B-vitamins are water-soluble, and you can get most of them from real (i.e. not processed) foods. So if that’s primarily what you eat, you may have most of them covered. If not, then choose a good quality vitamin B-complex supplement.
But B12 is different and many of us are likely not to have high enough levels because we don’t absorb them effectively. In fact, a Tufts University study suggests 40 percent of us between ages 26 and 83 are in the “low normal” range, where we may be experiencing symptoms.
Vitamin B12 deficiency can lead to abnormal neurologic and psychiatric symptoms including ataxia (shaky movements and unsteady gait), muscle weakness, spasticity, incontinence, hypotension, vision problems, dementia, psychoses and mood disturbances.
A 2008 study from Oxford University found that vitamin B12-deficient older adults are six times more likely to develop brain shrinkage, a main cause of dementia and Alzheimer’s disease.