances small enough to be absorbed and then used by our cells.
Energy, building and maintenance
Sugars and fats serve mainly as fuel for all the vital functions. Protein is used first to build tissues during growth, then to maintain and renew them; any surplus can also be burned to provide energy. Water, minerals and vitamins provide no energy, but the body cannot do without them.
Metabolism and its enzymes
Metabolism covers all the chemical changes that nutrients undergo to produce energy and make the body’s components. Each reaction is carried out by a specialised tool, an enzyme, and there are a great many of them. To work properly, an enzyme sometimes needs a cofactor, a substance that makes it more efficient and is most often a vitamin.
Amino acids, the links in the protein chain
A protein is a chain of amino acids, and human proteins are built from twenty different amino acids. Some, called essential amino acids, cannot be made by the body, so they must come from food. The amino acids in the blood have two sources: protein from meals, once digested, and the body’s own proteins, which wear out and are constantly replaced.
Anabolism and catabolism
The amino acids in the blood are used first to make the body’s proteins: this is anabolism, a process that uses energy and makes growth possible. An ordinary diet generally provides far more protein than the body needs. The surplus is broken down by enzymes, often one per amino acid, and yields a little energy: this is catabolism. The intermediate steps of this breakdown produce organic acids.
Living well with the diet
Disorders of amino acid catabolism
These genetic disorders prevent the body from breaking down one or more amino acids normally. Digestion itself works normally.
A missing enzyme
From birth, one of the enzymes responsible for breaking down an amino acid, or a small group of amino acids, does not work. This is called an enzyme block. In milder forms, the enzyme keeps some activity, but not enough: this is a partial deficiency, with what is called residual activity.
An intoxication disorder
The block acts like a dam: the substances upstream of it build up, while those that should be produced downstream run short. It is mainly the substances that build up, which become toxic at high levels, that cause the signs of the disease. Hence the name intoxication disorders.
Two main families
In aminoacidopathies, one amino acid, or a few, builds up: phenylketonuria and maple syrup urine disease are two examples. In organic acidurias, also called organic acidaemias, the toxic substance is an organic acid, a molecule formed along the way as an amino acid is broken down. Methylmalonic and propionic acidurias belong to this group.
Slow intoxication or acute crisis
Intoxication can be chronic, with signs that develop slowly, or acute, with a sudden deterioration called decompensation. The two can combine, with crises occurring against a background of slow intoxication. Phenylketonuria is the exception: it does not cause acute decompensation, only chronic intoxication.
How the disease is passed on
These disorders are inherited and autosomal recessive: the affected child has received an altered gene from each of their two parents. The parents, who carry this change on only one chromosome, show no signs of the disease: they are known as healthy carriers. For each pregnancy of this couple, the chance that the child will be affected is one in four. In rare cases, the change arose spontaneously in the child and only one parent carries it.
A lifelong disease, but treatable
These rare diseases are present from birth and stay with the person for life: there is no cure for them today. They are, however, treated with a specific diet, sometimes combined with medicines, which must be followed without a break. Understanding it well helps you apply it every day and explain it early to your child, so that they gradually become independent.
Living well with the diet
The principles of treatment
Treatment relies mainly on a diet specific to each disease, sometimes combined with medicines. The amounts are set by your medical team: never change the diet without their advice.
The goals
Whatever the disease, treatment aims for your child to grow normally in weight, height and head circumference, with good nutritional status. It also aims for normal psychomotor development and stable metabolic balance over time. Finally, it seeks to prevent acute decompensation (phenylketonuria does not cause it) by avoiding any period when the body breaks down its own proteins.
Restricting, never eliminating
The diet greatly reduces dietary protein to prevent intoxication, but it never eliminates it. Natural foods must provide the small amount of the monitored amino acid that the body needs to grow and renew its proteins, and which it cannot make itself. With no protein at all, deficiencies would develop and growth would be compromised.
Three categories of food
Forbidden foods are high in protein: most animal products (meat, fish, eggs, milk and dairy products) and some plant foods such as cereals, bread or cakes. Some may nevertheless be allowed in controlled amounts, for example milk during the first months or in milder forms. Controlled foods, mainly fruit and vegetables, potatoes included, are weighed and counted in “exchanges”: in phenylketonuria, one exchange is by convention 20 mg of phenylalanine, whereas for the other diseases the system varies from one team to another. Foods allowed freely contain almost no protein and provide energy through sugars and fats.
