Bioactive compounds with strawberries and blueberries and their potential health effects based on human intervention studies: a brief overview


abstract

Strawberries and blueberries are two of the most consumed berries. Berries are generally characterized by their highly nutritious compounds, including minerals, vitamins, fatty acids and dietary fiber, as well as their high content and high diversity of bioactive compounds such as phenolic compounds and organic acids. These bioactive compounds have been associated with protective effects against chronic diseases such as cardiovascular disease, cancer, Alzheimer’s and other disorders. This article reviews 16 human intervention studies examining the beneficial health effects of diet of strawberry or blueberry consumption on inflammation, cardiovascular disease, or cognitive function and mental health.

Keyword: anthocyanidins, polyphenols, berries, cardiovascular disease, inflammation

1. Introduction

Cardiovascular disease (CVD) is still the leading cause of death and disability in the world. CVDs describe several diseases involving the heart, brain and blood vessels. Coronary heart disease (heart attack) and cerebrovascular disease (stroke) are two major CVDs caused by arteriosclerosis, the pathological process in the walls of blood vessels. In arteriosclerosis, deposits of fat and cholesterol (plaques) in blood vessels lead to narrow vessels and diminished blood flow. A blood clot may occur when the plate bursts. Depending on the site of development, in a coronary artery or in the brain, a blood clot can cause a heart attack or stroke. The main metabolic risk factors for CVDs are obesity / obesity, high blood pressure (hypertension), high blood sugar (diabetes) and raised blood lipids (eg cholesterol). The prevalence and extent of these metabolic risk factors largely depends on behavioral risk factors such as physical activity and diet. Overweight (BMI ≥ 25 kg / m2) and obesity (BMI ≥ 30 kg / m.)2) is the result of an unbalanced energy intake / consumption and strongly related to the other metabolic risk factors. Increasing body mass index increases the risk of coronary heart disease, ischemic stroke and type 2 diabetes mellitus[[[[1].

A major contributing factor to the development, progression and complication of chronic diseases, such as type 2 diabetes, CVD and Alzheimer’s, is a persistent pro-inflammatory condition. Inflammation is known as the innate, protective, and temporary response of the innate immune system to pathogens and damage stimuli, characterized by the production of pro- and anti-inflammatory cytokines. Cytokines are small soluble proteins that act as signals between immune cells to coordinate the inflammatory response. Among cytokines, interleukin 1β (IL-1β), interleukin-6 (IL 6), and tumor necrosis factor-alpha (TNF-α) are frequently induced and act as pro-inflammatory and alarm cytokines[[[[2.3.4]. In addition to the production of TNF-α, IL-1 and IL-6, endothelial dysfunction, oxidative stress in vascular endothelial cells, accumulation of macrophages and inflammasome formation characterize the inflammatory process, leading to atherogenesis, the plate-forming process.[[[[5]. Other inflammatory status biomarkers measured in humans are acute phase proteins (i.e., C-reactive protein (CRP), fibrinogen, serum amyloid A), chemokines (i.e., monocyte chemoattractant protein (MCP) -1), and adhesion molecules (i.e. E-selectin, P-selectin, sVCAM-1). In addition to classic inflammatory stimuli, acute inflammatory stress can be induced by a single energy-tight meal that provides an excess of readily available carbohydrates and fat. In the long run, poor diet can lead to obesity known as a chronic, low-quality inflammatory condition[[[[4]. A chronic, low degree of inflammatory condition can lead to, for example, tissue damage, endothelial dysfunction, thrombosis, insulin resistance, and high blood pressure, which can result in cardiovascular disease, diabetes, some cancers, gout, neurodegenerative diseases, and many others.[[[[6].

Over 350 million people worldwide are suffering from severe depressive disorder. Impaired cognitive and executive functioning are two common symptoms of depression. Executive function describes cognitive processes such as working memory, planning, problem solving, cognitive flexibility, inhibitory control, directing attention, thoughts and therefore behavior. Depressive symptoms, such as negative self-perception and low mood, are thought to be maintained by impaired executive function through endurance and rumination. Flavonoids consumption is associated with a reduced risk of developing depression[[[[7].

Berries are characterized by their highly nutritious compounds, including minerals, vitamins, fatty acids and dietary fiber. They also contain high content and wide diversity of non-essential biologically active components, such as organic acids or polyphenols, with their subclasses, tannins and flavonoids[[[[3.4.8]. Anthocyanins, a subclass of flavonoids, are important bioactive compounds in berries responsible for the red-blue-purple staining of berries[[[[3.4]. Bioactive compounds are believed to have the ability to provide and activate cellular antioxidant protection, remove free radicals, inhibit inflammatory gene expression, and consequently protect against oxidation-induced and inflammatory cell damage and cytotoxicity. Therefore, bioactive compounds have been associated with protective effects against chronic diseases such as cardiovascular disease (CVD), cancer, Alzheimer’s, depression and other disorders.[[[[4.7.8.9].

