Scientific opinion on the tolerable upper intake level for selenium

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. 2023 Jan 20;21(1):e07704. doi: 10.2903/j.efsa.2023.7704

Reference Study Country	Design N randomised/completed Duration^(a) Reftcruitment criteria	Subject characteristics at baseline^(b)	Intervention^(b)	Outcomes assessed	Results^(b)
Hawkes et al. (2008) USA	RCT G1, placebo: 27/20 G2, 300 μg Se/d: 27/22 Duration: 48 wk (+ 48 wk follow up) Aged 19–45 yr, healthy men; non‐smokers; no use of Se shampoos, Se supplements providing > 50 μg/d, thyroid medications, weight loss drugs, or anabolic steroids; no weight loss > 10 lb within last 6 mo; no exercise > 3 h per wk.	Sex: M Age (yr): 18–45 BMI (kg/m ² ): NR Ethnicity: NR Plasma/serum Se: NR Se intake (μg/d): 135 ± 57 (by 3‐d diet records, during the 48 wk of supplementation)	Selenised yeast (300 μg Se/d) vs placebo Adherence, pill count (%): 93 ± 5.3%	Fasting serum glucose at baseline and at 48 wk and 96 wk	Fasting serum glucose (mmol/L) G1: 4.83 ± 0.59 G2: 4.97 ± 0.54	Fasting serum glucose (mmol/L) At 48 wk G1: 4.80 ± 0.46 G2: 4.90 ± 0.56 At 96 wk G1: 5.04 ± 0.53 G2: 4.92 ± 0.44
Mesdaghinia et al. (2017) Iran	RCT G1, placebo: 30/30 G2, 100 Se μg/d: 30/30 Duration: 10 wk, between 17 and 27 wk of gestation Pregnant women at risk for IUGR; no use of Se supplement during past 3 mos; non‐smokers; no hypothyroidism or hyperthyroidism, UTI, preeclampsia, HT, diseases related to increased inflammation, and kidney or liver diseases	Sex: F Age (yr) G1: 28.1 ± 4.9 G2: 30.5 ± 5.5 BMI (kg/m ² ) G1: 22.5 ± 3.2 G2: 21.2 ± 4.2 Ethnicity: NR Se intake: NR	Selenised yeast (100 Se μg/d) vs placebo Adherence, pill count (%): 100	Fasting serum glucose, HOMA‐IR, HOMA‐B at baseline and after 10 wk	Fasting serum glucose (mg/dL) G1: 92.6 ± 9.6 G2: 90.4 ± 11.6 HOMA‐IR G1: 3.5 ± 1.5 G2: 3.7 ± 1.7 HOMA‐B G1: 57.1 ± 24.7 G2: 62.0 ± 26.0	Fasting serum glucose (mg/dL) G1: 91.6 ± 11.6 G2: 89.2 ± 12.6 p = 0.90 HOMA‐IR G1: 4.2 ± 2.1 G2: 3.2 ± 1.0 p = 0.02 HOMA‐B G1: 72.5 ± 43.4 G2: 55.6 ± 21.0 p = 0.02
Navas‐Carretero et al. (2011) Spain	RCT G1, non‐enriched chicken: 16/13 G2, Se‐enriched chicken: 16/11 Duration: 10 wk Aged 20–45 yr, BMI > 18.5 and < 30 kg/m², no medication or dietary treatment, and maintained weight (±3 kg) for the last 3 mo; no metabolic diseases (e.g. diabetes, thyroid impairments, other endocrine disturbances); no gastric and peptic ulcer problems, HTN, constipation, or diarrhoea	Sex: M and F Age (yr): 20–45 