The amino acid mixture
By limiting protein, the diet also limits the other essential amino acids, which could slow growth. An amino acid mixture, in powder or liquid form, makes up for this shortfall: it contains the essential amino acids except the one or ones that are toxic, and usually provides vitamins, minerals and trace elements. It is taken every day, for life, as prescribed; for some diseases, its use is decided case by case.
Reduced-protein foods
Special foods with almost no protein replace those that contain too much: pasta, rice, bread, flour, biscuits, a drink that replaces milk, egg or cheese substitutes, spread. They provide the energy that would otherwise be lacking and make it possible to put together menus that look like ordinary ones. Introduced gradually, they help to vary meals, and this variety makes the diet easier to accept in the long term. In the end, the diet looks like a vegan diet of weighed fruit and vegetables, completed by these foods and, depending on the disease, by an amino acid mixture.
Medicines and follow-up
In some forms, medicines are added to the diet: cofactors, often vitamins, stimulate the deficient enzyme (BH4 in phenylketonuria, or vitamin B12 in some methylmalonic acidurias), and scavengers such as carnitine help to eliminate toxic substances. They are only really effective in a few rare forms. Follow-up relies on regular consultations and blood or urine tests, within a specialist team. The doctor coordinates care, the dietitian trains you in the diet and adapts it to the results, and the psychologist, social worker or geneticist support you as needed.
Living well with the diet
Phenylketonuria (PKU)
A rare genetic disease, phenylketonuria prevents the body from breaking down phenylalanine normally. It was the first inherited metabolic disorder for which a dietary treatment was developed.
The disease
An enzyme, phenylalanine hydroxylase, does not work or works poorly: it no longer converts phenylalanine into tyrosine, and phenylalanine builds up. Depending on how much activity this enzyme has left, a distinction is made between classic PKU, atypical PKU, which tolerates more phenylalanine, and permanent mild hyperphenylalaninaemia, which does not usually require a diet. At birth, the enzyme may still be immature, and tolerance may improve during the first few years.
BH4-responsive forms
To work, phenylalanine hydroxylase needs a cofactor, BH4 (tetrahydrobiopterin). In some forms, mainly atypical and very rarely classic, a BH4-based medicine taken by mouth increases the enzyme’s activity and allows the diet to be broadened, sometimes to the point of stopping the amino acid mixture. This responsiveness must first be tested, and your doctor will tell you whether this treatment is right for you, particularly depending on age or in pregnancy. BH4 synthesis deficiencies are a different disease, with different treatment and follow-up.
Your child’s diet
As for any child, the introduction of solid foods starts between 4 and 6 months, but you count the phenylalanine in each fruit and vegetable introduced, one at a time, to stay within the prescribed daily total. Every day, your child takes all of their amino acid mixture, without being forced and without the rule being relaxed. If they refuse it from the bottle, ask your dietitian whether it can be given more concentrated, mixed into baby cereal or fruit, or replaced by another mixture. This is not a slimming diet: avoid “light” products, and be aware that aspartame, used to sweeten some light fizzy drinks, juices and fruit compotes, is a precursor of phenylalanine and is one of the forbidden foods.
In adolescence
The diet is often partly relaxed after the age of 10, and again in adolescence, because the brain copes better with higher phenylalanine levels. This relaxation is decided with your team and must not go too far. An excess does not show straight away, but it can lead to difficulty concentrating at school, tiredness, irritability or a change in behaviour.
Planning a pregnancy
If you have PKU, it is very unlikely that your baby will have the disease, but the baby’s liver will only be able to eliminate phenylalanine at the end of pregnancy: until then, the baby is exposed to your own levels. To protect the baby from an intoxication that can cause malformations, the strict diet must be resumed and well balanced before conception, without weight loss, with blood tests at least once a week. As soon as you have made your decision, see the team with your partner: they will check your vitamins and minerals and help you choose mixtures that suit you. It is your doctor who will tell you when to stop contraception, once your weight is stable, your levels are within the set targets and you yourself are ready to keep to the diet for several months.
