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Nutrients 2019, 11, 1177; doi:10.3390/nu11051177 www.mdpi.com/journal/nutrients
Article
Effect of 12-Week Daily Intake of the High-Lycopene
Tomato (Solanum Lycopersicum), A Variety Named
“PR-7”, on Lipid Metabolism: A Randomized,
Double-Blind, Placebo-Controlled, Parallel-Group
Study
Mie Nishimura
1
, Naoki Tominaga
2
, Yuko Ishikawa-Takano
3
, Mari Maeda-Yamamoto
4
and
Jun Nishihira
1,
*
1
Department of Medical Management and Informatics, Hokkaido Information University, Ebetsu,
Hokkaido 069-8585, Japan; mnishimura@do-johodai.ac.jp
2
Plant Breeding ＆ Experiment Station, Takii & Co., Ltd., Konan, Shiga 520-3231, Japan; naoki-
tominaga@takii.co.jp
3
Functional Food Factor Laboratory, Food Function Division, National Food Research Institute, National
Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki 305-8642, Japan; yuko@affrc.go.jp
4
National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki 305-8517, Japan;
marimy@affrc.go.jp
* Correspondence: nishihira@do-johodai.ac.jp; Tel.: +81-011-385-4411
Received: 18 April 2019; Accepted: 22 May 2019; Published: 25 May 2019
Abstract: Tomato (Solanum lycopersicum) is a rich source of lycopene, a carotenoid that confers
various positive biological effects such as improved lipid metabolism. Here, we conducted a
randomized, double-blind, placebo-controlled, parallel-group comparative study to investigate the
effects of regular and continuous intake of a new high-lycopene tomato, a variety named PR-7, for
12 weeks, based on 74 healthy Japanese subjects with low-density lipoprotein cholesterol (LDL-C)
levels ≥120 to <160 mg/dL. The subjects were randomly assigned to either the high-lycopene tomato
or placebo (lycopene-free tomato) group. Each subject in the high-lycopene group ingested 50 g of
semidried PR-7 (lycopene, 22.0–27.8 mg/day) each day for 12 weeks, while subjects in the placebo
group ingested placebo semidried tomato. Medical interviews were conducted, vital signs were
monitored, body composition was determined, and blood and saliva samples were taken at weeks
0 (baseline), 4, 8, and 12. The primary outcome assessed was LDL-C. The intake of high-lycopene
tomato increased lycopene levels in this group compared to levels in the placebo group (p < 0.001).
In addition, high-lycopene tomato intake improved LDL-C (p = 0.027). The intake of high-lycopene
tomato, PR-7, reduced LDL-C and was confirmed to be safe.
Keywords: LDL-cholesterol; lipid metabolism; lycopene; PR-7; randomized controlled trial;
semidried tomato.
1. Introduction
Dyslipidemia is a major risk factor for coronary heart disease, and in Japan, the number of
patients with this condition is increasing. Through a survey, the Ministry of Health, Labor and
Welfare reported that 2.1 million patients received treatment for this condition in 2014. It is well
known that dietary improvements are important for the prevention of dyslipidemia, and research on
functional foods that affect lipid metabolism is receiving increased attention. In 2015, the system of
Nutrients 2019, 11, 1177 2 of 13
“Foods with Function Claims” was established in Japan. As this system permits health claims for
fresh vegetables, the research on and development of such vegetables containing highly functional
components, also known as “functional vegetables”, is expected.
Lycopene, a carotenoid, has antioxidant effects and exhibits the highest physical quenching rate
constant for singlet oxygen [1]. It has also been reported to inhibit the production of serum lipid
peroxide and oxidize low-density lipoprotein (LDL) in a concentration-dependent manner [2]. A
previous clinical trial with obese subjects suggested that the continuous ingestion of a diet containing
high lycopene increased serum high-density lipoprotein (HDL)-2 and HDL-3, which are subtypes of
HDL cholesterol (HDL-C) [3]. The biological mechanism was suggested to be through a reduction in
3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase activity in the liver [4], activation
of LDL-receptors [5], and increased expression of the ABCA1 transporter gene, which is the key
component of HDL-C production [6]. An epidemiological survey also revealed that the continuous
intake of lycopene contributes to the prevention of prostate cancer [7] and reduces risks related to the
onset of cardiovascular disease [8].
Tomato (Solanum lycopersicum) is the main source of lycopene, possessing an amount that
normally ranges from 3 to 5 mg lycopene per 100 g of raw tomato [9]. Takii & Co., Ltd. succeeded in
breeding a high-lycopene tomato variety named “PR-7” (GOCHISO TOMATO), using a high-
lycopene line selected from an edible tomato. PR-7 contains more lycopene than conventional
tomatoes. This makes it possible to obtain the required amounts of lycopene from raw tomatoes to
improve lipid metabolism. In addition, PR-7 contains high amounts of glutamic acid.
The effects of lycopene and tomato on lipid metabolism have been shown in previous clinical
trials; however, almost all trials used tomato juice or tomato extract as the test food in double-blind,
placebo-controlled studies [10–12]. This is because it is difficult to produce a placebo for raw tomato
and to deliver such food products to subjects. We therefore opted to produce semidried tomato
(semidried tomato contained 22% water content) and used lycopene-free tomato as the placebo. By
using this test food in a double-blind, placebo-controlled study, we demonstrated that semidried
tomato is similar to raw tomato and its lycopene-induced effect is the same as that of processed
tomato such as juice or extract.
In 2017, we conducted a pilot clinical trial called “Effect of Daily Ingestion of High-Lycopene
Tomato PR-7 on Lipid Metabolism for 8 Weeks: A Randomized, Double-Blind, Placebo-Controlled,
Parallel-Group (UMIN registration number: UMIN000026524)”. In this pilot study, continuous intake
of 50 g of semidried PR-7 for 8 weeks tended to improve the lipid profile; therefore, we expected that
the effect of ingesting high-lycopene tomato on lipid metabolism could be improved by extending
the intake period.
Thus, we conducted a randomized, double-blind, placebo-controlled, parallel-group
comparative study to evaluate the effects of continuous intake of PR-7 for 12 weeks using healthy
subjects with LDL-C levels ≥120 to <160 mg/dL.
