Vegetable Extracts and Nutrients Useful in the Recovery from Helicobacter pylori Infection: A Systematic Review on Clinical Trials

Helicobacter pylori (H. pylori) infections affect almost half of the world’s population, with gradually increasing incidence in developed countries. Eradication of H. pylori may provide significant benefits to the affected individual by healing a number of gastrointestinal and extra-digestive disorders. But due to increased microbial resistance and lack of patient adherence to the therapy, the eradication rate of H. pylori is below 80% with current pharmacological therapies. The usage of botanicals for their therapeutic purposes and medicinal properties have been increased in last decades. They can be use as alternative H. pylori treatments, especially against drug-resistant strains. Epidemiological studies have revealed that people with lower vegetable and micronutrient intake may be at increased risk of H. pylori infection. We have undertaken a review of clinical trials to evaluate the efficacy of vegetable extracts and micronutrients in patients with H. pylori. Various databases, such as Google Scholar, PubMed, Scopus, Web of Science, and the Cochrane Library, were searched for the articles published in English. A total of 24 clinical studies (15 for vegetable extracts and 9 for micronutrients) were selected to be reviewed and summarized in this article. Vegetable extracts (Broccoli sprouts, curcumin, Burdock complex, and Nigella sativa) and micronutrients (vitamin C and E) were not found to be as effective as single agents in H. pylori eradication, rather their efficacy synergized with conventional pharmacological therapies. Conversely, GutGard was found to be significantly effective as a single agent when compared to placebo control.


Introduction
Helicobacter pylori is a Gram-negative, spiral shaped microaerophilic bacterium, infecting half of the world population. However, the incidence of infection has been gradually decreasing in developed countries due to reduced family sizes, decreased overcrowding, and improved sanitization. The prevalence in developing countries is around 90%, while in developed countries (except Japan), the prevalence of infection falls below 40% [1,2]. H. pylori is a nasty pathogen that can persist in the stomach of infected persons for a lifetime, if left untreated. It provokes a chronic gastric inflammatory response, resulting in the development of several gastric pathological conditions including superficial gastritis, chronic atrophic gastritis, peptic ulcers, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma [3]. In 1994, it was regarded as a primary factor for the development of gastric cancer and was classified as a group-I carcinogen by The International Agency for Research on Cancer [4] H. pylori bacteria have also been identified in extra-gastric tissues in the head and neck regions, with unknown origin and pathogenicity [5]. The possible mechanisms of diffusions are gastric reflux and nasal or oral routes, where laryngopharyngeal reflux may contribute to many sinonasal, laryngeal, pharyngeal, and middle ear disorders; however, there is no clear evidence of the active role of H. pylori in otorhinolaryngological diseases [5]. H. pylori infection has also been linked with some extra-digestive diseases i.e., iron deficiency anemia [6], idiopathic thrombocytopenic purpura [7,8], hepatobiliary diseases [9,10], nonalcoholic fatty liver disease [11], diabetes mellitus [12,13], cardiovascular disorders [14,15], neurodegeneration (Alzheimer's disease, Parkinson's disease, and glaucoma) [16][17][18], and osteoporosis [19][20][21]. Osteoporosis, with the burden of bone fragility and osteoporotic fractures it brings, is a common multifactorial disorder of increasing incidence. A large meta-analysis demonstrated that patients with H. pylori infection are at a high risk of developing osteoporosis [21]. Interestingly, recent data suggests that osteoporosis and many of the extra-digestive diseases associated with H. pylori infection share risk factors and pathogenetic pathways [19]. In this connection, it can be noted that diabetes mellitus, a prominent extra-digestive disease associated to H. pylori infection, adversely impacts on skeleton and bone health, and is associated with an increased risk of osteoporosis and fragility fractures [22]. Infection with the most virulent strains (in particular, cagA+) appears to be associated with higher inflammatory response and elevated risk of gastroduodenal and extra-digestive diseases. Though details still remain unclear, person-to-person transmission and familial spread are the most common routes of the infection transmission [23,24].
