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.
The vegan diet, rich in fruits, vegetables, whole grains, and legumes, provides an abundance of vitamins and minerals to meet oneâs nutritional needs. However, there is one vitamin, called vitamin B 12, which does present a genuine nutritional issue, although one that is easily solved.