2. Materials and Methods
2.1. Study Design
This placebo-controlled, randomized, double-blind, parallel-group comparative study was
conducted at Hokkaido Information University, Health Information Science Research Center (Ebetsu,
Hokkaido, Japan). The schedule for the trial is summarized in Table 1. Written informed consent was
obtained from subjects on their first visit prior to being enrolled. The subjects ingested 50 g semidried
tomato (active or placebo) every day for 12 weeks without cooking. Medical interviews,
measurements of vital signs and body composition, saliva and urinary assessments, and
hematological and biological assessments were conducted during the second (week 0; baseline), third
(week 4), fourth (week 8), and fifth (week 12) visits. In addition, all subjects completed a Food
Frequency Questionnaire Based on Food groups (FFQg) (Kenpakusha, Tokyo, Japan) at visits 2–4.
During the entire course of this study, subjects were asked to maintain their daily activities including
food consumption and exercise habits, to avoid any supplements, tomatoes, and processed foods
Nutrients 2019, 11, 1177 3 of 13
containing tomatoes, and to avoid drinking any vegetable juices; the test food was the only tomato
derivative that was allowed to be consumed. The subjects used a diary to record their daily activities,
which was reviewed by a medical doctor or nurse at each visit.
The primary outcome assessed was the change in LDL-C. Secondary outcomes assessed were as
follows: lipid profiles comprising total cholesterol (TC), HDL-C, triglycerides (TG), LDL-C/HDL-C
ratio, and non-HDL; adiponectin; serum lycopene; serum β-carotene; malondialdehyde LDL-C
(MDA-LDL); lectin-like oxidized LDL receptor-1 (LOX) index; soluble LOX LDL receptor-1 (sLOX-
1); LOX-1 ligand containing apolipoprotein B (LAB); lipid peroxidases (LPO); saliva volume; salivary
chromogranin A (CGA); results of the visual analog scale (VAS) questionnaire on fatigue and stress;
the Profile of Mood States Second Edition (POMS-2) full-length version for adults. The efficacy of the
active test food was evaluated at week 12 and its safety at weeks 4, 8, and 12.
Table 1. Clinical trial schedule.
POMS-2: Profile of Mood States Second Edition; ●: performed.
2.2. Study Subjects
We screened 234 volunteers on their first visit, and all provided written informed consent to
participate in this study. After screening, 100 healthy Japanese subjects were enrolled in the study
(ages, ≥30 to <70 years; LDL-C, ≥120 to <160 mg/dL). The range of LDL-C was based on the “Guideline
for Prevention of Arteriosclerosis Disease” published by the Japan Atherosclerosis Society. It defines
the range of 120–139 mg/dL as representing borderline high cholesterol and the range of 140–159
mg/dL as indicating mild hypercholesterolemia. Inclusion and exclusion criteria are summarized in
Table 2. The eligible subjects were randomly assigned to either the active test food (PR-7) or placebo
food (lycopene-free tomato) groups stratified by sex, age, and LDL-C during the first visit.
Assignments were computer generated based on stratified block randomization at a third-party data
center (Media Educational Center, Hokkaido Institute of Information Technology, Ebetsu, Hokkaido,
Japan). Medical doctors, nurses, clinical research coordinators, and statistical analysts were blinded
to the assignment information during the trial period. The test foods were controlled by the food-
controlled numbers printed on the food package. The information was disclosed only after all
analytical data were collected and the subjects in the efficacy analysis and the method used for
statistical analyses were finalized.
Item Guidance &
Agreement Screening Randomization Test Food-Intake Period
Week 0 Week 4 Week 8 Week 12
Visit Visit 1 － Visit 2 Visit 3 Visit 4 Visit 5
Date Apr 20–23, 2018 May 21, 2018 June 9–
11, 2018
July 7–9,
2018
Aug 4–6,
2018
Sept 1–3,
2018
Medical interview ● ● ● ● ●
Vital sign
measurement
● ● ● ● ●
Body composition
measurement
● ● ● ● ●
Blood sampling ● ● ● ● ●
Urinary and
salivary test
● ● ● ●
VAS questionnaire
and POMS-2
● ● ● ●
Food Frequency
Questionnaire
● ● ● ●
Nutrients 2019, 11, 1177 4 of 13
Table 2. Inclusion and exclusion criteria.
Inclusion
criteria
1. Age, ≥30 years and <70 years old
2. LDL-C, ≥120 m
g
/dL and <160 m
g
/dL
Main exclusion
criteria
1. Sub
j
ects who
p
artici
p
ated in the
p
ilot stud
y
2. Sub
j
ects who usuall
y
do not consume raw tomatoes
3. Sub
j
ects who usuall
y
consume tomato
j
uice
4. Sub
j
ects under
p
h
y
sician’s advice, treatment, and/or medication for d
y
sli
p
idemia and/or diabetes
5. Sub
j
ects with a BMI ≥30 k
g
/m2
6. Sub
j
ects with familial h
yp
ercholesterolemia
7. Subjects with serious cerebrovascular, cardiac, hepatic, renal, gastrointestinal diseases, and/or
affected
by
infectious diseases re
q
uirin
g
re
p
orts to the authorities
8. Subjects with a major surgical history relevant to the digestive system, such as gastrectomy,
g
astrorrha
p
h
y
, enterectom
y
, etc.
9. Sub
j
ects with unusuall
y
hi
g
h and/or low blood
p
ressure and/or abnormal hematolo
g
ical data
10. Sub
j
ects with severe anemia
11. Pre- or
p
ost-meno
p
ausal women com
p
lainin
g
of obvious
p
h
y
sical chan
g
es
12. Subjects at risk of allergic reactions to drugs or foods especially due to tomato, Japanese cedar,
J
a
p
anese c
yp
ress, or
g
rass
13. Subjects who regularly take medications, functional foods, and/or supplements, which would affect
b
lood li
p
id and/or
g
lucose metabolism
14. Alcohol addicts or sub
j
ects with an eatin
g
disorder
15. Subjects who donated either 400 mL of whole blood within 16 weeks (women) or 12 weeks (men),
200 mL of whole blood within 4 weeks (men and women), or blood components within 2 weeks (men
and women
)
p
rior to the current stud
y
.
