J Cancer Prev 2021; 26(1): 1-17
Published online March 30, 2021
© Korean Society of Cancer Prevention
1School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden, 2Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, Pulau Pinang, Malaysia
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Patients with cancer are prone to several debilitating side effects including fatigue, insomnia, depression and cognitive disturbances. Beetroot (
Keywords: Beetroot, Betacyanin, Betaxanthin, Betanin, Cancer
Patients with cancer are prone to several debilitating effects due to chemotherapy or the disease itself. The behavioural disturbances experienced by patients with cancer include fatigue, insomnia, depression, and cognitive disturbances. These symptoms are very common and may persist for months or years even after completion of treatment and may affect patient’s quality of life. Functional foods have long been linked to improve human performance and health, and hence are considered beneficial as part of the cancer patients’ diet.
Interestingly, in the Traditional Persian Medicine practices, beetroot is one of the foods used in the prevention and managing of metastatic progression of cancer . It is also widely used in other medicinal systems including the Arab, traditional Chinese and Ayurvedic medicine. Beetroot, juiced or blended, is a popular functional food among breast, prostate and colorectal cancer patients as reported in Trinidad. A study at two clinical sites on the island revealed that beetroot is being consumed by patients for the purpose of treatment, health improvement and amelioration of side effects associated with chemotherapy treatment . Similarly, beetroot is also the most frequently used alternative dietetic measure among patients with cancer in Germany  and among a majority of gastrointestinal cancer patients in Serbia .
Red beetroot is highly popular and widely used for cancer patients in some parts of the world. Although there is paucity of data indicating its direct role in cancer treatment and chemoprevention its antioxidant, anti-inflammatory and other supplementary effects are potentially beneficial for patients with cancer at certain stages of disease including during chemotherapy and post-chemotherapy. This narrative review aims highlight to provide the valuable phytochemical components present in red beetroot, the current knowledge on its health benefits as a possible chemopreventive functional food and to identify related research gaps in this area of research.
To summarize the current literature on beetroot and cancer, three databases such as Pubmed, Sciencedirect and Springerlink were screened. The search terms used included beet, beetroot, sugar beet, beta vulgaris, cancer, antioxidant, anti-inflammatory, cardioprotective, anti-tumor, chemoprevention, fatigue, performance and clinical trials using Boolean operator “AND” in various combinations. Articles were first screened by year (2000 to 2021), followed by title, language and abstract. Only relevant articles were selected, and additional articles were sourced by examining the bibliographic list. Flowchart illustrating the brief search strategy is shown in Figure 1.
Phytochemicals present in beetroot are found to be beneficial for the human health. Betalains, pigments derived from betalamic acid, are an important group of bioactive phytochemicals in beetroot. Structurally, betalains are compounds with positive nitrogen in a polyene system and this cyclic amine reactive group has been considered an important contributor to their reducing properties . According to a recent study, red beetroot has the richest source of betalains among all tested plants such as prickly pear (
Other classes of phytochemicals found in beetroot include phenolics and flavonoids. Some betalains are also phenolic compounds, namely, isobetanin, prebetanin and neobetanin, vulgaxanthin I, vulgaxanthin II and indicaxanthin . Other phenolic compounds isolated from beetroot include 5,5,6,6-tetrahydroxy-3,3-biindolyl, N-trans-feruloyltyramine, N-trans-feruloylhomovanillylamine, and phenolic acids such as 4-hydroxybenzoic acid, chlorogenic acid, caffeic acid, catechin hydrate and epicatechin [25-27]. On the other hand, flavonoids are, in general, secondary metabolites with a polyphenolic structure. They are typical biologically active compounds with health-promoting properties and are important components used for various applications. The flavonoids present in beetroot include betagarin, betavulgarin, cochliophilin A and dihydroisorhamnetin . Other flavonoid compounds isolated are 3,5-dihydroxy-6,7-methylenedioxyflavanone, 2,5-dihydroxy-6,7-methylenedioxyisoflavone, quercetin, rutin and kaempferol [20,24,28-31]. The major contributor to the earthy flavor in red beet is geosmin (
The basic nutritional composition of beetroot includes sugars, dietary fibre, fatty acids, minerals and vitamins (Table 1) [27,34]. Among sugars present, sucrose is the main component. Fatty acids are present in combination of saturated, monounsaturated and polyunsaturated acids which occur in minimal amounts. Minerals such as sodium, potassium, calcium and magnesium are present in relatively high concentrations while aluminium, barium, boron, copper, iron, manganese and zinc are found at lower levels. Beetroot are also rich in both vitamins A and C . Moreover, beetroot contains a substantial amount of both non-essential and essential amino acids. Examples are methionine, threonine, lysine, leucine, isoleucine, tryptophan, phenylalanine, valine, tyrosine, cysteine, alanine, histidine, arginine, serine, proline, glycine and aspartic acid . Interestingly, a large amount of glutamine is also present in beets . Glutamine is a non-essential amino acid and is a precursor in nucleotide, glucose and protein synthesis . Its metabolism produces large quantities of glutamate, a component required for glutathione synthesis. Glutathione is important for the maintenance of the cellular redox state [37,38]. In addition, γ-aminobutyric acid (GABA) and β-alanine were also isolated from the red beetroot [35,39]. Interestingly, GABA is known to be potentially useful as a component of functional food. As an important inhibitory neurotransmitter in the nervous systems, GABA has antioxidant, anti-anxiety, anti-hypertensive properties [40,41].
