Scientific opinion on the tolerable upper intake level for folate

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. 2023 Nov 13;21(11):e08353. doi: 10.2903/j.efsa.2023.8353

Reference Study name Country Study design Follow‐up Funding	Original cohort (N total) Exclusion criteria Study population	Ascertainment of outcome	Exposure groups n/person‐years Exposure assessment method	Incident cases	Model covariates	Results
Weinstein et al. (2003) ATBC Study NCC Finland Follow up: NR Public	N = 29,133 Population sampled: Male smokers, 50–69 yrs Exclusion criteria: NR % lost to follow‐up: 8 cases and 10 controls n = 224 cases and 454 controls Age: NR Matching criteria: Controls matched on age, clinic, intervention group, date of baseline blood draw	Cases were defined as incident prostate cancers diagnosed through 1994 with available serum	Unit of measurement Serum Folate (nmol/L) (min‐max): Q1 (ref): ≤6.87 Q2: 6.88–8.69 Q3: 8.70–10.79 Q4: >10.79 Person‐years: NA Radioassay method Prostate cancer cases reported greater use of vitamin/mineral supplements than did controls	N cases/controls Q1 (ref): 56/118 Q2: 55/109 Q3: 52/114 Q4: 61/113	Adjusted for: Benign prostatic hyperplasia	OR (95% CI) Serum folate versus Prostate cancer: Q1 (ref): 1.00 Q2: 1.10 (0.69–1.75) Q3: 1.04 (0.64–1.67) Q4: 1.20 (0.74–1.94) p for trend = 0.52
Johansson et al. (2008) EPIC Germany, Greece, Italy, the Netherlands, Spain, Sweden, UK NCC 14 yrs Public	N = 519,978 Population sampled: Individuals across Europe Exclusion criteria: Cases with no available blood sample and those who had missing information on the date of blood donation or who had a history of another cancer (except non‐melanoma skin cancer) at the time of blood donation 238 cases from Sweden had been used in previous study and were excluded. % lost to follow‐up: NR N = Cases: 869 Controls: 1174 Age at blood collection (mean ± SD): Cases: 59.1 ± 6.7 Controls: 58.3 ± 6.8 Matching criteria: Study centre, age at enrolment, time of day of blood collection, time between blood draw and last consumption of food or drink	In Italy, the Netherlands, Spain, Sweden and the UK incident cancer cases identified through record linkage with regional or national cancer registries. In Germany and Greece a combination of methods, including health insurance records, cancer and pathology registries, and active follow‐up through study subjects and next‐of‐kin	Unit of measurement Circulating Folate concentration (nmol/L) (min‐max): Q1 (ref): <4.82 Q2: 4.83–6.77 Q3: 6.78–9.87 Q4: 9.89–16.52 Q5: ≥16.55 Person yrs: NR Folate concentrations were determined by a Lactobacillus casei microbiological assay	N cases/controls Q1 (ref): 117/229 Q2: 119/232 Q3: 162/229 Q4: 250/233 Q5: 207/227	Model 1: crude Model 2: Adjusted for BMI, smoking status, alcohol intake, physical Activity, marital status, educational level	RR (95% CI) Circulating folate versus prostate cancer: Model 1 Q1 (ref): 1.00 Q2: 0.99 (0.73–1.36) Q3: 1.15 (0.83–1.61) Q4: 1.52 (1.06–2.18) Q5: 1.23 (0.84–1.81) p for trend: 0.62 Model 2 Q1 (ref): 1.00 Q2: 1.02 (0.74–1.39) Q3: 1.18 (0.84–1.66) Q4: 1.62 (1.12–2.34) Q5: 1.30 (0.88–1.93) p for trend 0.46
