Diabetics, however, need to exercise caution, since they have an abnormal glutamine metabolism. A much higher percentage of their glutamine is broken down for the production of glucose by the liver and the kidneys, a process called glutamine gluconeogenesis. True, this excessive breakdown of glutamine into glucose in diabetes occurs without any supplementation, since the muscle and the fatty tissue release so much glutamine in response to the endocrine pathology. Thus the diabetic retina is prone to damage through glutamate excitotoxicity, since the glia are not converting enough glutamate to glutamine. The use of high doses of antioxidants, including vitamin E and various polyphenols, should be beneficial, as well as supplementation with taurine.
Taurine is the one amino acid that seems to be very helpful to diabetics.
We have already said that glutamine is heavily used by all rapidly dividing cells. This includes many types of tumors. Thus is would seem plausible to argue that this is certainly the amino acid that cancer patients should avoid. In reality, however, glutamine is frequently used as an adjuvant treatment of advanced cancer. It has been shown to prolong survival by slowing down catabolic wasting.