by Dr. Thomas K. Lo

   Parkinson’s Disease

What Is Parkinson’s Disease?

Parkinson’s disease is a progressive neurodegenerative disease, the second most common disorder of this type after Alzheimer’s disease. It progresses slowly as small clusters of dopaminergic neurons in the midbrain die. The gradual loss of these neurons results in reduction of a critical neurotransmitter called dopamine, a chemical responsible for transmitting messages to parts of the brain that coordinate muscle movement.

Studies have shown that the symptoms of Parkinson’s usually appear when 50 percent or more of the dopamine neurons in the midbrain have been lost. Symptoms begin gradually and typically worsen over time.

How Many People Does Parkinson’s Disease Affect?

It is difficult to know exactly how many people have Parkinson’s disease, but it is estimated that at least 500,000 people in the U.S. currently have the disease. The average age of onset is about 60, and prevalence is increasing as the population ages.

The majority of people diagnosed have late-onset sporadic Parkinson’s, which does not have a clear genetic cause. About 10 percent have early-onset Parkinson’s that often begins before the age of 50. Parkinson’s strikes people of all races, ethnic groups, nationalities, and income levels. Actor Michael J. Fox, singer Linda Ronstadt, former U.S. Attorney General Janet Reno, and boxer Muhammad Ali, are among the celebrities who lived or are living with Parkinson’s.

What Causes Parkinson’s Disease?

The exact cause of Parkinson’s disease is unknown. Most researchers agree that the disease is caused by both genetic and environmental factors, and by interactions among these factors.

A full understanding of Parkinson’s risk requires integrated efforts to study both genetic and environmental factors. If environmental exposures can be identified, it may lead to new targets for prevention and intervention.

What Are the Symptoms of Parkinson’s Disease?

Common motor symptoms of Parkinson’s are tremors or shaking in hands, arms, legs, jaw, and face, also rigidity or stiffness of limbs and trunk, slowness of movement, and difficulties with balance, speech, and coordination. There are also non-motor symptoms, which may develop years before the onset of motor problems. These may include poor sense of smell, constipation, depression, cognitive impairment, and fatigue.


Accumulating evidence indicates that pesticide exposure is associated with an increased risk for developing Parkinson’s disease. Many animal studies have provided evidence for this, and several human studies are beginning to reveal that some specific pesticides and classes of pesticides may be linked to Parkinson’s.

Organochlorine insecticides comprise the pesticide class most commonly associated with the disease. Most of these chemicals were banned in the 1970s and 1980s, but because their chemical structures resist breakdown, they can remain in the environment and food chain for a long time. The organochlorine class includes pesticides like DDT, used for mosquito control, and dieldrin, used for termites.

A study published in 2011 by NIEHS (National Institute of Environmental Health Sciences) researchers and collaborators at the Parkinson’s Institute and Clinical Center in Sunnyvale, Calif., showed a link between the occupational use of two pesticides, rotenone and paraquat, and Parkinson’s. People who reported use of either pesticide developed the disease 2.5 times more often than nonusers did.

Rotenone directly inhibits the function of mitochondria, the structures that create energy to run the cell, while paraquat increases production within cells of certain damaging oxygen derivatives. People who used other pesticides with a similar mechanism of action were also more likely to develop Parkinson’s.

Dietary Factors

Both in-house researchers and grantees are continuing to explore the role that diet and lifestyle play in the onset, progression, and treatment of Parkinson’s disease.

How much fat a person consumes in their diet is one area under study. Unfortunately, the findings over the years have been inconsistent. However, in a new study, NIEHS researchers and their collaborators discovered that some fats in a person’s diet may be associated with lower risk for Parkinson’s.

Researchers are also exploring the role of vitamin D deficiency in the development of Parkinson’s. Vitamin D, which can enter the body through food or sunlight, plays an important role in maintaining good balance and muscle strength, and in protecting the body from infections and diseases. Researchers are looking into if working outdoors may help reduce the risk of Parkinson’s.

Another dietary component under study is the possible role of caffeine in the onset and progression of Parkinson’s. Animal studies have shown that caffeine can protect the brain’s dopaminergic neurons, indicating caffeine may reduce the risk of the disease. Researchers also looked at data from a large sample of older Americans, and found that higher caffeine intake was associated with lower risk of Parkinson’s in both men and women. A collaborative study found that coffee consumption may be more protective among individuals with one genotype as compared to individuals with another genotype.


NIEHS in-house researchers have shown that exercise may protect against Parkinson’s disease. In a large population of U.S. older adults, higher levels of moderate to vigorous physical activity in midlife were associated with lower risk of Parkinson’s.

Exercise may also benefit patients with the disease, by improving balance and reducing depression, and increasing overall quality of life. For example, a recent study found that tai chi training in patients with mild to moderate Parkinson’s improved balance and reduced falls.

Identifying Symptoms

Identifying premotor symptoms that may occur years before the disease sets in is one new area of research that NIEHS is pursuing. By thinking of Parkinson’s as a systemic illness that takes decades to develop, researchers will be better poised to understand the cause of the disease and its initial progression. Some of the early warning indicators of premotor symptoms include constipation, loss of smell, excessive daytime sleepiness, mood or anxiety disorders, and sleep disorders. Many of these symptoms may occur years before Parkinson’s disease is diagnosed. Although it is difficult to identify a single early symptom that is specifically tied to the disease, researchers are working to identify whether a combination of symptoms may help characterize high-risk populations.

Free Consultation

If you are struggling with health issues, call the Advanced Chiropractic & Nutritional Healing Center at 240-651-1650 for a free consultation. Dr. Lo uses Nutritional Response Testing ® to analyze the body to determine the underlying causes of ill or non-optimum health.

The office is located at 7310 Grove Road #107, Frederick, MD. Check out the website at

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