Introduction. The Journal of Nutrition Nutritional Epidemiology. Amanda J. MacFarlane, 3,4,6 *YipuShi, 7 and Linda S. Greene-Finestone 5,6.

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1 The Journal of Nutrition Nutritional Epidemiology High-Dose Compared with Low-Dose Vitamin B-12 Supplement Use Is Not Associated with Higher Vitamin B-12 Status in Children, Adolescents, and Older Adults 1,2 Amanda J. MacFarlane, 3,4,6 *YipuShi, 7 and Linda S. Greene-Finestone 5,6 3 Nutrition Research Division, Health Canada, Ottawa, ON, Canada; 4 Department of Biochemistry, Microbiology, and Immunology and 5 Division of Physical Medicine and Rehabilitation, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada; 6 Department of Biology, Faculty of Science, Carleton University, Ottawa, ON, Canada; and 7 Social Determinants and Science Integration Directorate, Public Health Agency of Canada, Ottawa, ON, Canada Abstract Over-the-counter vitamin supplements on the Canadian market are permitted to contain a daily vitamin B-12 dose of up to 1000 mg. Our objective was to determine the association between total daily vitamin B-12 supplement dose and markers of vitamin B-12 status in Canadians. Blood collected from a nationally representative sample aged 6 79 y (n = ~5600) in the Canadian Health Measures Survey ( ) was analyzed for serum vitamin B-12 and plasma total homocysteine (thcy). Total daily intake of vitamin B-12 from single and multivitamin supplements was calculated. Individuals that indicated proton pump inhibitor or vitamin B-12 injection treatment were excluded from the supplement dose and thcy analyses; folate-deficient individuals were also excluded from the thcy analysis. Twenty-three percent of children, 12.3% of adolescents, and 25.5% of adults consumed a vitamin B-12 containing supplement. Supplement users had 33% higher serum vitamin B-12 and 4.2% higher prevalence of adequacy than did non supplement users. Children and adolescents consuming >10 mg/d supplemental vitamin B-12 did not demonstrate higher serum vitamin B-12, higher prevalence of serum vitamin B-12 adequacy, or lower thcy than did those consuming >0 10 mg/d. The association between serum vitamin B-12 reached a plateau at doses of >25 and >10 25 mg/d in adults aged and y, respectively. The prevalences of serum vitamin B-12 adequacy and normal thcy, and thcy did not differ by vitamin B-12 supplement dose in adults >45 y. In this cross-sectional study, vitamin B-12 supplement doses >10 25 mg/d were not associated with higher vitamin B-12 status in children, adolescents, or older adults compared with lower doses. J. Nutr. 144: , Introduction Vitamin B-12 is an essential water-soluble vitamin that is a cofactor for methionine synthase and methylmalonyl-coa mutase. Inadequate intakes of vitamin B-12 can cause macrocytic anemia and can lead to irreversible neurological damage and cognitive decline. Vitamin B-12 deficiency has also been associated with increased risk of neural tube defects (1,2). Serum vitamin B-12 and holotranscobalamin are circulating biomarkers of vitamin B-12 status, whereas serum methylmalonic acid (MMA) 8 and plasma total homocysteine (thcy) are functional biomarkers of status. 1 Supported by Health Canada and the Public Health Agency of Canada. 2 Author disclosures: A. J. MacFarlane, Y. Shi, and L. S. Greene-Finestone, no conflicts of interest. 8 Abbreviations used: CHMS, Canadian Health Measures Survey; DIN, Drug Identification Number; MEC, mobile examination center; MMA, methylmalonic acid; NPN, Natural Health Product Identification Number; thcy, plasma total homocysteine. * To whom correspondence should be addressed. amanda.macfarlane@ hc-sc.gc.ca. The RDA for vitamin B-12 for adults (2.4 mg/d) was set on the basis of the amount of vitamin B-12 required to maintain adequate hematologic status and serum vitamin B-12 in persons with pernicious anemia or with known low dietary vitamin B-12 intakes (3) with consideration for its bioavailability and absorption. It was assumed that 50% of dietary vitamin B-12 is absorbed by healthy adults with normal gastric function. However, a smaller proportion of vitamin B-12 is absorbed in individuals consuming foods