In one small study, patients on a high-protein diet were compared with two groups of patients on low-protein diets, one of whom had protein evenly distributed throughout the day and the other of whom consumed 90 per cent of the daily quota of protein solely during the evening meal. Those consuming protein only in the evening enjoyed significant improvement in symptoms, including a lessening of tapping and tremor (Neurology, 1989; 39: 552-6).
Research shows that a low-protein diet can also eliminate the inevitable 'on-off' effect of L-dopa, in which its effectiveness fluctuates throughout the day. In another double-blind study, patients on low-protein diets were significantly better on low-protein diets; nevertheless, a patient's symptoms didn't correlate with the amount of L-dopa; indeed, three patients on the high-protein diet had the highest peaks of L-dopa and yet the worse performance and greatest number of off hours. This suggests that large quantities of protein somehow block the effectiveness of L-dopa (Neurology, 1989; 39: 549-52).
If you do start on a low-protein diet, it's important that you are monitored by your doctor, as your levels of L-dopa may have to be reduced. L-dopa itself reduces levels of S-adenosyl methionine (SAMe), an essential sulphur amino acid (J Neurol Neurosurg Psychiatry, 1990; 53: 569-72). Two studies have examined patients taking L-methionine. In one, patients were started with only 1 g per day and gradually increased to 5 g per day). After several months, two-thirds of the patients had improved in most parameters, including ease of movement, a lessening of involuntary movement, muscular strength, and even concentration, mood and sleep (South Med J, 1984; 77: 1577). Another study showed that the benefits of SAMe were similar to those of L-dopa (Rev Neurol, 1982; 138: 297-303).
Besides SAMe, it might be prudent to take supplements of several other amino acids, which are often deficient in Parkinson's patients. These deficiencies may be responsible for the 'on-off' fluctuation of L-dopa's effectiveness in patients. Perhaps the most significant is L-tryptophan, which helps to regulate mood. Parkinson's patients are often deficient in this vital amino acid because L-dopa competes with L-tryptophan. Regular L-dopa supplementation can lead to malabsorption of L-tryptophan, which can in turn lead to depression and a number of other symptoms which are usually categorised as side effects of the drug.
In one case study of a small number of patients, supplementing with tryptophan improved the mental disturbances which had been observed in them (Acta Med Scand, 1973; 194: 181-9). Supplementing with tryptophan (2 g three times per day) can also help the physical symptoms of Parkinson's. In one study where patients all received L-dopa, but only half were also given tryptophan, all improved on various motor skills, but only those receiving the tryptophan also improved in functional ability, mood and drive (Lancet, 1972; I: 654-7).
Besides tryptophan, Parkinson's patients also may need supplements of D-phenylalanine, which is also often diminished (Arzneim Forsch, 1973; 23: 884-5) in this disease, and L-tyrosine, levels of which can drop because of the low-protein diet. In fact, studies have shown that L-tyrosine, a precursor of L-dopa, on its own can work better than L-dopa and with fewer side effects (C R Acad Sci III, 1989; 309: 43-7; Life Sci, 1982; 30: 627-32).
Just make sure not to take any of the amino acids at the same time you are taking L-dopa because they compete for movement across the blood-brain barrier. Taking them simultaneously could increase fluctuations in your response to L-dopa.