After urgent treatment in the acute initial phase, dietary treatment must be introduced and followed for life.

It has several objectives:

• limiting the intake of natural proteins (from food) but ensuring the basic requirements for leucine, valine and isoleucine are covered;
• ensuring the protein synthesis needed to maintain good general health;
• satisfying the appetite and pleasure in food of the growing child.

Despite this diet, acute complications may still occur during episodes of decompensation triggered by intercurrent infections.

Initially, low-protein products (see list) may be consumed. As their name suggests, their low-protein content enables to avoid a too high intake of the three amino acids involved in MSUD.

Under controlled conditions (calculation of protein intake) it is therefore possible to avoid overconsumption (which could cause symptoms of MSUD to appear)

However, the patient needs larger amounts of other amino acids than of valine, leucine and isoleucine, to ensure their health remains stable (for growth and to keep the organs in good health).

With this aim in mind, amino acid mixes are available to supplement the diet. These mixes are free of the amino acids that are potentially dangerous for the patient (see list).

The foods that are allowed in controlled quantities are fruits and vegetables. Sugar and fats may be consumed without restriction (provided a balanced diet is maintained).

Leucine is an amino acid (AA). Several Aas combine to make a protein. There are 20 Aas.

Leucine, isoleucine and valine are branched chain amino acids.

Theses amino acids are essential.

In Mapple syrup urine disease, leucine level must be < 5mg %.

Some of the low-protein products available on the Internet or by using the order form are reimbursed and some are not.

For a product to be refunded, it must be registered on the list of products distributed by the AGEPS (the French Central Hospital Pharmacy). Sweets and chocolates are not refunded by French Social Security because they are considered to be non-essential comfort foods.

The amino acid mixes and low protein products can be supplied by the AGEPS or by hospital pharmacist. Amino acid mixes are all refunded.