with large amounts of vitamin B-12; for example, only 5% of a 25-mg dose is absorbed (4 6). Approximately 1% of vitamin B-12 at supraphysiologic doses $100 mg of crystalline vitamin B-12 can be absorbed independent of intrinsic factor mediated transport (5). An Upper Tolerable Intake Level has not been set for vitamin B-12 because of the lack of evidence of adverse reactions at high doses, including in adults treated with 1 to 5 mg of parenterally administered vitamin B-12 (7,8). The RDA for children and adolescents was set by extrapolating down and rounding up from adult values and an Upper Tolerable Intake Level has not been set (3). ã 2014 American Society for Nutrition. Manuscript received December 24, Initial review completed January 23, Revision accepted March 10, First published online April 3, 2014; doi: /jn

2 The Institute of Medicine recommends, as does Health Canada, that adults >50 y consume vitamin B-12 in crystalline form because of an increase in the prevalence of atrophic gastritis and reduced vitamin B-12 bioavailability among older age groups. In Canada, food fortification with vitamin B-12 is restricted, leaving vitamin supplements as the main source of crystalline vitamin B-12. The maximum allowable amount in supplements is 1000 mg/d for all age groups (9,10). Vitamin supplements for sale in Canada contain a wide range of daily vitamin B-12 doses ( mg), with products targeting children containing a broad, but more limited, range ( mg) (11). High-dose oral supplementation with vitamin B-12 ( mg/d) can normalize serum vitamin B-12 in individuals with demonstrated vitamin B-12 deficiency, observations made primarily in older adults (12 15). Studies of the relation between vitamin B-12 supplement dose and status in the general population with a low prevalence of serum vitamin B-12 deficiency, as observed in the Canadian population (16), are limited and, to our knowledge, have not included children and adolescents. We aimed to determine the association of oral vitamin B-12 supplement use and dose with serum vitamin B-12 and thcy in the Canadian population by using data from the Canadian Health Measures Survey (CHMS), cycle 1. Participants and Methods Survey design and study population. The CHMS, cycle 1, is a comprehensive, direct health measures survey that collects information on sociodemographic characteristics, risk factors, and health outcomes and includes blood, urine, and anthropometric measures (17). The CHMS, cycle 1, represents ~96% of the Canadian household population aged 6 79 y. It excludes persons living in remote areas, on Aboriginal reserves or Crown lands, in institutions, and full-time members of the Canadian Forces. Data from ~5600 persons over a 2-y period ( ) were collected. A household interview included demographic information and an in-depth health questionnaire. A visit to a mobile examination center (MEC) included physical measure tests and the collection of blood and urine samples. Ethics. The CHMS, cycle 1, was reviewed and approved by the Health Canada Research Ethics Board. Participation in the survey was voluntary, and written informed consent was obtained from participants. Blood analyses. Blood was collected and processed at the MEC. Samples were shipped frozen to the Health Canada Nutrition Laboratory for analysis. Serum vitamin B-12 and RBC folate were analyzed by using the Immulite 2000 immunoassay (Siemens Canada). Plasma thcy was analyzed by using the Ortho Clinical Diagnostics VITROS 5,1 FS. The cutoffs for vitamin B-12 status were deficient (<148 pmol/l) and adequate ($148 pmol/l). The cutoff for folate deficiency was <320 nmol/l. The cutoff for normal thcy was <13 mmol/l for adults and the 85th percentile or less of thcy distribution for children or adolescents. Identification of supplement users and determination of daily dose. Study participants were queried about supplement use in the 30 d before the MEC interview. Drug Identification Numbers (DINs) and Natural Health Product Identification Numbers (NPNs) of supplements were collected. The list of supplement DINs and NPNs in the CHMS database was used to query the Drug Product Database (18) and the Licensed Natural Health Products