Essén et al. (2019) Swedish Apolopoprotein Mortality Risk Sweden PC 13 yrs (mean) Mixed	N = 812,073 Population sampled: Individuals mainly from Stockholm area, men aged 30 yrs and older Exclusion criteria: NR % lost to follow‐up: NR N = 8783 Age mean ± SD: 64 ± 15.2	Swedish National Cancer Register, to which reporting is mandated, the National Prostate Cancer Register	Unit of measurement Serum Folate (nmol/L) (min‐max): Categories defined based on specific cut‐off values G1: <5 G2: 5–32 G3: >32	Incident cases/controls: G1: 6/65 G2: 646/8030 G3: 51/688	Model 1: Crude Model 2: Adjusted for age Model 3: model 2 and education level, SES, CCI, serum glucose, triglycerides, cholesterol, fasting status	HR (95% CI) Serum Folate vs. prostate cancer: Model 1 G1: 1.77 (0.79–3.95) G2 (ref): 1.00 G3: 1.01 (0.76–1.34) p for trend: 0.40 Model 2 G1: 1.42 (0.63–3.16) G2 (ref): 1.00 G3: 0.82 (0.62–1.09) p for trend: 0.13 Model 3 G1: NA G2 (ref): 1.00 G3: 0.73 (0.48–1.10) p for trend: 0.07
Hultdin et al. (2005) Northern Sweden Heatlh and Disease Cohort Sweden NCC 4.9 yrs Mixed	N = 37,776 Population sampled: In one sub cohort general population upon turning 40, 50 and 60 yrs invited to complete a survey and participate in future research, in the other random selection Exclusion criteria: NR % lost to follow‐up: NR N = 768 Age at recruitment (mean ± SD) Cases: 58.2 ± 4.9 Controls: 58.2 ± 3.9 Matching criteria: Controls (2:1) matched for age, recruitment date and subcohort	Incident cases of prostate cancer were identified through linkage with the regional cancer registry	Unit of measurement Plasma Folate (nmol/L) (min‐max): Q1 (ref): <5.85 Q2: 5.85–7.70 Q3: 7.70–10.30 Q4: >10.30 Radioassay method	Incident cases/ controls: Q1 (ref): 60/130 Q2: 58/134 Q3: 58/133 Q4: 77/111	Model 1: Crude Model 2: Adjusted for p‐cobalamin, homocysteine, BMI, smoking	OR (95% CI) Plasma Folate vs. prostate cancer: Model 1 Q1 (ref): 1.00 Q2: 0.94 (0.60–1.47) Q3: 0.95 (0.61–1.48) Q4: 1.60 (1.03–2.49) p for trend: 0.02 Model 2 Q1 (ref): 1.00 Q2: 0.78 (0.46–1.32) Q3: 0.76 (0.44–1.31) Q4: 1.30 (0.74–2.24) p for trend: 0.17
Rossi et al. (2006) 1969 Busselton Health survey Australia PC 23 yrs Public	N = NR Population sampled: General population, 40–90 yrs Exclusion criteria: History of cancer % lost to follow‐up: NR n = 1035 Age (mean): 55 years	Cancer morbidity was obtained by linkage to the death register, cancer register and hospital admissions. The event of interest was the first of cancer registration, hospital admission for cancer or cancer death (individuals censored at the time of the first event)	Serum folate (μg/L, min‐max): Q1: < 3.00 Q2: 3.00–4.49 Q3: 4.50–5.99 Q4: ≥ 6.00 (ref) RBC folate (μg/L, min‐max): Q1: 0.0–199.9 Q2: 200.0–274.9 Q3: 275–349.9 Q4: ≥ 350.0 (ref) In‐house