Dietary nitrate found in green leafy and root vegetables such as beetroot is an important source of nitric oxide (NO) formed via the nitrate-nitrite-NO pathway . Ingested inorganic NO3- is metabolized in vivo to bioactive nitrite (NO2-) and NO2- exerts its effects by conversion to functional nitrogen oxides, including NO . NO is an important biologically active and signalling molecule involved in a multiple physiologic process, especially regulation of blood pressure and blood flow. It is a potent dilator, reduces systemic blood pressure and inhibits atherogenesis by reducing inflammatory cell recruitment and platelet aggregation . NO-mediated signalling is crucial for protecting the heart against cellular injury or death. It also regulates mitochondrial respiration by inhibiting cytochrome
Antioxidant and anti-inflammatory activities
Red beetroot has been ranked among the ten most potent antioxidant vegetables . Betacyanins are known to be a class of compounds with radical scavenging and antioxidant activities [18,48]. On the other hand, betanin, consisting of a phenolic and a cyclic amine group, is shown to be a very good electron donor, acting as antioxidants . Hence, its consumption may increases the protection against free radicals. Several earlier studies have also indicated that beetroot is an essential source of natural antioxidants [25,49-53]. Apparently, the antioxidant effects of beetroot is not limited to its tubers, but also evident in its leaves .
The antioxidant and anti-inflammatory capacity of beetroot has been evaluated in both in vitro and in vivo experiments. Beetroot ethanol extract (lyophilized) has shown substantial antioxidant, electron-donating ability and radical scavenging activities and was found to inhibit the nitric oxide production in lipopolysaccharide-treated mouse macrophage RAW 264.7 cells . Antioxidant activity, evaluated using the cell-free system and three standard spectrophotometric tests, have shown that red beetroot extracts displayed the strongest antioxidant potential as compared with other vegetable extracts . However, in the same study, there were no significant cytotoxic nor any protective effects against oxidative DNA damage in HT29 (human colon adenocarcinoma) cells challenged with reactive oxygen species (ROS) when 10% (v/v) water extracts of red beetroot was tested . Similarly, the water extracts were not found to induce the activity of phase II detoxification enzymes significantly. This is in contrary to earlier published studies. Esatbeyoglu and co-workers reported that betanin significantly reduced H2O2-induced DNA damage in HT29 cells . Betanin at a low concentration (15 µM) functioned as a free radical scavenger and as an inducer of endogenous cellular enzymatic antioxidant defence mechanisms . However, the exact amount of betanin contained in the 10% (v/v) water extract used in the earlier study was unclear and hence, difficult to compare with results of studies that used betanin alone.
In another study, the antioxidant capacity of betanin was also found to be prominent as it significantly diminished the intracellular ROS level elevated by phorbol myristate acetate (PMA) stimulation (~3 fold) and significantly enhanced caspase-3 activity in stimulated neutrophils . Betanin also decreased the content of DNA in the Comet tails in the PMA-stimulated neutrophils . Similar observation was found in another work using Caco-2 intestinal cells. Betanin was found to reduce DNA damage caused by H2O2 and significantly enhanced caspase-3 activity in both neutrophils and Caco-2 cells . Based on these findings, betanin is likely to be responsible for the effect of beetroot products on oxidative DNA damage and apoptosis in neutrophils. Since cytokines and other inflammatory mediators produced by the white blood cells are direct contributors to cancer initiation, promotion and metastasis, functional food which mitigates chronic inflammation is thought to be an important cancer prevention strategy.