Database (11) to determine the vitamin B-12 content and recommended daily dose of products. A total daily dose of vitamin B-12 from all single and multivitamin supplement sources was calculated. Supplement groups were selected that would approximate the RDA and be within the linear range of serum vitamin B-12 (>0 10 and >10 25 mg/d), with consideration for doses that are associated with decreasing fractional absorption or intrinsic factor independent absorption of crystalline vitamin B-12 (> and >100 mg/d). Individuals treated with injectable vitamin B-12 or proton pump inhibitors were identified by cross-referencing the CHMS database with DINs or NPNs for those products. Statistical analyses. The CHMS used a complex sampling strategy that allowed for nationally representative estimates with 15 collection sites (19). The relatively low number of collection sites restricts the statistical analysis to 11 df (df = 15 primary sampling units 4 regions = 11) (19). Individuals identified as being treated with injectable vitamin B-12 or taking a proton pump inhibitor were excluded from the vitamin B-12 supplement dose and thcy analyses. Folate-deficient individuals were also excluded from the thcy analysis because folate deficiency can increase thcy independent of vitamin B-12. Estimates were calculated by using data weighted to represent the Canadian population aged 6 to 79 y. Descriptive statistics (geometric mean and prevalence) were determined for age, sex, or supplement dose groups. Bootstrap weights were applied and the 11 df defined for all variance estimations of means and proportions to account for the complex sample design (19). The distribution of serum vitamin B-12 and thcy was examined by plotting histograms; skewed variables were log transformed for comparisons. StudentÕs t test with an a P = 0.05 was used to determine significance. The Bonferroni correction method was applied when performing multiple comparisons. Data are presented as geometric means or percentages (95% CIs). Analyses were performed by using SAS Enterprise Guide 4 software (SAS Institute), BOOTVAR 3.2-SAS version [Statistics Canada (20)], and SUDAAN (RTI International). Results It was estimated that 24.2% of Canadians aged 6 79 y consumed vitamin B-12 containing supplements (Table 1). Adolescents had a lower prevalence of supplement use than did the other age groups. Men aged y and women aged y had a higher supplement use than did other age groups. Supplement use among adults aged y was higher in women than in men. Age-associated differences in serum vitamin B-12 and prevalence of adequacy were observed among non supplement users. Children had higher serum vitamin B-12 and prevalence of adequacy than did the other age groups, and adolescents had higher serum vitamin B-12 than did adults. Among non supplement-using men, serum vitamin B-12 was lower in men aged y than in younger men, but the prevalence of adequacy did not differ by age. Serum vitamin B-12 and prevalence of adequacy did not differ significantly between women and agematched men. Among non supplement-using women, those aged y had higher serum vitamin B-12 than did those aged y. Women aged y also had a higher prevalence of adequacy than did younger women. Supplement use was associated with higher serum vitamin B-12 concentrations, and generally, higher prevalence of adequate status. Supplement-consuming boys aged 6 11 y had higher serum vitamin B-12 than did all other male age groups, but the prevalence of adequacy was similar across ages. Serum vitamin B-12 did not differ between the supplement-consuming adolescent boysõ or menõs age groups. Girls that consumed supplements had higher serum vitamin B-12 and prevalence of adequacy than did women. Young women who consumed supplements had lower serum vitamin B-12 than did women aged y. The prevalence of adequacy was higher in adolescent girls than in women, but it did not differ between the womenõs age groups. Children and adolescents. Of the 23.0% of children who consumed vitamin B-12 containing supplements, the majority consumed >0 10 mg/d vitamin B-12 (Table 2). Although supplement use was associated with higher serum vitamin B-12, 916 MacFarlane et al.