16. Pre
g
nant or lactatin
g
women or women who ex
p
ect to be
p
re
g
nant durin
g
this stud
y
17. Subjects who currently participate in other clinical trials or have participated in a trial within the last
4 weeks
p
rior to the current stud
y
18. Any other medical and/or health reasons unfavorable to participation in the current study, as judged
by
the
p
rinci
p
al investi
g
ator
2.3. Preparation of the Test Food
The tomato, a variety named PR-7 (Solanum lycopersicum) that was bred by Takii & Co, Ltd
(Kyoto, Japan) and harvested from Kasai (Hyogo, Japan) and Hokuto (Yamanshi, Japan), was used
as the active test food; a lycopene-free tomato harvested from Ishii-cho (Tokushima, Japan) was used
as the placebo. To prepare the semidried tomato: 1) raw tomatoes were disinfected; 2) the calyx on
each tomato was removed prior to slicing; 3) slices were dried and vacuum-packed; 4) packed tomato
was disinfected and refrigerated; 5) bacterial tests, physicochemical tests, and sensory inspections
were conducted. Analyses of the nutrient composition of the active test food and the placebo were
conducted using the methods established by the Japan Food Research Laboratories (Hokkaido,
Japan) and are presented in Table 3. Lycopene was measured using nine randomly extracted samples.
β-Carotene level was measured using high-performance liquid chromatography at Takii & Co., Ltd.
The levels of calories and carbohydrates were different between test foods. However, compared to
the daily intake of nutrition from the diet, this difference was insignificant; therefore, we considered
that this would not affect our data. The active test food and placebo were prepared under strict
quality-control protocols and were identical in appearance.
Table 3. Nutrient compositions of the active test and placebo foods based on daily consumption.
Nutrient Active Test Food Placebo Food
Calories (kcal) 57.5 45.7
Water (g) 33.2 36.5
Proteins (g) 2.1 2.1
Lipids (g) 0.4 0.4
Carbohydrates (g) 12.8 9.8
Ash (g) 1.7 1.2
Total fiber (g) 2.6 2.6
Sodium (mg) 3.1 2.3
Lycopene (mg) 22.0–27.8 n.d.
β-Carotene (mg) 2.8-3.3 n.d.
n.d.: not detected.
Nutrients 2019, 11, 1177 5 of 13
2.4. Physical, Hematological, Biological, Urinary, and Salivary Assessments
Blood was collected from subjects after a 12-h fast and used for the following hematological
examinations: white blood cell (WBC), red blood cell (RBC), hemoglobin (Hb), hematocrit (Ht), and
blood platelet (Plt) counts. Biological examinations included the following: liver function (aspartate
aminotransferase [AST], alanine aminotransferase [ALT], gamma-glutamyl transpeptidase [γ-GTP],
alkaline phosphatase [ALP], and lactate dehydrogenase [LDH]); renal function (blood urea nitrogen
[BUN], creatinine [CRE], and uric acid [UA]); lipid profiles (TC, LDL-C, HLD-C, and TG); blood
glucose profiles (fasting plasma glucose [FPG], hemoglobin [Hb]A1c, and homeostatic model
assessment of insulin resistance [HOMA-IR]); adiponectin levels; serum carotenoids (lycopene and
β-carotene); and oxidative markers (MDA-LDL, LOX index, sLOX-1, LAB, and LPO).
Saliva was collected using a Salivette® Cotton Swab (Sarstedt K.K., Tokyo, Japan); subjects were
asked to chew the swab for 60 s to stimulate salivation. Saliva volume and chromogranin A (CGA)
were then assessed.
Urine was first collected in the morning, from which, pH, sugar, protein, occult blood,
urobilinogen, and ketones were qualitatively assessed.
Blood, saliva, and urine tests were analyzed at Sapporo Clinical Laboratory, Inc. (Hokkaido,
Japan). Measurements of serum carotenoid and oxidative markers were analyzed at NK Medico Co.,
Ltd (Tokyo, Japan). Body composition and blood pressure were measured using a Body Composition
Analyzer DC-320 (Tanita Corp, Tokyo, Japan) and an Automatic Blood Pressure Monitor HEM-
7080IC (Omron Co., Ltd., Kyoto, Japan), respectively.
2.5. VAS Questionnaire Assessing Fatigue, Stress, and Profile of Mood States
To evaluate the effects of high-lycopene tomato on fatigue and stress, subjects completed a VAS
questionnaire with eight questions assessing fatigue and stress. Subjects were instructed to place an
“X” along a 100-mm line to provide a rating from the worst to the best condition for each question
based on their current health condition. The left end of the line (0 mm) was defined as the worst
condition and the right end (100 mm), the best condition. The questionnaire results were assessed by
evaluating the length from the beginning of the line on the left to the “X.” An increase in VAS score
indicated an improvement in each symptom.
The POMS-2 questionnaire was used to evaluate the effects of high-lycopene tomato on mood
[13]. Total Mood Disturbance (TMD) scores were assessed using the POMS-2 full version for adults,
which comprised 65 questions (Success Bell, Tokyo, Japan). Subjects selected from five answers
ranging from “not at all” to “quite a lot” based on their mood state over the previous week.
2.6. Food Frequency Questionnaire
The FFQg is a semi-quantitative dietary assessment and is used to estimate nutrient intake based
on the subjects’ regular diet [14,15]. This questionnaire comprised 29 food groups and 10 types of
cooking methods. For each question, subjects reported the weekly amount and frequency of food
intake for the past month at each visit, from which regular and nutrient intakes (calories, protein, fat,
carbohydrates, dietary fiber, and salt) were estimated.
2.7. Assessment of Safety
We further assessed the incidence of adverse effects or symptoms and abnormal changes in
laboratory variables. The severity of adverse effects and their relation to the test food were classified
according to protocol criteria set by the investigator. Laboratory variables were assessed according
to the guideline of side effect criteria defined by the Japanese Society of Chemotherapy [16]. All
adverse effects were reported as follows: symptoms, occurrence date, severity, relation to test food,
continuation or discontinuation, treatment, and outcome. Adverse effects were monitored during the
intervention for 12 weeks.