BMI (kg/m ² ) G1: 24.2 ± 2.1 G2: 24.1 ± 2.7 Ethnicity: NR Blood Se (μg/dL) G1: 14.2 ± 1.4 G2: 14.6 ± 1.7 Se intake: NR	200 g of Se‐enriched chicken breast (25.5 Se μg/100 g), 4 times/wk, vs non‐enriched chicken breasts (6.5 Se μg/100 g) Adherence: NR No significant difference between groups in blood Se changes (μg/dL) G1: +0.7 ± 0.9 G2: +0.2 ± 1.4	Fasting serum glucose, fasting insulin and HOMA‐IR at baseline and 10 wk	Fasting serum glucose (mg/dL) G1: 81.7 ± 6.1 G2: 87.3 ± 5.1 Fasting insulin (mU/L) G1: 4.9 ± 2.2 G2: 5.2 ± 3.6 HOMA‐IR G1: 1.0 ± 0.5 G2: 1.1 ± 0.8	Change from baseline Fasting serum glucose (mg/dL) G1: −0.9 ± 4.1 G2: −5.2 ± 4.7 Fasting insulin (mU/L) G1: 0.3 ± 2.3 G2: −0.5 ± 1.4 HOMA‐IR G1: 0.05 ± 0.5 G2: −0.16 ± 0.32
Richie et al., 2014 USA	RCT G1, placebo: 34/18 G2, 200 μg Se/d as SY: 33/16 G3: 285 μg Se/d as SY: 32/15 G4: 200 μg Se/d as SeMet: 31/20 Duration: 9 mo (+ 3 mo of follow‐up) Aged 20–79 yr, healthy men, non‐smokers, normal serum PSA, no history or evidence of diabetes, prostate cancer, liver, or kidney disease, no use of Se supplements providing > 50 μg/d	Sex: M Age (yr) G1: 48.1 ± 14.6 (22–70) G2: 50.7 ± 16.2 (23–78) G3: 51.3 ± 12.0 (25–72) G4: 54.0 ± 13.4 (30–75) BMI (kg/m ² ) G1: 30.0 ± 4.79 (22.0–38.3) G2: 28.0 ± 3.20 (22.4–34.9) G3: 27.8 ± 3.14 (23.7–34.2) G4: 28.5 ± 3.79 (23.0–36.4) Ethnicity (Caucasians, %) G1: 94 G2: 94 G3: 87 G4: 85 Plasma Se (μg/L): ca. 137 Se intake: NR	Selenised yeast (200 or 285 μg /d) vs selenomethionine (200 μg /d) vs placebo Adherence, pill count (%): 95 Plasma Se (μg/L) at 9 mo G1: 146 G2: 207 G3: 253 G4: 263	Fasting blood glucose at baseline and at 9 mo (data at 3, 6 and 12 mo visits not extracted)	Fasting blood glucose (mg/dL, mean ± SE) G1: 84.7 ± 2.29 G2: 91.6 ± 1.65 G3: 82.7 ± 2.45 G4: 91.0 ± 2.07	Change from baseline Fasting blood glucose (mg/dL, mean ± SE) G1: 3.72 ± 2.76 G2: −1.44 ± 2.75 G3: 1.60 ± 5.31 G4: −1.75 ± 2.46
Diseased individuals
Jamilian et al. (2015) Iran	RCT G1, placebo: 35/35 G1, 200 μg Se/d: 35/35 Duration: 8 wk Aged 18–40 yr, with PCOS, before menopause; no use of Se supplements and metformin in the last 3 mo; non‐smokers; no diabetes or hypothyroidism; no special diet, oral conceptive, ovulation induction agents	Sex: F Age (yr) G1: 25.7 ± 4.8 G2: 25.4 ± 5.1 BMI (kg/m ² ) G1: 25.2 ± 4.1 G2: 25.0 ± 3.7 Ethnicity: NR Serum/plasma Se: NR Se dietary intake (μg/day, mean ± SD) (by 3‐d dietary records measured at week 2, 4, 6) G1: 58.5 ± 8.0 G2: 56.1 ± 10.5	Selenised yeast (200 μg