3 TABLE 1 Prevalence of vitamin B-12 supplement use and its relation with vitamin B-12 status by age and sex in Canadians 1 Non supplement users Supplement users Prevalence of vitamin B-12 supplement use 2 n Serum vitamin B-12 Prevalence of adequate serum vitamin B-12 $148 pmol/l n Serum vitamin B-12 Prevalence of adequate serum vitamin B-12 $148 pmol/l % pmol/l % pmol/l % Both males and females 6 79 y 24.2 (21.5, 26.8) (281, 297)* 94.4 (93.0, 95.7)* (372, 396) 98.6 (97.4, 99.9) Males 6 11 y 21.1 (12.0, 30.2) 3,a (382, 444)*,a 99.7 (99.1, 100) a (461, 513) a 100 (100, 100) a y 8.7 (6.1, 11.4) b (312, 346)*, **,b 98.6 (96.7, 100) a,b (339, 458) b 100 (100, 100) a y 20.1 (13.9, 26.3) a (277, 307)*,c 96.4 (93.2, 99.5)*,b,c (327, 375) b 99.7 (99.1, 100) a y 20.0 (14.2, 25.8) a (251, 279)*,d 93.2 (89.1, 97.3) c (326, 388) b 97.6 (94.5, 100) b y 26.3 (21.6, 31.0) c (253, 289)*,c,d 93.7 (90.9, 96.5)*,c (351, 418) b 99.5 (97.9, 100) a y 21.2 (17.0, 25.5)** (271, 290)* 95.0 (93.2, 96.8)* (345, 373) 99.1 (98.3, 100) Females 6 11 y 24.5 (16.9, 32.1) a (404, 457)*,a 99.8 (99.3, 100) a (466, 540) a 100 (100, 100) a y 16.1 (9.5, 22.7) 3,b (269, 306)*,b 92.9 (87.1, 98.8)*,b (346, 435) b,c 100 (100, 100) a y 26.5 (22.4, 30.7) a (253, 291)*,c 90.7 (85.5, 95.8)*,c (337, 376) c 98.6 (97.5, 99.7) b y 32.2 (24.5, 39.8) c (233, 309)*,c 93.8 (89.3, 98.4) b (369, 456) b,c 96.5 (90.4, 100) b y 34.0 (28.1, 39.8) c (281, 327)*,b 94.0 (90.5, 97.5)*,b (386, 457) b 98.6 (96.9, 100) b y 29.6 (25.8, 33.4) (257, 296)* 92.2 (88.7, 95.7)* (370, 403) 97.9 (95.8, 100) 1 Values are percentages (95% CIs) or geometric means (95% CIs) unless otherwise indicated. Estimates in a column within a sex category without a common letter differ, P # (t test with Bonferroni correction for multiple comparisons). *Different from supplement users, P # 0.05 (StudentÕs t test). **Different from females, P # 0.05 (StudentÕs t test). 2 Includes all participants of the CHMS with a valid serum vitamin B-12 measure. 3 CV for estimates between 16.6% and 33.3%; interpret with caution. there was no significant difference in serum vitamin B-12 between high-dose (>10 mg/d) and low-dose (>0 10 mg/d) groups. The prevalence of adequate vitamin B-12 status was high among children, with nearly 100% of supplement nonusers and users having adequate status. thcy was low among children; thcy and the prevalence of normal thcy did not differ by supplement use. Only 12.3% of adolescents consumed vitamin B-12 containing supplements (Table 2), with approximately half consuming >0 10 mg/d and the remainder consuming >10 mg/d (Table 2). Supplement use was associated with higher serum vitamin B-12 and prevalence of adequate vitamin B-12 status, but no differences were observed between the supplement dose groups. Serum vitamin B-12 in adolescents consuming >25 mg/d of TABLE 2 Prevalence of vitamin B-12 supplement use and its relation with serum vitamin B-12 and thcy status in Canadian children aged 6 11 y and adolescents aged y 1 Vitamin B-12 supplement Prevalence of vitamin use and dose n 2 B-12 supplement use Serum vitamin B-12 Prevalence of adequate serum Plasma vitamin B-12 $148 pmol/l n 3 thcy Prevalence of normal thcy 4 % pmol/l % mmol/l % Children Nonusers (69.1, 85.0) 420 (403, 437) a 99.7 (99.4, 100) (3.5, 4.3) 82.2 (73.1, 91.4) Users (15.0, 30.9) 494 (472, 518)* 100 (100, 100) (3.2, 4.1) 86.9 (75.4, 98.4)*.0 10 mg (13.7, 28.0) 497 (475, 520) b 100 (100, 100) (3.2, 4.1) 87.1 (74.4, 99.5).10 mg 16 S (381, 585) a,b 100 (100, 100) (3.1, 5.5) 84.5 (55.5, 100) Adolescents Nonusers (83.6, 91.8) 308 (301, 317) a 96.0 (93.1, 98.8) a (5.2, 5.8) a 83.4 (78.3, 88.5) a Users (8.1, 16.4) 390 (357, 427)* 100 (100, 100)* (4.7, 5.4)* 97.8 (94.5, 100)*.0 10 mg (3.8, 8.9) (333, 484) b 100 (100, 100) b (4.4, 5.6) b 97.6 (93.2, 100) b mg 31 S (319, 541) a,b 100 (100, 100) b (4.0, 6.2) a,b 97.1 (89.2, 100) a,b.25 mg 15 S (271, 348) a,b 100 (100, 100) b (4.1, 7.3) a,b 100 (100, 100) a,b 1 Values are percentages (95% CIs) or geometric means (95% CIs) unless otherwise indicated. Estimates in a column within an age group without a common letter differ, P # 0.03 (t test with Bonferroni correction for multiple comparisons). *Different from supplement nonusers P # 0.05 (StudentÕs t test). S, suppressed; thcy, total plasma homocysteine. 2 Includes individuals with a valid serum vitamin B-12 measure and excludes individuals using proton pump inhibitors and individuals treated with vitamin B-12 injections. 3 Includes individuals with valid serum vitamin B-12 and plasma thcy measures and excludes individuals using proton pump inhibitors, treated with vitamin B-12 injections, and with folate deficiency (RBC folate,320 nmol/l). 4 Normal plasma thcy was considered to be a value below the 85th percentile for thcy in children aged 6 11 y or a value below the 85th percentile for thcy in adolescents aged y. 5 CV for estimates.33.3%; data suppressed. 6 CV for estimates between 16.6% and 33.3%; interpret with caution. Vitamin B-12 supplement use and status 917

4 supplemental vitamin B-12 was comparable to that in non supplement-consuming adolescents. Adolescent vitamin B-12 supplement users had lower thcy and a higher prevalence of normal thcy (#85th percentile of thcy) than did non supplement users. There were no differences in thcy or prevalence of normal thcy among the supplement dose groups. Adults. A total of 25.5% of adults used vitamin B-12 containing supplements (Table 3). For all adults combined, serum vitamin B-12 was positively associated with total daily supplemental vitamin B-12 dose, as was the prevalence of vitamin B-12 adequacy. thcy, although lower in supplement users compared with nonusers, did not differ by supplement dose (Table 3). The prevalence of normal thcy (#13 mmol/l) was higher in supplement users than in nonusers, and a daily dose > mg/d was associated with a higher prevalence of normal thcy than did the doses of >0 10 and >100 mg/d. Absolute thcy increased with age regardless of supplement use or dose. Although serum vitamin B-12 and the prevalence of adequacy did not differ between adult age groups who did not consume supplements, increasing age was associated with higher serum vitamin B-12 among supplement users. Young adults aged y consuming supplements had lower serum vitamin vitamin B-12 than did older adults aged y. However, there were no differences in the prevalence of adequacy in supplement users of differing ages. Supplement dose was positively associated with serum vitamin B-12 in young adults (20 45 y). However, the association of serum vitamin B-12 with supplement dose reached a plateau at > mg/d for middle-aged adults (46 59 y) and at >10 25 mg/d for older adults (60 79 y). The prevalence of adequacy did not differ between the supplement doses for adults aged y. thcy was lower and the prevalence of normal thcy was higher in supplement users but did not differ by dose. Discussion