Rani H. Singh, Ph.D., R.D., L.D. and Pennie A.Graham, R.N.

Dr. Randi Singh is a nutritionist at Emory University in Atlanta, Georgia, and a nutritional advisor for our support group.Dr. Singh submitted the following article on a subject we families deal with every day. She offers advice and the promise of more help on the way.

It can be a major challenge to successfully meet the special dietary needs of persons with MSUD while maintaining both food variety and satisfaction. It requires an understanding of the amount of leucine in different foods, how to calculate the amount of leucine eaten, and how to use this information to make food choices while remaining within recommended daily intake ranges.Another challenge is learning how to include foods with unknown leucine values. At times, it seems to require an advanced degree in mathematics to determine serving sizes and food options. This tedious approach to daily food intake can discourage one from comparing foods, adding new foods, and correctly calculating leucine intake.

In a recent random survey of the MSUD population in a number of states, we found that several different systems were being used to calculate leucine. Many families counted total protein grams (g). Others counted milligrams (mg) of leucine. Still others used an exchange system in which 20 to 30 mg

of leucine was counted as one leucine exchange.While all of these systems can work well when managed correctly, we found that little agreement exists about which system works the best and is least cumbersome in the hectic pace of daily living.

When children are young and parents control the diet, counting leucine in milligrams seems the preferred and easiest way to keep track of dietary leucine intake. As children grow and are exposed to food from outside sources, it becomes more difficult to determine exactly how much leucine is present in the meals they eat at daycare, school and away from home.

As children mature and begin to take more control of their own dietary choices, they may want to add new foods to their diet.More complex math is required to figure protein grams and leucine milligrams from the available information about foods on the market. This is frequently a stumbling block to making good dietary decisions for themselves.

We have a special metabolic camp held each summer for persons with PKU and MSUD 10 years and older. At the camp, have been working with several management systems to devise a simple, easy way to insure dietary compliance while providing the campers with a better understanding of their dietary options and giving them a sense of mastery over the food related decisions in their lives.

The program we utilize is based on two basic principles:

1) 30 mg of leucine = 1 leucine exchange.
2) Leucine = approx. 6% protein (an average determined by the 3.5% to 8.5% leucine/protein ratio in different foods).

Understanding these two principles allows children to quickly estimate leucine values and make healthy dietary decisions.

For example, a 1 oz. bag of potato chips has 2 grams of protein. To determine the leucine value, the child can simply follow these steps:

  1. 1. Convert grams to milligrams by moving the decimal point 3 places to the right:
    2.0 g = 2000.0 mg protein
  2. 2. Multiply the mg by 6%:
    2000 mg x .06 = 120 mg
  3. 3. Divide the mg of leucine by 30 to find the number of exchanges:
    120 mg ?30 = 4 exchanges

Note: An even easier way to estimate leucine is to remember that 1 g of protein = approximately 2 leucine exchanges.

Having determined the exchange value, the child can decide whether or not to spend 4 exchanges of their daily leucine intake on a bag of chips.

Response to this system, while still preliminary, has been encouraging. The campers have indicated they feel comfortable with this system and are more readily able to make the correct food choices for themselves. They also appear to better understand how their choices impact their overall health.

As a result of this positive response, we are now developing a pocket-sized booklet which lists the amounts of protein (in grams), leucine (in milligrams) and the number of leucine exchanges for many foods. These amounts are converted into household measures for easy use. The source of this information is a detailed computer data base (Amino Acid Analyzer, Ross Nutritionals). By including all three methods of measurement, we hope that this booklet will be a tool to assist all families with MSUD, regardless which system they currently use to calculate leucine intake.

In the near future, we will be surveying dietitians and consumers about the food list to confirm the results we have already seen in our camp population. Once this is completed, and all comments and suggestions have been included, we hope to distribute this booklet to the general MSUD population - possibly by the end of this year. It is our hope that this new, simpler approach to the dietary challenges of living with MSUD will help families implement more variety, satisfaction and control into their food choices.

If you would like to provide input at this stage, please e-mail me, Dr. Singh, at: This email address is being protected from spambots. You need JavaScript enabled to view it.. We welcome your comments and suggestions.


The MSUD Family Support Group is currently funding several research projects and we are proactively looking for researchers interested in developing new treatments or finding a cure for MSUD. Significant funding is necessary if we are to accomplish this goal.
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