Beetroot juice containing 79.3 mg/100 mL of betaxanthines and 159.6 mg/100 mL of betacyanins was found to be protective against N-nitrosodiethylamine (NDEA)-induced oxidative stress and liver injury in male rats. NDEA is a food-born carcinogen and is present in smoked or salted meat . The metabolic activation of NDEA by the hepatic microsomal cytochrome P450 system produces ethyl diazonium ion as a reactive intermediate which elicits DNA alkylation and subsequently promotes carcinogenesis. In this study, rats treated with beetroot juice prior to NDEA administration exhibited a significant reduction of DNA damage in blood leukocytes. Beetroot juice also restored the activity of some of the antioxidant enzymes in the liver and prevented xenobiotic-induced oxidative stress . In addition, beetroot juice was found to reduce the levels of liver injury biomrkers including ALT, SDH, GGT and bilirubin and reduced DNA damage triggered by NDEA treatment . The protective effect of beetroot juice against oxidative damages and the metabolic alterations induced by beetroot feeding may likely safeguard against liver damage . Furthermore, the ethanol extract of beetroot was found to exert similar protective effects on hepatotoxicity by altering various indicators of liver damage induced by lipopolysaccharide or alcohol in experimental rats .
The anti-inflammatory effects of betalains and beetroot extract appear to be mediated by interfering with the NF-κB signalling cascade . The transcription factor NF-κB promotes immunity directly by activating gene targets that up-regulates the inflammatory molecules such as chemokines and cytokines that stimulate the phagocytic cells . In an animal model study to investigate the protective effect of beetroot extract on gentamicin-induced nephrotoxicity, up-regulation of nuclear expression of NF-κB (p65), production of TNF-α and interleukin-16 (IL-6), myeloperoxidase activity, and the nitric oxide level were significantly down regulated upon beetroot supplementation . Beetroot extract treatment also significantly reduced the expression of cleaved caspase-3 and Bax protein and up-regulated the anti-apoptotic Bcl-2 protein in the kidney cells. It ameliorated the extent of histologic renal injury and reduced inflammatory infiltration in the tubules .
Betalains were also reported to supress COX-2 expression, a pro-inflammatory enzyme responsible for prostaglandin biosynthesis [62-64]. The COX-2 inhibitory effects of betanin were found to be comparable to or greater than compounds such as lycopene, chlorophyll, bixin, b-carotene and cyanidin-3-
Anti-proliferative and other chemopreventive properties
The anti-proliferative and chemopreventive activities of beetroot were demonstrated in both in vitro as well as in vivo (animal) studies. Betanin is also a major betacyanin component isolated from
In addition, both betanin and betaine extracted from beetroots have demonstrated anti-proliferative effects against hepatocellular cells . On the other hand, betacyanins tested in combination with vitexin-2-
Furthermore, Nowacki and co-workers  found that betanin-enriched beetroot extract induced apoptosis in breast cancer cells. Betanin/isobetanin-enriched concentrate produced from red beetroots inhibited proliferation of cancer cells and induced their death but has limited effects towards normal cells. The concentrate appeared to inhibit aggregated cancer cell proliferation (3D cell culture) through inhibition of the cell cycle progression, by decreasing the G1 cell number, promoting the increase of S phase and down regulating cyclin A2 and cyclin B1 levels in the breast cancer cells . Further, expression of FAS, TRAILR4, Bad and p53 (apoptotic-related proteins) was significantly induced and the mitochondrial membrane potential was clearly MCF-7 cells treated with betanin-enriched red beetroot. Suggesting that both intrinsic and extrinsic pathways were involved . Although lysosomal vacuole formation was observed in the extract-treated MCF-7 cells, there was insufficient evidence of autophagy. In a recent study, betavulgarin, isolated from beetroot was found to suppress the growth, migration, colony formation, and mammosphere formation in breast cancer cell lines. This compound also reduced the proportion of the CD44+/CD24- subpopulation and the expression of the self-renewal-related genes such as
Oral consumption of red beetroot food color, in the form of commercial dye E162, inhibited N-nitrosomethylbenzylamine (NMBA)-induced tumor formation in the rat esophagus. The number of NMBA-induced esophageal papillomas were significantly reduced by almost half in animals receiving the food color as compared with controls . In addition, the levels of inflammation and angiogenesis in the beetroot-treated animals were also reduced with a concurrent increase in the apoptotic rate. The mechanisms of chemoprevention with red beetroot appeared to involve reduction of cell proliferation, angiogenesis, inflammation and stimulation of apoptosis. Since red beetroot color contains betanins, these effects may be mediated through inhibition of oxygen radical-induced signal transduction .