In clinical settings, high-dose oral vitamin B-12 supplementation has been shown to improve, and even normalize, status in individuals with marginal or deficient vitamin B-12 status (12 15,21). Whether a dose-dependent association exists between daily vitamin B-12 supplement intake and vitamin B-12 status in the general population with a low prevalence of deficiency, and including children and adolescents, has not been determined. Our data show that whereas supplement use was associated with higher TABLE 3 Prevalence of vitamin B-12 supplement use and its relation with serum vitamin B-12 and thcy status in Canadian adults 1 Vitamin B-12 supplement Prevalence of vitamin use and dose n 2 B-12 supplement use Serum vitamin B-12 Prevalence of adequate serum Plasma vitamin B-12 $148 pmol/l n 3 thcy Prevalence of normal thcy #13 mmol/l % pmol/l % mmol/l % Age y Nonusers (72.0, 77.1) 278 (268, 289) a 93.6 (91.8, 95.4) a (7.4, 8.3) a 93.0 (90.8, 95.1) a Users (22.9, 28.0) 374 (362, 387)* 98.4 (96.9, 99.8)* (6.4, 7.3)* 97.6 (96.3, 98.9)*.0 10 mg (5.8, 7.8) 328 (298, 363) b,d,e 95.9 (91.5, 100) b (6.4, 7.4) b 96.7 (92.1, 100) b mg (9.1, 12.7) 373 (350, 397) c 99.3 (98.1, 100) b (6.4, 7.5) b 98.2 (96.8, 100) c mg (4.6, 6.6) 410 (369, 454) d 99.2 (98.3, 100) c (6.2, 7.3) b 98.0 (95.6, 100) c.100 mg (1.5, 2.7) 459 (415, 508) d 99.8 (99.5, 100) d (5.5, 7.6) b 96.5 (92.9, 100) b Age y Nonusers (73.9, 79.8) 282 (272, 292) a 93.7 (90.9, 96.4) a (6.6, 7.5)**,a 96.1 (94.5, 97.8)**,a Users (20.2, 26.1)** 353 (337, 370)*, ** 99.1 (98.5, 99.7)* (5.6, 6.5)*, ** 99.5 (98.6, 100)*.0 10 mg (6.6, 9.4) 322 (283, 365) b 99.0 (97.5, 100) b (5.9, 6.7)**,b 100 (100, 100)**,b mg (7.6, 10.8)** 349 (309, 395) b 98.7 (96.1, 100) b (5.1, 6.6)**,b 98.6 (96.5, 100) b mg (3.2, 6.1) 382 (308, 472) c 100 (100, 100) c (5.4, 6.9)**,b 100 (100, 100) b.100 mg (0.7, 1.9) (401, 598) d 99.5 (98.3, 100) c (4.0, 7.4)**,b 100 (100, 100) b Age y Nonusers (68.3, 79.3) 267 (248, 286) a 93.5 (90.9, 96.0) a (7.8, 8.7)**,a 93.3 (89.8, 96.9)**,a Users (20.7, 31.7) 390 (361, 422)* 96.8 (92.7, 100)* (6.8, 7.6)*, ** 96.6 (92.9, 100).0 10 mg (3.1, 8.6) (257, 437) b 86.9 (68.5, 100) b (6.3, 9.3) a,b 90.0 (71.9, 100) b mg (6.6, 13.5) 369 (336, 406) b 100 (100, 100) b (7.0, 8.0) b 100 (100, 100)**,b mg (5.3, 9.5) 447 (420, 475) b,c 99.5 (98.4, 100) b (6.1, 7.7) b 96.9 (92.8, 100) b.100 mg (1.2, 4.9) (354, 587) c 100 (100, 100) b (5.4, 7.5) b 97.4 (89.5, 100) b Age y Nonusers (65.7, 73.4) 285 (270, 302) a 93.7 (91.4, 96.1) a (9.3, 10.4) a 82.9 (78.5, 87.3) a Users (26.6, 34.3) 402 (386, 419)* 98.9 (97.7, 100)* (7.8, 8.9)* 95.1 (93.3, 97.0)*.0 10 mg (2.8, 7.4) (309, 392) b 98.4 (94.9, 100) b (7.7, 9.6) b 94.2 (89.1, 99.3) b mg (12.7, 21.1) 415 (388, 444) c 99.5 (98.1, 100) b (7.8, 9.0) b 96.0 (92.3, 99.7) b mg (4.0, 7.2) 405 (369, 445) b,c 97.2 (92.2, 100) b (7.1, 9.2) b 95.7 (84.9, 100) b.100 mg (1.8, 4.0) 429 (378, 488) b,c 100 (100, 100) b (7.3, 9.3) b 90.7 (73.6, 100) b 1 Values are percentages (95% CIs) or geometric means (95% CIs) unless otherwise indicated. Estimates in a column within an age group without a common letter differ, P # (t test with Bonferroni correction for multiple comparisons). *Different from supplement nonusers. P # 0.05 (StudentÕs t test). **Different from adults aged y, P # 0.05 (StudentÕs t test). thcy, total plasma homocysteine. 2 Includes individuals with a valid serum vitamin B-12 measure and excludes individuals using proton pump inhibitors or treated with vitamin B-12 injections. 3 Includes individuals with valid serum vitamin B-12 and plasma thcy measures and excludes individuals using proton pump inhibitors or treated with vitamin B-12 injections or with RBC folate,320 nmol/l. 4 CV for estimates between 16.6% and 33.3%; interpret with caution. 918 MacFarlane et al.

