A report from Scotland shows that lack of vitamins B12, pyridoxine or folic acid is a common cause of dementia in older people (American Journal of Clinical Nutrition, Volume 75, Issue 5, 2002).

This study shows that eight percent of older people lack one or more of three vitamins: folic acid, B12, and pyridoxine, which raises blood levels of homocysteine to cause dementia.

All older people who appear to be losing their ability to reason or think clearly, or suffer mood disorders such as depression, should have blood tests for homocysteine, folic acid, pyridoxine and vitamin B12. If these tests are normal, they need tests for thyroid function, cholesterol and other causes of arterial damage. If homocysteine levels are high or B12, folic acid or pyridoxine levels are low, these people should take large amounts of whole grains and leafy green vegetables for folic acid and pyridoxine, and 1000 micrograms of B12 in a pill each day.

A study from Austria shows that many doctors miss the correct diagnosis of B12 deficiency because people with a deficiency often have normal blood levels of that vitamin (Acta Medica Austriaca, Volume 29, Issue 2, 2002). Many people suffer from vitamin B12 deficiency because they have low blood levels of homotranscobalamine II, the protein that transports B12 into the mitochondria where it acts. So you can have normal levels of B12 and still be deficient. When your body lacks B12, your red blood cells do not mature properly and are much larger than normal, and a poison called homocysteine accumulates in your bloodstream. Much more dependable tests for B12 deficiency are MCV, a test that measures the size of red blood cells; and blood levels of homocysteine, the poison that damages your arteries and brain cells.