Se/d) vs placebo Adherence, pills count (%): > 90%	Fasting plasma glucose, fasting serum insulin, HOMA‐IR, HOMA‐B at baseline and at 8 wk	Fasting plasma glucose (mmol/L) G1: 5.15 ± 0.39 G2: 4.91 ± 0.52 Fasting insulin (pmol/L) G1: 73.58 ± 59.50 G2: 80.69 ± 42.28 HOMA‐IR G1: 2.78 ± 2.25 G2: 3.00 ± 1.69 HOMA‐B G1: 2.78 ± 2.25 G2: 3.00 ± 1.69	Change from baseline (adjusted for baseline value, age and BMI) Fasting plasma glucose (mmol/L) G1: 0.05 ± 0.09 G2: −0.29 ± 0.09 p = 0.010 Fasting insulin (pmol/L) G1: 7.32 ± 9.73 G2: −28.09 ± 9.73 p = 0.012 HOMA‐IR G1: 0.38 ± 0.39 G2: −1.11 ± 0.39 p = 0.010 HOMA‐B G1: 3.06 ± 5.97 G2: −17.59 ± 5.97 p = 0.017
Karamali et al. (2015) Iran	RCT G1, placebo: 28/28 G2, 200 μg Se/d: 28/28 Duration: 6 mo Aged 18–55 yr, with cervical intraepithelial neoplasia grade 1; no history of cervical cancer or other cancers of the lower genital tract; no history of hysterectomy or destructive therapy of the cervix; not pregnant.	Sex: F Age (yr) G1: 38.3 ± 9.2 G2: 38.3 ± 9.1 BMI (kg/m ² ) G1: 28.7 ± 3.9 G2: 28.6 ± 4.0 Ethnicity: NR Serum/plasma Se: NR Se intake: NR	Selenised yeast (200 μg Se/d) vs placebo Adherence, pills count (%): > 90%	Fasting plasma glucose, serum insulin, HOMA‐IR, HOMA‐B at baseline and 6 mo	Fasting plasma glucose (mg/dL) G1: 89.4 ± 8.3 G2: 94.5 ± 12.1 Fasting insulin (μIU/mL) G1: 12.7 ± 4.4 G2: 13.9 ± 4.5 HOMA‐IR G1: 2.8 ± 1.0 G2: 3.3 ± 1.4 HOMA‐B G1: 48.1 ± 18.2 G2: 48.9 ± 14.0	Change from baseline (adjusted for baseline value, age and BMI) (mean ± SE) Fasting plasma glucose (mg/dL) G1: 0.3 ± 1.7 G2: −5.9 ± 1.7 p = 0.01 Fasting insulin (μIU/mL) G1: 1.9 ± 1.1 G2: −4.5 ± 1.1 p < 0.001 HOMA‐IR G1: 0.3 ± 0.2 G2: −1.2 ± 0.2 p < 0.001 HOMA‐B G1: 9.7 ± 4.9 G2: −14.7 ± 4.9 p = 0.001
Hosseinzadeh et al. (2016) Iran	RCT G1, placebo: 30/27 G2, 200 μg Se/d: 30/26 Duration: 12 wk Aged 18–42 yr, with PCOS; non‐smokers; no congenital adrenal hyperplasia, Cushing's syndrome, androgen‐secreting tumours and hyperprolactinemia; no diabetes, hypo‐ or hyperthyroidism, renal dysfunction, liver disease or cardiovascular disease; no use of medications affecting metabolic and hormonal profile; no use of Se supplement in past 3 mo.	