5 serum vitamin B-12, a higher prevalence of vitamin B-12 adequacy, and lower thcy, the associations were not dose dependent in all age groups. We found a positive association between supplement dose and serum vitamin B-12 in adults aged y. However, children and adolescents did not show higher status when consuming daily vitamin B-12 doses >10 mg, and older adults had no improvement at intakes >10 25 mg. We suggest that supplemental vitamin B-12 intakes of mg/d provide maximal vitamin B-12 status in these age groups in the general population and that higher doses may provide little additional benefit. Most studies examining the relation between vitamin B-12 intake and status have been in adults. The few studies in children have been in populations at risk of deficiency, such as children undergoing dialysis or who are vegetarian, making the data inapplicable to children in the general population. We found that children, and to a lesser extent adolescents, had better vitamin B-12 status than did adults, as demonstrated by higher serum vitamin B-12 and prevalence of adequacy, and that vitamin B-12 status was higher still in those consuming supplements. However, our study also provides the first evidence, to our knowledge, that children and adolescents may not benefit from supplemental vitamin B-12 intakes >10 mg/d. The mean usual daily dietary vitamin B-12 intake from food for Canadian children aged 4 18 y ranges from 3.3 to 5.5 mg/d (22), suggesting that total vitamin B-12 intakes above ~15 mg/d may not improve vitamin B-12 status in children and adolescents. It is recommended that persons >50 y consume crystalline vitamin B-12 because of the increasing risk of malabsorption with age. However, older Canadians had similar or even higher vitamin B-12 status than did younger adults, even among non supplement consumers. For example, the serum vitamin B-12 status of women who consumed vitamin B-12 supplements actually increased with age, such that women aged $46 y had higher serum vitamin B-12 than did women aged y. Also, the association between vitamin B-12 supplement dose and vitamin B-12 status differed by age, such that adults aged y demonstrated a positive relation between supplement intake and serum status, but older adults did not. Serum vitamin B-12 reached a plateau at doses > mg/d in adults aged y and at doses >10 25 mg/d in adults aged y. The absolute serum vitamin B-12 values achieved in older adults at all supplement doses were similar when compared with younger adults. We also observed no dose response for thcy or prevalence of normal thcy. The lack of a decrease in vitamin B-12 status with increasing age in adults confirms our previous observations that older Canadians may have better vitamin B-12 status than older adults elsewhere (16, 23 25). In Canada, the main source of crystalline vitamin B-12 is vitamin supplements because its use for fortification is restricted and foods such as breakfast cereals are not fortified. Therefore, the data indicate that even if ageassociated malabsorption is an issue for older Canadians, they are able to achieve and maintain a