Strawberries (Fragaria) and blueberries (Vaccinium) are two of the most sought-after berries in fresh and frozen forms, as well as in processed and derived products such as dried and canned forms, yogurt, beverages, jams and jellies[[[[3.10.11.12.13]. Numerous in vitro and in vivo studies have shown that strawberries and blueberries, among other foods, help to provide and reduce the risk of developing more chronic diseases[[[[2.13]. Strawberries and blueberries are very different in the amount of different subclasses of bioactive compounds. The chemical compositions of strawberries and blueberries are compared in.

Table 1

Chemical composition of strawberries and blueberries[[[[14].

Strawberry (Highbush) Blueberry
flavonoids
Anthocyanidins (mg / kg FW) 73.0 134
Flavanols (mg / kg FW) 9.1 1.1
Flavonols (mg / kg FW) 2.3 38.7
phenolic acids
Hydroxybenzoic acids (mg / kg FW) 5.7 1.5
Hydroxycinnamic acids (mg / kg FW) 7.1 135.0

Literature research was conducted in June 2018. To review most current research, google scholars and the Food Science and Technology Abstracts (FSTA) database were used to identify topic related articles published later than January 2011. The searches used the following terms and text words alone and in combination: “strawberries”, “blueberries”, “berries”, “bioactive compounds”, “health effects”, “human intervention”, “inflammation”, “cardiovascular disease”, “cognitive function” and “cancer”. In vitro as well as in vivo studies performed with animals were excluded.This paper reviews 16 human intervention studies examining the beneficial health effects of strawberry or blueberry consumption.

2. Strawberries

2.1. composition

With approx. 60 mg per 100 g of fresh fruit are strawberries especially known for their high vitamin C. Strawberries also provide several other vitamins to a lesser extent, such as thiamine, riboflavin, niacin and vitamin B6, and contain fat-soluble vitamins including carotenoids, vitamin A, vitamin E and vitamin K. Among fruits, strawberries are one of the richest natural folate sources (43 µg per 100 g of fresh fruit) and show a remarkably high antioxidant activity. Strawberries are also a good source of manganese, iodine, magnesium, copper, iron and phosphorus[[[[3.15.16]. In addition, strawberries are rich in bioactive compounds, mainly represented by flavonoids, especially anthocyanidins, followed by phenolic acids such as hydroxycinnamic and hydroxybenzoic acids.[[[[14].

2.2. inflammation

Seven clinical trials investigating the effects of strawberry intervention on inflammatory markers were identified. Among the seven studies, three tested post-prandial effects and four long-term food effects on inflammation. Two studies were conducted with obese participants, three with abdominally obese subjects, one with type two diabetic participants and one with obese people with osteoarthritis.

In a cross-over design, the effect of strawberry antioxidants in drinking form is shaped on meal-induced postprandial inflammatory response and insulin response over a period of 6 hours. Therefore, 24 obese adults consumed a high carbohydrate, moderate fat meal to increase the markers of oxidative stress and insulin resistance accompanied by either a single serving strawberry or a placebo drink. Results showed a significant decrease in high-sensitivity c-reactive protein (hs-CRP) and a reduction in postprandial insulin response (IL-6) of the strawberry drink, but not of placebo. No significant differences were found for plasminogen activator inhibitor (PAI) -1, IL-1β and TNF-α among treatments[[[[17]. In contrast, a similar study with the same 24 overweight adults was conducted over six weeks and showed significant attenuation of PAI-1 concentration and IL-1β response in the strawberry group, but no differences in platelet aggregation, hs-CRP, TNF – α, IL-6, insulin or glucose were found among the treatments[[[[18]. Despite a similar experimental setup, Edirisinghe et al.[[[[17]and Ellis et al.[[[[18]reported different effects on postprandial PAI-1, IL-1β, IL-6 and hs-CRP concentrations at strawberry intake over different time periods. However, in both studies an anti-inflammatory effect was found, although represented in a decrease in various biomarkers of inflammation.