Sex: F Age (yr, mean ± SE) G1: 28.90 ± 1.17 G2: 29.23 ± 0.96 BMI (kg/m ² , mean ± SE) G1: 28.39 ± 0.72 G2: 27.4 ± 0.88 Ethnicity: NR Serum/plasma Se: NR Se intake (μg/d, mean ± SE) (6‐d 24‐h recall) G1: 36.4 ± 2.5 G2: 28.3 ± 3.1	Selenised yeast (200 μg Se/d) vs placebo Adherence, pills count (%): > 90%	Fasting serum glucose, fasting insulin, HOMA‐IR at baseline and 12 wk	Fasting serum glucose (mg/dL, mean ± SE) G1: 87.11 ± 1.90 G2: 87.34 ± 2.45 Fasting insulin (mU/L, mean ± SE) G1: 10.04 ± 1.07 G2: 7.81 ± 0.91 HOMA‐IR (mean ± SE) G1: 2.20 ± 0.26 G2: 1.74 ± 0.25	Change from baseline (adjusted for baseline value and BMI) Fasting serum glucose (mg/dL, mean ± SE) G1: 1.53 ± 2.11 G2: 5.38 ± 3.02 p = 0.14 Fasting insulin (mU/L, mean ± SE) G1: −1.5 ± 0.83 G2: 0.74 ± 0.99 p = 0.056 HOMA‐IR (mean ± SE) G1: −0.37 ± 0.20 G2: 0.30 ± 0.25 p = 0.017
Raygan et al. (2018) Iran	RCT G1, placebo: 30/27 G2, 200 μg Se/d: 30/26 Duration: 12 wk Aged 45–85 yr; with CHF; no use of Se supplements within the past 3 mo; no acute myocardial infarction or cardiac surgery within the past 3 mo; no renal or hepatic failure	Sex (% F): 69.81 Age (yr) G1: 68.5 ± 7.7 G2: 70.7 ± 10.3 BMI (kg/m ² ) G1: 26.2 ± 4.3 G2: 25.7 ± 4.1 Ethnicity: NR Serum/plasma Se: NR Se intake (μg/d) (through 3‐d dietary records at week 1, 5, 9 and 12) G1: 56.3 ± 7.6 G2: 55.6 ± 10.1	Selenised yeast (200 μg Se/d) vs placebo Adherence, pills count (%): > 90%	Fasting plasma glucose, fasting insulin, HOMA‐IR at baseline and 12 wk	Fasting plasma glucose (mmol/L) G1: 6.85 ± 1.92 G2: 6.18 ± 1.55 Fasting insulin (pmol/L) G1: 69.88 ± 38.49 G2: 79.33 ± 58.94 HOMA‐IR G1: 3.66 ± 2.67 G2: 4.05 ± 3.92	Change from baseline (adjusted for baseline value, age and BMI) Fasting plasma glucose (mmol/L) G1: 0.07 ± 1.07 G2: −0.42 ± 1.01 p = 0.05 Fasting insulin (pmol/L) G1: 13.73 ± 23.63 G2: −18.41 ± 27.53 p < 0.001 HOMA‐IR G1: 0.55 ± 1.20 G2: −1.01 ± 1.61 p < 0.001
Tamtaji et al. (2019) Iran	RCT G1, placebo: 30/26 G2, 200 Se μg/d: 30/26 Duration: 12 wk Aged 55–100 yr, with AD; no metabolic syndrome, diabetes, cardiovascular disease, chronic infections; no use of Se supplements	Sex: M and F Age (yr) G1: 78.5 ± 8.0 G2: 78.8 ± 10.2 BMI (kg/m ² ) G1: 21.5 ± 2.4 G2: 21.2 ± 1.2 Ethnicity: NR Serum/plasma Se: NR Se intake: NR	Selenised yeast (200 μg Se/d) vs placebo Adherence (checklist filled by a trained staff who was responsible to give the patients their supplements every day): 100%	Fasting plasma glucose, fasting insulin, HOMA‐IR at baseline and 12 wk	Fasting plasma glucose (mg/dL) G1: 88.7 ± 9.8 G2: 86.3 ± 13.7 Fasting insulin (μIU/mL) G1: 11.4 ± 2.1 G2: 11.3 ± 2.2 HOMA‐IR G1: 2.5 ± 0.6 G2: 2.4 ± 0.5	Change from baseline Fasting plasma glucose (mg/dL) G1: 1.1 ± 10.8 G2: 1.5 ± 10.0 Fasting insulin (μIU/mL) G1: 0.7 ± 2.0 G2: −1.0 ± 1.3 HOMA‐IR G1: 0.1 ± 0.4 G2: −0.2 ± 0.3