Eradication of H. pylori may provide significant benefits to the affected individual in term of the healing of a number of gastrointestinal complications and extra-gastrointestinal disorders [25]. The current pharmacological therapy is based on the combination of antimicrobial and antisecretory agents, as an increase in gastric pH by antisecretory agents is required for the bactericidal action of antibiotics. Many antibacterial entities are currently in practice for the treatment of H. pylori infections such as amoxicillin, tetracycline, clarithromycin, metronidazole, levofloxacin, bismuth subsalicylate, and rifabutin, while the only antisecretory class in use is proton pump inhibitors (PPIs) [26]. Different guidelines are available for treatments, where prescribers rely on triple therapy (amoxicillin, clarithromycin, and PPI) for 7-14 days as a first line therapy in most cases [27][28][29]. The eradication rate remains below 80% with this regimen, because of increased microbial resistance to clarithromycin, and switching to a quadruple therapy by the addition of bismuth-containing compounds has been suggested [30,31]. In addition to microbial resistance, lack of patient adherence to the therapy is an important factor responsible for treatment failure. The main cause of patient nonadherence is the complexity of the therapy involving at least three drugs, administered in frequent doses and for a long time. Other causes of nonadherence may include adverse drug reactions to the therapy with lack of immediate improvement, high cost of the medications, and recurrence of the infection after a successful eradication [3].
Considering these problems, novel therapeutic approaches, and the discovery of new molecules with antibacterial effects or adjuvants that may help patients to comply with the therapies have emerged. Natural extracts, especially those derived from botanical sources, have been used for their beneficial health effects and for the management of infectious disorders since ancient times [32]. A number of scientific studies have been reported the anti-H. pylori effects of natural products using in vitro and in vivo experimental models, either in the form of botanical extracts or pure compounds [33]. In this review, we focus on evaluating the efficacy of vegetable extracts and micronutrients against H. pylori by summarizing the most relevant clinical studies.

Methodology
The present study consists of an up-to-date review of clinical trials covering the importance of vegetable extracts and micronutrients supplementation, with regards to the eradication of H. pylori infections. The search involved all the clinical trials (randomized and non-randomized) involving the evaluation of vegetable extracts and micronutrients in patients with H. pylori and related gastrointestinal symptoms. We systematically searched databases including PubMed, Scopus, Web of Science and Cochrane Library for articles published in English language. The following terms were used in the literature search in all possible combinations: "Helicobacter pylori infection" and "vegetable extracts" or "cinnamon" or "broccoli sprouts" or "turmeric" or "curcumin" or "garlic" or "Sesamum indicum" or "Glycyrrhiza glabra" or "Nigella sativa" or "micronutrients" or "vitamins" or "vitamin C" or "vitamin E" or "minerals" or "zinc" or "polaprezinc" and "clinical trials". At first, two independent researchers performed the selection of studies, and the third investigator was involved to carefully reviewed the studies selected, with duplicated or nonrelevant studies being excluded after screening of title and abstracts. No limits were defined in the selection of clinical studies regarding randomization or nonrandomization and patient sex or age. All studies reporting in English language were selected for evaluation in writing this systematic review Overall, by systematic search of the databases, 37 potentially eligible studies were identified based on the inclusion criteria. After excluding duplicates and other articles due to valid reasons, we selected 25 articles to provide a systematic review. Figure 1 illustrates the PRISMA flow diagram for study selection. we focus on evaluating the efficacy of vegetable extracts and micronutrients against H. pylori by summarizing the most relevant clinical studies.