During pregnancy
Spread your phenylalanine over the day, cook varied meals and top up your energy with reduced-protein foods and small snacks. Take your mixture in 3 or 4 doses, preferably with meals that contain natural protein, and if you feel sick, drink it very cold, in small amounts at regular intervals. In the last trimester, the baby’s liver starts to eliminate phenylalanine, your tolerance increases markedly and your team can broaden the diet step by step. From the day you give birth, you return to your usual diet, and you can breastfeed without controlling phenylalanine.
Living well with the diet
Maple syrup urine disease (MSUD)
Maple syrup urine disease (MSUD), also called leucinosis, is an inherited autosomal recessive disease. Its diet is followed for life and calls for particular vigilance, as acute crises can occur.
The disease
Three amino acids known as branched-chain amino acids, leucine, valine and isoleucine, cannot be broken down, because the enzyme for the second step of their breakdown, common to all three, is missing. They build up, along with the corresponding keto acids, in the blood, urine and tissues, and it is mainly leucine that is toxic. In the classic form, the most common one, signs appear in the first week: impaired consciousness, refusal to drink, neurological signs, then, without treatment, rapid progression to coma and urine that smells of maple syrup. Later-onset or intermittent forms exist, and in exceptional cases some respond to vitamin B1 (thiamine).
The diet
The diet is calculated on leucine, which at the same time limits valine and isoleucine: a controlled amount of infant formula provides them at first, then, from the introduction of solid foods at around 4 to 6 months, fruit and vegetables counted in leucine exchanges (one exchange is 50 mg). Forbidden foods contain far too much: a single yoghurt already exceeds what a child with a severe neonatal form can tolerate in a whole day. An amino acid mixture free of leucine, valine and isoleucine, to be taken in full every day and in several doses, provides the other essential amino acids; valine or isoleucine capsules are sometimes added if tests show a shortfall. Reduced-protein foods top up energy and can be eaten freely, as they provide no toxic amino acids.
Situations with a risk of crisis
Acute decompensation can occur as soon as blood leucine rises above a certain threshold. Be particularly watchful in case of fever, a cold, nasopharyngitis, bronchitis, ear infection, teething, vomiting or diarrhoea, loss of appetite or fasting, a mistake or lapse in the diet, refusal of the mixture, failure to gain weight or weight loss. Vaccinations, a general anaesthetic or an operation, an accident or injury, a prolonged lack of leucine and a lack of valine or isoleucine are also risk situations. Finally, a crisis can be triggered for no obvious reason.
Warning signs
In babies, the first signs are feeding difficulties, vomiting and a floppy, drowsy baby who tires quickly. Later, the child may have clumsy movements and an unsteady walk, as if drunk, have mood changes, seem drowsy or, on the contrary, agitated. At school, they may slur their words, have trouble writing, reverse letters or leave out words in dictation, or seem unusually nauseous and off their food.
First steps to take
If your child shows any of these signs or is in a risk situation, do a urine ketone test (Acetest), which reveals any catabolism, see your doctor to look for an infection and have leucine, valine and isoleucine measured urgently in the blood. If the signs are mild and appetite is preserved, for example after a vaccination or during a slight, well-tolerated fever, apply the semi-emergency diet, if your centre has prescribed one for you. In case of a higher fever or illness, the prescribed emergency diet reduces or stops natural protein and increases energy with sugars, fats and reduced-protein foods, in small, frequent meals, while the amino acid mixture is continued. In all cases, call your metabolic disease reference centre straight away: the centre decides how long the emergency diet lasts, and it must not exceed 3 to 4 days or be repeated at home without medical advice, as it would slow growth.
When to go to hospital
If the signs persist or worsen despite these measures, with vomiting, impaired consciousness or total refusal to eat, take your child to hospital immediately: decompensation treated too late can have serious consequences. Continuous enteral nutrition through a nasogastric tube may be started there, and sometimes a drip if the vomiting does not stop. Always keep the tube-feeding emergency diet with your documents, updated for your child’s age. A hospital near your home may not have the necessary products: bring the amino acid mixture, the other products and the written recipe for your child’s emergency diet.
Living well with the diet
Organic acidurias
Propionic acidaemia and methylmalonic acidaemia are among the rare diseases known as intoxication disorders, in which the intoxication can be acute or chronic. They require a diet, medicines and close monitoring, organised by your reference centre.
