Health Effects of Coffee Products on Oxidative Stress-Related Metabolic Disorders: An Updated Perspective ^†

Abstract

Coffee, rich in polyphenols, has been studied for its impact on obesity and oxidative stress. Its bioactive compounds combat oxidative stress, which is linked to chronic diseases. This study provides a comprehensive, artificial intelligence-enhanced review of the scientific literature, highlighting the impact of coffee and its derivatives on these disorders. Several studies show that coffee husks and green coffee supplements reduce body weight and inflammation by increasing antioxidant defenses. In conclusion, coffee and its derived products, including valorized by-products, represent a promising avenue for dietary strategies aimed at preventing and managing oxidative stress-associated metabolic disorders and promoting overall metabolic health.

1. Introduction

The Coffea genus, which is the scientific name for coffee plants, thrives predominantly in agroforestry systems [1]. Coffee, as a beverage, has become one of the most widely consumed drinks globally. This popularity has led to extensive research into its diverse chemical compounds, how they interact, and their overall impact on human health. Of particular interest is the role of its bioactive compounds, such as caffeine and polyphenols, in modulating obesity and oxidative stress-related disorders [2,3,4]. The coffee industry generates by-products such as husks, silver skin, pulp, and parchment. These materials represent a valuable source of polyphenols, which are compounds that have demonstrated significant health potential. The development of obesity is associated with a chronic inflammatory state and elevated levels of oxidative stress in adipose tissue, resulting from an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defenses [5,6]. In this context, the bioactive compounds present in coffee by-products emerge as promising agents to mitigate these disorders [7,8,9]. Among polyphenols, chlorogenic acid stands out for its potent antioxidant capacity and significant concentration in coffee, especially in coffee husk extract. Several studies have shown that supplementation with green coffee extract produces a considerable reduction in body weight, inflammation and an overall improvement in metabolic health [8,9,10]. This action is largely attributed to the ability of chlorogenic acid to neutralize free radicals and mitigate oxidative stress, which are crucial factors in the progression of obesity [11]. This literature review aims to explore, with the support of artificial intelligence tools through Jupyter Notebook (v7.4.2) (Google Colab), the effect of coffee and the consumption of coffee derivatives on the prevention and management of obesity and oxidative stress.

2. Methods

A bibliographic search was conducted using the keyword “Coffee Therapy” in the Scopus and PubMed databases. The 1830 retrieved articles were downloaded as a CSV file. Leveraging artificial intelligence applied to natural language processing, a Jupyter Notebook (v7.4.2) in Google Colab was used to process, analyze, and select the most relevant bibliography [12]; of these, approximately 20% (366) were publications from the last 5 years. A selection was made among publications from 2012 onwards based on their affinity with the following inclusion criteria: (i) published in English; (ii) focused on the bioactive composition of coffee; and (iii) focused on the use of coffee for the treatment of obesity. Articles that did not address the relationship between coffee (or its polyphenols) and obesity/comorbidities were excluded. A total of 89 articles were reviewed. Overall, 51 publications focused on the therapeutic effects of coffee with its bioactive composition also included. Of these studies, 15 were in vivo trials (7 studies on humans: 4 on phase 4 trials and 3 on phase 1 trials), 27 were in vitro studies, and 9 were review articles. It is important to note that 38 of these publications were from the last five years. These studies were incorporated into the body of the article and other relevant sections addressing the antioxidant capacity of coffee and its derivatives, as well as its therapeutic effect on obesity and reactive oxygen species (ROS).

3. Results and Discussion

Caffeic and chlorogenic acids, which are polyphenols found in coffee, have shown the potential to mitigate the negative health effects of obesity. Obesity often leads to the production of pro-inflammatory cytokines and altered metabolic regulation [6,13]. These processes are linked to degenerative diseases [14] and oxidative stress, which contributes to insulin resistance and other complications [15]. Just like plants [15], the human body utilizes both endogenous antioxidants Superoxide Dismutase (SOD), Catalase (CAT), Glutathione Peroxidase (GPX), and exogenous antioxidants, such as polyphenols [7,16,17] (Figure 1). These polyphenols are particularly important because they not only regulate lipid metabolism but can also influence obesity and reduce the risk of mortality from cardiovascular diseases [18]. This relevance has been corroborated in a large-scale evaluation that included 40,725 adults, consolidating the evidence on its benefits for the cardiovascular system [18]. The diverse structural forms of polyphenols enable them to tackle the complexity of obesity through various mechanisms of action. One key mechanism is the reduction in oxidative stress via their antioxidant capacity. Indeed, the literature provides evidence (

Table 1. Antioxidant capacity of coffee and its by-products using the following methods: ferric reducing/antioxidant power activity (FRAP) and free radical scavenging activity (DPPH and ABTS).