Reference

Study

Country

Design

N randomised/completed

Duration^(a)

Reftcruitment criteria

Subject characteristics at baseline^(b)

Intervention^(b)

Outcomes assessed

Results^(b)

Baseline

End of trial

Hawkes et al. (2008)

USA

RCT

G1, placebo: 27/20

G2, 300 μg Se/d: 27/22

Duration: 48 wk (+ 48 wk follow up)

Aged 19–45 yr, healthy men; non‐smokers; no use of Se shampoos, Se supplements providing > 50 μg/d, thyroid medications, weight loss

drugs, or anabolic steroids; no weight loss > 10 lb within last 6 mo; no exercise > 3 h per wk.

Sex: M

Age (yr): 18–45

BMI (kg/m ² ): NR

Ethnicity: NR

Plasma/serum Se: NR

Se intake (μg/d): 135 ± 57 (by 3‐d diet records, during the 48 wk of supplementation)

Selenised yeast (300 μg Se/d) vs placebo

Adherence, pill count (%): 93 ± 5.3%

Fasting serum glucose at baseline and at 48 wk and 96 wk

Fasting serum glucose (mmol/L)

G1: 4.83 ± 0.59

G2: 4.97 ± 0.54

Fasting serum glucose (mmol/L)

At 48 wk G1: 4.80 ± 0.46

G2: 4.90 ± 0.56

At 96 wk

G1: 5.04 ± 0.53

G2: 4.92 ± 0.44

Mesdaghinia et al. (2017)

Iran

RCT

G1, placebo: 30/30

G2, 100 Se μg/d: 30/30

Duration: 10 wk, between 17 and 27 wk of gestation

Pregnant women at risk for IUGR; no use of Se supplement during past 3 mos; non‐smokers; no hypothyroidism or hyperthyroidism, UTI, preeclampsia, HT, diseases related to increased inflammation, and kidney or liver diseases

Sex: F

Age (yr) G1: 28.1 ± 4.9

G2: 30.5 ± 5.5

BMI (kg/m ² )

G1: 22.5 ± 3.2

G2: 21.2 ± 4.2

Ethnicity: NR

Se intake: NR

Selenised yeast (100 Se μg/d) vs placebo

Adherence, pill count (%):

100

Fasting serum glucose, HOMA‐IR, HOMA‐B at baseline and after 10 wk

Fasting serum glucose (mg/dL) G1: 92.6 ± 9.6

G2: 90.4 ± 11.6

HOMA‐IR

G1: 3.5 ± 1.5

G2: 3.7 ± 1.7

HOMA‐B

G1: 57.1 ± 24.7

G2: 62.0 ± 26.0

Fasting serum glucose (mg/dL)

G1: 91.6 ± 11.6

G2: 89.2 ± 12.6

p = 0.90

HOMA‐IR

G1: 4.2 ± 2.1

G2: 3.2 ± 1.0

p = 0.02

HOMA‐B

G1: 72.5 ± 43.4

G2: 55.6 ± 21.0

p = 0.02

Navas‐Carretero et al. (2011)

Spain

RCT

G1, non‐enriched chicken: 16/13

G2, Se‐enriched chicken: 16/11

Duration: 10 wk

Aged 20–45 yr, BMI > 18.5 and < 30 kg/m², no medication or dietary treatment, and maintained weight (±3 kg) for the last 3 mo; no metabolic diseases (e.g. diabetes, thyroid impairments, other endocrine disturbances); no gastric and peptic ulcer problems, HTN, constipation, or diarrhoea

Sex: M and F

Age (yr): 20–45

BMI (kg/m ² )

G1: 24.2 ± 2.1

G2: 24.1 ± 2.7

Ethnicity: NR

Blood Se (μg/dL)

G1: 14.2 ± 1.4

G2: 14.6 ± 1.7

Se intake: NR

200 g of Se‐enriched chicken breast (25.5 Se μg/100 g), 4 times/wk, vs non‐enriched chicken breasts (6.5 Se μg/100 g)

Adherence: NR

No significant difference between groups in blood Se changes (μg/dL)

G1: +0.7 ± 0.9

G2: +0.2 ± 1.4

Fasting serum glucose, fasting insulin and HOMA‐IR at baseline and 10 wk

Fasting serum glucose (mg/dL)

G1: 81.7 ± 6.1

G2: 87.3 ± 5.1

Fasting insulin (mU/L)

G1: 4.9 ± 2.2

G2: 5.2 ± 3.6

HOMA‐IR

G1: 1.0 ± 0.5

G2: 1.1 ± 0.8

Change from baseline

Fasting serum glucose (mg/dL)

