TABLE 3.
Human studies assessing the association between vitamin B-12 and the gut microbiome1
| First author, year (ref) | Country | Study design (duration, if applicable) | Participants | n | Sex, % female | BMI,2 kg/m2 | B12 exposure | Baseline B12 status or intake2 | Specimen | DNA extraction | Sequencing | Multiple comparison method |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Boran, 2020 (43) | Turkey | Cross-sectional | 4–6-mo-old healthy term, exclusively breastfed infants (53.4% vaginal delivery), with (n = 60) and without (n = 28) B12 deficiency (<150 pmol/L) | 88 | 50 | Not reported; ≥2500 g3 | Serum total B12 | 119.5 (93.0, 162.8) pmol/L | Stool | DNA extraction: QuickGene (Kurabo, Osaka, Japan) | 16S rRNA V4 region, Illumina MiSeq | FDR |
| Uncontrolled before and after (4 wk) | 4–6-mo-old healthy term, exclusively breastfed infants with B12 deficiency (<150 pmol/L) | 11 | Not reported | Not reported; ≥2500 g3 | Intramuscular HC, 250—500 μg 2× weekly (1 wk) then 500 μg weekly (3 wk) | Before (n = 60): 100.7 (81.9, 121.4); after (n = 11): 770.3 (360.0, 1106.7) pmol/L | ||||||
| Babakobi, 2020 (41) | Israel | Cohort (3 mo) | Healthy women (25–40 y) who gave birth vaginally, and their infants born at term, recruited 1–2 d postpartum | 22 | Infants: 64 | 23.3 ± 4.6 (range: 19–37) | B12 intake, FFQ, past 12 mo | Not reported | Infant stool swab | PowerSoil DNA extraction kit (MO BIO) | 16S rRNA V3–V4 region, Illumina MiSeq | FDR |
| Carrothers, 2015 (40) | USA | Cohort (3 mo) | Lactating women (self-reported breastfeeding; 25–37 y) | 20 | 100 | 23.5 ± 3.3 (range: 19.3–34.5)4 | B12 intake, 24HR (excluded supplements) | 4.7 ± 3.1 (range: 1.3–13.1) μg/d | Stool | QIAamp DNA Stool Mini Kit (Qiagen) | 16S rRNA V1–V3 region, Illumina MiSeq | Not reported |
| Gurwara, 2019 (35) | USA | Cross-sectional | Male veterans (50–75 y), with an endoscopically normal colon after an elective colonoscopy procedure July 2013–April 2016 | 35 | 0 | 33.6 ± 6.5 and 33.9 ± 6.63 (n = 97) | B12 intake, FFQ, past 12 mo | 2.38 (1.73–2.99) μg/d | Colonic mucosal samples | MO BIO PowerLyzer UltraClean Tissue & Cell DNA Isolation Kits (MO BIO Laboratories) | 16S rRNA V4 region, Illumina MiSeq platform | FDR |
| Herman, 2020 (36) | USA | Cross-sectional | Healthy children 2–9 y (not breastfeeding, ∼84% ever breastfed; n = 30, 2–3 y; n = 45, 4–9 y) | 75 | 2–3 y: 57;4–9 y: 62 | 2–3 y: 30% ow/ob, 3% uw;4–9 y: 31% ow/ob, 9% uw | B12 intake, three 24HRs (included supplements) | 2–3 y: 4.31 ± 1.78; 4–9 y: 5.6 ± 7.36 μg/d | Stool swab | MO BIO PowerSoil isolation kit (MO BIO) | 16S rRNA V4 region, Illumina MiSeq platform | FDR |
| Mörkl, 2018 (33) | Austria | Cross-sectional | Females (18–40 y; 24.6 ± 4.6 y), not pregnant or lactating, including patients with anorexia nervosa (n = 17), athletes (n = 20), and women with normal (n = 25), overweight (n = 21), or obese (n = 19) BMI | 102 | 100 | 24.28 ± 6.5 | B12 intake, two 24HRs | 3.19 ± 1.58 and 4.14 ± 2.13μg/d | Stool | PowerLyzer PowerSoil DNA Isolation Kit (MO BIO) | 16S rRNA V1–V2 region, Ion Torrent PGM using the Ion 400BP Sequencing Kit | Not reported |
| Selma-Royo, 2021 (37) | Spain | Nested cross-sectional | Mother-infant dyads at delivery with a healthy pregnancy; 62% vaginal delivery; mothers were ≥18 y [35 (31.0, 36.25) y] | 73 | Infants: 45 | 21.8 (20.43, 24.13)43323 ± 416 g3 | Maternal B12 intake, FFQ | 10 ± 8 μg/d | Maternal and infant stool swabs | Master-Pure DNA extraction kit (Epicentre) | 16S rRNA V3–V4 region, Illumina MiSeq | FDR |
| Seura, 2017 (38) | Japan | Cross-sectional | Healthy, normal weight women, 20–22 y | 28 | 100 | Not reported | B12 intake, 3 food records (excluded supplements) | Not reported | Stool collected in guanidine thiocyanate | Not reported | T-RFLP method | Not reported |
| Shah, 2017 (42) | Not specified | Cohort (9 mo) | Healthy participants | 9 | Not reported | Not reported | B12 intake, NIH Dietary History Questionnaire | Not reported | Stool and colonic mucosal sample | Not reported | 16S rRNA, 454 Roche Titanium | Not reported |
| Tamura, 2017 (34) | Japan | Cross-sectional | Healthy older adults (range: 65–84 y; 72.1 ± 0.6 y) | 56 | 45 | 23.1 ± 0.4 | B12 intake, FFQ, past 1 wk | 6.83 ± 0.33 μg/d | Stool | Magtration System 12GC and GC series MagDEA DNA 200 reaction cartridge (Precision System Science) | 16S rRNA, Illumina MiSeq | Not reported |
| Valentini, 2015 (39) | France, Germany, Italy | Cohort within randomized trial (8 wk) | Healthy older adults (65–85 y; 70.1 ± 3.9 y), with BMI 22–30 kg/m2 and ECOG 0–2 | 69 | 51 | 26.8 ± 3.59 | Total serum B12 | 297.3 ± 20.0 and 307.7 ± 28.1 pmol/L | Stool | QIAamp DNA Stool Kit (Qiagen)5 | 16S rDNA gene targeted qPCR for Clostridium cluster IV and Bifidobacteria | Not reported |
1
B12, vitamin B-12; ECOG, Eastern Cooperative Oncology Group Performance Status; FDR, false discovery rate; FFQ, food-frequency questionnaire, HC, hydroxycobalamin; ob, obese; ow, overweight; PGM, Personal Genome Machine; ref, reference; rRNA, ribosomal RNA; T-RFLP, terminal restriction fragment length polymorphism; uw, underweight; 24HR, 24-h dietary recall.
2
Numbers are presented as either median (IQR) or mean ± SD.
3
Infant birth weight.
4
Prepregnancy BMI.
5
Provided by study authors via e-mail correspondence.