High serum carotenoids are associated with lower risk for developing elevated serum alanine aminotransferase among Japanese subjects: the Mikkabi cohort study

Associations of serum carotenoids with all-cause and cardiovascular mortality in adults with MAFLD

BACKGROUND AND AIMS

The associations between serum carotenoids and mortality are contradictory in various metabolic-associated diseases. This study aimed to examine the associations of five major serum carotenoids with mortality among adults with metabolic dysfunction-associated fatty liver disease (MAFLD).

METHODS AND RESULTS

This analysis included 3040 individuals with MAFLD from the Third National Health and Nutrition Examination Survey (NHANES III). All-cause and cardiovascular mortality were ascertained by linkage to the National Death Index through December 31, 2019. Cox proportional hazards regression models were employed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), and restricted cubic spline (RCS) analyses were performed to assess the linearity of the associations. During a follow-up period of 826,547 person-years, 1325 all-cause and 429 cardiovascular deaths occurred. For all-cause mortality, compared with those in the lowest quartiles, the multivariable-adjusted HRs (95% CIs) in the highest quartiles were 0.63 (0.49-0.81) for α-carotene; 0.65 (0.52-0.80) for β-carotene; 0.64 (0.51-0.81) for β-cryptoxanthin; 0.73 (0.56-0.95) for lycopene; and 0.69 (0.52-0.91) for lutein/zeaxanthin. For cardiovascular mortality, the multivariable-adjusted HRs (95% CIs) in the highest quartiles were 0.51 (0.33-0.78) for α-carotene; 0.54 (0.35-0.82) for β-carotene; 0.52 (0.34-0.80) for β-cryptoxanthin; 0.63 (0.44-0.90) for lycopene; and 0.62 (0.39-0.99) for lutein/zeaxanthin. Besides, serum α-carotene, β-cryptoxanthin, and lycopene exhibited linear correlations with all-cause mortality in MAFLD adults, and four serum carotenoids, except β-carotene, were linearly correlated with cardiovascular mortality.

CONCLUSIONS

Lower serum α-carotene, β-carotene, β-cryptoxanthin, lycopene, and lutein/zeaxanthin concentrations were associated with higher risk of all-cause and cardiovascular mortality in US adults with MAFLD.

Association between carotenoid intake and metabolic dysfunction-associated fatty liver disease among US adults: A cross-sectional study

Carotenoids have been recognized for their potential health benefits due to their antioxidant properties. There is limited research on the association between metabolic dysfunction-associated fatty liver disease (MAFLD) and carotenoids. This study aimed to investigate the effect of carotenoid intake on the risk of MAFLD. We retrospectively analyzed 2722 adults aged ≥ 18 from the National Health and Nutrition Examination Survey 2017-2018. Hepatic steatosis was identified by elastography, and carotenoid consumption was evaluated through two 24-hour dietary recall interviews. Weighted logistic regression models, subgroup analyses, and restricted cubic splines were used for analyses. The weighted prevalence of MAFLD was 51.90%. Weighted logistic regression analysis demonstrated that intake of β-carotene, lutein/zeaxanthin, and lycopene was associated with a lower risk of MAFLD after adjusting for various covariates. Compared to the lowest tertile, a significant inverse correlation was observed between the highest total lycopene intake and MAFLD among females in the gender subgroup analysis. Restricted cubic spline regression analysis revealed a U-shaped association between lycopene consumption and MAFLD risk (P < .001), with an inflection point of approximately 9.48 mg/day. Moreover, the nonlinear relationship was particularly significant in females and absent in males. In summary, increased β-carotene, lutein/zeaxanthin, and lycopene consumption was associated with a decreased risk of MAFLD. The relationship between total lycopene intake and MAFLD was nonlinear, primarily in females. These findings have significant implications for the potential prevention and management of MAFLD.