G1: −0.9 ± 4.1

G2: −5.2 ± 4.7

Fasting insulin (mU/L)

G1: 0.3 ± 2.3

G2: −0.5 ± 1.4

HOMA‐IR

G1: 0.05 ± 0.5

G2: −0.16 ± 0.32

Richie et al., 2014

USA

RCT

G1, placebo: 34/18 G2, 200 μg Se/d as SY: 33/16

G3: 285 μg Se/d as SY: 32/15

G4: 200 μg Se/d as SeMet: 31/20

Duration: 9 mo (+ 3 mo of follow‐up)

Aged 20–79 yr, healthy men, non‐smokers, normal serum PSA, no history or evidence of diabetes, prostate cancer, liver, or kidney disease, no use of Se supplements providing > 50 μg/d

Sex: M

Age (yr) G1: 48.1 ± 14.6 (22–70)

G2: 50.7 ± 16.2 (23–78)

G3: 51.3 ± 12.0 (25–72)

G4: 54.0 ± 13.4 (30–75)

BMI (kg/m ² )

G1: 30.0 ± 4.79 (22.0–38.3)

G2: 28.0 ± 3.20 (22.4–34.9)

G3: 27.8 ± 3.14 (23.7–34.2)

G4: 28.5 ± 3.79 (23.0–36.4)

Ethnicity (Caucasians, %)

G1: 94 G2: 94 G3: 87

G4: 85

Plasma Se (μg/L): ca. 137

Se intake: NR

Selenised yeast (200 or 285 μg /d) vs selenomethionine

(200 μg /d) vs placebo

Adherence, pill count (%):

Plasma Se (μg/L) at 9 mo

G1: 146

G2: 207

G3: 253

G4: 263

Fasting blood glucose at baseline and at 9 mo (data at 3, 6 and 12 mo visits not extracted)

Fasting blood glucose (mg/dL, mean ± SE)

G1: 84.7 ± 2.29

G2: 91.6 ± 1.65

G3: 82.7 ± 2.45

G4: 91.0 ± 2.07

Change from baseline

Fasting blood glucose (mg/dL, mean ± SE)

G1: 3.72 ± 2.76

G2: −1.44 ± 2.75

G3: 1.60 ± 5.31

G4: −1.75 ± 2.46

Diseased individuals

Jamilian et al. (2015)

Iran

RCT

G1, placebo: 35/35

G1, 200 μg Se/d: 35/35

Duration: 8 wk

Aged 18–40 yr, with PCOS, before menopause; no use of Se supplements and metformin in the last 3 mo; non‐smokers; no diabetes or hypothyroidism; no special diet, oral conceptive, ovulation induction agents

Sex: F

Age (yr)

G1: 25.7 ± 4.8

G2: 25.4 ± 5.1

BMI (kg/m ² )

G1: 25.2 ± 4.1

G2: 25.0 ± 3.7

Ethnicity: NR

Serum/plasma Se: NR

Se dietary intake (μg/day, mean ± SD) (by 3‐d dietary records measured at week 2, 4, 6)

G1: 58.5 ± 8.0

G2: 56.1 ± 10.5

Selenised yeast (200 μg Se/d) vs placebo

Adherence, pills count (%): > 90%

Fasting plasma glucose, fasting serum insulin, HOMA‐IR, HOMA‐B at baseline and at 8 wk

Fasting plasma glucose (mmol/L)

G1: 5.15 ± 0.39

G2: 4.91 ± 0.52

Fasting insulin (pmol/L)

G1: 73.58 ± 59.50

G2: 80.69 ± 42.28

HOMA‐IR

G1: 2.78 ± 2.25

G2: 3.00 ± 1.69

HOMA‐B

G1: 2.78 ± 2.25

G2: 3.00 ± 1.69

Change from baseline (adjusted for baseline value, age and BMI)

Fasting plasma glucose (mmol/L)

G1: 0.05 ± 0.09

G2: −0.29 ± 0.09

p = 0.010

Fasting insulin (pmol/L)

G1: 7.32 ± 9.73

G2: −28.09 ± 9.73

p = 0.012

HOMA‐IR

G1: 0.38 ± 0.39

G2: −1.11 ± 0.39

p = 0.010

HOMA‐B

G1: 3.06 ± 5.97

G2: −17.59 ± 5.97

p = 0.017

Karamali et al. (2015)

Iran

RCT

G1, placebo: 28/28

G2, 200 μg Se/d: 28/28

Duration: 6 mo

Aged 18–55 yr, with cervical intraepithelial neoplasia grade 1; no history of cervical cancer or other cancers of the lower genital tract; no history of hysterectomy or destructive therapy of the cervix; not pregnant.

