The editor of the National PKU News, Virginia Schuett, asked the three companies marketing medical food in the US to respond to questions PKU parents frequently ask about formulas. She summarized the responses in an article entitled "Answers to Your Questions about PKU Medical Foods (Formulas)" printed in the fall, 1994 issue. Mead Johnson, Ross Laboratories, and SHS North America provide formulas for MSUD and PKU so most of the information in the article is relevant to both disorders. I added MSUD references (italicized in parenthesis) where applicable.

Why can't the formula be made to smell and taste better, when it is the cornerstone of PKU (MSUD) treatment?
All of the companies acknowledge that the smell and taste of the medical foods (formulas) are problems for some people. All three have made major efforts in the past several years to improve the taste and smell, but this is not an easy task. The problem lies in the basic raw materials that need to be used. Formulas such as Lofenalac that are made to be low in phenylalanine through a chemical hydrolyzing process have a very distinct odor and flavor. Phe-free formulas (all of the other formulas distributed in the U.S.) are made of individual amino acids. Some of the essential amino acids contain sulfur and have a bad taste and smell. Certain non-essential amino acids required for extra nitrogen contribute to the undesirable properties. The vitamins and minerals that need to be included also add a strong taste. Due to the nutritional importance of most of the "offending" substances, it is not feasible to simply remove them.

Masking the flavor and smell is not easy either. No completely adequate coating to encapsulate the bad tasting amino acids has been found. Some flavoring agents actually strengthen the taste of the amino acids; some flavorings can trigger allergic reactions in some people. And of course not everyone likes the same flavor. Use of some ingredients that could improve taste would triple or quadruple the cost and they are not approved by the FDA.

One approach taken recently has been to decrease amounts of certain of the nonessential "bad-tasting" amino acids. The new formula distributed by SHS North America, Periflex, uses this approach. Phenex, (Ketonex) by Ross Laboratories, also is an attempt to improve the flavor and odor. Phenex (Ketonex) formula comes with an optional flavoring agent in two flavors. SHS is working on some innovative new presentations of the medical food that they hope will be available in the near future.

Why can't the formula be put into a pill form? Couldn't you just put in the necessary amino acids and leave out all the fat, carbohydrate, vitamins, and minerals to be obtained from another source?
This is a wonderful idea, but there are major obstacles to a pill becoming a successful alternative to other forms of the medical food. Even if only the required amount of amino acids were put into pill form, the pills either would need to be large, or the quantities required to replace all formula would be more than the average child or person could reasonably manage (40 to 60 or more pills per day!) Also, traditional pills require the use of binders and other ingredients to hold the tablets together. These ingredients cause tablets to be less soluble in the gastrointestinal tract. This would decrease the amount of amino acids available. Capsules could be used, but the shells contain protein in the form of gelatin.

There are other potential problems:

  • If the medical food did not contain minerals and vitamins, there would be the risk of the child or young person forgetting to take the supplement and becoming severely deficient.
  • For infant products, the Food and Drug Administration requires fat, carbohydrate, vitamins and minerals unless the company provides a major medial justification for an exemption.
  • Unless a phe-free (BCAA-free) supplement of fat and carbohydrate is used to supply calories, persons on the diet cannot eat enough regular table foods to meet energy needs without exceeding their phe (leucine) tolerance.

Despite the problems, the Milupa Company of Germany experimentally produced a pill many years ago that was tried mainly in Europe. The pills were not well accepted in the quantities required and the idea was abandoned. Recently, one young woman during her pregnancy hand-stuffed one of the formulas into empty capsules in order to maintain the diet. But she had to consume 90 to 100 capsules per day and the capsules added 100 mg phe.

Still, the idea of a pill continues to have appeal. Despite the technical and other difficulties mentioned above, SHS North America is exploring a pill form of the medical food as one partial alternative. Clinical trials have taken place in Europe. Results of their marketing research and the regulatory environment here in the U.S. will determine suitability of this product for the North American market.

Why are the formulas so expensive?
As you are aware, the PKU (MSUD) medical foods are made of many compounds. These are obtained from raw material manufacturers located in various parts of the world. The basic nature of the formulas is very complex. The raw materials are rare compounds isolated from batches of starter material. They are extracted and purified to high food or pharmacological grade compounds. Amino acids, and protein hydrolysates treated to remove most of the phenylalanine (leucine), are simply much more expensive per gram of protein than is whole protein in normal infant formulas

Strict quality controls and laboratory confirmation of the manufacturing process also add to costs. Frequent analysis of the formulas is needed to insure that the ingredients meet label specifications.

These and all other costs associated with production are increased on a per unit basis due to the small production of the formulas. Regular infant formula is made in huge batches (60,000 to 120,000 pounds or more); so the cost of analytical tests required by the FDA for it prior to product release and during shelf life is proportionately much smaller per unit.

Also, because of the number of people needing the medical foods, batch sizes made at any one time must be small enough so that it is not outdated by the time it reaches the consumer. This increases costs per unit. In this regard, many state health agencies do not appropriately manage their inventory and often return products after their maximum shelf-life has passed. These products must be destroyed. At least two of the companies have liberal refund policies for outdated products, adding to costs.

Finally, mark-up on the price of the products when they are distributed through pharmacies can be very substantial and is not controlled by the companies.

The suppliers claim there is so much expense involved in producing the formulas for so few people that they don't make a profit on them. So why do we have so many different companies coming up with new formulas?
In the U.S., only three companies provide medical foods. They are dedicated to providing quality nutritional products for people with inborn errors of metabolism, not to making big profits. The companies also help support many PKU-related activities such as parent and professional meetings. Mead Johnson, the first company to supply such products, has done so for over 35 years. A reflection of their interest in families is their program called "Helping Hands for Special Kids," which makes sure that children of financially needy families get the Mead Johnson formulas required (interested families should contact their physicians). Ross Laboratories entered the inborn errors of metabolism market a few years ago.

Major formula companies want to provide a complete line of products even if some products are made available at a loss to the company, for humanitarian or public relations reasons. This is also advantageous for selling products to some hospitals, and state health agencies that will not contract with a company for the regular baby formulas unless they have a complete line of metabolic formulas. SHS North America, a company based in England, is the only one of the companies that does not manufacture or market regular infant formulas. Their sole function is to provide disease-specific nutritional products that will help patients with PKU and other metabolic diseases.

"Three companies are better than one," I say. I think that we should all be glad to have the three trying to better the lives of those who have inborn errors of metabolism like PKU (MSUD).

Why couldn't there be a ready-to-use formula? It is very inconvenient to have to mix it up every day, especially when traveling or away from home.
There are many reasons why medical foods have been produced in powder form. These reasons include the following:

  • Powders have a longer shelf-life than liquids (about twice as long). Because of shorter shelf-life, a liquid form of the formula would cost considerably more per gram of protein than powder (up to twice as much or more).
  • Ready-to-use medical foods are difficult to make. This is due to the chemical reaction of amino acids and carbohydrate during processing and over the shelf-life of the product. Such a product would require careful animal and clinical testing to make sure all nutrients are available.
  • Powders allow for easier individualization and modification to suit changing nutritional needs over a lifetime. Use of a powdered product also allows people to concentrate the formula so that needed protein and calories can be provided in a smaller volume.
  • The processing required to make a shelf-stable, ready-to-use liquid would change the nutrient profile of the product and could alter the taste in an undesirable way.

Despite the potential barriers, SHS North America is exploring the technical aspects of producing a ready-to-use medical food.


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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