Nutrients 2019, 11, 1177 6 of 13
2.8. Ethics
The current clinical trial was conducted in compliance with the ethical guidelines on medical
research with humans (Ministry of Education, Culture, Sports, Science and Technology, and Ministry
of Health, Labor and Welfare) and the Declaration of Helsinki (revised by the Fortaleza General
Meeting of the World Medical Association). The trial protocol was approved by the ethics committee
of Hokkaido Information University (Ebetsu, Hokkaido, Japan; approved on 21 February, 2018;
approval number: 2017-25). This trial is registered at www.umin.ac.jp/ctr/index.htm (registered on
29 March, 2018; registration number: UMIN000031975).
2.9. Statistical Analysis
Student’s t-tests were used to analyze primary and secondary outcomes, hematological and
biological examinations, and food frequency questionnaire values by comparing the changes in
subject values between the two groups. Changes in subject values were analyzed using repeated
measures of analysis of variance between groups. For subject characteristics, t Fisher’s exact
probability test was used for sex and the Mann–Whitney U-test was used for intake rate; Student’s t-
tests were used for other subject characteristics. Based on subgroup analysis, we analyzed LDL-C in
subjects for whom LDL-C levels were 120–139 mg/dL (borderline high cholesterol subjects) and 140–
159 mg/dL (mild hypercholesterolemia subjects). All statistical analyses were performed using SPSS
v. 25 (IBM Japan, Ltd., Tokyo, Japan), and p < 0.05 was considered statistically significant.
2.10. Sample Size
Prior to this study, we conducted a placebo-controlled, double-blind, parallel-group comparison
test (registered at www.umin.ac.jp/ctr/index.htm; registration number, UMIN000026524; date of
registration, 13 March, 2017) over an 8-week intake period with the same dosages used in this trial.
Based on preliminary data, the sample size was calculated to detect an intergroup difference of 8.70
with respect to changes in LDL-C from baseline to week 8 (SD = 13.7) and an effect size of 0.63 using
a two-sided paired t-test with a statistical power of 80% and an α of 5%. These results indicated that
a sample size of 80 (40 in each group) was necessary. Assuming a 20% loss in follow-up, 100 subjects
(50 in each group) were enrolled.
3. Results
3.1. Subject Dropouts and Characteristics
Subject involvement throughout the trial period is presented in Figure 1. Subjects who provided
informed consent (n = 234) were assessed for eligibility, and after the screening, 100 subjects were
enrolled in this study. All enrolled subjects were randomized into one of the two intervention groups
(placebo group, n = 50; active test food group, n = 50). Prior to trial initiation, two subjects dropped
out because of personal reasons, one subject dropped out because of difficulty ingesting the test food,
three subjects dropped out because of personal reasons after the study began, and one subject
dropped out after beginning other medical treatments. Finally, 93 subjects completed this trial—47
in the active test food group and 46 in the placebo group. There was no reason to stop this study in
the middle, and we did not conduct an interim analysis; therefore, the study was completed as
planned on 3 September 2018. Ninety-eight subjects, excluding the two subjects who dropped out
because of personal reasons before the start of the trial, were included in the safety analysis. We
excluded 19 subjects in the efficacy analysis because of abnormal value variations from mild sickness
or disordered lifestyle (n = 5), compliance problems (n = 3), missing primary outcomes due to absence
(n = 1), not being accustomed to eating raw tomatoes (n = 6), and regularly drinking tomato juice (n =
4). The efficacy analysis comprised 33 subjects in the active test food group and 41 in the placebo
group. Sex ratio, mean age, height, body mass index (BMI), LDL-C at visit 1, and the intake rate for
each group are presented in Table 4. These characteristics did not significantly differ between the two
groups, confirming the appropriate allocation of the number of subjects to each group.
Nutrients 2019, 11, 1177 7 of 13
Figure 1. Subject selection.
Table 4. Characteristics of subjects and intake rates of test foods in the active test food and placebo
groups.
Characteristic Placebo Active p
Subjects, n 41 33 -
Male, n 17 8 0.14
Age, years 53.9 ± 9.1 53.7 ± 7.8 0.91
Height, cm 162.7 ± 8.8 160.4 ± 8.3 0.27
Body mass index, kg/m
2
21.7 ± 2.8 22.1 ± 3.0 0.59
LDL cholesterol, mg/dL 137.3 ± 12.4 139.2 ± 12.5 0.51
Intake rate, % 99.8 ± 0.5 99.9 ± 0.4 0.45
3.2. Effect of High-Lycopene Tomato on LDL-C
The intake of the active test food significantly improved LDL-C in this group compared to that
in the placebo group (∆Week 12: placebo, 4.1 ± 15.7 mg/dL; high-lycopene tomato, −3.7 ± 13.8 mg/dL;
p = 0.027; Figure 2, Table 5). Based on a subgroup analysis, LDL-C was significantly decreased at week
12 (∆Week 12: placebo, 4.3 ± 15.1 mg/dL; high-lycopene tomato, −5.1 ± 9.5 mg/dL; p = 0.030) following
the ingestion of high-lycopene tomato in subjects with LDL-C ranging from 120–139 mg/dL (Table 5).
In subjects with LDL-C ranging from 140–159 mg/dL, LDL-C decreased at week 12 but this was not
significant (Table 5).
Nutrients 2019, 11, 1177 8 of 13
Table 5. Lipid profiles and adiponectin levels for the placebo and active food test groups.