On the other hand, two of the seven identified studies performed with abdominally obese individuals observed no significant influence of strawberry consumption on inflammatory markers tested. In another 6-hour postprandial study, 21 abdominally obese individuals with insulin resistance received a standard high-fat breakfast with one of four drinks containing 0, 10, 20 or 40 g of freeze-dried strawberries (FDS). In this four-arm, placebo-controlled, 6-hour postprandial, crossover study, Park et al. reported some effects on CVD-related biomarker, as described in Section 2.3, but no effect on the measured inflammatory biomarker IL-6 was found[[[[19]. In a seven-week double-blind, randomized, cross-sectional trial, 20 obese people received a clear diet and either strawberry powder (equivalent to four servings of 80 g frozen strawberries) or a placebo in the form of a drink. Zunino et al. reported no influence on cytokine concentrations of IL-1β, IL-6 and TNF-α in the clinical trial[[[[20]. The two studies in this section, which show no significant effect on inflammatory markers, primarily investigated the effect of strawberry intervention on CVD and are therefore also listed in Section 2.3.

Basu et al.[[[[21](also listed in Section 2.3), Moazen et al.[[[[22]and Shell et al.[[[[23]reported anti-inflammatory effects of strawberry consumption in people with type II diabetes mellitus and obese people with osteoarthritis or elevated serum lipids. In a 12-week randomized dose-response controlled trial, 60 people with abdominal fat and elevated serum lipids were assigned to consume one of four drinks: a low or high dose of FDS drink (25 g / day or 50 g / day ) or a low or high dose calorie and fiber matched beverage. No effects on hs-CRP and adhesion molecules were observed among the treatments. A significant decrease in serum melondialdehyde, a biomarker for oxidative stress, was found by both FDS groups compared to control groups[[[[21]. Thirty-six subjects with type II diabetes mellitus consumed either 50 g of FDS daily or a matched placebo drink in a randomized, double-blind, controlled trial for six weeks. Results showed a significant increase in markers for total serum antioxidant status, while serum melondialdehyde, glycated hemoglobin (Hb) A1c, and hs-CRP concentrations decreased significantly. Serum glucose concentrations and anthropometric indices did not change significantly[[[[22]. In a double-blind crossover study, 17 obese adults with osteoarthritis were randomly assigned to consume either an FDS drink (50 g / day) or a control drink daily for 12 weeks with a two-week washout phase to examine the effects of diet strawberries on pain, markers of inflammation and quality of life indicators. The study showed a decrease in IL-6, IL-1, and matrix metalloproteinase, which are serum biomarkers for inflammation and cartilage degradation, after FDS drinking, but not after controlling for beverage consumption. In addition, constant, intermittent, and total pain were only significantly reduced by FDS beverage consumption, but no differences were found for hs-CRP, nitrite, glucose, and lipid profiles.[[[[23].

In five of seven studies, an anti-inflammatory effect overall was presented by a decrease in some cytokine or acute phase protein concentrations or a decrease in oxidative stress. In two studies, no significant anti-inflammatory effect was observed.

2.3. heart disease

Several intervention studies suggest that consumption of berries has a significant potential in the prevention and treatment of most of the above risk factors[[[[6]. Consistent with the studies presented in Section 2.2five human intervention studies examining the effect of strawberry consumption on CVD-related markers were identified. Among these five studies, four were performed with abdominal obese subjects and one with postmenopausal women. The main metabolic risk factors for CVDs are obesity / obesity, high blood pressure (hypertension), high blood sugar (diabetes) and raised blood lipids (eg cholesterol). Biomarkers for CVD measured in humans are viz. systolic and diastolic blood pressure, insulin and glucose concentrations, distribution and size of blood lipids and antioxidant markers such as plasma antioxidant capacity, whole blood glutathione, superoxide discompass levels and serum catalase activity.

In addition to the results presented in Section 2.2, Park et al. reported a significant reduction in postprandial plasma insulin concentrations, insulin: glucose ratio and glucose and insulin increase in 21 abdominally obese subjects with insulin resistance receiving a 40 g FDS drink. A significant reduction in oxidized low-density lipoprotein was shown by 20 g of FDS drink compared to all other beverages[[[[19]. In addition to IL-1 β, IL-6, TNF-α concentrations, the seven-week double-blind, randomized, cross-sectional study with 20 obese subjects receiving a prepared diet and either strawberry powder (corresponding to four servings of 80 g frozen) strawberries) or a placebo observed no differences in blood pressure and medium and large HDL cholesterol particles. However, a reduction in plasma concentrations of small HDL particles and low HDL cholesterol was observed, as well as an increase in LDL particle size following the three-week strawberry intervention, but not the placebo intervention.[[[[20]. In previous studies, LDL and HDL particle distribution and size have been linked to health status, in detail, to metabolic syndrome and insulin resistance.[[[[20.24.25.26].

