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.
While a well-planned, balanced vegan diet is suitable to meet all recommendations for nutrients in every stage of life, improperly-planned vegan diets may be deficient in vitamin B12, vitamin D, calcium, iodine, iron, zinc, riboflavin (vitamin B2), long-chain fatty acids EPA and DHA, and omega-3 fatty acids.