Dietary antioxidants and liver enzymes in Rafsanjan, a Region in Southeast Iran

Oxidative stress has been considered the main contributor to liver injury. Dietary antioxidants would be expected to improve liver function. The hepatoprotective effects of antioxidants are controversial. In the present study, the associations of some dietary antioxidants and the levels of serum liver enzymes were examined. This cross-sectional study was conducted using the Rafsanjan Cohort Study (RCS) data as a population-based prospective cohort which is a part of the Prospective Epidemiological Research Studies in IrAN (PERSIAN). A total of 9942 participants aged 35-70 years old were included in this study. Among this population, 4631 (46.59%) were male, and 5311 (53.42%) were female. Dietary intakes were collected by a validated food frequency questionnaire (FFQ) with 128 items. Aspartate transaminase (AST), Alanine transaminase (ALT), γ-glutamyl transferase (GGT), and Alkaline phosphatase (ALP) were measured by a biotecnica analyzer. Dichotomous logistics regression models were used to investigate the association between the elevated liver enzymes and intake of dietary antioxidants using crude and adjusted models. In the adjusted model, in subjects with higher consumption of Se, Vit A, Vit E, β-carotene, α-carotene, and β-cryptoxanthin, the odds ratios of elevated ALP were decreased compared to the reference group (ORs 0.79 (0.64-0.96), 0.80 (0.66-0.98), 0.73 (0.60-0.89), 0.79 (0.64-0.96), 0.78 (0.64-0.95), 0.80 (0.66-0.98), and 0.79 (0.64-0.98), respectively). Subjects with higher consumption of Se, Vit A, Vit E, and provitamin A carotenoids (β-carotene, α-carotene, β-cryptoxanthin) showed decreased odds of elevated ALP. These findings support the hypothesis that Se, Vit A, Vit E, and provitamin A carotenoids may be associated with improvements in ALP and act as suppressors against the development of liver injury.

Diet-derived antioxidants and nonalcoholic fatty liver disease: a Mendelian randomization study

BACKGROUND

Whether supplementation with diet-derived antioxidants is beneficial for nonalcoholic fatty liver disease (NAFLD) is still controversial and we hope to answer this question using population-based genetic data.

METHODS

A total of 8485 NAFLD cases and 658,849 healthy controls from four independent NAFLD genome-wide association studies were enrolled in this study. Genetic variants closely associated with the diet-derived antioxidants were selected to predict their circulating levels. A bi-directional Mendelian randomization (MR) design was employed to assess their causations.

RESULTS

Genetic correlation analyses suggested inverse associations between diet-derived antioxidants and NAFLD. MR analyses indicated that the odds ratio (OR) of per standard deviation increase in genetically predicted toenail and blood selenium was 1.179 for NAFLD (95% confidence interval [1.083-1.284]). Also, the genetically elevated selenium level was causally associated with increased levels of C-reactive protein, fibrinogen, alkaline phosphatase and glycated hemoglobin. The OR of 1 µg/dL increase in genetically predicted serum lycopene was 1.082 (95%CI [1.051-1.113]). No other causal associations were found for NAFLD. However, we observed protective effects of genetically predicted β-carotene (OR = 0.929[0.911-0.947]) and retinol (OR = 0.483[0.460-0.508]) on type 2 diabetes (T2D), and further they could reduce the serum levels of blood lipids and glucose. Reverse MR analysis suggested genetically predicated NAFLD status would not affect the levels of diet-derived antioxidants.

CONCLUSION

Overall, we observed the positive associations of genetically predicted selenium and lycopene with NAFLD. However, the genetically predicted β-carotene and retinol levels were inversely associated with the risk of T2D.

Preventive Effects of β-Cryptoxanthin, a Potent Antioxidant and Provitamin A Carotenoid, on Lifestyle-Related Diseases-A Central Focus on Its Effects on Non-Alcoholic Fatty Liver Disease (NAFLD)