serum vitamin B-12 status that is similar to that of younger adults perhaps due to better diet and/or compliance in taking supplements as recommended. A recent meta-analysis found a similar relation of diminishing returns between increasing vitamin B-12 intake and status markers in a study population with participants without severe deficiencies (26). Also, the Framingham Offspring Study and the Hordaland Homocysteine Study showed that vitamin B-12 intake from food and supplements was associated with higher serum vitamin B-12 up to ~10 mg/d (24,27). Vitamin B-12 saturation was shown to be reached with vitamin B-12 intakes ranging from 4 to 7 mg/d for the vitamin B-12 status markers serum vitamin B-12, homocysteine, MMA, and holo-transcobalamin (28 30). We and others have observed that vitamin B-12 supplement intake was associated with lower thcy, but it was not dose responsive even at supraphysiologic doses (21). Certain limitations of our analysis must be highlighted. Although serum vitamin B-12 can reflect the broad range in status seen in a population, the use of the serum vitamin B-12 cutoff of <148 pmol/l to define deficiency could misclassify 3 5% of clinically deficient individuals as adequate (31). The use of MMA would improve the sensitivity to detect vitamin B-12 deficiency (31), but unfortunately it was not measured. The CHMS survey did not inquire about the frequency of supplement use, only whether the product had been used in the last month and the last time it was used. Although a previous analysis demonstrated that the majority of supplement users are daily users (32), this may vary with sex and age and could add variability to the findings. The CHMS also collected limited dietary intake data, which we have not included in our analysis; these data could explain observed differences in status between younger and older adults. Also, the small number of individuals consuming high vitamin B-12 supplement doses prevented us from identifying clinical or sociodemographic characteristics associated with high-dose supplement use. Strengths of the study include using a large representative sample and a wide life-span range (6 79 y). We also excluded individuals treated with proton pump inhibitors or vitamin B-12 injections, which can inhibit vitamin B-12 absorption or indicate clinical vitamin B-12 deficiency, respectively, to ensure that our data were applicable to the general population. In conclusion, this cross-sectional study in the general Canadian population with a low prevalence of vitamin B-12 deficiency indicates that the daily consumption of supplemental vitamin B-12 up to 10 mg by children and adolescents and up to mg by older adults is associated with higher vitamin B-12 status. However, these segments of the general population may not benefit from supplemental vitamin B-12 above these doses, because they are not associated with any additional increase in vitamin B-12 status. Acknowledgments The authors thank Dawn Warner, Chris Oster, and Chris Bonspiel of Statistics Canada for their help. A.J.M. designed the research and had primary responsibility for the final content; Y.S. performed the statistical analysis; and A.J.M., Y.S., and L.S.G.-F. analyzed the data and wrote the manuscript. All authors read and approved the final manuscript. Literature Cited 1. Molloy AM, Kirke PN, Troendle JF, Burke H, Sutton M, Brody LC, Scott JM, Mills JL. 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