automated microbiological assay system n/person years: Men: 20,254	Incident cases Prostate cancer morbidity Serum folate: Q1: 10 Q2: 16 Q3: 9 Q4: 17 (ref) RBC folate: Q1: 14 Q2: 13 Q3: 8 Q4: 17 (ref)	Age and sex and baseline cancer‐risk factors based on established risk factors for each cancer outcome: smoking, alcohol and BMI for all cancers, including prostate cancer	HR (95% CI) Serum folate vs. prostate cancer morbidity (2 μg/L decrease in serum folate): 1.18 (0.90, 1.51), p = 0.24 RBC folate vs. prostate Cancer morbidity (100 μg/L decrease in RBC folate): 1.20 (0.96, 1.52), p = 0.10 Serum folate vs. prostate Cancer morbidity: Q1: 2.50 (1.09, 5.75) Q2: 1.30 (0.64, 2.64 Q3: 0.58 (0.25, 1.32) Q4: 1.0 (ref) RBC folate vs. prostate cancer morbidity: Q1: 1.51 (0.72, 3.17) Q2: 1.02 (0.49, 2.13) Q3: 0.97 (0.41, 2.25) Q4: 1.0 (ref)
Beilby et al. (2010) Australia NCC 14 yrs Public	N = 6903 Population sampled: former Wittenoom crocidolite mine and mill workers Exclusion criteria: NR % lost to follow‐up: NR N = Cases: 96 Controls: 225 Age at diagnosis (mean ± SD): Cases: 69.8 ± 7.2 Controls: 69.3 ± 6.7	Prostate cancer cases were histologically confirmed cases identified through record linkage with the Western Australian Cancer Registry and the Australian National Cancer Statistics Clearing House.	Unit of measurement: Serum folate (μg/L, min‐max): T1: 1.50–3.80 T2: 3.90–6.20 T3: 6.30–45.1 Automated immunoassay	Incident cases/controls: T1: 33/70 T2: 32/70 T3: 27/74	Adjusted for age, administered vitamin A supplement	OR (95% CI) Serum folate versus prostate Cancer T1 (ref): 1.00 T2: 1.10 (0.57–2.11) T3: 1.09 (0.48–2.46) p for trend: 0.83 Continuous OR (95% CI): 0.99 (0.56–1.77)
de Vogel et al. (2013) JANUS cohort Norway NCC 15.6 years (mean) Public	N = 317,000 Population sampled: Individuals who participated in health screening surveys or were Red Cross blood donors in Norway between 1973 and 2004 Exclusion criteria: Residency outside Norway, diagnosed cancer other than non‐melanoma skin cancer % lost to follow‐up: NR N= Cases 3000 Controls: 3000 Age at serum sampling (mean ± SD) Cases: 49.1 ± 8.7 Controls: 49.1 ± 8.7 Matching criteria: Controls were matched by age at serum sampling, date of serum sampling and country of residence	Cancer incidence data were obtained from the Cancer Registry of Norway	Unit of measurement: Serum folate (nmol/L) (min‐max): Q1: <10.9 Q2: 10.9–12.8 Q3: 12.8–14.7 Q4: 14.7–17.5 Q5: ≥17.5 p‐Aminobenzoylglutamate Equivalents	Incident cases/control Q1: 585/577 Q2: 566/601 Q3: 556/596 Q4: 590/614 Q5: 703/612	Model 1: Crude Model 2: Adjusted for education, smoking, physical activity, BMI, serum creatinine	OR (95% CI) Serum folate concentration vs. prostate Cancer Model 1 Q1 (ref): 1.00 Q2: 0.93 (0.79–1.10) Q3: 0.93 (0.79–1.10) Q4: 0.96 (0.81–1.14) Q5: 1.17 (0.99–1.39) p trend: 0.02 Model 2 Q1 (ref): 1.00 Q2: 0.92 (0.78–1.09) Q3: 0.92 (0.77–1.09) Q4: 0.94 (0.80–1.12) Q5: 1.15 (0.97–1.37) p trend: 0.04

