People are generally exposed to a wide range of toxins including food components, environmental toxins, and pharmaceuticals. We have complex enzyme systems in the liver to detoxify these substances. These systems vary from individual to individual depending upon genetics, lifestyle, and environment. Although some studies are contradictory, there is a general consensus that the ability to detoxify and eliminate these substances affects the onset and course of PD. Patients with familial and non-familial PD have been shown to have liver enzyme genes associated with poor liver function. A diminished ability of the liver to remove neurotoxins such as pesticides could increase the risk of PD. The reason PD risk increases with age may be the reduced ability of the aging liver to detoxify, which would result in increased levels of xenobiotics remaining in the bloodstream.
Epidemiological and experimental data suggest an increased risk of PD in individuals exposed to neuro-toxicants such as herbicides and pesticides. The results of a California study showed a dose response for insecticide use28 and another study showed a dose-response relation between PD risk and lifetime exposure to field crop farming and to grain farming. Pesticides are also directly toxic to mitochondria, which have been shown to be dysfunctional in PD patients. Very telling is a postmortem study of twenty PD patients by Dr. Lora Fleming, at the University of Miami School of Medicine. Pesticide residues were assayed in twenty PD brains, seven brains with Alzheimer’s disease (AD) and fourteen non-neurological controls. Dieldrin, an organochlorine pesticide for locust control was found in six of twenty PD brains, one of seven AD brains, and in none of the controls.
Dieldrin is a lipid-soluble, long-lasting mitochondrial poison and may well play a role in PD given the mitochondrial defects in this disorder. DDT was found in a majority of the PD, AD, and control brains, confirming the widespread human exposure to environmental chemicals. Susceptibility to the effects of pesticides and other xenobiotics may depend on variability in toxin metabolism related to differences found in PD patient liver enzyme genes compared to those of controls. One study examining several xenobiotics found a similar increase in PD risk among people who used cleaning supplies in their work. Of interest is that cigarette smoking appears to reduce the PD risk. This is thought to be related to the increase in certain detoxification enzymes (cytochrome P450) in smokers due to the poly-aromatic hydrocarbons in tobacco smoke.
However, the serious risks of smoking far outweigh this protective benefit. Heavy metal intoxication is a serious issue in the United States with estimates of 25 percent of the population having significant heavy metal toxicity. Sources of toxicity are numerous including mercury toxicity from silver dental amalgam. A study in Singapore examined mercury intake by looking at fish consumption, ethnic over-the-counter medication use, occupational exposure, and possession of dental amalgam fillings. They found a monotonic dose-response association between PD and blood mercury levels. Blood and urine were good predictors of PD but hair levels were not. A multicenter study in Germany found more frequent exposure to heavy metals, and a larger number of amalgam-filled teeth, in PD patients than in controls.
Dr. J. M. Gorell found a significant association of PD in individuals in the Detroit area with more than a twenty-year exposure to copper and manganese. There was a stronger correlation of PD with more than twenty years of exposure to lead-copper, lead-iron and iron-copper than to any one metal alone. Their conclusion is that “chronic exposure to these metals is associated with PD, and that they may act alone or together over time to help produce the disease.” The overloading of brain tissue with heavy metals also may worsen PD neurodegeneration by triggering inflammatory processes. It should be added that much progress in PD research stemmed from studies on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a designer heroin-like drug that resulted in very rapid onset PD in the individuals using it.
Not only did the discoveries around MPTP strengthen concerns regarding xenobiotic toxicity but its mechanism of injury served as a template for understanding the role of glutamate and the mitochondria in PD. MPTP is converted to the active neurotoxic agent MPP(+) by astrocytes, cells that provide structural and physiological support to neurons. In turn, MPP(+) impairs astrocyte metabolism and reduces glutamate reuptake. This results in an increase of extracellular glutamate, which is an excito-toxic neurotransmitter. In addition, MPP(+) inhibits complex I of the mitochondrial electron transport chain and increases free radical production. All these changes result in a cascade of events ending in programmed cell death (apoptosis).
Vitamins & Minerals Used For Detoxification
PD patients in general should strengthen their bodies’ detoxification abilities with high-potency vitamin-mineral supplements. Unless anemia is present, iron should be avoided as well as copper in the vitamin-mineral supplement. In particular, one should emphasize minerals like calcium, magnesium, zinc, and chromium- and sulfur-containing amino acids (methionine, cysteine, and taurine), and high sulfur-containing foods such as garlic, onions, and eggs. In addition, water-soluble fibers including guar gum, oat bran, pectin, psyllium seed, and ground flaxseed are helpful. It is important to note that organic produce is not only significantly higher in vitamins and minerals but also lower in heavy metals and herbicides. For these reasons, organic produce is strongly recommended.
In PD patients with known toxin exposure, the use of liver supportive herbs appears to be indicated to help reduce any ongoing toxicity contributing to progression of the disease. The primary hepatic protective herb is milk thistle, either as a liquid extract or a solid, standardized extract, at 175 mg twice/day. Two other liver herbs, turmeric (900 mg/day) and schizandra (500–1,000 mg/day) may actually have a more specific effect on increasing the liver’s detoxifying ability. Schizandra probably is best used when there is toxic exposure or some type of acute illness involving fatigue or respiratory involvement. We have not recommended it clinically for long-term use in PD. A blended extract with multiple liver herbs probably would be superior to taking one herb alone.
The Benefits Of A Full Detoxification Program
A full detoxification program is more complex and requires a complete evaluation of the individual. Hair and urine analysis for heavy metals may be helpful, although a more sensitive measure of body burden requires an oral or intravenous challenge with a heavy-metal chelator, 2,3-dimercapto-1-propanesulfonic acid (DMPS). Mercury is tightly bound in the body to molecular species called sulfhydryl groups and may not be excreted enough to be detected on standard heavy metal assays of hair or urine. Another substance, 2,3-dimercaptosuccinic acid (DMSA), also can be given intravenously or by mouth for detection of increased body burdens of heavy metals.
If toxic levels of heavy metals are found, then treatment by someone experienced with detoxification and the issues surrounding the CNS, liver, and kidney is recommended.
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