{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T14:34:30Z","timestamp":1793975670053,"version":"4.8.0"},"reference-count":153,"publisher":"Annual Reviews","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Annu. Rev. Nutr."],"published-print":{"date-parts":[[1999,7]]},"abstract":"<jats:p>\n                    \u25aa Abstract\u2002 Vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    deficiency is estimated to affect 10%\u201315% of people over the age of 60, and the laboratory diagnosis is usually based on low serum vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    levels or elevated serum methylmalonic acid and homocysteine levels. Although elderly people with low vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    status frequently lack the classical signs and symptoms of vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    deficiency, e.g. megaloblastic anemia, precise evaluation and treatment in this population is important. Absorption of crystalline vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    does not decline with advancing age. However, compared with the younger population, absorption of protein-bound vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    is decreased in the elderly, owing to a high prevalence of atrophic gastritis in this age group. Atrophic gastritis results in a low acid-pepsin secretion by the gastric mucosa, which in turn results in a reduced release of free vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    from food proteins. Furthermore, hypochlorhydria in atrophic gastritis results in bacterial overgrowth of the stomach and small intestine, and these bacteria may bind vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    for their own use. The ability to absorb crystalline vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    remains intact in older people with atrophic gastritis. The 1998 recommended daily allowance for vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    is 2.4 \u03bcg, but elderly people should try to obtain their vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    from either supplements or fortified foods (e.g. fortified ready-to-eat breakfast cereals) to ensure adequate absorption from the gastrointestinal tract. Because the American food supply is now being fortified with folic acid, concern is increasing about neurologic exacerbation in individuals with marginal vitamin B\n                    <jats:sub>12<\/jats:sub>\n                    status and high-dose folate intake.\n                  <\/jats:p>","DOI":"10.1146\/annurev.nutr.19.1.357","type":"journal-article","created":{"date-parts":[[2002,7,27]],"date-time":"2002-07-27T07:45:50Z","timestamp":1027755950000},"page":"357-377","source":"Crossref","is-referenced-by-count":412,"title":["VITAMIN B\n                    <sub>12<\/sub>\n                    DEFICIENCY IN THE ELDERLY"],"prefix":"10.1146","volume":"19","author":[{"given":"H.W.","family":"Baik","sequence":"first","affiliation":[{"name":"USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"R.M.","family":"Russell","sequence":"additional","affiliation":[{"name":"USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111;"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"22","reference":[{"key":"b1","unstructured":"Deleted in proof"},{"key":"b2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1532-5415.1972.tb00776.x"},{"key":"b3","unstructured":"Adams JF. 1962.\n                      \n                        The measurement of the total assayable vitamin B\n                        12\n                        in the body.\n                      \n                      In\n                      \n                        Vitamin B\n                        12\n                        und Intrinsic Factor\n                      \n                      . 2.\n                      Europaisches Symposion\n                      , ed. 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