Large doses of vitamin B6 have been reported to counteract the beneficial effect of L-dopa through a presumed increase in LAAD activity. Although diets should be modified so as to decrease B6 intake, vitamin B6 should not be omitted from the diet. Vitamin B6 is essential for metabolizing all amino acids, synthesis of neurotransmitters, and other key metabolic functions. A deficiency in vitamin B6 may cause headache, anemia, nausea, and vomiting. Having said this, it should also be noted that vitamin B6 does not play a significant role in clinical settings today because LAAD inhibitors have been part of commercial L-dopa preparations.
Vitamin E is one of the most important antioxidant.
Free radical accumulation is thought to mediate tissue injury, particularly in diseases of aging, and vitamin E is essential in retarding these destructive processes. Basically the role of vitamin E in PD is to slow the gradual progression of the disease and allow patients afflicted with the disease to live a longer and fuller life. Vitamin C is also an effective scavenger of oxidative free radicals. However, vitamin C's potentially beneficial effects in PD contrast with potentially negative effects such as vitamin C's ability to inhibit the dopamine-sensitive enzyme adenylate cyclase, thus making it hard to predict what its ultimate effect in PD might be. Aspartame has become a popular artificial sweetener in food products and carbonated diet beverages.