In another study, oral administration of betanin in Institute of Cancer Research (ICR) mice inhibited PMA-induced promotion of mouse skin tumors and glycerol-induced promotion of lung tumors as compared with control . Betanin, in the form of beetroot extract, also significantly decreased tumor multiplicity and burden in two mouse lung tumor models . Subsequent immunohistochemical characterization revealed that betanin reduced angiogenesis and induced apoptosis in treated mice as well as in human cancer cells in vitro .
Apart from fresh beetroot juice, beetroot juice fermented with
Clinical experiences on beetroot extracts or juice in cancer are currently lacking to support the findings of both in vitro and animal studies. Only an isolated case report on an elderly patient diagnosed with chronic lymphocytic leukemia and her clinical experiences with beetroot juice was published. The patient who refused chlorambucil after a recurrence of disease, was started with beetroot-carrot juice . In the clinical follow-up duration, administration of beetroot-carrot juice alone induced a reduction in lymphocyte and peripheral blood leukocytes count by 14.7% and 43.13%, respectively with a concurrent decrease in the uric acid level. Administration of beetroot-carrot juice for 15 days resulted in an improved appetite, a sense of general well-being and increased vigor. However, upon discontinuation of the beetroot-carrot juice for 1 month, the patient experienced an increase in cell counts and up-regulation of the uric acid level. Interestingly, her condition was reversed when beetroot-carrot juice was reintroduced. This observation provides single but limited evidence for the effectiveness of the beetroot-carrot juice in eliminating malignant leukemic cells .
Polyphenol-rich foods are generally known to have anti-neoplastic effects. A clinical trial demonstrated significant short-term reduction of the prostate-specific antigen (PSA) level following supplementation with polyphenol-rich diet among elderly men . Reduction in the serum PSA level is an endpoint biomarker for hormone-refractory human prostate cancer intervention. Since beetroot contains significant polyphenolic flavonoid antioxidants, its ability to inhibit manifestation of biomarkers of cancer is expected. However, there is certainly limited information on the direct effects of beetroot and its chemical composition on tumour markers i.e., cancer antigen (CA) 125, 15-3, 19-9 and carcinoembryonic antigen (CEA). Prospective clinical studies using beetroot may provide better insight into its underlying mechanisms when given along with standard therapies. A summary of cancer prevention effects of beetroot is shown in Table 2.
Dietary supplementation of beetroot juice has been shown to mitigate anthracycline-induced cardiotoxicity . Doxorubicin and epirubicin are anthracyclines and are usually part of breast cancer treatment protocol. Anthracyclines are important chemotherapeutic agents but unfortunately, chronic administration of anthracyclines induces cardiomyopathy and congestive heart failure . For example, doxorubicin, a quinone-containing anthracycline antibiotic, is widely used to treat solid tumors such as breast and ovarian cancer. However, its clinical use is hampered by its adverse reaction such as cardiomyopathy and congestive heart failure. Although epirubicin or idarubicin, as second-generation analogs, may show improvements in their therapeutic index, there is still risk of cardiomyopathy . One of the commonly known mechanisms of doxorubicin-induced cardiotoxicity is generation of ROS, which induces the apoptosis of the cardiomyocytes . Thus, doxorubicin elicits the formation of hydrogen peroxide and superoxide anions (O2−) through redox cycling of their aglycones which explains its anti-tumor activities .