Reference

Study name

Country Study design Follow‐up Funding

Original cohort (N total) Exclusion criteria Study population

Ascertainment of outcome

Exposure groups n/person‐years Exposure assessment method

Incident cases

Model covariates

Results

Weinstein et al. (2003)

ATBC Study

NCC

Finland

Follow up: NR

Public

N = 29,133

Population sampled:

Male smokers,

50–69 yrs

Exclusion criteria: NR

% lost to follow‐up: 8 cases and 10 controls

n = 224 cases and 454 controls

Age: NR

Matching criteria: Controls matched on age, clinic, intervention group, date of baseline blood draw

Cases were defined as incident prostate cancers diagnosed through 1994 with available serum

Unit of measurement

Serum Folate (nmol/L) (min‐max):

Q1 (ref): ≤6.87

Q2: 6.88–8.69

Q3: 8.70–10.79

Q4: >10.79

Person‐years: NA

Radioassay method

Prostate cancer cases reported greater use of vitamin/mineral supplements than did controls

N cases/controls

Q1 (ref): 56/118

Q2: 55/109

Q3: 52/114

Q4: 61/113

Adjusted for: Benign prostatic hyperplasia

OR (95% CI)

Serum folate versus Prostate cancer:

Q1 (ref): 1.00

Q2: 1.10 (0.69–1.75)

Q3: 1.04 (0.64–1.67)

Q4: 1.20 (0.74–1.94)

p for trend = 0.52

Johansson et al. (2008)

EPIC

Germany, Greece, Italy, the Netherlands, Spain, Sweden, UK

NCC

14 yrs

Public

N = 519,978

Population sampled: Individuals across Europe

Exclusion criteria:

Cases with no available blood sample and those who had missing information on the date of blood donation or who had a history of another cancer (except non‐melanoma skin cancer) at the time of blood donation

238 cases from Sweden had been used in previous study and were excluded.

% lost to follow‐up: NR

N =

Cases: 869

Controls: 1174

Age at blood collection (mean ± SD):

Cases: 59.1 ± 6.7

Controls: 58.3 ± 6.8

Matching criteria: Study centre, age at enrolment, time of day of blood collection, time between blood draw and last consumption of food or drink

In Italy, the Netherlands, Spain, Sweden and the UK incident cancer cases identified through record linkage with regional or national cancer registries.

In Germany and Greece a combination of methods, including health insurance records, cancer and pathology registries, and active follow‐up through study subjects and next‐of‐kin

Unit of measurement

Circulating Folate concentration (nmol/L) (min‐max):

Q1 (ref): <4.82

Q2: 4.83–6.77

Q3: 6.78–9.87

Q4: 9.89–16.52

Q5: ≥16.55

Person yrs: NR

Folate concentrations were determined by a Lactobacillus casei microbiological assay

N cases/controls

Q1 (ref): 117/229

Q2: 119/232

Q3: 162/229

Q4: 250/233

Q5: 207/227

Model 1: crude

Model 2: Adjusted for BMI, smoking status, alcohol intake, physical Activity, marital status, educational level

RR (95% CI)

Circulating folate versus prostate cancer:

Model 1

Q1 (ref): 1.00

Q2: 0.99 (0.73–1.36)

Q3: 1.15 (0.83–1.61)

Q4: 1.52 (1.06–2.18)

Q5: 1.23 (0.84–1.81)

p for trend: 0.62

Model 2

Q1 (ref): 1.00

Q2: 1.02 (0.74–1.39)

Q3: 1.18 (0.84–1.66)

Q4: 1.62 (1.12–2.34)

Q5: 1.30 (0.88–1.93)

p for trend 0.46

Essén et al. (2019)

Swedish Apolopoprotein Mortality Risk

Sweden

13 yrs (mean)

Mixed

N = 812,073

Population sampled: Individuals mainly from Stockholm area, men aged 30 yrs and older

Exclusion criteria: NR

% lost to follow‐up: NR

N = 8783

Age mean ± SD:

64 ± 15.2

Swedish National

Cancer Register, to which reporting is mandated, the

National Prostate Cancer Register

Unit of measurement

Serum Folate (nmol/L) (min‐max): Categories defined based on specific cut‐off values

