Age-related hearing loss, vitamin B-12, and folate in elderly women.
BACKGROUND: Hearing impairment is 1 of the 4 most prevalent chronic conditions in the elderly. However, the biological basis of age-related hearing loss is unknown. OBJECTIVE: The objective was to test the hypothesis that age-related hearing loss may be associated with poor vitamin B-12 and folate status. DESIGN: A thorough audiometric assessment was conducted in 55 healthy women aged 60-71 y. Hearing function was determined by the average of pure-tone air conduction thresholds at 0.5, 1, 2, and 4 kHz and was categorized into 2 groups for logistic regression analyses: normal hearing (<20 dB hearing level; n = 44) and impaired hearing (> or = 20 dB hearing level; n = 11). RESULTS: Mean age was the same (65 y) for the normal hearing and impaired hearing groups. Pure-tone averages were inversely correlated with serum vitamin B-12 (r = -0.58, P = 0.0001) and red cell folate (r = -0.37, P = 0.01). Women with impaired hearing had 38% lower serum vitamin B-12 (236 compared with 380 pmol/L, respectively, P = 0.008) and 31% lower red cell folate (425 compared with 619 nmol/L, respectively, P = 0.02) than women with normal hearing. Among participants who did not take supplements containing vitamin B-12 or folate, women with impaired hearing had 48% lower serum vitamin B-12 (156 compared with 302 pmol/L, respectively, P = 0.0007) and 43% lower red cell folate (288 compared with 502 nmol/L, respectively, P = 0.001) than women with normal hearing. CONCLUSION: Poor vitamin B-12 and folate status may be associated with age-related auditory dysfunction. (+info)
Ambulatory management of common forms of anemia.
Anemia is a prevalent condition with a variety of underlying causes. Once the etiology has been established, many forms of anemia can be easily managed by the family physician. Iron deficiency, the most common form of anemia, may be treated orally or, rarely, parenterally. Vitamin B12 deficiency has traditionally been treated with intramuscular injections, although oral and intranasal preparations are also available. The treatment of folate deficiency is straightforward, relying on oral supplements. Folic acid supplementation is also recommended for women of child-bearing age to reduce their risk of neural tube defects. Current research focuses on folate's role in reducing the risk of premature cardiovascular disease. (+info)
Risk of persistent cobalamin deficiency in adolescents fed a macrobiotic diet in early life.
BACKGROUND: Cobalamin deficiency has been described in children consuming macrobiotic diets. OBJECTIVE: We investigated whether moderate consumption of animal products is sufficient for achieving normal cobalamin function in 73 adolescents who had received a macrobiotic diet until 6 y of age and had then switched to a lactovegetarian, lactoovovegetarian, or omnivorous diet (macrobiotic adolescents). DESIGN: Hematologic indexes and serum concentrations of methylmalonic acid (MMA), total homocysteine (tHcy), and folate were measured. Current consumption frequency of animal products and cobalamin intake from dairy products were assessed by questionnaire. Data from 94 age-matched adolescents who received an omnivorous diet from birth were used as a reference. RESULTS: Serum cobalamin concentrations were significantly lower and concentrations of MMA and folate and mean corpuscular volume (MCV) were significantly higher in macrobiotic adolescents than in control adolescents: of macrobiotic adolescents, 21% had abnormal MMA concentrations (>0.41 micromol/L), 37% had abnormal cobalamin concentrations (<218 pmol/L), 10% had abnormal tHcy concentrations (> 12.8 micromol/L), and 15% had abnormal MCV (> 89 fL). In macrobiotic adolescents, dairy products (200 g milk or yogurt and 22 g cheese/d) supplied on average 0.95 microg cobalamin/d; additionally, these adolescents consumed fish, meat, or chicken 2-3 times/wk. In girls, meat consumption contributed more to cobalamin status than the consumption of dairy products, whereas in boys these food groups were equally important. CONCLUSIONS: A substantial number of the formerly strict macrobiotic adolescents still had impaired cobalamin function. Thus, moderate consumption of animal products is not sufficient for restoring normal cobalamin status in subjects with inadequate cobalamin intake during the early years of life. (+info)
Immunomodulation by vitamin B12: augmentation of CD8+ T lymphocytes and natural killer (NK) cell activity in vitamin B12-deficient patients by methyl-B12 treatment.
It has been suggested that vitamin B12 (vit.B12) plays an important role in immune system regulation, but the details are still obscure. In order to examine the action of vit.B12 on cells of the human immune system, lymphocyte subpopulations and NK cell activity were evaluated in 11 patients with vit.B12 deficiency anaemia and in 13 control subjects. Decreases in the number of lymphocytes and CD8+ cells and in the proportion of CD4+ cells, an abnormally high CD4/CD8 ratio, and suppressed NK cell activity were noted in patients compared with control subjects. In all 11 patients and eight control subjects, these immune parameters were evaluated before and after methyl-B12 injection. The lymphocyte counts and number of CD8+ cells increased both in patients and in control subjects. The high CD4/CD8 ratio and suppressed NK cell activity were improved by methyl-B12 treatment. Augmentation of CD3-CD16+ cells occurred in patients after methyl-B12 treatment. In contrast, antibody-dependent cell-mediated cytotoxicity (ADCC) activity, lectin-stimulated lymphocyte blast formation, and serum levels of immunoglobulins were not changed by methyl-B12 treatment. These results indicate that vit.B12 might play an important role in cellular immunity, especially relativing to CD8+ cells and the NK cell system, which suggests effects on cytotoxic cells. We conclude that vit.B12 acts as an immunomodulator for cellular immunity. (+info)
Blood folate and vitamin B12: United States, 1988-94.
