Introduction
Parkinson’s
disease is a chronic disorder typically affecting people
older than age fifty-five years. The condition is caused by the death of nerve
cells in certain parts of the brain, leading to characteristic problems with
movement. These problems include a “pill rolling” tremor in the hands (so called
because it appears that the person is rolling a small object between thumb and
forefinger), difficulty initiating walking, a shuffling gait, decreased facial
expressiveness, and trouble speaking. Thinking ability may become impaired in
later stages of the disease, and depression is common.
Although the underlying cause of Parkinson’s disease is unknown, many researchers
believe that free
radicals may play a role in destroying some of the nerve
cells. The nerve cells that are affected in Parkinson’s disease work by supplying
the neurotransmitter dopamine to another part of the brain. Most treatments for
Parkinson’s disease work by artificially increasing the brain’s dopamine levels.
Simply taking dopamine pills will not work, however, because the substance cannot
travel from the bloodstream into the brain. Instead, most people with Parkinson’s
disease take levodopa (L-dopa), which can pass into the brain and be converted
there into dopamine. Many people take levodopa with carbidopa, a drug that
increases the amount of levodopa available to make dopamine.
Initially, levodopa produces dramatic improvement in symptoms; however, over time,
levodopa becomes less effective and more likely to produce side effects. Other
drugs may be useful too, including bromocriptine, trihexyphenidyl, entacapone,
tolcapone, selegiline, and pergolide. There are also surgical treatments that can
decrease symptoms, such as pallidotomy and deep brain stimulation.
Principal Proposed Natural Treatments
Cytidinediphosphocholine. Cytidinediphosphocholine (CDP-choline)
is a substance that occurs naturally in the human body. It is closely related to
choline, a nutrient commonly put in the B vitamin family.
For reasons that are not completely clear, CDP-choline seems to increase the
amount of dopamine in the brain. On this basis, it has been tried for Parkinson’s
disease. Support for the use of CDP-choline also comes from studies in which the
supplement was administered by injection.
In a four-week, single-blind study of seventy-four people with Parkinson’s disease, researchers tested whether oral CDP-choline might help levodopa be more effective. Researchers divided participants into two groups: One group received their usual levodopa dose, the other received one-half their usual dose without knowing what dosage they were getting. All the participants took 400 milligrams (mg) of oral CDP-choline three times daily. Even though 50 percent of the participants were taking only one-half their usual dose of levodopa, both groups scored equally well on standardized tests designed to evaluate the severity of Parkinson’s disease symptoms.
In general, CDP-choline appears to be safe. The study of oral CDP-choline for Parkinson’s disease reported only a few brief, nonspecific side effects such as nausea, dizziness, and fatigue. In a study of 2,817 elderly people who took oral CDP-choline for up to sixty days for problems other than Parkinson’s disease, side effects were few and mild and reported in only about 5 percent of participants. Two-thirds ofthese side effects were gastrointestinal (nausea, stomach pain, and diarrhea), and none required stopping CDP-choline. The dose in this study was 550 to 650 mg per day, about one-half the dose used for Parkinson’s disease.
Parkinson’s disease, which often attacks older people, is characterized by debilitating symptoms that become more severe as the disease progresses.
Coenzyme Q
10. The supplement coenzyme Q10
(CoQ10) has been widely advertised as effective for treating
Parkinson’s disease. However, there is only minimal evidence that it works, and
there is some evidence that it does not.
A study published in 2002 raised hopes that CoQ10 might help slow the progression of Parkinson’s disease. In this sixteen-month, double-blind, placebo-controlled trial, eighty people with Parkinson’s disease were given either CoQ10 (at a dose of 300, 600, or 1,200 mg daily) or placebo. Participants in this trial had early stages of the disease and did not yet need medication. The results appeared to suggest that the supplement, especially at the highest dose, might have slowed disease progression. However, for a variety of statistical reasons, the results were quite inconclusive.
A subsequent double-blind, placebo-controlled study of twenty-eight people with Parkinson’s disease (that was well-controlled by medications) indicated that 360 mg of CoQ10 daily could produce a mild improvement in some symptoms. Based on these results, a more substantial study was undertaken, enrolling 131 people with Parkinson’s disease (again, well-controlled by medications). It did not work. While benefits were seen in both the placebo group and the CoQ10 group, the supplement failed to prove more effective than placebo.
Other Proposed Natural Treatments
Several other natural products have been studied for preventing or treating Parkinson’s disease, with mixed results.
S-adenosylmethionine. Whether a symptom of the disease or a
response to disability, depression affects many people with Parkinson’s disease,
and the long-term use of levodopa may contribute to this problem. Research
suggests that levodopa can deplete the brain of a substance called
S-adenosylmethionine (SAMe). As SAMe has been found in a
number of small studies to have antidepressant effects, it is possible that
depleting it might trigger depression.
Researchers conducted a trial to determine if taking SAMe supplements could decrease depression in twenty-one people with Parkinson’s disease who were taking levodopa. In this double-blind study, each participant received either a combination of oral and injected SAMe or a placebo daily for thirty days, followed by the alternative treatment for another thirty days. Although other symptoms of Parkinson’s did not change, depression improved after two weeks in 72 percent of those taking SAMe, while only 30 percent noted improvement with placebo. It is not known if oral SAMe alone would have similar effects.
Although SAMe might appear to be an excellent accompaniment to levodopa, there is another side to the issue. During treatment with levodopa, SAMe participates in breaking down levodopa and gets used up in the process. It is possible that taking extra SAMe could lead to the decreased effectiveness of levodopa. In the foregoing short-term study, SAMe did not interfere with levodopa’s effects, but longer-term use might do so. For persons who have Parkinson’s disease, it is safest to use SAMe only under the supervision of a physician.
