There are 17 vitamins B needed by the human body and 11 of them are instrumental for optimal health. Here are two examples: if you get short of B-1, you get type 2 diabetes; if you get short of B-12, you become anemic. Depression, anxiety, brain fog, and a general feeling of being unwell ride this horse. You can handle 1/3 more stress on a good quality B-Complex. Positive effects are experienced within a few weeks.