Humans usually get dietary carotenoids from foods such as green and yellow vegetables and algae. Carotenoids have been reported to effectively reduce the risk of developing lifestyle-related diseases. β-Cryptoxanthin, which is an antioxidative carotenoid and a type of provitamin A, is metabolically converted to vitamin A. β-Cryptoxanthin has recently gained attention for its risk-reducing effects on lifestyle-related diseases, especially on non-alcoholic fatty liver disease (NAFLD), from epidemiological, interventional, and mechanistic studies. Retinoids (vitamin A) have also been reported to be useful as a therapeutic agent for NAFLD. Provitamin A is known to serve as a supply source of retinoids through metabolic conversion by the regulated activity of β-carotene 15,15′-monooxygenase 1 (BCMO1) to the retina only when retinoids are deficient. From mechanistic studies using NAFLD-model mice, β-cryptoxanthin has been shown to contribute to the improvement of NAFLD through a multifaceted approach, including improved insulin resistance, suppression of oxidative stress and inflammation, a reduction of macrophages and a shift of their subsets, and control of lipid metabolism by peroxisome proliferator-activated receptor (PPAR) family activation, which are also expected to have clinical applications. β-Cryptoxanthin has the potential to prevent lifestyle-related diseases from different angles, not only as an antioxidant but also as a retinoid precursor.

Cross-Sectional Study on the Association between Dietary Non-Enzymatic Antioxidant Capacity and Serum Liver Enzymes: The Furukawa Nutrition and Health Study

We examined the association of dietary non-enzymatic antioxidant capacity (NEAC) in overall diet, and separately from foods and beverages, with serum liver enzymes in a Japanese working population. This cross-sectional study was conducted among 1791 employees aged 18–69 years, who underwent a comprehensive health checkup in 2012–2013. A brief validated self-administered diet-history questionnaire was used for dietary assessment, and dietary NEAC intake was determined from databases of NEAC values, obtained using ferric reducing-antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. The dietary NEAC intake was calculated by multiplying the estimated NEAC values by the amounts consumed and summing the resulting values. A multiple-regression analysis was performed to explore the association between dietary NEAC intake and the serum levels of liver enzymes (aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT)), after adjustment for confounding factors. No significant associations were found between overall dietary NEAC intake and AST (FRAP, p for trend = 0.97; ORAC, p = 0.72), ALT (FRAP, p = 0.73; ORAC, p = 0.92), and GGT (FRAP, p = 0.96; ORAC, p = 0.19) levels. Food-derived, but not beverage-derived, NEAC intake was inversely associated with serum GGT levels (FRAP, p for trend = 0.001; ORAC, p = 0.02), particularly among older participants and those with high serum ferritin concentrations. The results imply that overall dietary NEAC intake is not associated with liver dysfunction, and that the NEAC values from foods may be inversely associated with serum GGT levels.

Carotenoids and fatty liver disease: Current knowledge and research gaps

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to β-carotene and lycopene, but also including β-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from β-carotene and β-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from β-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Dietary Carotenoids and Non-Alcoholic Fatty Liver Disease among US Adults, NHANES 2003⁻2014

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent worldwide. Oxidative stress is thought to be a major mechanism, and previous epidemiological studies found higher serum levels of antioxidant carotenoids were associated with reduced risk for development and progression of NAFLD. The objective of this analysis is to examine cross-sectional associations between dietary and serum levels of carotenoids in relation to NAFLD among a nationally representative sample of US adults. We used data from the 2003–2014 National Health and Nutrition Examination Survey (NHANES). Dietary carotenoid intake was estimated from a 24-hour recall, while serum carotenoids were measured from 2003 to 2006. The NAFLD status was determined based upon US Fatty Liver Index (FLI) value ≥30. Regression models were used to estimate associations between carotenoids and NAFLD by controlling for covariates and adjusting for survey design variables. Overall, 33% of participants were classified as having NAFLD. Intake of all carotenoids, with the exception of lycopene, was lower among those with NAFLD. This association was significant for the highest quartiles of intake of α-carotene, β-carotene, β-cryptoxanthin, and lutein/zeaxanthin. For serum measures, the highest level of all carotenoids was associated with significantly reduced odds of NAFLD. In conclusion, higher intake and serum levels of most carotenoids were associated with lower odds of having NAFLD. Identification of such modifiable lifestyle factors provide an opportunity to limit or prevent the disease and its progression.

