Authorities in the United States and Canada have recently advised pers
ons with diabetes to limit their protein intake to the level recommend
ed for normal adults, and consider further reductions in the presence
of incipient renal disease. This recommendation ignores metabolic data
indicating that conventional insulin therapy fails to fully normalize
the abnormal protein metabolism characteristic of untreated diabetes.
The residual abnormality is an increased or poorly regulated rate of
amino acid catabolism. It is proposed in this review that the large am
ount of protein in the customary diet compensates for this increased a
mino acid catabolism, and thus protects many diabetic individuals from
protein malnutrition. If this is true, protein restriction to a level
that still meets the requirement of an individual with normal insulin
metabolism could be too little for someone with diabetes. The current
assumption that the protein requirement in diabetes is equal to the v
alue set for normal individuals should be reconsidered.