Vitamin B12 deficiency

Nature 
Symptoms of vitamin B-12 deficiency include anemia, balance disturbances, a lack of vibration sensation and confusion. Dementia can occur in advanced cases.
Incidence 
Vitamin B-12 deficiency may be far more prevalent than thought. In a US study reported in 2001, nearly 40 percent of the men and women were found to be in the low-normal range, and more than 16 percent were outright deficient. The study of 2,999 people in the USA found that 39% of individuals had low-to-normal blood levels of the vitamin, 17% had levels low enough to cause symptoms of deficiency, and 9% were deficient. Those aged 26-49 had the same vitamin-B12 status as those aged 65-83, thus young people are as likely to suffer from the problem as the elderly.
Type 
(G) Very specific problems