Inflammation provoked due to ROS generation and oxidative stress is a major adverse effect, especially on the heart [82,83]. Hence, improving the antioxidant defences of cardiomyocytes is an important strategy to protect against doxorubicin-induced oxidative death . In an animal study to determine the protective effect of beetroot juice against doxorubicin-induced cardiotoxicity, the combination of beetroot juice with doxorubicin significantly reduced doxorubicin toxicity in rat cardiomyocytes by reducing generation of ROS . Therefore, beetroot juice supplement is postulated to be cardioprotective in patients treated with anthracycline chemotherapeutic drugs. The clinical application of beetroot juice as an adjunct therapy to combat against cardiotoxicity caused by anthracycline drugs is promising and would have a beneficial public health impact .
Ameliorating cancer-related fatigue
Fatigue is a common adverse condition which affects the quality of life of patients with cancer . It is one of the most frequently reported complaints among cancer patients [86,87]. As high as 60% to 93% of patients undergoing radiotherapy and 80% to 96% of patients on chemotherapy experienced fatigue [87,88]. Fatigue is reported as one of the most distressing symptoms associated with cancer and its treatment . It is an independent predictor of poor quality of life and patient satisfaction . In addition, the degree of anemia was also found to be predictive of the degree of fatigue among patients with cancer .
Off-treatment fatigue, weakness, and less vitality were more prevalent among women who had breast cancer as compared with women who had benign breast problems . In an epidemiology study, breast cancer survivors were found to be complaining of lethargy more frequently than the reference group. A significant number of the breast cancer survivors experienced sleep disturbances, pain and depression which were associated with severe fatigue . In one meta-analysis, one in four breast cancer survivors suffered from severe fatigue. Some of the risk factors included chemotherapy, higher disease stages and combination cancer therapy . In one longitudinal study, persistent fatigue continued to be a challenge for breast carcinoma survivors .
The pathogenesis of cancer-related fatigue is currently not well understood. However, its development may be caused by a variety of mechanisms . Cancer-related fatigue could be related to the effects of cancer or its treatment on sleep or circadian rhythms, muscle energy metabolism and central nervous system . Findings from animal and human research suggest that several cancer-related symptoms, notably fatigue and stress, may involved the actions of proinflammatory cytokines . In addition, there were studies which showed links between fatigue and inflammatory markers. Fatigued cancer survivors are characterized by an increased level of TNF-α, monocyte production of IL-6, elevated plasma IL-1 receptor antagonist and soluble IL-6 receptor (sIL-6R/CD126) levels, etc., indicative of immune activation [99,100]. Furthermore, the pathogenesis of fatigue is also thought to be related to hormonal changes such as deprivation of androgen or premature menopause in women [101-103]. The usual approaches to treatment of cancer-related fatigue include either pharmacologic management or non-pharmacologic intervention such as patient education. Interestingly, in a systematic review of 77 randomized controlled trials involving non-pharmacologic treatments of cancer-related fatigue, results were promising for non-pharmacologic intervention . These include psychoeducation, hypnosis, exercise, relaxation and cognitive–behavioral interventions.
Functional foods have been increasingly accepted as part of a healthy lifestyle and foods. A nitrate-dietary supplementation with beetroot juice is postulated as a nutritional strategy in patients undergoing chemotherapy and post-chemotherapy due its antioxidant and chemopreventive activities. Symptoms of fatigue may be ameliorated with beetroot supplementation due its high content of dietary nitrates and subsequent production of NO. NO is a ubiquitous signalling molecule with important physiological functions in human tissues .
NO plays a crucial role in skeletal muscle metabolic and vascular control. Beetroot juice contains high levels of inorganic nitrate (NO3−), which serves as a precursor of NO. Beetroot supplementation provides dietary inorganic nitrate (NO3−) which positively affect muscle metabolic and haemodynamic function [106,107]. Oral NO3− intake, either as beetroot juice or pure sodium NO3−, are found to enhance endurance exercise performance and capacity in young healthy volunteers [107-112]. In humans, acute (2 to 3 hours) and chronic (3 to 6 days) dietary nitrate consumption has been shown to improve exercise tolerance and reduce blood pressure [112,113]. In addition, beetroot supplementation ameliorates the muscle metabolic perturbations that occur during exercise, improves muscle oxygenation and elevates human mitochondrial efficiency [113-115]. In healthy elderly subjects, serum nitrate concentrations were found to be inversely associated with general fatigue scores based on a self-rating scale (Multidimensional Fatigue Inventory) [116,117]. Similarly, in another study, the level of the job strain appeared to be directly proportional to the fatigue among women but inversely associated with NO levels. NO has the capability to buffer the association between fatigue and job strain . Hence, based on these observations, beetroot juice supplementation and its ability to increase exercise performance and tolerance in healthy subjects may ameliorate cancer-related fatigue. Currently, there are yet any studies to provide direct evidence supporting beetroot’s effects on combating fatigue among patients with cancer.
