It's vitamin B-12 & Mayo Clinic experts routinely recommend that older adults consider B-12 supplements OR food fortified with this critical vitamin. Vitamin B-12 plays a role in red blood cell formation, cell metabolism, nerve function & bone health. A deficiency of vitamin B-12 can be associated with tingling or prickly feelings in legs or hands, difficulty walking, forgetfulness, changes in personality, weakness & anemia (shortage of red blood cells). This tingling feeling should not be confused with the tingling feeling that WNBC's Chris Matthews experienced when Barack Obama was first elected to the presidency! From 5 to 15% of adults have vitamin B-12 deficiency. It develops slowly & is more common with increasing age. Since the symptoms are similar to many other conditions associated with aging, it's sometimes overlooked. The primary natural sources of vitamin B-12 are meats, fish, shellfish, eggs & milk. SOME breakfast cereals are fortified with vitamin B-12. Diagnosis of vitamin B-12 deficiency typically involves several blood tests. Once it's diagnosed, other testing may be indicated to look for an underlying cause. Treatment involves addressing the underlying condition, if possible. Your doctor may recommend injections (ouch!!) of high doses of vitamin B-12 or high-dose oral supplements. The body responds rapidly to high-dose vitamin B-12, with nerve symptoms subsiding over weeks to months. Typically, the degree of improvement is influenced by the severity & duration of the nerve symptoms. In advanced cases, nerve problems may not improve. People who eat meat or cereals fortified with vitamin B-12 are likely getting the recommended daily intake of 2.4 micrograms. Older adults may benefit from a daily supplement to prevent deficiency. Vitamin B-12 is not toxic so there are no concerns about an overdose. The Mayo Clinic Health Minute is heard weekday evenings on KSEN/K-96 at 5:30 during out Action Packed 5 O'Clock News Hour. As for Chris Matthews...who knows...