Variable Week 0 ∆Week 4 ∆Week 8 ∆Week 12 Time × Food Interaction
,
p
b
LDL-C (mg/dL)
Placebo (n = 41) 133.4 ± 15.6 1.9 ± 12.1 −4.0 ± 12.4 4.1 ± 15.7
0.13 Active (n = 33) 140.2 ± 16.9 −0.2 ± 15.5 −5.9 ± 13.0 −3.7 ± 13.8
p
a
0.078 0.514 0.511 0.027 *
LDL-C
subjects whose
LDL-C was 120–
139 mg/dL
(mg/dL)
Placebo (n = 41) 122.1±10.1 1.8±8.5 -2.0±10.6 4.3±15.1
0.048 *
Active (n = 33) 127.8±10.1 3.2±11.9 -6.2±7.8 -5.1±9.5
p
a
0.100 0.686 0.180 0.030 *
LDL-C
subjects whose
LDL-C was 140–
159 mg/dL
(mg/dL)
Placebo (n = 41) 143.2 ± 12.6 2.0 ± 14.9 −5.7 ± 13.9 4.0 ± 16.6
0.354
Active (n = 33) 153.4 ± 11.8 −3.9 ± 18.3 −5.6 ± 17.2 −2.2 ± 17.5
p
a
0.016* 0.286 0.981 0.276
TC (mg/dL)
Placebo (n = 41) 222.5 ± 23.9 0.9 ± 15.1 −1.5 ± 18.0 7.9 ± 21.7
0.20
Active (n = 33) 231.8 ± 24.6 −1.6 ± 18.5 −1.3 ± 17.0 1.2 ± 19.1
p
a
0.10 0.51 0.96 0.17
HDL-C (mg/dL)
Placebo (n = 41) 75.2 ± 17.5 −1.0 ± 5.8 −1.9 ± 7.5 −0.6 ± 8.4
0.76
Active (n = 33) 80.7 ± 17.4 −3.0 ± 7.3 −3.0 ± 6.5 −2.7 ± 7.8
p
a
0.18 0.21 0.49 0.27
TG (mg/dL)
Placebo (n = 41) 86.6 ± 30.7 −2.4±25.5 −3.7 ± 28.5 0.4 ± 24.8
0.83
Active (n = 33) 80.8 ± 32.8 −3.2±24.1 −0.9 ± 20.6 3.2 ± 31.2
p
a
0.43 0.89 0.64 0.66
LDL-C/HDL-C
ratio
Placebo (n = 41) 1.9 ± 0.4 0.1 ± 0.2 0.0 ± 0.2 0.1 ± 0.2
0.24
Active (n = 33) 1.8 ± 0.4 0.1 ± 0.2 0.0 ± 0.2 0.0 ± 0.2
p
a
0.67 0.67 0.72 0.33
non-HDL (mg/dL)
Placebo (n = 41) 147.3 ± 15.9 1.9 ± 14.0 0.4 ± 14.1 8.5 ± 17.0
0.20
Active (n = 33) 151.2 ± 16.9 1.4 ± 14.1 1.8 ± 13.2 3.9 ± 15.6
p
a
0.32 0.87 0.67 0.24
Adiponectin
(μg/mL)
Placebo (n = 41) 10.9 ± 5.9 −0.3 ± 1.1 −0.6 ± 1.3 −0.5 ± 1.2
0.005 **
Active (n = 33) 13.6 ± 7.1 0.1 ± 1.1 −0.6 ± 1.4 −1.0 ± 1.0
p
a
0.085 0.17 0.97 0.053
Values are shown as the mean ± standard deviation. p
a
: Student’s t-test was performed. p
b
: repeated
measures of analysis of variance was performed. * p < 0.05, ** p < 0.01 vs. placebo group. ∆Week 4: changes
in values from baseline to week 4; ∆Week 8: changes in values from baseline to week 8; ∆Week 12:
changes in values from baseline to week 12; LDL-C: low-density lipoprotein cholesterol; TC: total
cholesterol; HDL-C: high-density lipoprotein cholesterol; TG: triglycerides; LDL-C/HDL-C ratio: LDL
cholesterol/HDL cholesterol ratio; non-HDL: non-low-density lipoprotein cholesterol.
Figure 2. Changes in low-density lipoprotein cholesterol (LDL-C) in all subjects. A Student’s t-test
was conducted for data analysis. Statistical significance: * p < 0.05 vs. placebo group. Values are
presented as the mean ± standard error. Number of subjects (n): placebo: n = 41, active: n = 33.
3.3. Effect of High-Lycopene Tomato on Lipid Profile and Adiponectin Levels
The effects of high-lycopene tomato on lipid profiles comprising TC, LDL-C, HDL-C, TG, LDL-
C/HDL-C ratio, and non-HDL and on adiponectin are summarized in Table 5. There were no
Nutrients 2019, 11, 1177 9 of 13
differences between the high-lycopene tomato and placebo groups in terms of changes in these
parameters.
3.4. Effect of High-Lycopene Tomato on Serum Carotenoid Levels
To confirm the effects of high-lycopene tomato on serum carotenoid levels, changes in lycopene
and β-carotene contents were evaluated (Table 6). The intake of high-lycopene tomato increased
lycopene levels compared to the corresponding levels in the placebo group (∆Week 12: placebo, −24.2
± 49.3 μg/dL; high-lycopene tomato, 22.7 ± 47.9 μg/dL; p < 0.001). In addition, β-carotene levels
increased in the high-lycopene tomato group compared to those in the placebo group at week 12
(∆Week 12: placebo, −0.9 ± 13.6 μg/dL; high-lycopene tomato, 12.0 ± 24.5 μg/dL; p = 0.009).
Table 6. Serum carotenoid levels for the placebo and active food test groups.
Variable Week 0 ∆Week 4 ∆Week 8 ∆Week 12 Time × Food Interaction
,
p b
Lycopene
(μg/dL)
Placebo (n = 41) 75.2 ± 45.9 −26.1 ± 36.2 −20.5 ± 47.8 −24.2 ± 49.3
0.64
Active (n = 33) 85.9 ± 53.0 14.1 ± 49.0 25.4 ± 42.0 22.7 ± 47.9
p a 0.36 p < 0.001 ** p < 0.001 ** p < 0.001 **
β-carotene
(μg/dL)
Placebo (n = 41) 37.6 ± 29.2 −2.2 ± 10.6 −0.3 ± 13.9 −0.9 ± 13.6
0.45
Active (n = 33) 51.8 ± 45 10.9 ± 20.9 16.2 ± 25.1 12.0 ± 24.5
p a 0.13 0.002 ** 0.001 ** 0.009 **
Values are shown as the mean ± standard deviation. p a: Student’s t-test was performed. p b: repeated
measures of analysis of variance was performed.** p < 0.01 vs. placebo group. ∆Week 4: changes in
values from baseline to week 4; ∆Week 8: changes in values from baseline to week 8; ∆Week 12:
changes in value from baseline to week 12.
3.5. Effect of High-Lycopene Tomato on Oxidative Markers
When the oxidative markers MDA-LDL, LOX index, sLOX-1, LAB, and LPO were examined, no
statistically significant differences were found between the high-lycopene tomato and placebo groups
(Table 7).
Table 7. Oxidative marker levels for the placebo and active food test groups.