Beetroot is a vegetable rich in micro-nutrients and bioactive constituents with health beneficial properties and has been gaining attention as a health promoting functional food. The multiple bioactive constituents include the water-soluble betalains consisting of betacyanins and betaxanthins, polyphenols, flavonoids and saponins. Beetroot extracts and betacyanins have been extensively studied both in vitro and in vivo. A variety of studies have demonstrated that beetroot extracts and betanin pigments were effective in preventing experimentally induced carcinogenesis. On the other hand, the flavonoids and polyphenolic components present in abundance in beetroot support its significant anti-inflammatory and antioxidant capacities. Although most in vitro and in vivo studies have shown promising results, the molecular mechanisms of betanin chemoprevention have not been completely elucidated and clinical studies on beetroot and cancer are still lacking. In addition, the different extract preparation methods and the lack of pharmacokinetic studies with betanin alone make it difficult to determine if the therapeutic concentration or dosage used in these studies are indeed achievable in human plasma concentration.
In fact, despite containing the richest amount of anti-oxidant compounds, the red beet extract showed neither stronger cytotoxic effect towards HT29 human colon cancer cells, nor the ability to up-regulate the enzymes involved in detoxification as compared with other vegetable or herbal extracts . Although beetroot supplementation has been studied in humans, most clinical studies were performed on a limited sample size and focussed on exercise performance and endurance in healthy cohorts. Two relevant clinical trials involving beetroot and cancer are listed in the ClinicalTrials.gov (US National Library of Medicine) database, which have yet to be published. So far, there has been no clinical study which specifically examines the association between beetroot supplementation and chemo-prevention or cancer-related symptoms such as fatigue, quality of life and well-being or prognosis of disease. Evidence supporting the use of beetroot in managing fatigue and/or managing the harsh side effects of chemotherapy is inevitable for its clinical application. Both epidemiological and randomized clinical studies on beetroot supplementation and patient with cancer are certainly warranted.
Although beetroot, especially nitrates and the betalains, are well absorbed and has good bioavailability in humans, there are still insufficient data on its efficacy and long term safety of beetroot supplementation to propose the food as a long-term strategy in managing diseases like cancer. In pregnancy, nitrate-rich dietary supplementation may be problematic as it may cause a wide range of unexpected maternal and fatal adverse reactions such as thyroid problems, alteration in embryonic cells, methemoglobinemia and other disorders . Hence, intake of excessive beetroot during pregnancy may pose a health hazard. Although beetroot intake provokes no immediate negative health consequences, long term supplementation of beetroot juice should be cautioned in patients with metabolic syndromes or diabetes due to its high sucrose content. In addition, due to beetroot’s rich oxalate content, this vegetable can be harmful if taken in large quantities, particularly for individuals at risk of calcium oxalate stone formation in the kidneys . The excretion of red or pink urine after intake of beetroot occurs in 10% to 14% of the population. This symptom appeared to be more common in malabsorption and iron deficiency cases . Furthermore, the composition of volatile compounds such as pyridines and 4-methyl-pyridines in beetroot would also warrant further studies with regards to their toxicological properties . In addition, their possible interactions with anticancer drugs should also be considered, since a recent case report described a woman who developed methotrexate intoxication after drinking beetroot juice as a herbal remedy .
In summary, beetroot is a valuable vegetable to be consumed for health maintenance and has great potential to be used for chemoprevention and in patients with cancer to manage fatigue and other side effects of chemotherapy (Fig. 3). However, long term safety assessment of dietary beetroot supplementation and relevant translational studies are necessary for the clinical setting.
The authors would like to acknowledge the Smartfund Challenge Grant (MOSTI) and FRGS Grant (KPT).
No potential conflicts of interest were disclosed.
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