Methodology
The present study consists of an up-to-date review of clinical trials covering the importance of vegetable extracts and micronutrients supplementation, with regards to the eradication of H. pylori infections. The search involved all the clinical trials (randomized and non-randomized) involving the evaluation of vegetable extracts and micronutrients in patients with H. pylori and related gastrointestinal symptoms. We systematically searched databases including PubMed, Scopus, Web of Science and Cochrane Library for articles published in English language. The following terms were used in the literature search in all possible combinations: "Helicobacter pylori infection" and "vegetable extracts" or "cinnamon" or "broccoli sprouts" or "turmeric" or "curcumin" or "garlic" or "Sesamum indicum" or "Glycyrrhiza glabra" or "Nigella sativa" or "micronutrients" or "vitamins" or "vitamin C" or "vitamin E" or "minerals" or "zinc" or "polaprezinc" and "clinical trials". At first, two independent researchers performed the selection of studies, and the third investigator was involved to carefully reviewed the studies selected, with duplicated or non-relevant studies being excluded after screening of title and abstracts. No limits were defined in the selection of clinical studies regarding randomization or nonrandomization and patient sex or age. All studies reporting in English language were selected for evaluation in writing this systematic review Overall, by systematic search of the databases, 37 potentially eligible studies were identified based on the inclusion criteria. After excluding duplicates and other articles due to valid reasons, we selected 25 articles to provide a systematic review. Figure 1 illustrates the PRISMA flow diagram for study selection.

Preclinical Studies on H. pylori Infections
Plants and spices have gained increased popularity for therapeutic purposes owing to their medicinal properties, in combination with their broad flexibility and favorable safety profiles, and they can be used as alternative anti-H. pylori formulations especially against drug-resistant strains [34]. There are hundreds of scientific publications describing the active antibacterial role of herbal products and nutrients against H. pylori [3]. Epidemiological studies have revealed that people with lower vegetable and micronutrients intake may be at increased risk of H. pylori infections [35,36]. Vegetable extracts can act against H. pylori infection via multiple mechanisms such as antibacterial, anti-adhesive and antiinflammatory activities [37]. Pisum Sativum L. germinated in the dark have been showed to inhibit H. pylori growth in vitro in a dose dependent manner [38]. Allium tuberosum Rottler ex Spreng. extract was found to inhibit all 21 of the tested strains of H. pylori in vitro, with growth inhibitory zones ranging from 12 to 29 mm [39]. Another study showed the bactericidal effects of olive oil polyphenolic compounds against eight strains of H. pylori in vitro, and most importantly three of these were resistant to certain antibiotics [40]. These polyphenols could diffuse from oil into gastric juice and can be stable for hours in acidic environments.
Garlic (Allium sativum L.) oil significantly suppressed the H. pylori viability in vitro at concentrations of 2-32 mg in postprandial gastric volumes of 0.25-1 L [41]. In another study, garlic extracts suppressed the early stages of H. pylori induced gastritis in Mongolian gerbils when administered four hours following H. pylori inoculation at 1, 2, and 4% concentrations [42]. Isothiocyanate sulphoraphane (an abundant compound in broccoli sprouts) has been reported as a potent bacteriostatic agent against bacterium H. pylori (in vitro tested against 48 strains). It was effective in eradicating H. pylori from human gastric xenografts in nude mice [43]. An in vivo approach of evaluating the efficacy of fresh broccoli sprouts demonstrated that oral treatment of C57BL mice with sulphoraphane rich broccoli sprouts resulted in the reduction of H. pylori colonization, mucosal expression of TNF-α and IL-1β and alleviated corpus inflammation [44]. Anti-adhesive effects have been found with Abelmoschus esculentus (L.) Moench (okra) on H. pylori by Messing et al. using human gastric adenocarcinoma cell-lines in a dose dependent fashion (0.2-2 mg/mL) [45]. The analysis of the structures of polysaccharides from immature okra have confirmed the presence of acetylated rhamnogalacturonan-I polymers, decorated with short galactose side chains, possessing anti-adhesive potential [46].
