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 much stricter than an ovo-lacto-vegetarian diet. Vegans do not consume any animal products, including meat, fish, eggs, dairy, and animal by-products, such as gelatin. The strictest vegans wonât eat honey, use beeswax, or wear clothing made from animal-based materials, such as leather, wool, and silk.