The disease
Two enzymes are involved, which take part in breaking down four amino acids: threonine, methionine, valine and isoleucine. The block lies far down the chain: it is not these amino acids that build up, but their derivatives, propionic acid or methylmalonic acid, which are toxic mainly to the brain, but also to the heart, kidneys or liver. These derivatives come from protein in meals and from the body’s own proteins, but also from certain gut bacteria and, more rarely, from certain fatty acids that are scarce in the diet. Treatment aims to limit their production without causing deficiencies, while allowing your child to grow and develop normally.
The diet
The diet limits protein while providing enough essential amino acids for growth, and it must be rich enough in energy to curb catabolism, which is encouraged by infections, fasting or the poor appetite common in these children. Controlled foods are infant formula, preferably low in protein, sometimes certain dairy products, as well as fruit and vegetables, counted according to the system chosen by your team, in valine exchanges (one exchange is 25 mg) or in protein exchanges. Reduced-protein foods are allowed freely, and energy is often topped up with oil and maltodextrin. Depending on age and test results, an amino acid mixture free of threonine, methionine, valine and isoleucine may be prescribed, but not routinely.
Enteral nutrition
In early childhood, continuous enteral nutrition, at least overnight, is often necessary: it is given through a pump and a nasogastric tube, and sometimes through a gastrostomy. The ward nurses train you before you go home, then home nurses can help you, the aim being for you to become independent quickly. The equipment is installed in your home by a provider, who stays in touch with the care team if there are any problems. Involve your child in placing their tube: they will feel responsible for their treatment.
Medicines
L-carnitine binds to propionic acid and methylmalonic acid so that they are eliminated in the urine, and makes up for any carnitine deficiency. Antibiotics given in rotation change the gut flora, so that gut bacteria produce less propionic acid. Vitamin B12 can improve the enzyme’s activity and allow the diet to be broadened in some methylmalonic acidaemias that respond to this vitamin, and biotin (vitamin H) is sometimes offered in propionic acidaemia. These treatments are prescribed and adjusted by your doctor: do not stop them or change the doses without their advice.
Monitoring and key skills
When things are stable, the team monitors weight, height, head circumference and general condition at regular consultations, and adapts the diet according to urine tests, appetite and eating behaviour. Learn to spot the signs of imbalance: tiredness and dark circles under the eyes, apathy, nausea, vomiting, marked loss of appetite, clumsy movements, tremors, unsteady gait. Know how to do an Acetest, which detects ketones in fresh urine and signals catabolism, and, if the doctor asks, how to collect all the urine over a full day, keeping it in the fridge. Your team will give you and explain an emergency diet and a semi-emergency diet, as well as the situations in which to start them; some teams ask to be called before any change.
When to contact the team straight away
Vomiting, diarrhoea, fever whatever the cause, infections, an anaesthetic or an operation and prolonged fasting carry a risk of acute decompensation. In these situations, follow the plan your reference centre has explained to you, depending on whether or not your child has signs. If you are worried, if your child is not their usual self, particularly with digestive problems, or if they pick at their meals when their appetite is usually good, contact the centre that follows them straight away. Do not hesitate to ask for them to be admitted to hospital: admission must not come too late.
Living well with the diet
Chronic kidney disease
At stages 3 to 5 of chronic kidney disease, a low-protein diet may be part of treatment. It is planned and monitored with your medical team.
What is it?
Chronic kidney disease is when the structure or function of the kidneys has been abnormal for more than 3 months, with consequences for health. It is identified by markers of kidney damage or by a drop in their filtration rate. Its complications can affect the whole body: cardiovascular disease, high blood pressure, anaemia, malnutrition, bone disease, neuropathy and reduced quality of life. A history of diabetes is one of the factors that increase the risk.
Why limit protein
Less protein on the plate means less urea produced and less work for the kidneys. A moderate protein intake, with little salt, can thus slow the progression of kidney disease, except when it is linked to diabetes. Before the dialysis stage, diet has a major influence on progression and complications.
Intake set by your team
For adults, the current recommendation is between 0.6 and 0.8 g of protein per kilo of body weight per day, with appropriate nutritional education and follow-up. A stricter restriction, down to 0.3 g per kilo per day, remains possible, but only with essential amino acid supplementation and under close medical supervision. Your personal intake is set by your medical team: do not cut down your protein on your own.