Glycyrrhiza glabra L. (liquorice) has proven useful in the treatment of peptic ulcers in traditional therapeutic systems such as Chinese, Kampo and Indian medicine, supported by numerous studies evaluating the in vitro anti-H. pylori effects of liquorice [47][48][49]. A flavonoid rich extract of G. glabra has been found to be active against H. pylori with minimal inhibitory concentration (MIC) values of 32-64 µg/mL, with glabridin (the major flavonoid present in the extract) being the most potent antibacterial compound [50]. The anti-H. pylori mechanisms reported were inhibition of DNA gyrase, dihydrofolate reductase or protein synthesis. Moreover, no significant effects were found on the adhesion of H. pylori bacterium to the human gastric adenocarcinoma cell-line. The in vivo model revealed a reduction of H. pylori colonization in C57BL mice, when treated with G. glabra extract at a dose of 25 mg/kg for 3 weeks [51]. Dietary supplementation of mice with Angelica keiskei inhibited H. pylori induced gastric inflammation, perhaps due to its antioxidant activity [52]. It was shown to prevent the increase of H. pylori induced lipid peroxide and myeloperoxidase activity, inhibited the neutrophils infiltration, and downregulated the expression of inflammatory mediators including interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). The mastic gum derived from Pistacia lentiscus L. was reported to eliminate H. pylori pathogens in 1998 [53]. The essential oil isolated from P. lentiscus leaves was found to be effective against all H. pylori clinical isolates including drug resistant strains [54]. The reduction of H. pylori colonization with mastic gum extract was supported by in vivo study conducted by Paraschos and colleagues; Molecules 2021, 26, 2272 5 of 15 however, attenuation of H. pylori-associated chronic inflammation was not observed with the treatment [55].
DNA damaging free radicals are usual products of chronic H. pylori infections, and supplementation with antioxidants such as vitamins (C and E) and carotenoid (astaxanthin) may be a useful strategy in combating H. pylori pathogenesis, with fruits and vegetables being the main dietary sources of these antioxidants [56]. Most of studies have been performed with vitamin C, which is known to highly concentrate in gastric mucosa and gastric juice, and which may influence the course of H. pylori infections and lower the risk of gastric cancer through several mechanisms [57,58]. It positively regulates the stimulation and activity of granulocytes, macrophages, and lymphocytes, and the production of immunoglobulin [36]. Vitamin C at high doses has been shown to inhibit the colonization of H. pylori in the stomach of Mongolian gerbils [59]. Wang et al. reported the in vitro inhibition of H. pylori growth and in vivo decrease in colonization levels and inflammation scores in mice treated with vitamin C and astaxanthin [60]. Treatment with astaxanthin may alters immune response to H. pylori by shifting Th1 response towards Th2 cell-response [61].

Vegetable Extracts and H. pylori Infections: Clinical Studies
A total of 16 studies reported the bioactivity of the vegetable extracts in patients with H. pylori infections and related symptoms or conditions (Table 1). Nir et al. conducted a randomized control trial (RCT) to evaluate the effects of cinnamon extract against H. pylori infection in human subjects who underwent gastroscopy [62]. Fifteen patients (4 males and 11 females) aged 16-79 years were treated with alcoholic cinnamon extract (40 mg twice daily) for 4 weeks, while eight patients (1 male and 7 females) aged 35-79 years were given placebo. Twenty-three patients completed the trial, and seven were excluded from the final analysis for one of the following reasons: (1) Negligible count on urea breath test despite of the presence of bacteria, (2) noncompliance to the therapy, and (3) receiving antibiotics during the study period. The results were evaluated by a 13 C urea breath test, which showed a slight improvement in urea breath counts; however, no significant difference was found between groups before and after treatment. Triple therapy twice a day for one week + turmeric tablets (700 mg) thrice a day for 28 days.
Triple therapy (omeprazole, amoxicillin, and metronidazole) twice a day for one week.
Significantly decrease in MDA levels and increase in TAC of the gastric mucosa in triple therapy + curcumin treated patients.
[67] A comparative study evaluated the potential of broccoli sprouts powder and standard triple therapy to eradicate H. pylori in patients with type 2 diabetes, either administered alone or in combination [64]. Eighty-six diabetic patients with positive H. pylori stool antigen test were randomized to receive broccoli sprout powder (6 g/day) for 4 weeks, standard triple therapy (omeprazole 20 mg, clarithromycin 500 mg, amoxicillin 1000 mg, twice a day) for 14 days, or a combination of broccoli sprout powder and standard triple therapy. At the end of the treatment period, H. pylori eradication was assessed by an H. pylori stool antigen test, which showed H. pylori eradication rates of 56%, 89.3%, and 91.7% with broccoli sprout powder, standard triple therapy, and combination of both, respectively. In addition, broccoli sprout powder also improved cardiovascular risk factors.
