Table 2.
Characteristics of the included studies.
| Sample Size, Sex | Participant, Age (Years) | Sample Size, Sex | Intervention/Control | Lycopene Dosage Per Day | Duration (Intake Period) | Outcome (Blood Biomarkers of Glucose Metabolism) | Study Design |
|---|---|---|---|---|---|---|---|
| Olfer’ev 2004 [36], Russia |
Type 2 diabetic postmenopausal women, mean age 66.4 | I: 20 (all F) C: 15 (all F) |
I: Tomato extract capsule (3/day) C: Placebo capsule (3/day) |
I: 30 mg C: 0 mg |
12 weeks | FBG | RCT-P |
| Engelhard 2006 [37], Israel |
Grade-1 hypertensive subjects, age range 30–73 | I: 31 (13 F/18 M) C: 31 (13 F/18 M) |
I: Tomato extract capsule (1/day) C: Placebo capsule (1/day) |
I: 15 mg C: 0 mg |
8 weeks | FBG | non-RCT-C |
| Devaraj 2008 [39], USA | Healthy subjects, age range ≥40 | I1: 21 (17 F/4 M) I2: 17 (13 F/4 M) I3: 21 (14 F/7 M) C: 18 (14 F/4 M) |
I1: Lycopene capsule (1/day) I2: Lycopene capsule (1/day) I3: Lycopene capsule (1/day) C: Placebo capsule (1/day) |
I1: 6.5 mg I2: 15 mg I3: 30 mg C: 0 mg |
8 weeks | FBG | RCT-P |
| Thies 2012 [41], UK | Moderate overweight subjects, age range 40–65 | I1: 68 (40 F/28 M) I2: 81 (46 F/35 M) C: 76 (46 F/30 M) |
I1: Low-tomato diet and tomato extract capsule (1/day) I2: High-tomato diet C: Low-tomato diet |
I1: 10 mg I2: 32–50 mg C: 0.3 mg |
12 weeks | FBG Insulin HOMA-IR QUICKI |
RCT-P |
| Zeng 2013 [42], China | Type 2 diabetic patients, age range ≥60 | I: 58 C: 59 |
I: Lycopene capsule (4/day) C: Placebo capsule (4/day) |
I: 30 mg C: 0 mg |
6 months | FBG PBG HbA1c |
RCT-P |
| Tsitsimpikou 2014 [44], Greece | Metabolic syndrome subjects, mean age 54.9 | I: 15 (2 F/13 M) C: 12 (1 F/11 M) |
I: Tomato juice C: None |
I: NA C: 0 mg |
2 months | FBG Insulin FIRI |
non-RCT-P |
| Deplanque 2016 [45], France | Healthy subjects, mean age 34.9 | I: 75 C: 70 |
I: Tomato extract capsule (1/day) C: Placebo capsule (1/day) |
I: 15 mg C: 0 mg |
2 weeks | FBG | RCT-P |
| Chernyshova 2019 [46], Russia | Healthy subjects, mean age 33.4 | I: 10 (5 F/5 M) C: 10 (5 F/5 M) |
I: Lycopene-enriched ice cream (50 g/day) C: Ice cream (50 g/day) |
I: 7 mg C: 0 mg |
4 weeks | FBG | RCT-C |
| Nishimura 2019 [47], Japan |
Healthy subjects, age range 30–70 | I: 49 C: 49 |
I: Semidried high-lycopene tomato (50 g/day) C: Semidried lycopene-free tomato (50 g/day) |
I: 22.0–27.8 mg C: 0 mg |
12 weeks | FBG HbA1c HOMA-IR |
RCT-P |
| Takagi 2020 [49], Japan | Obese men, age range 40–65 | I1: 7 (all M) I2: 5 (all M) C1: 7 (all M) C2: 5 (all M) |
I1: Carrot and kale juice (high lycopene + high lutein) (200 mL/day) I2: Carrot and cabbage juice (high lycopene + low lutein) (200 mL/day) C1: Carrot and kale juice (low lycopene + high lutein) (200 mL/day) C2: Carrot and cabbage juice (low lycopene + low lutein) (200 mL/day) |
I1: 7.56 mg I2: 8.6 mg C1: 0 mg C2: 0 mg |
8 weeks | FBG | RCT-P |
I, intervention group; C, control group; F, female; M, male; FBG, fasting blood glucose; HOMA-IR, homeostasis model assessment-insulin resistance; QUICKI, Quantitative Insulin-Sensitivity Check Index; PBG, postprandial blood glucose; HbA1c, Hemoglobin A1c; FIRI, Fasting Insulin Resistance Index; RCT-P, randomized controlled parallel trial; RCT-C, randomized controlled crossover trial; NA, not available.