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 consists of plant-based foods only. In other words, vegans do not consume any meat or dairy products. A vegan diet is formed on the basis of a food pyramid different from that of a conventional meat-based diet. Thus, from bottom to top the vegan food pyramid includes grains, legumes and nuts, vegetables, fruits, and fats.