A RCT by Chang and colleagues did not show any improvement in H. pylori density with Brassica oleracea L. (broccoli sprout) extract but it inhibited the lipid peroxidation in gastric mucosa and thus could be beneficial for cytoprotection in H. pylori induced gastritis [65]. Volunteer subjects (n = 100) were evaluated, and eligible candidates were randomly assigned into three groups i.e., group A (n = 33) including H. pylori positive, broccoli sprout extract containing sulforaphane treatment subjects, group B (n = 28) including placebo subjects, and group C (n = 28) including H. pylori negative, broccoli sprout extract containing sulforaphane treatment patients. Patients were treated either with placebo or broccoli sprout capsules containing 250-mg standardized broccoli sprout yielding 1000 mg sulforaphane twice daily for 4 weeks. Result analysis revealed that urea breath test values or ammonia concentration were not significantly affected by treatment with broccoli sprout extract in H. pylori positive patients; however, malondialdehyde (MDA) values were significantly reduced in the intervention groups (groups A and C).
Two clinical studies showed an improvement of dyspeptic symptoms with curcumin in H. pylori positive patients, with no effects on H. pylori eradication. Twenty-five H. pylori positive patients including both males and females (mean age of 50 ± 12 years) with functional dyspepsia were treated with curcumin 30 mg, bovine lactoferrin 100 mg, N-acetylcysteine 600 mg, and pantoprazole 20 mg twice daily for 7 days [66]. Results revealed a significant improvement in the severity of symptoms and serologic signs of gastric inflammation in all patients, but H. pylori was eradicated in only three patients (the eradication rate was 12%). In a randomized double-blind placebo-controlled parallel-group trial, patients with peptic ulcer were assigned a standard triple therapy (clarithromycin 500 mg, amoxicillin 1000 mg, and pantoprazole 40 mg twice daily), and were randomized to receive either curcumin (500 mg/day) or placebo as adjuncts to standard triple therapy [67]. Adjunctive therapy with curcumin resulted in a greater improvement of dyspeptic symptoms as measured by Hong Kong dyspepsia index (HKDI) scores, however no significant effects were observed on H. pylori eradication with curcumin adjunction.
Judaki et al. observed an amelioration of oxidative stress and histopathologic changes with curcumin in combination with triple therapy in chronic gastritis associated with H. pylori infection [68]. Patients were randomized to receive triple therapy or curcumin in combination with triple therapy, 50 patients each. Treatment with triple therapy included omeprazole, amoxicillin, and metronidazole twice a day for one week, where turmeric tablets were administered at a dosage of 700 mg thrice a day for 28 days. Triple therapy in combination with curcumin significantly reduced MDA concentrations with an increase in total antioxidant capacity, as compared to patients treated with triple therapy alone.
Garlic consumption showed an eradication of H. pylori in RCT, though the results were not considerable when compared with placebo group [69]. Thirty-six patients (47% males and 53% females), with mean ages of 40.87 ± 16.45 years in the treatment group and 35.40 ± 11.26 years in the control group, were randomized to receive either two tablets of garlic powder daily (2 g each) or 2 tablets of placebo for 8 weeks. At the end of the experimental period, urea breath tests showed 87% H. pylori negative cases in the treatment group and 73% H. pylori negative cases in the control group. A pilot study conducted earlier, demonstrated non-satisfactory results with the intake of gastric oil capsules on H. pylori eradication [70]. Twenty dyspeptic patients aged 18-75 years with positive H. pylori were assigned to receive garlic oil capsules (4 mg) four times daily with meals for 14 days. Five patients completed the study, and no evidence of symptomatic improvement or H. pylori eradication was noted with garlic oil.