Variable Week 0 ∆Week 4 ∆Week 8 ∆Week 12 Time × Food Interaction
,
p b
MDA-
LDL (U/L)
Placebo (n = 41) 156.6 ± 47.5 −45.6 ± 49.5 −19.5 ± 47.9 6.8 ± 54.5
0.94
Active (n = 33) 151.5 ± 45.2 −41.3 ± 32.7 −14.9 ± 48.7 7.8 ± 46.9
p a 0.65 0.65 0.68 0.94
LOX-
index
Placebo (n = 41) 459.7 ± 514.9 −141.2 ± 299.2 −43.8 ± 287.2 698.5 ± 3527.1
0.41
Active (n = 33) 303.1 ± 118.4 −40.8 ± 165.7 45.2 ± 250.3 278.8 ± 311.4
p a 0.066 0.089 0.17 0.50
sLOX-1
(pg/mL)
Placebo (n = 41) 472.3 ± 511.1 11.3 ± 243.2 19.3 ± 176.2 675.0 ± 3688.7
0.39
Active (n = 33) 291.7 ± 127.1 127.6 ± 333.5 103.9 ± 196.3 226.0 ± 242.1
p a 0.034 * 0.087 0.055 0.49
LAB (μg・
cs/mL)
Placebo (n = 41) 1.1 ± 0.3 −0.4 ± 0.3 −0.2 ± 0.3 0.0 ± 0.3
0.23
Active (n = 33) 1.1 ± 0.2 −0.4 ± 0.3 −0.2 ± 0.3 0.1 ± 0.3
p a 0.67 0.63 0.63 0.48
LPO
(nmol/mL)
Placebo (n = 41) 4.2 ± 0.6 −1.1 ± 0.6 −0.7 ± 0.6 −0.5 ± 0.6
0.34
Active (n = 33) 4.1 ± 0.5 −1.2 ± 0.6 −0.7 ± 0.5 −0.5 ± 0.4
p a 0.83 0.32 0.87 0.93
Values are shown as the mean ± standard deviation. p a: Student’s t-test was performed. p b: repeated
measures of analysis of variance was performed. * p < 0.05 vs. placebo group. ∆Week 4: changes in
values from baseline to week 4; ∆Week 8: changes in values from baseline to week 8; ∆Week 12:
changes in value from baseline to week 12; MDA-LDL: malondialdehyde LDL-C; sLOX-1: soluble
lectin-like oxidized LDL receptor-1; LAB: LOX-1 ligand containing apolipoprotein B; LPO: lipid
peroxidases.
Nutrients 2019, 11, 1177 10 of 13
3.6. Effect of High-Lycopene Tomato on Fatigue and Stress
To determine the effects of high-lycopene tomato on fatigue and stress, we evaluated changes in
saliva volume, CGA, and results of the VAS and POMS-2 questionnaires. There were no statistically
significant differences between the high-lycopene tomato and placebo groups (data not shown).
3.7. Assessment of Dietary Nutrients among Subjects during the Study
To assess dietary nutrients, subjects completed the FFQg, which revealed no statistically
significant differences in the intake of calories, proteins, lipids, carbohydrates, dietary fiber, and salt
between the high-lycopene tomato and placebo groups (Supplementary Table S1), suggesting that
dietary nutrients from meals did not affect the results of this trial.
3.8. Safety
To analyze the safety of high-lycopene tomato, we evaluated vital signs (SBP, DBP, and pulse
rate), body composition (body weight [BW], BFR, and BMI), complete blood counts (WBC, RBC, Hb,
Ht, and Plt), liver function (AST, ALT, γ-GTP, ALP, and LDH), renal function (BUN, CRE, and UA),
and blood glucose profiles (FPG, HbA1c, and HOMA-IR) in the subjects (Supplementary Table S2),
in addition to performing qualitative urinary assessments (pH, sugar, protein, occult blood,
urobilinogen, and ketones) (data not shown). Mild adverse effects were observed in each group, with
20 adverse effects observed in the high-lycopene tomato group as follows: digestive symptoms (n =
9); malaise (n = 1); nasal discharge and cough (n = 1); numbness of limb (n = 1); skin symptoms (n =
2); abnormal value of prostate marker (n = 1); variation in γ-GTP value (n = 3); variation in UA value
(n = 2). In the placebo group, 21 adverse effects were observed as follows: digestive symptoms (n =
3); injury (n = 1); stomatitis (n = 1); backache (n = 1); skin symptoms (n = 2); toothache (n = 1); urinary
occult blood (n = 1); nasal symptoms (n = 3); variation in ALT (n = 1); variation in DBP (n = 1); variation
in Hb (n = 1); variation in Ht (n = 1); variation in RBC (n = 1); variation in UA (n = 2); variation in γ-
GTP (n = 1). All subjects displayed mild symptoms and recovered within a few days. In addition, no
symptoms were associated with variations in laboratory test values; the principal investigator
inferred that there were no side effects and no serious adverse effects in this trial. Thus, the intake of
high-lycopene tomato had no or minimal unfavorable effects, even at 200 g/day (as a raw tomato).
4. Discussion
In this clinical trial, we assessed the effect of daily intake of high-lycopene tomato for 12 weeks
on lipid profiles in Japanese subjects with LDL-C levels ≥120 mg/dL and <160 mg/dL. The intake of
high-lycopene tomato increased lycopene levels in subjects administered this food compared to those
in the placebo group. In addition, LDL-C, the primary outcome, was improved in the high-lycopene
tomato group.
A previous meta-analysis demonstrated that LDL-C decreases when more than 25 mg per day
of lycopene is ingested [17]. The biological mechanism was associated with a reduction in 3-hydroxy-
3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase activity in the liver [4], activation of LDL-
receptors [5], and increased expression of the ABCA1 transporter gene, the key component of HDL-
C production [6]. Likewise, these results were observed in our clinical trial using semidried tomato.
To our knowledge, this is the first study to investigate the effect of semidried tomato, which is similar
to raw tomato, on lipid profiles based on a double-blind, placebo-controlled trial.
The intake of high-lycopene tomato increased the level of lycopene compared to the
corresponding level in the placebo group. In the present clinical trial, subjects were asked to refrain
from ingesting tomatoes and processed foods containing tomatoes, and to avoid drinking vegetable
juices; thus, the test food was thought to be the only tomato derivative consumed. Serum lycopene
was decreased in the placebo group. In addition, serum β-carotene was increased in the high-
lycopene tomato group. The level of β-carotene contained in the active test food was less than 4
mg/day, but 20 mg/day β-carotene was previously found to be required for an effect on lipid
Nutrients 2019, 11, 1177 11 of 13
metabolism [18]. These results suggest that the improvement of LDL-C in our clinical trial was mainly
due to the effect of lycopene.
MDA-LDL and LPO were not affected by actively consuming the test food; however, based on
the exploratory analysis, a positive correlation was observed between the change in LDL-C and the
change in MDA-LDL in the active test food group (Pearson correlation coefficient, r = 0.444, p = 0.010).