Keeping enough energy
When protein is reduced, you need to check that the diet still provides enough energy: nutritional follow-up is strongly recommended. Reduced-protein foods help to build meals, as they provide calories without the elements that need to be limited, such as phosphorus. For the same amount of phosphorus, reduced-protein pasta can thus provide eight times more energy than ordinary pasta.
A diet for the long term
The eating plan is followed over the long term, and it is consistency that counts. Yet it weighs on everyday life, and an overly rigid framework makes it hard to stick to. If the diet feels too much of a burden, talk to your medical team rather than giving it up or changing it on your own.
Living well with the diet
Day to day
With a little planning, your child can share meals, school, sport and holidays with other children. Some situations, however, call for a quick response.
At the table, as a family
Eat together as a family as much as possible, with dishes close to everyone else’s: your child learns to eat by watching their brothers and sisters or by eating with you. Involve them in the shopping and cooking, vary flavours, textures and colours, and think of herbs, spices and vegetable stocks. A cupboard within their reach, filled with allowed foods, means they do not hear only about what is forbidden. Set limits as you would for any child, without overprotecting them, and never give them a forbidden food, even a small amount, as a treat.
Nursery, school and activities
Explain the diet to the people who look after your child, give them the list of forbidden foods and provide the amino acid mixture, the meals or the special foods. At school, agree in writing with the staff how the diet will be applied, and provide a meal that looks like the canteen menu so that your child eats with the others, under supervision. For a birthday, bring a cake or ingredients that all the children can share, and for residential school trips to the countryside or the snow, contact the head teacher, the cook and the class teacher in advance. All sports are possible, avoiding overly sustained effort in organic acidurias, and the amino acid mixture is still taken in full, ideally in 3 or 4 doses at meals that contain natural protein.
Weekends, holidays and travel
Prepare every trip: plan a sufficient stock of special foods and amino acid mixture, accommodation where you can cook simple meals, and agree on menus with the people hosting your child. Ask your team whether the destination is reasonable, find out where the nearest hospital is and always carry the emergency certificate, as well as, for maple syrup urine disease and organic acidurias, the emergency diets and products. For travel abroad, take a medical certificate stating that these special foods are for your child’s diet, to avoid being held up at customs. Few holidays without parents can manage the diet: ask your team or a parents’ association for advice.
When your child refuses to eat
A young child can go through phases of refusal without being ill: take the plate away without insisting or distracting them, with no dessert or replacement food: hunger will help them eat at the next meal. Both parents should keep the same attitude, and an amino acid mixture that is too large, too diluted or too thick can explain a lack of appetite or refusal: check this with your dietitian. The mixture remains essential every day, and if this moment becomes too difficult for you, the team’s psychologist can help. In maple syrup urine disease and organic acidurias, unusual refusal in a child who normally eats well can signal decompensation: contact your team.
Fever, vomiting, diarrhoea
In phenylketonuria, fever raises phenylalanine levels, which is not serious if it does not last: offer sweet foods that are easy to swallow, and the mixture in small amounts at regular intervals. If there is vomiting or diarrhoea, see your doctor to find the cause, and do not use anti-diarrhoea milk, which is often high in protein. In maple syrup urine disease and organic acidurias, these same situations can trigger decompensation: apply the plan set by your centre without delay and let them know. Do not prolong or repeat an emergency diet without the team’s advice.
When to call the medical team
Call your metabolic disease reference centre as soon as your child does not seem their usual self, especially with maple syrup urine disease or an organic aciduria. Warning signs are unusual drowsiness or agitation, clumsy movements, an unsteady walk, tremors, extreme tiredness, vomiting or refusal to eat or take the mixture. If impaired consciousness, vomiting or food refusal persist or worsen, go to hospital straight away, with your documents and emergency products. For any question, however simple, contact the team: regular contact helps them advise you better.
Taranis know-how.
Since 1979, Taranis has been creating varied, enjoyable foods designed for everyday life despite the constraints of a restricted diet under medical supervision. Its research and development team creates reduced-protein recipes whose taste and texture come close to those of ordinary products, working with specialist hospital departments, prescribers and the people who follow the diet. The products are made to precise specifications, with checks at every stage of production, and most of them are foods for special medical purposes.
Reviewed by Steeve Roland, physiotherapist, over 20 years in clinical nutrition, founder of BSNUTRITION · Updated on
Publisher: BS NUTRITION SA, Rue de l’Industrie 20, 1400 Nivelles, Belgium. Legal notice