Graham and Lang performed a prospective crossover study in healthy H. pylori infected adults (average age: 41.4 years) to investigate the H. pylori treatment potential of garlic and jalapeño peppers [71]. Twelve subjects were participated in the study and were received garlic (10 freshly sliced cloves), capsaicin (six freshly sliced large jalapeño peppers) and two tablets of bismuth subsalicylate, via test meals on separate days. Neither garlic nor capsaicin possessed any beneficial effects on H. pylori eradication, as the median urease activity for garlic was 28.5 before and 39.8 after, while for capsaicin it was 43.7 before and 46.6 after. Bismuth showed a marked inhibitory potential with 55.8 vs. 14.3 median urease activity before and after therapy. A randomized, double-blind placebo-controlled clinical trial exhibited a positive response with Burdock complex (comprised of Arctium lappa L., Angelica sinensis (Oliv.) Diels, Lithospermum erythrorhizon Siebold & Zucc., and Sesamum indicum L. oil) against H. pylori [72]. Forty volunteers were randomly assigned to Burdock complex or placebo (n = 20 each), and they were directed to consume two bottles of Burdock complex or placebo (2 × 10 mL) every day after breakfast and dinner for eight weeks. Result analysis revealed a significant decrease in urea breath counts and inflammatory markers (TNF-α and IL-8) with improved antioxidant capacity (total phenolic contents, superoxide dismutase, and catalase).
GutGard (Root extract of Glycyrrhiza glabra L.) demonstrated considerable efficacy against H. pylori in a randomized, double-blind placebo-controlled study [73]. Participants diagnosed with H. pylori were assigned to receive GutGard 150 mg (n = 55) or placebo (n = 52) daily for 60 days. At the end of experiment, H. pylori stool antigen (HpSA) test was found negative in about 56% of patients treated with GutGard while HpSA was negative in only 4% of patients in placebo group. Salem and colleagues conducted a comparative study of Nigella sativa and standard triple therapy in eradication of H. pylori in patients (n = 88; 32 males and 56 females; age range of 18-65 years) with non-ulcer dyspepsia [74]. Patients were randomized to four groups i.e., triple therapy (clarithromycin, amoxicillin, and omeprazole), 1-g N. sativa + 40 mg omeprazole, 2-g N. sativa + 40 mg omeprazole, and 3-g N. sativa + 40 mg omeprazole. The difference in H. pylori eradication rate was not significant between triple therapy (82.6%) and 2-g N. sativa (66.7%), while the eradication rates demonstrated by 1-and 3-g N. sativa were less significant. However, the improvement of dyspeptic symptoms was similar in all groups.
The efficacy of G. glabra has also been evaluated in patients with H. pylori synergistically with a probiotic strain Lactobacillus paracasei, in randomized, double-blind, placebocontrolled trials [75]. A total of 142 patients were randomly allocated to the treatment group (fermented milk containing 1.0 × 10 6 CFU/mL L. paracasei HP7 and 100 mg G. glabra) or placebo group (fermented milk only) once daily for 8 weeks. A significant improvement in gastrointestinal symptoms, 13 C-urea breath test scores, and chronic inflammation was observed in the treatment group. Addition of G. glabra to a clarithromycin-based regimen showed increased efficacy in H. pylori eradication [76]. In RCT, 120 patients affected by non-ulcer dyspepsia or peptic ulcer disease were randomized into a treatment group (clarithromycin based triple regimen + G. glabra 380 mg twice daily) or a control group (clarithromycin based triple regimen) for 2 weeks. H. pylori eradication rate for treatment and control groups was found to be as 83.3% and 62.5%, respectively.
A double-blind, randomized controlled clinical trial demonstrated significant improvement in patients with functional dyspepsia with adjuvant supplementation of honey-based N. sativa formulation [77]. Patients (n = 70) with functional dyspepsia according to ROME III criteria, confirmed by upper gastrointestinal endoscopy, were allocated a treatment of a combination of anti-secretory agent and honey-based formulation of N. sativa (5 mL N. sativa) once daily or placebo for 8 weeks. The mean Hong Kong index of dyspepsia scores and H. pylori infection rates were significantly lower in the N. sativa treated group, with no serious adverse event being reported.
