For those asking about diet and PKU, a 1997 article may be of interest to you.
The article is "Transitory hyperphenylalaninaemia in children with continuously
treated phynylketonuria" by Griffiths, Smith, and Harvie (American Journal on
Mental Retardation, vol 102, pages 27-36).
One quote from the article is:
"Current treatment recommendations are for dietary restriction to be implemented
within the first month of life and maintained until at least 10 years of age,
with control well within the 120 to 600 micro-mol/l range."
The citation for this recommendation is a 1993 article by Legido et al,
"Treatment variables and intellectual outcome in children with classic
phenylketonuria" in Clinical Pediatrics, vol 32, pages 417-425.
The Griffin article experimentally manipulated the diet of youngsters from 10 to
16 years of age in a blind manner. They concluded:
"The results showed that changes in IQ, everyday memory, and behavior ratings
did not parallel significant elevation and reduction of blood phenylalanine
levels over 3-month periods of experimental dietary manipulation." (p. 32).
They acknowledge that these are short-term results and do not imply a lack of
long-term effects. However, Griffiths also did a study of the long-term effects
of stopping the diet at age 10 (Griffiths, Patterson, & Harvie, 1995,
Neuropsychological effects of subsequent exposure to phenylalanine in
adolescents and young adults with early treated phenylketonuria, Journal of
Intellectual Disability Research, vol 39, 365-372.) I have not read the
article, but the 1997 article by Griffiths sums up the results this way:
"Well-controlled children who discontinue diet at age 10 and subsequently are
exposed to high phenylalanine throughout adolescence or early adulthood do not
appear to show significant deterioration in cognitive and motor ability."
(Griffiths et al., 1997, p. 34).
In other words, the research by Peter Griffiths shows no short-term or long-term
effects of stopping the diet after the age of 10.
Given this research evidence, I was greatly intrigued by Stephen Black's
quotation of sources that dietary restrictions should be maintained for life.
The March of Dimes does indeed strike me as a credible source, and when the
website says that the diet needs to be adhered to perhaps for life, I suspect
there may be good reason to say so. But does this term "perhaps" mean that
perhaps all need to stay on the diet, or does it mean that perhaps some need to
stay on the diet? Also, the site does not say what mental or physical problems
occur after age 10 and what the effect size is. The website gives three
citations, none of which deal with research on the diet after the age of 10.
Thanks, Stephen, for the Verp and Lin (1993) citation. I will look them up and
see if they cite credible research for the lifelong diet.
Dave Kerby
Department of Psychology
Northeast Louisiana University
Monroe, Louisiana