In a 12-week randomized dose-response controlled trial, 60 people with abdominal fat and elevated serum lipids were assigned to consume one of four drinks: a low or high dose of FDS drink (25 g / day or 50 g / day ) or a low or high dose calorie and fiber matched beverage. The results showed a significant reduction in serum total and LDL cholesterol and NMR-derived small LDL particles with the high FDS dose compared to the low FDS dose and placebo drinks. No effects were found on the measurement of fat, blood pressure, glycemia and serum concentrations of HDL cholesterol and triglycerides[[[[21]. In a similar study with the same experimental setup, Basu et al. reported a marked increase in plasma antioxidant capacity and whole blood glutathione at the end of intervention at both FDS doses vs. controls. Apart from the plasma antioxidant capacity, blood glutathione was significantly higher in HD-FDS versus LD-FDS. Serum catalase activity was increased only in LD-FDS compared to controls. No effects on glutathione peroxidase and glutathione reductase enzyme activities, plasma copper, iron, selenium and zinc, which also play an important role in antioxidant and pro-oxidant activities, were not shown.[[[[27].

In an eight-week, randomized, double-blind, placebo-controlled, parallel intervention, 60 postmenopausal women were either assigned to consume one of three drinks twice a day containing a total of 0 g, 25 g or 50 g FDS. A decrease in systolic blood pressure and brachial and femoral ankle pulse rate, a measured marker of arterial stiffness, was shown by 25 g of FDS drink compared to baseline, but not to the other groups. An increase in plasma nitric oxide metabolite levels was shown by 50 g of FDS drink, but not the other beverages. In all three groups (0 g, 25 g or 50 g FDS), serum levels of superoxide dismutase increased at four weeks, returning to baseline levels after eight weeks. No significant effect on diastolic blood pressure and metabolites was observed in all groups[[[[28].

Overall, the effect of strawberry consumption on cardiovascular disease has been studied in five intervention studies. Park et al.[[[[19]and Basu et al.[[[[27]reported antioxidant effects and Zunino et al.[[[[20]and Basu et al.[[[[21]reported some positive effects on the distribution and size of blood lipids of strawberry consumption in obese individuals. In 60 postmenopausal women, a decrease in systolic blood pressure, arterial stiffness and antioxidant effects was reported following eight weeks of strawberry intervention.[[[[28].

2.4. Cognitive functioning and mental health

No studies investigating the effect of strawberry intervention on cognitive functions were identified during literature research.

Blueberries

3.1. composition

Blueberries are nutritious fruits as they contain many dietary fiber (3–3.5% of their fruit weight) and antioxidants such as vitamin C, B complex, E and A. Blueberries also provide large amounts of selenium, zinc, iron, and manganese and contains b-carotene, lutein and zeaxanthin[[[[9.12.13.29]. In addition, blueberries are rich in bioactive compounds, mainly represented by flavonoids, especially anthocyanidins and flavonols, as well as by phenolic acids and hydroxycinnamic acids.[[[[14].

3.2. inflammation

Three clinical trials investigating the effects of blueberry intervention on markers associated with inflammation were identified. A study was conducted with individuals with metabolic syndrome, one with men with cardiovascular risk factors and one with women with at least two risk factors for type 2 diabetes.

In a double-blind, placebo-controlled study, 44 people with metabolic syndrome consumed either a blueberry smoothie (yogurt and a milk-based smoothie with 22.5 g of freeze-dried blueberry powder added) or a placebo smoothie (identical smoothie without blueberry powder) twice daily. In the blueberry group, endothelial function, expressed as reactive hyperemia index, improved significantly more compared to the placebo group.[[[[30]. On the other hand, no significant differences were detected for markers of endothelial function and total plasma nitric oxide and soluble vascular adhesion molecule in a six-week randomized, placebo-controlled, crossover intervention with 18 male volunteers with cardiovascular risk factors receiving a wild blueberry drink (25 g freeze-dried powder giving 375 mg of ACNs) or a placebo drink. However, in contrast to the intake of placebo drinks, the intake of wild blueberries markedly reduced the levels of endogenously oxidized DNA bases and the levels of H2ISLAND2-induced DNA damage in this study[[[[31]. No influence on inflammatory markers, adhesion molecules, oxidative stress, and endothelial function was found in a single-blind, randomized, placebo-controlled, crossover design study, 19 women with at least two risk factors for type 2 diabetes taking 240 ml of wild blueberry juice or a placebo – drink for seven days[[[[32].

Whereas Stull et al.[[[[30]showed an improvement in endothelial function following six-week consumption of blueberries, Riso et al.[[[[31]and Stote et al.[[[[32]reported no significant influence on endothelial function and other inflammatory related markers with the exception of an antioxidant effect. The absence of an effect of blueberry intervention on inflammation studied by Stote et al.[[[[32]could be based on the relatively short one-week intervention period. Whereas Stull et al. and Riso et al. both performed clinical trials over six weeks, the 44 people with metabolic syndrome received 45 g of freeze-dried blueberry powder per day. day (2 × 22.5 g)[[[[30]and the 18 male subjects with cardiovascular risk factors received 25 g of freeze-dried wild blueberry powder per day. day[[[[31]. The different dose and type of blueberry powder intake, which provide different amounts of bioactive compounds, could be related to the effect on endothelial function.