Mastic gum demonstrated nonsignificant effects on H. pylori eradication in a randomized pilot study [77], however the antimicrobial effects were consistent in preclinical studies. Fifty-two patients were randomized in four groups to receive either pure mastic gum (350 mg, three times daily) for 14 days (group A), pure mastic gum (1 g, three times daily) for 14 days (group B), combination of pure mastic gum (350 mg three times daily) and pantoprazole (20 mg twice daily) for 14 days (group C) or standard therapy (pantoprazole 20 mg, amoxicillin 1 g and clarithromycin 500 mg) for 10 days (group D). H. pylori eradication was confirmed with urea breath test 5 weeks after the completion of eradication therapy, which revealed a H. pylori eradication in 4/13 patients in group A and in 5/13 patients in group B, while none of the patients treated showed eradication in group C. Briefly, there were no significant differences in the mean values of urea breath test in these three groups. On the other hand, the patients treated with standard therapy appeared to have significant eradication of the infection, i.e., 10/13 patients with negative urea breath test [78].

Micronutrients and H. pylori Infections: Clinical Studies
Overall, the 9 human studies included in this review have demonstrated the efficacy of nutrients against H. pylori infections ( Table 2). RCT conducted by Zojaji et al. revealed a significant increase in H. pylori eradication rate with the augmentation of standard therapy with vitamin C [79]. Patients were randomized into group A (n = 162; mean age: 45 years) receiving standard therapy (amoxicillin 1 g, metronidazole 500 mg, bismuth 240 mg and omeprazole 40 mg) and group B (n = 150; mean age: 43 years) receiving the same regimen plus vitamin C 500 mg/day, for two weeks. The H. pylori eradication rates in group A and group B were 48.8% and 78% respectively, showing negative urea breath tests. Sezikli et al. observed the improved eradication rates of H. pylori by the co-supplementation of triple therapy with vitamins C and E [80]. Two hundred patients were randomized to receive either standard triple therapy (lansoprazole, amoxicillin, and clarithromycin) for 14 days plus vitamins C (500 mg) and E (200 mg) for 30 days or standard triple therapy alone for 14 days. Urea breath test showed significantly higher eradication rates in patients receiving vitamins C and E. H. pylori eradication rates in group A was significantly higher as compared to group B. [79] RCT 160 patients were randomized in group A (mean age: 44 ± 10) and group B (mean age: 43 ± 11) Conventional therapy for 2 weeks plus vitamins C (1000 mg/day) and E (400 IU/day) for 1 month (Group B).
H. pylori eradication rates were significantly higher in group B. No difference was found in TAC among both groups. [80] RCT 117 patients were randomized into 4 groups: conventional therapy, vitamins (C and E), combination of both or placebo.
Triple therapy alone ( Bismuth chelate, tetracycline, and metronidazole for 2 weeks ), vitamins C (200 mg) and E (50 mg) twice a day for 4 weeks, or combination of both treatments.

Placebo
No significant effect was found on MDA levels and ROS with vitamins supplementation. [81] RCT 171 H. pylori infected patients.
Combination of clarithromycin 250 and vitamin C showed higher eradication rates than clarithromycin 250 mg, and equivalent eradication rates to clarithromycin 500 mg. Triple therapy for 2 weeks plus vitamins C (500 mg/day) and E (100 U/day) for 1 month (Group B).Quadruple therapy for 2 weeks plus vitamins C (500 mg/day) and E (100 U/day) for 1 month (Group D).
No difference was found in H. pylori eradication rates among Groups A and B, and similarly Group C and D. [83]  Another trial conducted by Sezikli et al. investigated the synergistic effects of vitamin C and vitamin E in H. pylori eradication rates when co-supplemented with triple therapy, and their possible link with oxidative stress alteration [81]. The study included 160 patients, randomized to receive either conventional anti-H. pylori therapy (lansoprazole, amoxicillin, clarithromycin, and bismuth subcitrate) for 2 weeks plus vitamins C (1000 mg/day) and E (400 IU/day) for one month, or conventional therapy alone for 2 weeks. H. pylori eradication rates were significantly higher in patients receiving vitamins C and E; however, no difference was found in total antioxidant capacity between both groups. Supplementation with antioxidant vitamins (C and E) possessed no significant effects on mucosal reactive oxygen species damage in H. pylori induced gastritis [82]. H. pylori positive patients (n = 117) were randomized into four groups to receive triple therapy alone (Bismuth chelate, tetracycline, and metronidazole for 2 weeks), vitamins C (200 mg) and E (50 mg) twice a day for 4 weeks, combination of both treatments or placebo MDA levels and reactive oxygen species were reduced in H. pylori eradicated patients, but no considerable effects were found with vitamin supplementation.
