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. 2023 Aug 7;77(11):1071–1083. doi: 10.1038/s41430-023-01318-3

Table 2.

Multivariable linear regression results for average nutritional biochemistry results and related independent variables for Sleeve Gastrectomy and Gastric Bypass participants.

Dependent Variable Independent Variablea Sleeve Gastrectomy Gastric Bypass
Difference (95% CI)b p value Difference (95% CI)b p value
Ferritin (ug/L)f Preop ref ref
1–3 months postop 16% (−1%, 33%) 0.07 21% (0%, 43%) 0.05
6 months postop −3% (−20%, 13%) 0.7 −10% (−38%, 18%) 0.5
12 months postop −12% (−32%, 8%) 0.2 −32% (−65%, 1%) 0.06
Oral iron supplement dosec −1% (−8%, 6%) 0.8 10% (1%, 20%) 0.02
Female −47% (−82%, −12%) 0.008 −77% (−117%, −36%) <0.001
CRP > 5 mg/L 15% (0%, 30%) 0.05 32% (9%, 54%) 0.006
Transferrin Saturation (%)f Preop ref ref
1–3 months postop 4.0 (2.0, 6.0) <0.001 2.4 (0.0, 4.7) 0.05
6 months postop 6.4 (3.8, 9.0) <0.001 4.8 (1.7, 7.9) 0.002
12 months postop 6.5 (3.8, 9.3) <0.001 6.8 (3.4, 10.2) <0.001
Oral iron supplement dosec −0.1 (−0.9, 0.7) 0.8 −0.2 (−1.4, 0.9) 0.7
Female −2.2 (−6.1, 1.6) 0.3 0.1 (−2.5, 2.7) 0.9
CRP > 5 mg/L −3.5 (−6.0, −1.1) 0.004 −2.0 (−4.3, 0.3) 0.08
Vitamin B12 (pmol/L) Preop ref ref
1–3 months postop −2% (−14%, 10%) 0.8 13% (−1%, 27%) 0.08
6 months postop −8% (−21%, 4%) 0.2 −7% (−26%, 12%) 0.5
12 months postop −5% (−20%, 10%) 0.5 −11% (−31%, 9%) 0.3
Oral vitamin B12 supplement dosec 4% (0%, 8%) 0.03 4% (0%, 8%) 0.04
IM vitamin B12 supplementationd 92% (47%, 138%) <0.001 102% (69%, 135%) <0.001
Metformine 2% (−10%, 14%) 0.7 1% (−13%, 15%) 0.9
CRP > 5 mg/L 6% (−4%, 16%) 0.3 10% (−4%, 23%) 0.2
Folate (nmol/L) Preop ref ref
1–3 months postop −2.7 (−5.9, 0.5) 0.1 −5.4 (−10.0, −0.7) 0.02
6 months postop −3.4 (−7.3, 0.5) 0.09 −3.7 (−9.1, 1.8) 0.2
12 months postop −4.1 (−8.2, 0.1) 0.06 −4.1 (−10.4, 2.1) 0.2
Oral folic acid supplement dosec 1.9 (1.4, 2.5) <0.001 1.4 (0.7, 2.2) <0.001
CRP > 5 mg/L −0.3 (−3.2, 2.5) 0.8 −3.4 (−7.4, 0.7) 0.1
Copper (umol/L) Preop ref ref
1–3 months postop −4.0% (−8.4%, 0.4%) 0.07 −1.2% (−6.1%, 3.7%) 0.6
6 months postop −1.0% (−6.0%, 3.9%) 0.7 −3.2% (−9.5%, 3.0%) 0.3
12 months postop −2.3% (−7.2%, 2.7%) 0.4 −7.2% (−13.6%, −0.9%) 0.02
Oral copper supplement dosec 0.3% (−0.5%, 1.0%) 0.4 0.1% (−0.7%, 0.8%) 0.8
CRP > 5 mg/L 11.3% (7.2%, 15.3%) <0.001 8.5% (4.7%, 12.4%) <0.001
Ceruloplasmin (umol/L) Preop ref ref
1–3 months postop −4% (−9%, 1%) 0.2 0% (−4%, 4%) 1
6 months postop −2% (−8%, 4%) 0.5 −3% (−9%, 2%) 0.3
12 months postop −2% (−9%, 4%) 0.5 −9% (−15%, −3%) 0.002
Oral copper supplement dosec −0.13% (−1.02%, 0.76%) 0.8 0.00% (−0.61%, 0.61%) 1
CRP > 5 mg/L 11% (6%, 16%) <0.001 10% (6%, 14%) <0.001
Vitamin D (nmol/L) Preop ref ref
1–3 months postop 13.9 (6.8, 20.9) <0.001 −6.7 (−13.4, −0.1) 0.05
6 months postop 10.4 (2.9, 19.9) 0.007 −7.4 (−16.7, 1.9) 0.1