G1: <5

G2: 5–32

G3: >32

Incident cases/controls:

G1: 6/65

G2: 646/8030

G3: 51/688

Model 1: Crude

Model 2: Adjusted for age

Model 3: model 2 and education level, SES, CCI, serum glucose, triglycerides, cholesterol, fasting status

HR (95% CI)

Serum Folate vs. prostate cancer:

Model 1

G1: 1.77 (0.79–3.95)

G2 (ref): 1.00

G3: 1.01 (0.76–1.34)

p for trend: 0.40

Model 2

G1: 1.42 (0.63–3.16)

G2 (ref): 1.00

G3: 0.82 (0.62–1.09)

p for trend: 0.13

Model 3

G1: NA

G2 (ref): 1.00

G3: 0.73 (0.48–1.10)

p for trend: 0.07

Hultdin et al. (2005)

Northern Sweden Heatlh and Disease Cohort

Sweden

NCC

4.9 yrs

Mixed

N = 37,776

Population sampled: In one sub cohort general population upon turning 40, 50 and 60 yrs invited to complete a survey and participate in future research, in the other random selection

Exclusion criteria: NR

% lost to follow‐up: NR

N = 768

Age at recruitment (mean ± SD)

Cases: 58.2 ± 4.9

Controls: 58.2 ± 3.9

Matching criteria: Controls (2:1) matched for age, recruitment date and subcohort

Incident cases of prostate cancer were identified through linkage with the regional cancer registry

Unit of measurement

Plasma Folate (nmol/L) (min‐max):

Q1 (ref): <5.85

Q2: 5.85–7.70

Q3: 7.70–10.30

Q4: >10.30

Radioassay method

Incident cases/ controls:

Q1 (ref): 60/130

Q2: 58/134

Q3: 58/133

Q4: 77/111

Model 1: Crude

Model 2:

Adjusted for p‐cobalamin, homocysteine, BMI, smoking

OR (95% CI)

Plasma Folate vs. prostate cancer:

Model 1

Q1 (ref): 1.00

Q2: 0.94 (0.60–1.47)

Q3: 0.95 (0.61–1.48)

Q4: 1.60 (1.03–2.49)

p for trend: 0.02

Model 2

Q1 (ref): 1.00

Q2: 0.78 (0.46–1.32)

Q3: 0.76 (0.44–1.31)

Q4: 1.30 (0.74–2.24)

p for trend: 0.17

Rossi et al. (2006)

1969 Busselton Health survey

Australia

23 yrs

Public

N = NR

Population sampled:

General population, 40–90 yrs

Exclusion criteria: History of cancer

% lost to follow‐up: NR

n = 1035

Age (mean):

55 years

Cancer morbidity was obtained

by linkage to the death register, cancer register and hospital admissions. The event of interest was the first of cancer registration, hospital admission for cancer or cancer death (individuals censored at the time of the first event)

Serum folate (μg/L, min‐max):

Q1: < 3.00

Q2: 3.00–4.49

Q3: 4.50–5.99

Q4: ≥ 6.00 (ref)

RBC folate (μg/L, min‐max):

Q1: 0.0–199.9

Q2: 200.0–274.9

Q3: 275–349.9

Q4: ≥ 350.0 (ref)

In‐house automated

microbiological assay system

n/person years:

Men: 20,254

Incident cases

Prostate cancer morbidity

Serum folate:

Q1: 10

Q2: 16

Q3: 9

Q4: 17 (ref)

RBC folate:

Q1: 14

Q2: 13

Q3: 8

Q4: 17 (ref)

Age and sex and baseline

cancer‐risk factors based on established risk factors for each cancer outcome: smoking, alcohol and BMI for all cancers, including

prostate cancer

HR (95% CI)

Serum folate vs. prostate cancer morbidity (2 μg/L decrease in serum folate):