3.3. heart disease

In addition to inflammation markers, the three clinical trials were examined in Section 3.2 also examined the influence of blueberry intervention on other CVD-related markers such as blood pressure, blood lipids, insulin sensitivity, etc. In addition to these three studies, a fourth study has been identified with postmenopausal women with pre- and stage 1 hypertension for this section.

In addition to improving endothelial function in 44 people with metabolic syndrome who consume 22.5 g of freeze-dried blueberry powder twice a day over six weeks, Stull et al. reported no difference in blood pressure and insulin sensitivity between blueberries and placebo groups[[[[30]. Also, no influence was found on blood pressure (systolic and diastolic) as well as Framingham reactive hyperemia index and augmentation index by Riso et al., Where 18 male subjects with cardiovascular risk factors consume 25 g of freeze-dried powder in wild blueberries for six weeks.[[[[31]. Stote et al. Observed a tendency to lower systolic blood pressure and increase serum concentrations of nitrates and nitrites, an index of nitric oxide production, in 19 women with at least two risk factors for type 2 diabetes after one week of 240 ml of wild blueberry juice. No significant changes in glucose, insulin, insulin sensitivity, triglycerides or blood pressure were detected.[[[[32]. In an eight-week, randomized, double-blind, placebo-controlled clinical trial, 48 postmenopausal women with pre- and phase 1 hypertension were randomly assigned to receive either 22 g of freeze-dried blueberry powder or 22 g of control powder in the form of a drink of 480 ml. At the end of systolic blood pressure, interventional diastolic blood pressure and brachial ankle pulse rate were significantly lower and nitric oxide levels were greater in the blueberry powder group compared to baseline values, whereas there were no changes in the control powder group.[[[[33].

In conclusion, these four intervention studies partially documented findings on the effect of blueberry consumption on blood pressure, insulin sensitivity, and oxidative stress. Three of four clinical trials examined showed no significant effects of blueberry consumption on measured CVD-related markers. Other than Stull et al.[[[[30], Riso et al.[[[[31](six week periods) and Stote et al.[[[[32](one week period), Johnson et al.[[[[33]reported a marked decrease in systolic and diastolic blood pressure after eight weeks of daily blueberry consumption.

3.4. Cognitive functioning and mental health

In relation to epidemiological evidence, the consumption of flavonoids is associated with a reduced risk of developing depression, a weakened rate of cognitive decline and a reduced risk of dementia.[[[[7.34]. Three studies examining the effects of blueberry intervention on cognitive function or mental health were identified. Two studies were conducted with healthy older adults and one with healthy young adults and children.

Two randomized, double-blind, placebo-controlled trials with 21 young adults (age: 20.1 ± 1.0 years) and 52 children (age: 8.2 ± 1.0 years) showed that the blueberry intervention (30 g freeze-dried wild blueberry with 30 ml of low flavonoid rocks orange squash and 220 ml of water) increased post-consumption positive affect results but had no effect on negative affect results (PANS-NU and PANS-C) compared with placebo intervention. There was also a significant main effect of session reduction of negative affect scores after both blueberry and placebo consumption.[[[[7]. Bowtell et al. investigated whether consumption of blueberries improved brain perfusion, task-related activation, and cognitive function. Favorable effects on cerebrovascular and cognitive function in healthy older adults were demonstrated in a randomized, double-blind, placebo-controlled trial after 12 weeks of supplementation with blueberry concentrate (30 ml / day containing 387 mg anthocyanidins per day). Specifically, brain activation responses in several task-related different areas and resting state perfusion in the gray matter from parietal and occipital lobes increased from baseline levels after 12 weeks of supplementation to blueberries, but not after placebo supplementation. A significant decrease in serum glutathione concentration was found in addition to blueberries and placebo. No significant differences were found between the groups and no significant changes in baseline brain activity, frontal lobe resting perfusion, protein carbonylation HNE adduct or malonaldehyde formation, and serum hs-CRP or BDNF concentration[[[[34]. In a randomized, double-blind, placebo-controlled trial, 37 participants were asked to consume either freeze-dried blueberry drink (24 g / day FDB, the equivalent of a cup of fresh blueberries) or a 90-day placebo tablet of blueberries. Participants in the blueberry group showed significantly fewer repetition errors in a learning test and reduced switching costs in a task switching test across study visits compared to controls, but no improvement in gait or balance was observed. In addition, in this study, no significant effect of blueberry consumption on either Geriatric Depression Scale or Mood State profile was observed.[[[[35].