Coffee Part	Ferric Reducing/Antioxidant Power Activity (FRAP)		Radical Scavenging Activity (DPPH)			Free Radical Scavenging (ABTS)
Coffee seed	100.164 ± 0.332 (µmol Fe2+/g dw) [1]	1104.4 ± 323.3 (µmol Trolox g−1 Sample) [28]	5.50 NS ± 1.00 (mmol TE/L) [34]	65.875 ± 1.129 (µmol trolox/g dw) [33]	98.5 ± 0.42 (mmolT/100 g) [35]	24.533 ± 0.202 (µmol trolox/g dw) [1]	110.1 ± 0.94 (mmolT/100 g) [35]	325.5 ± 81.0 (µmol Trolox g−1 Sample) [28]	20.62 ± 0.06 (gTrolox/100 g DW) [36]
Coffee pulp	35.41 ± 0.21 (mmol TE/g) [37]	487.47 ± 7.34 (µmol FSE/g dw) [38]	5.19 ± 0.60 (mg TE/g) [37]	0.77 ± 0.10 (g/100 g dw) [39]	73.10 ± 4.27 (%) [7].	21.49 ± 1.62 (mg TE/g dw) [38]	98.2 ± 0.8 (µM Trolox/g) [40]	52.3 ± 4.3 (µM Trolox/g) [40]	46.2 ± 2.2 (µM Trolox/g) [40]
Coffee husk	4.57 ± 0.21 (g/100 g dw) [39]	3136.4 ± 0.1 (μmol TE/g) [41]	0.29 ± 0.11 (g/100 g dw) [39]	78.56 ± 29.18 (mg eq. of CGA/g) [42]	84.95 ± 0.02 (%) [41]	97.21 ± 0.01 (%) [41]	249.25 ± 7.06 (mg eq. of CGA/g) [42]	17.48 (mmol TE/100 g dw) [43]	755.9 ± 47.97 (µmol Trolox.g −1) [44]
Coffee parchment	0.35 ± 0.02 (g/100 g dw) [39]	10.72 ± 0.000 (μmol Etrolox/ g) [45]	0.05 ± 0.00 (g/100 g dw) [39]	2.75 (mmol TE/100 g dw) [46]	0.77 (mmol TE/100 g dw) [46]	5.36 (mmol TE/100 g dw) [46]	2.94 (mmol TE/100 g dw) [46]	32.2 (mg TE/g) [47]	202.2 ± 39.3 (mg CGA eq./g) [48]
Coffee silver skin	4.05 ± 0.12 (g/100 g dw) [39]	1.55 ± 0.23 (mg Fe2+/g) [49]	0.19 ± 0.05 (g/100 g dw) [39]	39.42 ± 2.12 (%DPPH• inhibition) [49]	144.7 (mg TE/g) [50]	80.22 ± 0.47 (%ABTS inhibition •+) [49]	169.5 ± 26.7 (mg CGA eq./g) [48]	87.89 ± 2.41 (%ABTS inhibition •+) [49]	2.8 (µmoles eq. CGA/mL) [51]

