Parkinson's disease (PD) is a type of movement disorder. It happens when nerve cells in the brain don't produce enough of a brain chemical called dopamine. Sometimes it is genetic, but most cases do not seem to run in families. Exposure to chemicals in the environment might play a role.
Why Vegans are Often Deficient in Vitamin B12. The few plant foods that are sources of B12 are actually B12 analogs. An analog is a substance that blocks the uptake of true B12, so your body's need for the nutrient actually increases.
A vegan diet does not permit any foods derived from animal sources, such as meat, dairy products and eggs. Some vegans also avoid honey and gelatin, as well as products produced using animal byproducts, such as commercially produced wines and refined sugar. Vegans represent between 0.3 and 1 percent of the U.S. population, according to the Vegetarian Resource Group. A vegan diet eliminates the saturated fats and chemicals found in animal products; however, vegans may need to take certain vitamins to avoid deficiencies.