In addition, subjects with improved LDL-C levels due to intake of the active test food were also
suggested to have improved MDA-LDL. Regarding the antioxidant activity of carotenoids, lycopene
has been reported to possess the strongest singlet oxygen scavenging ability among the eight
carotenoids, as measured by the singlet oxygen absorption capacity method [19], and some
researchers have found that lycopene and tomato display antioxidant effects [20–22]. However, other
reports suggest that ingesting lycopene does not affect oxidative markers [23,24], although they
assessed various oxidative markers such as MDA-LDL, antioxidant capacity, 8-iso-PGF, and
antioxidant enzymes, and during the intake period, there was apparent variation in the antioxidant
effect. These findings suggest that a re-evaluation of oxidant markers and the intake period is
required.
The LOX index, sLOX-1, and LAB, did not significantly differ between the active test food and
placebo groups. The LOX index is a biomarker for the early risk of arteriosclerosis, cerebral infarction,
and myocardial infarction [25,26], and is calculated based on LAB and sLOX-1. sLOX-1 recognizes
not only oxLDL, but also other atherogenic lipoproteins, platelets, leukocytes, and CRP [27]. The
antioxidant effects of lycopene comprise the main mechanism associated with singlet oxygen
scavenging. Therefore, lycopene might be ineffective against LAB or sLOX-1, which are the products
of the peroxidation reaction. As subjects in our trials were healthy and the study period was too short
to investigate the effect of lycopene on the LOX index, additional studies with a longer intake period
are required to reveal the effect of tomato on the risk of arteriosclerosis.
One limitation of this study was the ingestion period. Hence, it is imperative to reconsider the
effects of long-term ingestion using other evaluation outcomes. As the absorption of lycopene is
understood to be influenced by food processing, cooking, and meal composition such as type and
amount of fat, subjects were asked to avoid cooking the test food to eliminate such effects on
absorption due to differences in cooking methods. Thus, it is also necessary to examine differences in
the effect of high-lycopene tomato based on various cooking methods. In addition, a previous study
suggested that the plasma lycopene half-life is approximately six days, based on results of the
continuous ingestion of 20 mg lycopene for eight days [28]. We thus need to consider the effect of
high-lycopene tomato after the end of the ingestion period.
5. Conclusions
In this 12-week randomized, double-blind, placebo-controlled, parallel-group comparative
study, the intake of high-lycopene semidried tomato, PR-7, reduced LDL-C and was confirmed to be
safe at a dosage of 200 g/day (as raw tomato). Tomato is an important component of the diet
worldwide, and our findings support the health benefits, especially with respect to lipid metabolism,
of consuming tomatoes rich in lycopene.
Supplementary Materials: The following are available online at www.mdpi.com/2072-6643/11/5/1177/s1, Table
S1: Nutrient composition of the diets of the subjects during the study; Table S2: Vital signs, body composition,
complete blood count, liver function, renal function, and blood glucose profiles.
Author Contributions: Conceptualization, M.N., N.T, Y. I.-T., M. M.-Y., and J.N.; Design of Test Food, N.T, Y.
I.-T., and M. M.-Y.; Investigation, J.N.; Formal Analysis, M.N.; Writing- Review and Editing, M.N. and J.N.
Funding: This research was supported by grants from the Project of the NARO Bio-oriented Technology
Research Advancement Institution (the special scheme project on regional developing strategy).
Acknowledgments: We thank Salad Bowl Co., Ltd., Hyogo Next Farm Co., Ltd., T-Farm Co., Ltd., and
Agrivision Co., Ltd., for providing the materials for the test foods. We also thank the staff at Hokkaido
Information University, Health Information Science Research Center (Anzai Y., Enya A., Fukuda Y., Hatakeyama
M., Ito M., Kamo S., Katsuyama-Kagami H., Miyao A., Ohshima M., Saito T., Sasaki M., Sato K., Shima N.,
Nutrients 2019, 11, 1177 12 of 13
Teramoto M., Tsutsumi H., Yamazaki N., and Yokomoto H.) for their technical assistance with the clinical trial.
We would like to thank Editage (www.editage.com) for English language editing and publication support.
Conflicts of Interest: The authors declare no conflicts of interest.
References
1. Di Mascio, P.; Kaiser, S.; Sies, H. Lycopene as the most efficient biological carotenoid singlet oxygen
quencher. Arch. Biochem. Biophys. 1989, 274, 532–538.
2. Okamura, T.; Kitamura, A.; Moriyama, Y.; Imano, H.; Sato, S.; Terao, A.; Naito, Y.; Nakagawa, Y.; Kiyama,
M.; Tamura, Y.; et al. Plasma level of homocysteine is correlated to extracranial carotid-artery
atherosclerosis in non-hypertensive Japanese. J. Cardiovasc. Risk 1999, 6, 371–377.
3. McEneny, J.; Wade, L.; Young, I.S.; Masson, L.; Duthie, G.; McGinty, A.; McMaster, C.; Thies, F. Lycopene
intervention reduces inflammation and improves HDL functionality in moderately overweight middle-
aged individuals. J. Nutr. Biochem. 2013, 24, 163–168.
4. Navarro-González, I.; Pérez-Sánchez, H.; Martín-Pozuelo, G.; García-Alonso, J.; Periago, M.J. The
inhibitory effects of bioactive compounds of tomato juice binding to hepatic HMGCR: In vivo study and
molecular modelling. PLoS ONE 2014, 9, e83968.
5. Fuhrman, B.; Elis, A.; Aviram, M. Hypocholesterolemic effect of lycopene and beta-carotene is related to
suppression of cholesterol synthesis and augmentation of LDL receptor activity in macrophages. Biochem.
Biophys. Res. Commun. 1997, 233, 658–662.
6. During, A.; Dawson, H.D.; Harrison E.H. Carotenoid transport is decreased and expression of the lipid
transporters SR-BI, NPC1L1, and ABCA1 is downregulated in Caco-2 cells treated with ezetimibe. J Nutr.
2005, 135, 2305–2312.
7. Chen, J.; Song, Y.; Zhang, L. Lycopene/tomato consumption and the risk of prostate cancer: a systematic
review and meta-analysis of prospective studies. J. Nutr. Sci. Vitaminol. 2013, 59, 213–223.