12 months postop 10.5 (1.0, 19.9) 0.03 −5.9 (−17.6, 5.8) 0.3
Oral vitamin D supplement dosec 0.5 (−0.5, 1.5) 0.3 3.0 (1.9, 4.2) <0.001
CRP > 5 mg/L 2.8 (−2.1, 7.7) 0.3 6.7 (−3.4, 16.6) 0.2
HbA1c (%) 1.3 (−1.5, 4.1) 0.4 −0.6 (−2.9, 1.7) 0.6
Vitamin B1 Hb (nmol/g Hb) Preop ref ref
1–3 months postop −11% (−20%, −1%) 0.03 −24% (−31%, −16%) <0.001
6 months postop −3% (−13%, 8%) 0.6 −9% (−18%, −1%) 0.05
12 months postop 2% (−8%, 12%) 0.7 −6% (−15%, 2%) 0.1
Oral vitamin B1 supplement dosec 7% (2%, 13%) 0.007 11% (8%, 14%) <0.001
CRP > 10 mg/L 10% (2%, 17%) 0.02 4% (−4%, 11%) 0.4
Vitamin A (umol/L) Preop ref
1–3 months postop −0.37 (−0.50, −0.23) <0.001
6 months postop −0.28 (−0.42, −0.13) <0.001
12 months postop −0.18 (−0.35, −0.01) 0.04
Oral vitamin A supplement dosec −0.014 (−0.031, 0.002) 0.1
CRP > 10 mg/L −0.13 (−0.24, −0.02) 0.02
Retinol Binding Protein (umol/L) Preop ref
1–3 months postop −0.50 (−0.64, −0.29) <0.001
6 months postop −0.33 (−0.51, −0.29) <0.001
12 months postop −0.2 (−0.4, 0.0) 0.06
Oral vitamin A supplement dosec −0.021 (−0.041, −0.001) 0.04
CRP > 5 mg/L −0.02 (−0.18, 0.13) 0.8
Vitamin E (umol/L) Preop ref
1–3 months postop −10.7 (−14.9, −6.6) <0.001
6 months postop −6.3 (−10.7, −1.9) 0.005
12 months postop −6.1 (−10.1, −2.2) 0.002
Oral vitamin E supplement dosec 0.86 (−0.03, 1.74) 0.06
CRP > 5 mg/L 3.46 (−0.07, 6.97) 0.06
Vitamin C (umol/L) Preop ref
1–3 months postop −2.9 (−12.1, 6.4) 0.5
6 months postop 2.3 (−8.3, 12.9) 0.7
12 months postop 5.1 (−6.5, 16.6) 0.4
Oral vitamin C supplement dosec 2.7 (0.7, 4.7) 0.008
CRP > 10 mg/L −2.4 (−10.5, 5.6) 0.6
Zinc (umol/L) Preop ref
1–3 months postop 0.67 (−0.03, 1.37) 0.06
6 months postop −1.44 (−2.43, −0.45) 0.005
12 months postop −1.10 (−1.82, −0.38) 0.003
Oral zinc supplement dosec 0.29 (0.06, 0.52) 0.02
CRP > 20 mg/L −1.08 (−2.54, 0.39) 0.2
Plasma Glutathione Peroxidase (U/L) Preop ref
1–3 months postop −6% (−17%, 4%) 0.3
6 months postop −5% (−18%, 7%) 0.4
12 months postop 14% (2%, 26%) 0.03
Oral selenium supplement dosec −0.3% (−2.6%, 2.0%) 0.8
CRP > 5 mg/L −9% (−17%, −1%) 0.03
HbA1c (%) 7% (5%, 9%) <0.001
Red Cell Glutathione Peroxidase (u/g Hb) Preop ref
1–3 months postop 3% (−5%, 11%) 0.5
6 months postop −1% (−12%, 10%) 0.9
12 months postop −5% (−16%, 5%) 0.3
Oral selenium supplement dosec 0.4% (−1.6%, 2.4%) 0.7
CRP > 5 mg/L −1% (−9%, 6%) 0.7
HbA1c (%) 1% (−2%, 3%) 0.6

ref reference category.

aUsing the Generalised Estimated Equation.

bDifference or % difference, where % difference was used for nutrition biochemistry variables that were logged due to not being normally distributed.

cOral supplementation dose is loge(supplementation dose/day +1) as is not normally distributed and contains zero values.

dPatient received any dose of IM vitamin B12 supplementation prior to their blood test at that timepoint.

eOn any dose of metformin at time of blood test.

fCases that used IV iron excluded from analysis.