Source: DGNews  |  Posted 2 years ago

MADISON, Wis -- April 1, 2009 -- A unique protein derived from whey -- known as glycomacropeptide (GMP) -- appears safe for people with the genetic condition known as phenylketonuria (PKU), according to 2 studies published in the Journal of Inherited Metabolic Disorder and the April issue of the American Journal of Clinical Nutrition.

GMP is the first known natural protein that is safe for this group, and these findings are poised to revolutionise the diet of patients with PKU where diet is a constant struggle since they can eat virtually no protein, and instead get their daily dose of this key macronutrient by drinking a bitter-tasting formula of amino acids.

"It's so important to individuals on the PKU diet to have new options, to have their diet liberalised. It's a quality-of-life issue," said lead author of both studies Denise Ney. "Adolescents have an especially difficult time [staying on the diet], but it's so critical that they do."

The first GMP human feeding trial was published in February in the Journal of Inherited Metabolic Disorders. In it, Ney and colleagues describe the experience of an individual with PKU who volunteered to consume an all-GMP diet for 10 weeks.

The amount of phenylalanine in the subjects' blood started going down after he ate the items for a couple of weeks.

"And because the subject enjoyed the GMP foods, he was more inclined to eat them throughout the day, which helps keep the body's protein metabolism running efficiently all day long," said Ney. "When he went back to the amino acid formula, he went back to drinking it all in one sitting."

In the newer study, published in the April issue of the American Journal of Clinical Nutrition, Ney conducted an 11-person trial of shorter duration involving PKU patients receiving care from University of Wisconsin's Waisman Center.

In the study, subjects adhered to the amino acid formula diet for 4 days, and then switched to the GMP diet for the following 4. In the end, no adverse health problems were found, and 10 of 11 subjects claimed to prefer the GMP diet, making the bottom line of this study the same as the first -- that GMP is safe and acceptable.

Variations were seen among individual subjects, but the overall blood phenylalanine levels measured after meals were comparable in the 2 diets. Additionally, the GMP diet improved protein metabolism compared with the amino acid formula.

SOURCE: University of Wisconsin-Madison