The RCT conducted by Chuang and colleagues revealed that an add on treatment of standard H. pylori therapy with vitamin C can reduce the daily dosage of clarithromycin while preserving the high eradication efficacy for clarithromycin susceptible H. pylori patients [83]. H. pylori infected patients (n = 171) were assigned to one-week triple therapies, including omeprazole and amoxicillin plus either one of the following twice daily: (1) Clarithromycin 250 mg; (2) clarithromycin 250 mg and vitamin C 500 mg; (3) clarithromycin 500 mg. The patients receiving a combination of clarithromycin 250 mg and vitamin C showed a higher eradication rate than clarithromycin 250 mg alone, where the equivalent rate of this combination was equivalent to clarithromycin 500 mg.
Conversely a study evaluating the effects of adjunctive supplementation of triple and quadruple therapies with vitamins C and E on the eradication rates of H. pylori, showed no benefits of such supplementation [84]. Patients were divided in four groups i.e., one receiving triple therapy (amoxicillin, clarithromycin, and lansoprazole) for 2 weeks, a second was assigned to receive triple therapy for 2 weeks plus vitamin C (500 mg/day) and E (100 U/day) for one month, a third receiving quadruple therapy (amoxicillin, clarithromycin, lansoprazole, and bismuth subcitrate) for 2 weeks, and patients in group four were randomized to receive quadruple therapy for 2 weeks plus vitamins C and E for one month. H. pylori eradication rates were accessed using a C14 urea breath test, showing no considerable difference in H. pylori eradication rates between groups A and B, and similarly groups C and D.
The efficacy of polaprezinc (chelated form of zinc and L-carnosine) was tested in a randomized, parallel-group, open-label, controlled, prospective multicenter study in combination with triple therapy for H. pylori, and was compared with the patients assigned to receive triple therapy (omeprazole, amoxicillin, and clarithromycin) alone [85]. The patients were randomized into three groups for 14-day treatment; (A) patients received polaprezinc 75 mg plus triple therapy twice daily, (B) patients received polaprezinc 150 mg plus triple therapy twice daily, and (C) patients received triple therapy alone. Patients in groups A and B showed significantly higher eradication rates compared to group C, whereas no significant difference was found among groups A and B. No serious events were reported with polaprezinc, but the adverse event rate for group B was higher than for group A.
Another clinical trial conducted by Kashimura et al. showed an improvement of infection eradication with lansoprazole, amoxycillin and clarithromycin, when combined with polaprezinc [86]. Patients (n = 66) suffering from dyspeptic symptoms with H. pylori infections were randomized to receive one of the two regimens for 7 days twice daily, i.e., lansoprazole, amoxycillin, and clarithromycin, or lansoprazole, amoxycillin, and clarithromycin plus polaprezinc. Supplementation of peptic ulcer patients with zinc sulfate 220 mg/day did not show any clinically relevant benefits, however patients with normal zinc levels were found to have better ulcer treatment [86]. Patients (n = 90) with active peptic ulcer disease were randomized into an intervention group receiving standard triple therapy plus zinc, and a control group receiving standard triple therapy plus placebo for 2 weeks.

Conclusions
This systematic review provides relevant information regarding the efficacy of vegetable extracts and micronutrients in patients with H. pylori in clinical settings. Human studies have shown that vegetable extracts and micronutrients are not effective as single agents in eradication of H. pylori infections, but they may synergize with conventional pharmacological therapies for improved efficacy when used in combination. Broccoli sprouts, curcumin, Burdock complex, and vitamins (C and E) were found to be effective when used in combination with standard triple therapies for H. pylori. Nigella sativa L. in combination with omeprazole showed similar results to standard triple therapy consisting of antibiotics and omeprazole. Conversely GutGard was found significantly effective as a single agent when compared to placebo control in both clinical trials. Polaprezinc showed good efficacy in combination with standard therapy, but zinc showed no synergistic benefits.