Role of vitamin E in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. NAFLD manifests as hepatic lipid accumulation, insulin resistance, and inflammation, and can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis. However, the underlying mechanisms of NAFLD, including those that drive its progression, are unclear. Both liver-resident (Kupffer cells) and recruited macrophages play a crucial role in the development of insulin resistance and NASH. Therefore, NALFD could potentially be ameliorated by modifying the polarization of macrophages/Kupffer cells. Reactive oxygen species induce oxidative stress, which is implicated in the progression of NASH. Micronutrients, including vitamins, are potent antioxidants that exert anti-inflammatory effects, and are used in the treatment of NAFLD. We review here the molecular mechanisms of the pathogenesis of NAFLD and the potential utility of vitamin E in its prevention and/or treatment. © 2018 IUBMB Life, 71(4):516-522, 2019.

Effect of a high-protein diet with β-cryptoxanthin supplementation on metabolic risk factors, oxidative and inflammatory biomarkers in non-alcoholic fatty liver disease (NAFLD): study protocol for a randomized controlled clinical trial

BACKGROUND

Excessive hepatic fat is associated with increased metabolic risk factors, production of inflammatory factors, and oxidative stress. High protein intake might trigger an increased hepatic lipid oxidation through an increase in hepatic energy expenditure. Furthermore, the majority of randomized controlled trials (RCT) in humans have failed to show whether carotenoids can be used to prevent and treat non-alcoholic fatty liver disease (NAFLD). However, it is notable and contradictory that NAFLD is rapidly escalating in Iran and other countries with lower intakes of fruit and vegetables (as sources of β-cryptoxanthin [β-CX] and carbohydrates) and higher intake of carbohydrates (as an agent of NAFLD); and the effects of β-CX and a high protein diet (HPD) on NAFLD need to be investigated further.

METHODS/DESIGN

This study will be conducted as a randomized, double-blind, placebo-controlled clinical trial for 12 weeks to receive daily β-CX 6 mg supplementation combined with a HPD on levels of metabolic factors, β-CX, glycemic and lipid profiles, inflammatory factors, adipocytokines, and body composition. Ninety-two eligible patients, aged 18-60 years, of both genders, who are obese and overweight (body mass index [BMI] 25-40 kg/m2) will be randomly assigned to four groups as follow: HPD + placebo; normal protein diet + β-CX (NPD + β-CX); HPD + β-CX; and NPD + placebo (control group). Two populations will be analyzed in this work. The intention-to-treat (ITT) population includes all patients who will be randomized, while the per-protocol (PP) population includes all individuals who complete the 12- week intervention (i.e. study completers).

DISCUSSION

Our findings from this trial will contribute to the knowledge of the relationship between β-CX supplementation and a HPD on NAFLD patients and determination of optimal macronutrient ratios without energy restriction.

TRIAL REGISTRATION

Iran clinical trials registry, IRCT2017060210181N10 . Registered on 20 June 2017.

No association between fruits or vegetables and non-alcoholic fatty liver disease in middle-aged men and women

OBJECTIVE

It has been hypothesized that fruit and vegetable intake is inversely associated with non-alcoholic fatty liver (NAFLD). However, some studies have speculated that fruit intake might be positively associated with NAFLD owing to the fructose content of the fruit. This might cause consumers to hesitate consuming fruit. The aim of this study was to assess the association between fruit and vegetable consumption and NAFLD.

METHODS

This was a cross-sectional study of 977 men and 1467 women, 40 to 69 y of age without current liver disease other than NAFLD and who did not report excess alcohol intake (i.e., ≥30 g/d in men and ≥20 g/d in women). Dietary intake was assessed using a validated diet history questionnaire. NAFLD was diagnosed from abdominal ultrasonography results. The association between quartiles of fruit or vegetable consumption and NAFLD prevalence was assessed using logistic regression analysis, with lowest category as reference.

