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Dr D
Paradoxically, although phenylalanine inhibits IAP, it also induces further production of IAP. Since non-secretors don't make very much to inhibit, the amount induced is more significant, since by the time the IAP is produced, the amino acid is long gone. I think vitamin A does that as well. At one point I was going to put it into the Phytocal minerals, but like Isa said, you can't give it to everybody.

For the more technically inclined, phenylalanine is called an 'uncompetitive inhibitor'. It only works when the concentrations of the enzyme substrate (IAP and some fat in this case) is high. On the other hand, the presence of phenylalanine and fat (but minus the IAP) seems to induce some production of IAP.

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D- and DL-phenylalanine
The unnatural stereoisomer D-phenylalanine (DPA) is available through conventional organic synthesis either as a single enantiomer or as a component of the racemic mixture. It does not participate in protein biosynthesis although it is found in proteins, in small amounts, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids remain unclear. Some D-amino acids, such as D-phenylalanine, may have pharmacological activity.

DL-Phenylalanine is marketed as a nutritional supplement for its putative analgesic and antidepressant activities. The putative analgesic activity of DL-phenylalanine may be explained by the possible blockage by D-phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A.[5] The mechanism of DL-phenylalanine's putative antidepressant activity may be accounted for by the precursor role of L-phenylalanine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.[citation needed] D-Phenylalanine is absorbed from the small intestine, following ingestion, and transported to the liver via the portal circulation. A fraction of D-phenylalanine appears to be converted to L-phenylalanine. D-Phenylalanine is distributed to the various tissues of the body via the systemic circulation. D-Phenylalanine appears to cross the blood-brain barrier with less efficiency than L-phenylalanine. A fraction of an ingested dose of D-phenylalanine is excreted in the urine.

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Dr D:
"[Q]uorn is high in protein, but the amino acid profile is very high in phenylalanine, which makes quorn inadvisable for most type A's -especially A non-secretors, who often lack adequate levels of the enzyme intestinal alkaline phosphatase (a fat-busting enzyme inactivated by phyenylalanine). Also, this
species of fungii may have immune suppressive effects, which may give some concern to those non-A individuals with infection disease susceptibilties."