1.18 (0.90, 1.51), p = 0.24

RBC folate vs. prostate Cancer morbidity (100 μg/L decrease in RBC folate):

1.20 (0.96, 1.52), p = 0.10

Serum folate vs. prostate Cancer morbidity:

Q1: 2.50 (1.09, 5.75)

Q2: 1.30 (0.64, 2.64

Q3: 0.58 (0.25, 1.32)

Q4: 1.0 (ref)

RBC folate vs. prostate cancer morbidity:

Q1: 1.51 (0.72, 3.17)

Q2: 1.02 (0.49, 2.13)

Q3: 0.97 (0.41, 2.25)

Q4: 1.0 (ref)

Beilby et al. (2010)

Australia

NCC

14 yrs

Public

N = 6903

Population sampled: former Wittenoom crocidolite mine and mill workers

Exclusion criteria: NR

% lost to follow‐up: NR

N =

Cases: 96

Controls: 225

Age at diagnosis (mean ± SD):

Cases: 69.8 ± 7.2

Controls: 69.3 ± 6.7

Prostate cancer cases were histologically confirmed cases identified through record linkage with the Western Australian Cancer Registry and the Australian National Cancer Statistics Clearing House.

Unit of measurement:

Serum folate (μg/L, min‐max):

T1: 1.50–3.80

T2: 3.90–6.20

T3: 6.30–45.1

Automated immunoassay

Incident cases/controls:

T1: 33/70

T2: 32/70

T3: 27/74

Adjusted for age, administered vitamin A supplement

OR (95% CI)

Serum folate versus prostate Cancer

T1 (ref): 1.00

T2: 1.10 (0.57–2.11)

T3: 1.09 (0.48–2.46)

p for trend: 0.83

Continuous OR (95% CI):

0.99 (0.56–1.77)

de Vogel et al. (2013)

JANUS cohort

Norway

NCC

15.6 years (mean)

Public

N = 317,000

Population sampled: Individuals who participated in health screening surveys or were Red Cross blood donors in Norway between 1973 and 2004

Exclusion criteria: Residency outside Norway, diagnosed cancer other than non‐melanoma skin cancer

% lost to follow‐up: NR

Cases 3000

Controls: 3000

Age at serum sampling (mean ± SD)

Cases: 49.1 ± 8.7

Controls: 49.1 ± 8.7

Matching criteria: Controls were matched by age at serum sampling, date of serum sampling and country of residence

Cancer incidence data were obtained from the Cancer Registry of Norway

Unit of measurement:

Serum folate (nmol/L) (min‐max):

Q1: <10.9

Q2: 10.9–12.8

Q3: 12.8–14.7

Q4: 14.7–17.5

Q5: ≥17.5

p‐Aminobenzoylglutamate Equivalents

Incident cases/control

Q1: 585/577

Q2: 566/601

Q3: 556/596

Q4: 590/614

Q5: 703/612

Model 1: Crude

Model 2:

Adjusted for education, smoking, physical activity, BMI, serum creatinine

OR (95% CI)

Serum folate concentration vs. prostate Cancer

Model 1

Q1 (ref): 1.00

Q2: 0.93 (0.79–1.10)

Q3: 0.93 (0.79–1.10)

Q4: 0.96 (0.81–1.14)

Q5: 1.17 (0.99–1.39)

p trend: 0.02

Model 2

Q1 (ref): 1.00

Q2: 0.92 (0.78–1.09)

Q3: 0.92 (0.77–1.09)

Q4: 0.94 (0.80–1.12)

Q5: 1.15 (0.97–1.37)

p trend: 0.04

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index; CI, Confidence Interval; EPIC, European Prospective Investigation into Cancer and Nutrition; G, Group; HR, Hazard ratio; NA, Not available; NCC, Nested case–control; NR, Not reported; OR, Odds ratio; PC, Prospective cohort; RBC, Red blood cell; SD, Standard deviation; SES, Socioeconomic status; yrs, years.