) of the antioxidant potential of polyphenols found in coffee and its by-products in reducing obesity and its associated comorbidities. A clear example of this is seen in the administration of coffee cherry pulp extracts to mice, which showed positive effects on regulating type 2 diabetes, obesity, and related complications [7]. This effect may be due to the fact that coffee extract, at concentrations of 400, 200, and 100 mg/kg, regulates oxidative stress through AMP-activated protein kinase (AMPK) signaling pathways [7]. Similarly, green coffee consumption has been linked to improvements in fasting glycemia in 25 women with abdominal obesity [19]. These effects could extend to modulating body weight, given the interconnectedness of these metabolic conditions. The potential anti-obesity action of coffee is largely attributed to its antioxidant properties [20]. Various studies, in vitro and in vivo, reveal that coffee extracts significantly reduce the content and accumulation of lipid droplets in 3T3-L1 adipocytes [21]. This suggests coffee’s ability to inhibit fat formation and storage in the body. Furthermore, coffee also appears to be a relevant factor in decreasing inflammation and improving insulin sensitivity in dysfunctional human adipocytes [22]. This positive impact on adipose tissue is partly due to its bioactive compound, N-methylpyridinium, which acts as a potent anti-inflammatory molecule [22]. Another key component is chlorogenic acid (CGA), a polyphenol that, in studies with obese mice, has been shown to inhibit lipogenesis and improve glucose metabolism [23]. Beyond its effects on obesity, CGA has also exhibited significant antioxidant properties. By reducing ROS production in 29 horses through the stimulation of regulatory T cells [24], CGA (at 50 µg/mL) may enhance performance and recovery in athletes. Surprisingly, this could also explain why the highest coffee consumption was observed in the evaluation of 923 obese individuals, who chose to drink it mainly for its reinforcing effect [25]; this is attributed to the caffeine content since in 160 women with obesity it was found to insight greater vigor/activity [4]. Coffee, as well as being a popular stimulant, has demonstrated various beneficial health effects supported by research. For instance, moderate coffee consumption, specifically between one and seven cups per week, in 1483 evaluated patients was associated with a reduction in body fat [13]. These positive effects can be partly attributed to coffee’s composition. Green coffee, in particular, has shown a remarkable antioxidant and anti-angiogenic capacity in cell line studies thanks to its high polyphenol content (317.04 ± 0.89 µg/mL gallic acid equivalent) [11]. Research in animal models has revealed that administering coffee pulp is associated with reductions in blood pressure, blood glucose, weight gain, insulin resistance, and oxidative stress [26]. These promising findings are further reinforced by human studies. For example, a 12-week supplementation program combining 500 mg of green coffee extract reduced total body weight and fat mass in 65 individuals with obesity [27]. Beyond the coffee bean itself, coffee leaf tea at a concentration of 12 mL/kg has shown antioxidant activity by combating free radicals in rats [9]. This effect is likely due to its total phenol content (56.53 ± 0.43 mgGAE/g), which has a protective and reparative effect on defective pancreatic beta cells. Furthermore, green coffee supplementation has been demonstrated to reduce body weight, body mass index (BMI), and waist circumference in 64 women with obesity who consumed a 400 mg extract for 8 weeks [28,29]. Its benefits extend to improving inflammation and metabolic health in rats [10] without affecting insulin sensitivity and even reducing body weight in animal models [8,30]. Many of these effects are attributed to coffee’s high chlorogenic acid content. The concentration of this compound can vary significantly depending on the drying method, species, and coffee by-product used, with reported values of 250 mg/kg, 2.92 ± 0.15 g/L, 3.13 ± 0.33 mg g-1 DW, 543.23 mg/L, and 200 mg [24,26,27,28,31,32,33]. Overall, the evidence suggests that polyphenols from coffee and its by-products exert beneficial effects on obesity through multiple mechanisms. These findings support the therapeutic potential of coffee and its components in preventing and managing obesity and its metabolic complications.

4. Conclusions

There is strong scientific evidence supporting the fundamental role of coffee consumption and its derivatives, particularly their bioactive compounds. Led by polyphenols such as chlorogenic acid, caffeic acid, and N-methylpyridinium, these compounds exert their effects by modulating critical factors linked to metabolic diseases. These include direct ROS scavenging, upregulation of endogenous antioxidant enzyme systems (SOD, CAT, GPx), anti-inflammatory actions, increased insulin sensitivity, glucose homeostasis regulation, and the modulation of lipid metabolism, encompassing anti-adipogenesis and lipolytic effects. Human studies demonstrate that green coffee extracts improve metabolic markers and reduce adiposity. Coffee by-products, such as husk, pulp, and silver skin, which are rich in chlorogenic acid, also offer benefits. Taken together, in vitro and in vivo research suggest that prolonged coffee consumption at low and moderate concentrations may have a positive impact on obesity. This positions coffee as an ally in the prevention and management of obesity and reduction in oxidative stress, thereby promoting better metabolic health. However, this work has limitations; further human studies, with improved methodology and at more advanced stages, are needed to reach more robust conclusions and formulate specific recommendations that can be extrapolated to broader populations. Therefore, future research should focus on enhancing the extraction and application of bioactive compounds present in coffee beans and their by-products to develop specific nutraceuticals that combat metabolic disorders linked to oxidative stress in humans.