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 more restrictive your diet is, the more challenging it can be to get all the nutrients you need. A vegan diet, for example, eliminates natural food sources of vitamin B-12, as well as milk products, which are good sources of calcium.With a little planning, however, you can be sure that your diet includes everything your body needs. This is because the vegan diet is rich in a vitamin called folate, which may mask deficiency in vitamin B-12 until severe problems occur. 2  For this reason, it's important for vegans to consider vitamin supplements, vitamin-enriched cereals and fortified soy products. 3  Vitamin D plays an important role in bone health.