Sex: F

Age (yr)

G1: 38.3 ± 9.2

G2: 38.3 ± 9.1

BMI (kg/m ² )

G1: 28.7 ± 3.9

G2: 28.6 ± 4.0

Ethnicity: NR

Serum/plasma Se: NR

Se intake: NR

Selenised yeast (200 μg Se/d) vs placebo

Adherence, pills count (%): > 90%

Fasting plasma glucose, serum insulin, HOMA‐IR, HOMA‐B at baseline and 6 mo

Fasting plasma glucose (mg/dL)

G1: 89.4 ± 8.3

G2: 94.5 ± 12.1

Fasting insulin (μIU/mL)

G1: 12.7 ± 4.4

G2: 13.9 ± 4.5

HOMA‐IR

G1: 2.8 ± 1.0

G2: 3.3 ± 1.4

HOMA‐B

G1: 48.1 ± 18.2

G2: 48.9 ± 14.0

Change from baseline (adjusted for baseline value, age and BMI) (mean ± SE)

Fasting plasma glucose (mg/dL)

G1: 0.3 ± 1.7

G2: −5.9 ± 1.7

p = 0.01

Fasting insulin (μIU/mL)

G1: 1.9 ± 1.1

G2: −4.5 ± 1.1

p < 0.001

HOMA‐IR

G1: 0.3 ± 0.2

G2: −1.2 ± 0.2

p < 0.001

HOMA‐B

G1: 9.7 ± 4.9

G2: −14.7 ± 4.9

p = 0.001

Hosseinzadeh et al. (2016)

Iran

RCT

G1, placebo: 30/27

G2, 200 μg Se/d: 30/26

Duration: 12 wk

Aged 18–42 yr, with PCOS; non‐smokers; no congenital adrenal hyperplasia, Cushing's syndrome, androgen‐secreting tumours and hyperprolactinemia; no diabetes, hypo‐ or hyperthyroidism, renal dysfunction, liver disease or cardiovascular disease; no use of medications affecting metabolic and hormonal profile; no use of Se supplement in past 3 mo.

Sex: F

Age (yr, mean ± SE)

G1: 28.90 ± 1.17

G2: 29.23 ± 0.96

BMI (kg/m ² , mean ± SE)

G1: 28.39 ± 0.72

G2: 27.4 ± 0.88

Ethnicity: NR

Serum/plasma Se: NR

Se intake (μg/d, mean ± SE) (6‐d 24‐h recall)

G1: 36.4 ± 2.5

G2: 28.3 ± 3.1

Selenised yeast (200 μg Se/d) vs placebo

Adherence, pills count (%): > 90%

Fasting serum glucose, fasting insulin, HOMA‐IR at baseline and 12 wk

Fasting serum glucose (mg/dL, mean ± SE)

G1: 87.11 ± 1.90

G2: 87.34 ± 2.45

Fasting insulin (mU/L, mean ± SE)

G1: 10.04 ± 1.07

G2: 7.81 ± 0.91

HOMA‐IR (mean ± SE)

G1: 2.20 ± 0.26

G2: 1.74 ± 0.25

Change from baseline (adjusted for baseline value and BMI)

Fasting serum glucose (mg/dL, mean ± SE)

G1: 1.53 ± 2.11

G2: 5.38 ± 3.02

p = 0.14

Fasting insulin (mU/L, mean ± SE)

G1: −1.5 ± 0.83

G2: 0.74 ± 0.99

p = 0.056

HOMA‐IR (mean ± SE)