RESULTS

The prevalence of NAFLD was 34.9% in men and 11.7% in women. Adjusted for age and lifestyle factors, fruit intake was inversely associated with NAFLD in both sexes. However, these associations disappeared after further adjustment for body mass index. Consumption of total vegetables was not associated with NAFLD. In women, a linear inverse association was demonstrated between green and yellow vegetable intake and NAFLD in the final model (P_trend = 0.04), but odds ratios for any intake category did not reach significance.

CONCLUSIONS

No obesity-independent association was found between fruit or vegetable intake and NAFLD. According to the findings of this study, Japanese do not need to restrict fruit consumption to limit fructose intake as a means of preventing NAFLD.

Micronutrients in Nonalcoholic Fatty Liver Disease Pathogenesis

Micronutrients include electrolytes, minerals, vitamins, and carotenoids, and are required in microgram or milligram quantities for cellular metabolism. The liver plays an important role in micronutrient metabolism and this metabolism often is altered in chronic liver diseases. Here, we review how the liver contributes to micronutrient metabolism; how impaired micronutrient metabolism may be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), a systemic disorder of energy, glucose, and lipid homeostasis; and how insights gained from micronutrient biology have informed NAFLD therapeutics. Finally, we highlight some of the challenges and opportunities that remain with investigating the contribution of micronutrients to NAFLD pathology and suggest strategies to incorporate our understanding into the care of NAFLD patients.

Higher serum carotenoids associated with improvement of non-alcoholic fatty liver disease in adults: a prospective study

PURPOSE

Previous studies have suggested that serum carotenoids might be inversely associated with non-alcoholic fatty liver disease (NAFLD), but little data came from longitudinal studies. We prospectively examined the associations between serum-carotenoid levels and NAFLD severity and the intermediary effects of retinol-binding protein 4 (RBP4), HOMA insulin-resistance index (HOMA-IR), body mass index (BMI), and serum triglycerides in middle-aged and elderly Chinese adults.

METHODS

This prospective study included 3336 Chinese adults (40-75 years). We assessed serum concentrations of carotenoids at baseline and determined serum RBP4, triglycerides, and HOMA-IR levels at year 3. Abdominal ultrasonography was conducted to assess the presence and degree of NAFLD at years 3 and 6.

RESULTS

The 2687 subjects who completed both NAFLD tests were classified into stable, improved and progressed groups according to changes in the degree of NAFLD between two visits. Analyses of covariance showed that ln-transformed serum concentrations of α-carotene, β-cryptoxanthin, β-carotene, lycopene, lutein/zeaxanthin, and total carotenoids were positively associated with NAFLD improvement (all p-trend < 0.05). After multivariable adjustment, mean differences in serum carotenoids were higher by 29.6% (β-carotene), 18.2% (α-carotene), 15.6% (β-cryptoxanthin), 11.5% (lycopene), 8.9% (lutein/zeaxanthin), and 16.6% (total carotenoids) in the improved vs. progressed subjects. Path analyses indicated the carotenoid-NAFLD association was mediated by lowering serum RBP4, triglycerides, HOMA-IR, and BMI, which were positively associated with the prevalence and progression of NAFLD.

CONCLUSIONS

In middle-aged and elderly adults, higher serum-carotenoid concentrations were favorably associated with NAFLD improvement, mediated by reducing serum RBP4, triglycerides, HOMA-IR, and BMI.

TRIAL REGISTRATIONS

This study has been registered at http://www.clinicaltrials.gov as NCT03179657.

Safety Evaluation and Plasma Carotenoid Accumulation in Healthy Adult Subjects after 12 Weeks of Paprika Oleoresin Supplementation