OBJECTIVES: This report presents national estimates of serum and red blood cell (RBC) folate and serum vitamin B12 distributions for persons 4 years and over, by sociodemographic variables. METHODS: The third National Health and Nutrition Examination Survey (NHANES III) (1988-94), provides information on the health and nutritional status of the civilian noninstitutionalized U.S. population. The analytic sample included 23,378 participants with serum folate data, 23,082 with RBC folate data, and 11,851 with serum vitamin B12 data. RESULTS: The mean serum and RBC folate concentrations are 7.2 and 196 nanograms per milliliter (ng/mL), respectively, and the mean serum vitamin B12 concentration is 518 picograms per milliliter (pg/mL). Non-Hispanic white people have higher mean serum and RBC folate concentrations than non-Hispanic black or Mexican American people. Serum vitamin B12 concentrations are lowest for older adults, and non-Hispanic black people have higher serum B12 concentrations than non-Hispanic white individuals. Only approximately 3 percent of the population has a serum B12 concentration less than 200 pg/mL. CONCLUSIONS: Inadequate folate status may be more prevalent among non-Hispanic black and Mexican American people. Data also suggest a modest prevalence of low serum B12 concentrations. Future assessments of folate and vitamin B12 status will be important to evaluate the impact of a recently enacted fortification policy. (+info)
Use of vitamin B12 injections among elderly patients by primary care practitioners in Ontario.
BACKGROUND: Excess use of parenteral vitamin B12 has been reported from audits of clinical practices. The authors assessed the use of vitamin B12 injections in patients aged 65 years and over in Ontario. METHODS: A cross-sectional analysis was conducted that included all elderly people covered by the Ontario Health Insurance Plan who received insured services from general practitioners or family physicians (GP/FPs). For each practice the proportion of elderly patients who received regular vitamin B12 injections between July 1996 and June 1997 was calculated. The frequency of injections was determined for each patient receiving regular B12 replacement. RESULTS: Of the 1,196,748 elderly patients (mean age 74.8 [standard deviation 6.8], 58.0% female) treated by 14,177 GP/FPs, 23,651 (2.0%) received regular B12 injections. The rate of B12 injections per patient, standardized for age and sex, varied between practices (range 0%-48.6%). Although no authoritative sources support the practice, 3303 (19.8%) of the 16,707 patients receiving long-term parenteral therapy had, on average, overly frequent injections (more than 1 injection every 4 weeks). For 76 (12.3%) of the 617 practices with 10 or more patients receiving regular vitamin B12 injections, the mean injection frequency was greater than once every 4 weeks. The proportion of patients in these 617 practices who received overly frequent injections varied extensively (0%-100%). INTERPRETATION: Our findings indicate that some primary care physicians in Ontario administer unnecessary vitamin B12 injections to elderly patients. (+info)
Cyanocobalamin (vitamin B-12) status in Seventh-day Adventist ministers in Australia.
As part of the Adventist Ministers' Health Study, a series of cross-sectional surveys conducted in 1992, 1994, and 1997, the serum vitamin B-12 status of 340 Australian Seventh-day Adventist ministers was assessed in 1997. The ministers in the study participated voluntarily. Of this group, 245 were either lactoovovegetarians or vegans who were not taking vitamin B-12 supplements. Their mean vitamin B-12 concentration was 199 pmol/L (range: 58-538 pmol/L), 53% of whom had values below the reference range for the method used (171-850 pmol/L) and 73% of whom had values <221 pmol/L, the lower limit recommended by Herbert. Dual-isotope Schillings test results in 36 lactoovovegetarians with abnormally low vitamin B-12 concentrations indicated that dietary deficiency was the cause in 70% of cases. Data from the dietary questionnaires supported dietary deficiency as the cause of low serum vitamin B-12 in this population of lactoovovegetarians and vegans, 56 (23%) of whom consumed sufficient servings of vitamin B-12-containing foods to obtain the minimum daily maintenance allowance of the vitamin (1 microg). (+info)
Cellular import of cobalamin (Vitamin B-12).
Recent studies have isolated and characterized human gastric intrinsic factor (IF) and transcobalamin II (TC II) genes, whose products mediate the import of cobalamin (Cbl; Vitamin B-12) across cellular plasma membranes. Analyses of cDNA and genomic clones of IF and TC II have provided some important insights into their sites of expression, structure and function. IF and TC II genes contain the same number, size and position of exons, and four of their eight intron-exon boundaries are identical. In addition, they share high homology in certain regions that are localized to different exons, indicating that IF and TC II may have evolved from a common ancestral gene. Both IF and TC II mediate transmembrane transport of Cbl via their respective receptors that function as oligomers in the plasma membrane. IF-mediated import of Cbl is limited to the apical membranes of epithelial cells; it occurs via a multipurpose receptor recently termed "cubilin," and the imported Cbl is usually exported out of these cells bound to endogenous TC II. On the other hand, TC II-mediated Cbl import occurs in all cells, including epithelial cells via a specific receptor, and the Cbl imported is usually retained, converted to its coenzyme forms, methyl-Cbl and 5'-deoxyadenosyl-Cbl, and utilized. (+info)