• Aanchal Taneja, MD

Diet and Parkinson Disease

We are what we eat. This is an old but a true saying, and now science has evidence to support it. There is mounting data demonstrating the relationship between Parkinson’s disease (PD) and the gastrointestinal system (GI).

The walls of our digestive system have 100 million nerve cells from the esophagus to the rectum. This is Enteric Nervous System (ENS), and in fact is called the “second brain.” The enteric nervous system communicates back and forth with our big brain. Food, therefore, has an impact on the brain. Researchers are finding evidence that irritation in the gastrointestinal system may send signals to the central nervous system (CNS), including the brain.

And what affects the GI system directly? It’s the food that we eat.

The nervous system in our gut enteric nervous system (ENS) has direct communication with the brain through the vagus nerve. There is evidence suggesting that Parkinson’s pathology may ascend from the gut to the brain via the vagus nerve. We all are aware that in Parkinson Disease, there is accumulation of misfolded α-synuclein, or Lewy Body. Studies have shown that this abnormal protein is present in the ENS even before the onset of PD motor symptoms. Several studies have also shown that removal of the vagus nerve was associated with a reduced risk for PD, as it prevented the protein from being transmitted from the vagus nerve to the brain. These studies further support that Parkinson Disease starts in the ENS and spreads to the central nervous system.

Now, what causes the abnormal deposition of protein or Lewy body? It is hypothesized that changes in the composition of gut microbes may cause alterations in the intestinal wall and permeability, affecting both the immune system and the ENS. The food that we eat can affect our intestine microbes and their balance. This may promote local inflammation and oxidative stress, which then initiates aggregation of a-synuclein, or Lewy pathology. This pathological process has been evidenced by the gastrointestinal complications associated with PD patients (trouble swallowing, nausea, constipation), as well as the presence of Lewy pathology in the neurons of the enteric nervous system.

Further evidence showing an association between the gastrointestinal tract and Parkinson’s disease has been explored in patients with gastrointestinal bacteria and inflammation. Products such as fruit, vegetables, and fish have been associated with decreased risk of development of PD, and fruits and vegetables may also be associated with decreased progression of PD. These findings have contributed to the Mediterranean diet being established as a potential diet for patients with PD.

This role of antioxidants has been considered in these cases as well, as a deficiency has been correlated with certain characteristics of PD. Antioxidants’ role in PD could explain why there has been an observed association between intake of fruits and vegetables, as well as foods containing carotenoids and B-carotene, both of which possess antioxidant properties, and decreased risk for PD.

An observational study in recent years demonstrated plant and fish-based diets as associated with the lowest PD severity, while significantly decreased progression of PD was associated with intake of vegetables, fruit, nuts and seeds, fish, olive and coconut oil, wine, and herbs and spices. This further demonstrates the use of the Mediterranean diet in management of PD. PD progression has also been associated with increased consumption of canned goods and soda, with a higher association demonstrated in diet soda.

In conclusion, the relationship between PD and the gastrointestinal system has been well established. The mechanisms of nutrition in pathogenesis most commonly involve the effects of inflammation, oxidative stress, and direct nerve damage, among others.

At this time, it is likely advisable for patients to follow a diet that is low in canned goods and soda, while high in the following:

• Fresh fruits

• Fresh vegetables

• Fish

• Nuts and seeds

• Oils such as olive and coconut

Thus, to take care of our brain and the pathologies that affect it, we must first take care of our gut through our diet.

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