8. Riccioni, G.; Mancini, B.; Di Ilio, E.; Bucciarelli, T.; D′Orazio, N. Protective effect of lycopene in
cardiovascular disease. Eur. Rev. Med. Pharmacol. Sci. 2008, 12, 183–190.
9. Stice, C.P.; Xia, H.; Wang, X.D. Tomato lycopene prevention of alcoholic fatty liver disease and
hepatocellular carcinoma development. Chronic. Dis. Transl. Med. 2018, 4, 211–224.
10. Kim, Y.; Kim, K.J.; Park, S.Y.; Lim, Y.; Kwon, O.; Lee, J.H.; Kim, J.Y. Differential responses of endothelial
integrity upon the intake of microencapsulated garlic, tomato extract or a mixture: A single-intake,
randomized, double-blind, placebo-controlled crossover trial. Food Funct. 2018, 9, 5426–5435.
11. Paetau, I.; Rao, D.; Wiley, E.R.; Brown, E.D.; Clevidence, B.A. Carotenoids in human buccal mucosa cells
after 4 wk of supplementation with tomato juice or lycopene supplements. Am. J. Clin. Nutr. 1999, 70, 490–
494.
12. Ghavipour, M.; Sotoudeh, G.; Ghorbani, M. Tomato juice consumption improves blood antioxidative
biomarkers in overweight and obese females. Clin. Nutr. 2015, 34, 805–809.
13. Murata, M.; Kondo, J.; Iwabuchi, N.; Takahashi, S.; Yamauchi, K.; Abe, F.; Miura, K. Effects of paraprobiotic
Lactobacillus paracasei MCC1849 supplementation on symptoms of the common cold and mood states in
healthy adults. Benef. Microb. 2018, 9, 855–864.
14. Tanaka, S.; Tanaka, S.; Iimuro, S.; Yamashita, H.; Katayama, S.; Ohashi, Y.; Akanuma, Y.; Yamada, N.; Sone,
H. Japan Diabetes Complications Study Group, Cohort profile: The Japan diabetes complications study: A
long-term follow-up of a randomised lifestyle intervention study of type 2 diabetes. Int. J. Epidemiol. 2014,
43, 1054–1062.
15. Horikawa, C.; Yoshimura, Y.; Kamada, C.; Tanaka, S.; Tanaka, S.; Takahashi, A.; Hanyu, O.; Araki, A.; Ito,
H.; Tanaka, A.; et al. Dietary intake in Japanese patients with type 2 diabetes: Analysis from Japan Diabetes
Complications Study. J. Diabetes Investig. 2014, 5, 176–187.
16. The criteria for evaluation of adverse reactions and clinical laboratory abnormalities in clinical trials with
antimicrobial agents. Chemotherapy 1991, 39, 687–689. Available online:
http://www.chemotherapy.or.jp/guideline/39_687.pdf (accessed on 11 April 2019).
17. Ried, K.; Fakler, P. Protective effect of lycopene on serum cholesterol and blood pressure: Meta-analyses of
intervention trials. Maturitas 2011, 68, 299–310.
18. Allard, J.P.; Royall, D.; Kurian, R.; Muggli, R.; Jeejeebhoy, K.N. Effects of beta-carotene supplementation
on lipid peroxidation in humans. Am. J. Clin. Nutr. 1994, 59, 884–890.
Nutrients 2019, 11, 1177 13 of 13
19. Aizawa, K.; Iwasaki, Y.; Ouchi, A.; Inakuma, T.; Nagaoka, S.; Terao, J.; Mukai, K. Development of singlet
oxygen absorption capacity (SOAC) assay method. 2. Measurements of the SOAC values for carotenoids
and food extracts. J. Agric. Food Chem. 2011, 59, 3717–3729.
20. Hadley, C.W.; Clinton, S.K.; Schwartz, S.J. The consumption of processed tomato products enhances
plasma lycopene concentrations in association with a reduced lipoprotein sensitivity to oxidative damage.
J. Nutr. 2003, 133, 727–732.
21. Visioli, F.; Riso, P.; Grande, S.; Galli, C.; Porrini, M. Protective activity of tomato products on in vivo
markers of lipid oxidation. Eur. J. Nutr. 2003, 42, 201–206.
22. Bose, K.S.; Agrawal, B.K. Effect of lycopene from cooked tomatoes on serum antioxidant enzymes, lipid
peroxidation rate and lipid profile in coronary heart disease. Singapore Med. J. 2007, 48, 415–420.
23. Briviba, K.; Kulling, S.E.; Moseneder, J.; Watzl, B.; Rechkemmer, G.; Bub, A. Effects of supplementing a
low-carotenoid diet with a tomato extract for 2 weeks on endogenous levels of DNA single strand breaks
and immune functions in healthy non-smokers and smokers. Carcinogenesis 2004, 25, 2373–2378.
24. Nelson, J.L.; Bernstein, P.S.; Schmidt, M.C.; Von Tress, M.S.; Askew, E.W., Dietary modification and
moderate antioxidant supplementation differentially affect serum carotenoids, antioxidant levels and
markers of oxidative stress in older humans. J. Nutr. 2003, 133, 3117–3123.
25. Hayashida, K.; Kume, N.; Murase, T.; Minami, M.; Nakagawa, D.; Inada, T.; Tanaka, M.; Ueda, A.;
Kominami, G.; Kambara, H.; et al. Serum soluble lectin-like oxidized low-density lipoprotein receptor-1
levels are elevated in acute coronary syndrome: A novel marker for early diagnosis. Circulation 2005, 112,
812–818.
26. Komiyama, M.; Wada, H.; Ono, K.; Yamakage, H.; Satoh-Asahara, N.; Shimada, S.; Akao, M.; Morimoto,
T.; Shimatsu, A.; Takahashi, Y.; et al. Smoking cessation reduces the lectin-like low-density lipoprotein
receptor index, an independent cardiovascular risk marker of vascular inflammation. Heart Vessels 2018,
33, 9–16.
27. Yoshimoto, R.; Fujita, Y.; Kakino, A.; Iwamoto, S.; Takaya, T.; Sawamura, T. The discovery of LOX-1, its
ligands and clinical significance. Cardiovasc. Drugs Ther. 2011, 25, 379–391.
28. Moran, N.E.; Erdman, J.W., Jr.; Clinton, S.K. Complex interactions between dietary and genetic factors
impact lycopene metabolism and distribution. Arch. Biochem. Biophys. 2013, 539, 171–180.
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