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 is naturally low in calcium, vitamin D, iron, vitamin B12, zinc and omega-3 fatty acids. Therefore, if you follow a vegan diet it is essential that you get enough of these nutrients through specific vegan food sources â and may even need to take additional supplements.