The impact of blueberry consumption on cognitive function and mental health has been examined in three studies. Whereas Miller et al.[[[[35]reported no significant effect on participants’ mood, Khalid et al.[[[[7]reported a positive effect on mood in both subject groups, citing better positive affect outcomes. In contrast to the post-consumption effect observed by Khalid et al., No long-term effect on the mood of Miller et al. after 45- and 90-day blueberry intervention. Bowtell et al. and Miller et al. also reported positive effects on cognitive function with reference to improvement in several tests.

4. Concluding remarks

Strawberries (Fragaria) and blueberries (Vaccinium) contains a wide variety of bioactive compounds, including many antioxidants with specific biochemical functions and beneficial health effects. The beneficial health effects are associated with protective effects against chronic diseases such as cardiovascular disease, cancer, Alzheimer’s and other disorders. In this paper, nine studies examining the effects of strawberry intervention and seven studies examining the effects of blueberry intervention on inflammation, cardiovascular disease, and cognitive function and mental health were reviewed. The type of intervention, the characteristics of the participants, the format of berries and placebo consumption, the dose of berries and the main results of the 16 studies reviewed are summarized in and.

Table 2

Effect of strawberry consumption on inflammation, cardiovascular disease and metabolic syndrome.

Intervention topics Format Dose / day Main findings references
postprandial,
randomized, single-blind,
placebo-controlled,
transverse engagement
24 obese men and women
(BMI: 29.2 ± 2.3 kg / m2; age: 50.9 ± 15.0 years)
High carbohydrate,
moderate fat meal + Berry group: Strawberry powder, water based beverage
Control group:
Placebo drink
10 g powder 1. Attenuation of the postprandial inflammatory response
2. Reduction in postprandial insulin response
3. No differences for PAL-1, IL-1β and TNF-α
[[[[17]
6-week, randomized,
single-blind,
placebo-controlled,
parallel intervention + post-prandial high
carbohydrates fat meal
24 obese and obese males and females
(BMI: 29.2 ± 2.3 kg / m2; age: 50.9 ± 15.0 years)
High carbohydrate,
moderate fat meal + Berry group: Strawberry powder, water based beverage
Control group: Placebo powder, water based drink
10 g powder 1. Attenuation of the postprandial PAL-1 concentration and IL-1β response
2. No differences for platelet aggregation, hsCRP, TNF-α, insulin or glucose
[[[[18]
postprandial,
randomized, controlled,
4-arm, crossover
intervention
21 men and women with abdominal obesity and insulin resistance (BMI 40.2 ± 7.2 kg / m2; alder 39,8 ± 13,8 år) Morgenmad med højt fedtindhold + frysetørret jordbærpulver, drikke Bærgruppe:
Gruppe 1: 10 g
Gruppe 2: 20 g
Gruppe 3: 40 g
Kontrolgruppe: 0 g pulver
(10 g pulver svarer til 110 g friske jordbær)
1. Reduktion i insulinkoncentrationer postprandial plasma, insulin: glukoseforhold og hastighed for glukose og insulin øges med 40 g FDS
2. Reduktion i oxideret lavdensitetslipoprotein med 20 g FDS
3. IL-6 var ikke forskellig blandt behandlinger
[[[[19]
7-ugers, randomiseret, dobbeltblind,
placebo-controlled, cross-over intervention
20 obese males and females
(13 Females: BMI, 35.6 ± 3.0 kg/m2; age, 31.8 ± 11.4 year;
7 Males: BMI, 32.3 ± 2.1 kg/m2; age, 29.4 ± 6.6 year)
Berry group: Strawberry powder, water-based beverage
Control group: Placebo powder, water-based beverage
Powder equivalent to 320 g frozen strawberries 1. Reduction in serum cholesterol, small HDL particles, small HDL-cholesterol and Na and CO2 concentrations in the blood
2. Increase in mean particle size of LDL
3. No difference in blood pressure
[[[[20]
12-week, randomized,
controlled, parallel