G1: −0.37 ± 0.20

G2: 0.30 ± 0.25

p = 0.017

Raygan et al. (2018)

Iran

RCT

G1, placebo: 30/27

G2, 200 μg Se/d: 30/26

Duration: 12 wk

Aged 45–85 yr; with CHF; no use of Se supplements within the past 3 mo; no acute myocardial infarction or cardiac surgery within the past 3 mo; no renal or hepatic failure

Sex (% F): 69.81

Age (yr)

G1: 68.5 ± 7.7

G2: 70.7 ± 10.3

BMI (kg/m ² )

G1: 26.2 ± 4.3

G2: 25.7 ± 4.1

Ethnicity: NR

Serum/plasma Se: NR

Se intake (μg/d) (through 3‐d dietary records at week 1, 5, 9 and 12)

G1: 56.3 ± 7.6

G2: 55.6 ± 10.1

Selenised yeast (200 μg Se/d) vs placebo

Adherence, pills count (%): > 90%

Fasting plasma glucose, fasting insulin, HOMA‐IR at baseline and 12 wk

Fasting plasma glucose (mmol/L)

G1: 6.85 ± 1.92

G2: 6.18 ± 1.55

Fasting insulin (pmol/L)

G1: 69.88 ± 38.49

G2: 79.33 ± 58.94

HOMA‐IR

G1: 3.66 ± 2.67

G2: 4.05 ± 3.92

Change from baseline (adjusted for baseline value, age and BMI)

Fasting plasma glucose (mmol/L)

G1: 0.07 ± 1.07

G2: −0.42 ± 1.01

p = 0.05

Fasting insulin (pmol/L)

G1: 13.73 ± 23.63

G2: −18.41 ± 27.53

p < 0.001

HOMA‐IR

G1: 0.55 ± 1.20

G2: −1.01 ± 1.61

p < 0.001

Tamtaji et al. (2019)

Iran

RCT

G1, placebo: 30/26

G2, 200 Se μg/d: 30/26

Duration: 12 wk

Aged 55–100 yr, with

AD; no metabolic syndrome, diabetes, cardiovascular disease, chronic infections; no use of Se supplements

Sex: M and F

Age (yr)

G1: 78.5 ± 8.0

G2: 78.8 ± 10.2

BMI (kg/m ² )

G1: 21.5 ± 2.4

G2: 21.2 ± 1.2

Ethnicity: NR

Serum/plasma Se: NR

Se intake: NR

Selenised yeast (200 μg Se/d) vs placebo

Adherence (checklist filled by a trained staff who was responsible to give the patients their supplements every day): 100%

Fasting plasma glucose, fasting insulin, HOMA‐IR at baseline and 12 wk

Fasting plasma glucose (mg/dL)

G1: 88.7 ± 9.8

G2: 86.3 ± 13.7

Fasting insulin (μIU/mL)

G1: 11.4 ± 2.1

G2: 11.3 ± 2.2

HOMA‐IR

G1: 2.5 ± 0.6

G2: 2.4 ± 0.5

Change from baseline

Fasting plasma glucose (mg/dL)

G1: 1.1 ± 10.8

G2: 1.5 ± 10.0

Fasting insulin (μIU/mL)

G1: 0.7 ± 2.0

G2: −1.0 ± 1.3

HOMA‐IR

G1: 0.1 ± 0.4

G2: −0.2 ± 0.3

AD: Alzheimer's disease; BMI: body mass index; CHF: congestive heart failure; d: day; F: females; Gx: group x; HOMA‐IR: Homeostatic model assessment of insulin resistance; HOMA‐B: Homeostatic model assessment of β‐cell function; HTN: hypertension; IUGR: intrauterine growth restriction; M: males; mo: month; NR: not reported; PCOS: polycystic ovary syndrome; PSA: prostate specific antigen; RCT: randomised controlled trial; SD: standard deviation; SE: standard error; Se: selenium; SeMet: selenomethionine; SY: selenised yeast; USA: United States of America; UTI: urinary tract infection; wk: week; yr: year.

(a) Duration = duration of the treatment phase, unless specified otherwise.

(b): Mean ± SD, unless specified otherwise.