Phosphatidylserine. Phosphatidylserine is a major component
of cell membranes. Several studies have found phosphatidylserine supplementation
effective for improving mental function in people with Alzheimer’s disease. One
trial examined its use in sixty-two people, all of whom had both Parkinson’s
disease and Alzheimer’s-type dementia. The results appeared to indicate some
benefit, but because of the incompleteness of the report on this trial, it is
difficult to draw conclusions.
Vitamin E. Because of indications that free radicals play a role
in causing Parkinson’s disease, treatment with high doses of vitamin E has
been tried to determine if it slows the progression of Parkinson’s disease.
However, a large study yielded disappointing results. In this trial, eight hundred
persons newly diagnosed with Parkinson’s disease took 2,000 international units of
tocopherol (synthetic vitamin E) or placebo daily for an average of fourteen
months. Vitamin E had no effect in delaying symptoms of the disease, and it failed
to reduce the side effects of levodopa.
Vitamin C. One problem with levodopa treatment for Parkinson’s disease is the on-off effect, in which a person taking levodopa will move more freely for some hours, followed by sudden “freezing up.” Vitamin C has been tried as a remedy for the on-off effect in a small double-blind study, but the results were so minimal that the researchers did not feel justified in recommending it.
Other treatments. The herb Mucuna pruriens contains L-dopa. One small study reportedly found evidence that the use of the herb as an L-dopa source offers advantages over purified L-dopa given as a medication itself.
Other proposed natural treatments for Parkinson’s disease have minimal or conflicting evidence supporting them. These treatments include nicotinamide adenine dinucleotide, glutathione, policosanol, and the amino acids D-phenylalanine and L-methionine. Caution is advised with the latter three, as they might affect the function of levodopa.
A two-year study failed to find more than minimal benefits at most with creatine,
and weak evidence hints that the supplement 5-hydroxytryptophan
(5-HTP) might be helpful for depression in people with
Parkinson’s disease. However, 5-HTP should not be combined with the drug
carbidopa.
A double-blind, placebo-controlled trial of ninety-nine people found that repetitive transcranial magnetic stimulation (rTMS) delivered in eight weekly treatments can improve Parkinson’s symptoms. A two-month, double-blind, placebo-controlled trial of eighteen people found that rTMS improved Parkinson’s symptoms. Similar benefits were seen in three other small controlled studies. Also, when combining the results of ten randomized trials in persons with Parkinson’s, researchers noted a significant benefit for rTMS (using higher frequencies).
A postural training method called the Alexander technique has shown some
promise. A small placebo-controlled study found that the use of bright lights,
best known as a treatment for seasonal affective disorder, may also help relieve
various symptoms of Parkinson’s disease, possibly by reducing levels of melatonin
in the brain.
In two studies, acupuncture failed to provide much benefit for Parkinson’s disease. In two comprehensive reviews of multiple clinical trials, independent sets of researchers concluded that there was no well-established evidence for acupuncture’s effectiveness in Parkinson’s.
Herbs and Supplements to Use with Caution
Persons with Parkinson’s disease should avoid taking the herb kava.
Preliminary reports suggest that kava may counter the effects of dopamine and
possibly reduce the effectiveness of medications for Parkinson’s.
Other substances may also interact with Parkinson’s drugs. Iron supplements can
interfere with the absorption of levodopa and carbidopa and should not be taken
within two hours of either medication. Amino acid supplements, such as
branched-chain
amino acids, can temporarily decrease levodopa’s
effectiveness, as may methionine and phenylalanine, two amino acids studied for
treatment of Parkinson’s disease.
Vitamin B6 in doses higher than 5 mg per day also might impair the effectiveness of levodopa and should be avoided. However, if one takes levodopa-carbidopa combinations, this restriction may not necessarily apply. One should consult a physician about an appropriate dose of vitamin B6.
Certain herbal formulas used in traditional Chinese herbal medicine to
treat upset stomach might reduce the effectiveness of levodopa. The supplement
5-HTP has a potentially dangerous interaction with carbidopa. Using the two
substances together may increase the chance of developing symptoms resembling
those of the disease scleroderma.
One report suggests that by amplifying the action of levodopa, policosanol might
increase side effects called dyskinesias. Finally, weak evidence
hints that prolonged (over many years) intake of high levels of iron and manganese
might increase the risk of developing Parkinson’s disease.
Bibliography
Bender, A., et al. “Creatine Supplementation in Parkinson Disease.” Neurology 67 (2006): 1262-1264.
Elahi, B., and R. Chen. “Effect of Transcranial Magnetic Stimulation on Parkinson Motor Function.” Movement Disorders 24 (2009): 357-363.
Katzenschlager, R., et al. “Mucuna pruriens in Parkinson’s Disease.” Journal of Neurology, Neurosurgery, and Psychiatry 75 (2004): 1672-1677.
Lam, Y. C., et al. “Efficacy and Safety of Acupuncture for Idiopathic Parkinson’s Disease.” Journal of Alternative and Complementary Medicine 14 (2008): 663-671.
Paus, S., et al. “Bright Light Therapy in Parkinson’s Disease.” Movement Disorders 22 (2007): 1495-1498.
Storch, A., et al. “Randomized, Double-Blind, Placebo-Controlled Trial on Symptomatic Effects of Coenzyme Q(10) in Parkinson Disease.” Archives of Neurology 64 (2007): 938-944.
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