intervention
60 males and females with abdominal adiposity and elevated serum lipids
LD-FDS: 15 subjects
(BMI, 34.5 ± 4.4 kg/m2; age, 50 ± 10 year)
HD-FDS: 15 subjects (BMI, 38.0 ± 7.1 kg/m2; age, 49 ± 11 year)
LD-C: 15 subjects (BMI, 37.0 ± 4.4 kg/m2; age, 48 ± 10 year)
HD-C: 15 subjects
(BMI, 35.0 ± 5.2 kg/m2; age 48 ± 10 year)
Berry group: Freeze-dried strawberry powder, water-based beverage
Control group: Placebo powder, calorie- and fiber-matched water-based beverage
Berry group:
Group 1 (LD-FDS): 25 g (equivalent to 250 g fresh strawberries);
Group 2 (HD-FDS): 50 g
(equivalent to 500 g fresh strawberries)
1. Reduction in serum total and LDL-cholesterol, and NMR-derived small LDL particles by HD-FDS
2. Increase in Serum catalase activity by LD-FDS
3. Decrease in serum malondialdehyde by LD-FDS and HD-FDS
4. No effects on adiposity, blood pressure, glycemia, and serum concentrations of HDL cholesterol and triglycerides, C-reactive protein and adhesion molecules
[[[[21]
6-week, randomized,
double-blind, placebo-controlled,
parallel intervention
36 males and females with type 2 diabetes
(berry group: n = 19; BMI, 27.36 ± 4.23 kg/m2; age 51.9 ± 8.2 year;
control group: n = 17; BMI, 28.58 ± 4.7 kg/m2; age 51.1 ± 13.8 year)
Berry group: Freeze-dried strawberry powder, water-based beverage
Control group: Iso-caloric drink with strawberry flavoring
50 g powder 1. Increase of total serum antioxidant status
2. Decrease of serum malondialdehyde, glycated hemoglobin HbA1c, and hs-CRP concentrations
3. No effects on serum glucose concentrations and anthropometric indices
[[[[22]
12-week, randomized, double-blind, placebo-controlled, cross-over intervention 17 males and females
with radiographic evidence of knee OA (BMI: 39.1 ± 1.5 kg/m2; age: 57 ± 7 year)
Berry group: Freeze-dried strawberry powder, water-based beverage
Control group: Placebo powder, water-based beverage
2 × 50 g powder 1. Decrease in interleukin (IL)-6, IL-1 and matrix metalloproteinase
2. Reduction in constant, intermittent, and total pain
3. No differences for hs-CRP, nitrite, glucose, and lipid profiles
[[[[23]
12-week, randomized,
controlled, parallel
intervention
60 males and females with abdominal adiposity and elevated serum lipids
(Age and BMI of subjects are identical to those in[[[[21])
Berry group: Freeze-dried strawberry powder, water-based beverage
Control group: Placebo powder, calorie- and fiber-matched water-based beverage
Berry group:
Group 1 (LD-FDS): 25 g (equivalent to 250 g fresh strawberries);
Group 2 (HD-FDS): 50 g (equivalent to 500 g fresh strawberries)
1. Increase in plasma antioxidant capacity
2. Increase in whole blood glutathione by LD-FDS and much higher by HD-FDS
3. No effects on glutathione peroxidase and glutathione reductase enzyme activities, plasma copper, iron, selenium and zinc
[[[[27]
8-week, randomized, double-blind, placebo-controlled, parallel intervention 60 postmenopausal women
(berry group 25 g FDS: n = 20; BMI, 31.0 ± 1.0 kg/m2; age 61 ± 1 year;
50 g FDS: n = 20; BMI, 32.7 ± 1.1 kg/m2; age 59 ± 1 year;
control group: n = 20; BMI, 32.1 ± 0.7 kg/m2; age 58 ± 1 year)
Berry groups: Freeze-dried strawberry powder, water-based beverage
Control group: Iso-caloric drink with strawberry flavoring
Berry group:
Group 1: 2 × 25 g FDS (equivalent to three cups of sliced fresh strawberries);
Group 2: 25 g FDS + 25 g placebo powder
(equivalent to 1.5 cups of sliced fresh strawberries)
1. Decrease of systolic BP and brachial- and femoral-ankle pulse wave velocity by 25 g FDS
2. Increase of plasma nitric oxide metabolite levels by 50 g FDS
3. No effect on diastolic blood pressure and metabolites
[[[[28]

Table 3

Effect of blueberry consumption on cardiovascular disease, metabolic syndrome, cognitive function, mood and associated risk factors.