Paprika oleoresin is obtained by solvent extraction from Capsicum annuum L. fruits and contains multiple carotenoids, such as capsanthin, β-carotene, zeaxanthin, and β-cryptoxanthin, which are considered protective against various diseases. Herein, we investigated the effect of paprika oleoresin supplementation on plasma carotenoid accumulation and evaluated the safety of the oleoresin. We used a double-blinded, placebo-controlled comparative clinical study design and tested the effects of varying doses in healthy adult subjects. In total, 33 subjects were randomly divided into three groups to take capsules containing 0, 20, or 100 mg of paprika oleoresin daily for 12 consecutive weeks. Plasma carotenoid concentrations were measured at 0, 4, 8, and 12 weeks, and the safety of paprika oleoresin capsules was investigated using analyses of blood biochemistry, hematology, and urine contents. In these experiments, β-cryptoxanthin and zeaxanthin dose-dependently accumulated in plasma within the dose range of the study over 12 consecutive weeks of paprika oleoresin supplementation. Moreover, β-cryptoxanthin accumulated to higher levels than the other paprika oleoresin carotenoids. In contrast, capsanthin was not detected in plasma before or during the 12-week treatment period. Finally, no adverse events were associated with intake of paprika oleoresin (20 and 100 mg/day) in safety evaluations. Paprika oleoresin is a suitable source of carotenoids, especially β-cryptoxanthin.

Development of functional agricultural products utilizing the new health claim labeling system in Japan

In April 2015, Consumer Affairs Agency of Japan launched a new food labeling system known as "Foods with Function Claims (FFC)." Under this system, the food industry independently evaluates scientific evidence on foods and describes their functional properties. As of May 23, 2017, 1023 FFC containing 8 fresh foods have been launched. Meanwhile, to clarify the health-promoting effects of agricultural products, National Agriculture and Food Research Organization (NARO) implemented the "Research Project on Development of Agricultural Products" and demonstrated the risk reduction of osteoporosis of β-cryptoxanthin rich Satsuma mandarins and the anti-allergic effect of the O-methylated catechin rich tea cultivar Benifuuki. These foods were subsequently released as FFC. Moreover, NARO elucidated the health-promoting effects of various functional agricultural products (β-glucan rich barley, β-conglycinin rich soybean, quercetin rich onion, etc.) and a healthy boxed lunch. This review focuses on new food labeling system or research examining functional aspects of agricultural products.

Mediterranean Diet and Multi-Ingredient-Based Interventions for the Management of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) comprises a wide spectrum of hepatic disorders, from simple steatosis to hepatic necro-inflammation leading to non-alcoholic steatohepatitis (NASH). Although the prevalence of these multifactorial pathologies is continuously increasing in the population, there is still not an established methodology for their treatment other than weight loss and a change in lifestyle habits, such as a hypocaloric diet and physical exercise. In this framework, there is increasing evidence that several food bioactives and dietary patterns are effective for reversing and preventing the onset of these pathologies. Some studies have claimed that better responses are obtained when treatments are performed under a multifaceted approach, using different bioactive compounds that act against complementary targets. Thus, in this work, current strategies for treating NAFLD and NASH based on multi-ingredient-based supplements or the Mediterranean diet, a dietary pattern rich in bioactive compounds, are reviewed. Furthermore, the usefulness of omics techniques to design effective multi-ingredient nutritional interventions and to predict and monitor their response against these disorders is also discussed.

Novel Action of Carotenoids on Non-Alcoholic Fatty Liver Disease: Macrophage Polarization and Liver Homeostasis

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. It is characterized by a wide spectrum of hepatic changes, which may progress to non-alcoholic steatohepatitis (NASH) and cirrhosis. NAFLD is considered a hepatic manifestation of metabolic syndrome; however, mechanisms underlying the onset and progression of NAFLD are still unclear. Resident and recruited macrophages are key players in the homeostatic function of the liver and in the progression of NAFLD to NASH. Progress has been made in understanding the molecular mechanisms underlying the polarized activation of macrophages. New NAFLD therapies will likely involve modification of macrophage polarization by restraining M1 activation or driving M2 activation. Carotenoids are potent antioxidants and anti-inflammatory micronutrients that have been used to prevent and treat NAFLD. In addition to their antioxidative action, carotenoids can regulate macrophage polarization and thereby halt the progression of NASH. In this review, we summarize the molecular mechanisms of macrophage polarization and the function of liver macrophages/Kupffer cells in NAFLD. From our review, we propose that dietary carotenoids, such as β-cryptoxanthin and astaxanthin, be used to prevent or treat NAFLD through the regulation of macrophage polarization and liver homeostasis.