Intervention Subjects Format Dose/day Main findings References
6-week randomized,
double-blind,
placebo-controlled,
parallel intervention
44 males and females with metabolic syndrome
(Blueberry group: BMI 35.2 ± 0.8 kg/m2; age 55 ± 2 year;
Control group: BMI 36.0 ± 1.1 kg/m2; age 59 ± 2 year)
Berry group: Blueberry powder, Smoothie
Control group: Identical smoothie without blueberry bioactives
45 g powder 1. Improved reactive hyperemia index (endothiel function)
2. No difference in blood pressure and insulin sensitivity
[[[[30]
6-week, randomized,
placebo-controlled,
crossover intervention
18 males with CVD risk factors
(BMI 24.8 ± 2.6 kg/m2; age 47.8 ± 9.7 year)
Berry group: Wild blueberry (WB) powder, water-based beverage
Control group: Placebo drink
25 g powder
(equivalent to 148 g fresh wild blueberry)
1. Reduction of levels of endogenously oxidized DNA bases and levels of H2O2-induced DNA damage
2. No significant differences for markers of endothelial function and the other variables
[[[[31]
1-week, randomized, single-blind, placebo-controlled, crossover intervention 19 females with at least two risk factors for type 2 diabetes
(BMI: 31.4 ± 2.9 kg/m2, age: 53 ± 6.3 year)
Berry group: Wild blueberry juice
Control group: Placebo beverage
240 mL juice 1. Trend for lowering systolic blood pressure and increased serum concentrations of nitrates and nitrites
2. No changes in glucose, insulin, insulin sensitivity, triglycerides, inflammatory markers, adhesion molecules, oxidative stress, endothelial function or blood pressure
[[[[32]
8-week, randomized,
double-blind,
placebo-controlled,
parallel intervention
48 postmenopausal women with pre- and stage 1-hypertension
(Blueberry group: BMI 30.1 ± 5.94 kg/m2; age 59.7 ± 4.58 year;
Control group: BMI 32.7 ± 6.79 kg/m2; age 57.3 ± 4.76 year)
Berry group: Freeze-dried blueberry powder, water-based beverage Control group: Placebo drink 22 g powder
(equivalent to one fresh cup blueberries)
1. Decrease in systolic blood pressure, diastolic blood pressure and brachial-ankle pulse wave velocity
2. Increase in Nitric oxide levels
[[[[33]
1: Randomized, double-blind, placebo-controlled, crossover intervention
2: Randomized, double-blind, placebo-controlled intervention
1:21 males and females (age: 20.1 ± 1.0)
2:52 males and females (age: 8.2 ± 1.0)
Berry group: Freeze-dried WB powder + low-flavonoid Rocks Orange Squash, water-based beverage
Control group: Vitamin C and sugar matched placebo drink + 30 mL low-flavonoid Rocks Orange Squash, water-based beverage
30 g powder
30 mL Orange Squash
1. Increase in post-consumption positive affect score
2. No effect on negative affect score
3. Session reduction of NA after both blueberry and placebo consumption
[[[[7]
12-week, randomized, double-blind, placebo-controlled intervention 26 males and females(Blueberry group: BMI 25.9 ± 3.3 kg/m2, age 67.5 ± 3.0 year;
Control group: BMI 27.1 ± 4.0 kg/m2, age 69.0 ± 3.3 year)
Berry group: Blueberry concentrate
Control group: Placebo concentrate
30 mL concentrate
(providing 387 mg anthocyanidins)
1. Increase in brain activation responses and resting-state perfusion in the gray matter of the parietal and occipital lobes
2. Decrease in serum glutathione concentration
3. No differences in brain activity, resting state perfusion in the frontal lobes, protein carbonylation HNE adduct or malonaldehyde formation and serum hsCRP or BDNF concentration
[[[[34]
90 days, randomized, double-blind, placebo-controlled intervention 37 males and females
with English fluency, ability to walk 20 min unassisted, and > 12 months postmenopausal
(Blueberry group: BMI 24.1 ± 3.7, age 67.8 ± 4.6 year,
Placebo group: BMI 24.0 ± 2.5, age 67.3 ± 4.8 year)
Berry group: Freeze-dried blueberry powder
Control group: Placebo powder
24 g powder
(equivalent to one cup of fresh blueberries)
1. Decrease in repetition errors and reduction in switch cost
2. No improvement in gait or balance
3. No effect of Geriatric Depression Scale or the Profile of Mood States
[[[[35]

Collectively, the sixteen investigated human intervention studies provide tendencies for an improvement in health by daily strawberry or blueberry consumption. In some studies, strawberry intervention selectively showed favorable effects on inflammation, insulin sensitivity, antioxidant status, insulin response and distribution or size of blood lipids, whereas some studies showed no effect on those attributes. Blueberry intervention showed positive effects in some cognitive tests and in some cases, selectively positive effects on blood pressure, endothelial function, insulin sensitivity or oxidative stress. However, several authors discussed the need for larger subject groups and longer trial periods to obtain more precise and consistent findings. Dose of anthocyanins, as well as age, overall health and predominantly sex of participants may have also influenced the results of the reviewed studies. It was also suggested to use fresh berries instead of powder. Most authors concluded that daily strawberry or blueberry consumption may have a positive effect on health., which should be investigated in further intervention studies.



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