The association of psoriasis with composite dietary antioxidant index and its components: a cross-sectional study from the National Health and Nutrition Examination Survey

Abstract

Background

Psoriasis is a chronic inflammatory skin disorder associated with various comorbidities. The role of nutrition and dietary antioxidants in psoriasis management has gained attention. The Composite Dietary Antioxidant Index (CDAI) quantifies overall dietary antioxidant intake, but its association with psoriasis remains unclear. This study aimed to investigate the association between the CDAI and psoriasis, as well as the relationship between individual components of CDAI and psoriasis risk.

Methods

Data from the US National Health and Nutrition Examination Survey (NHANES) were analyzed. Baseline characteristics, CDAI scores, and psoriasis status were assessed. Multivariable logistic regression and restricted cubic splines were employed to analyze the association.

Results

The study included 23,311 participants, with 621 diagnosed with psoriasis. Higher CDAI scores were associated with a lower odds ratio (OR) of psoriasis occurrence (OR = 0.72, 95% CI 0.56–0.92, P = 0.009 in Model 3). Vitamin E intake exhibited an inverse correlation with psoriasis risk (OR = 0.76, 95% CI 0.60–0.96, P = 0.039 in Model 3). Other CDAI components did not show significant associations with psoriasis.

Conclusion

This study demonstrates a significant inverse association between CDAI and psoriasis, indicating that higher dietary antioxidant intake is associated with a reduced risk of psoriasis. Specifically, higher vitamin E intake was associated with a lower likelihood of psoriasis. These findings underscore the potential role of dietary antioxidants in psoriasis management. Further research is warranted to elucidate the underlying mechanisms and explore targeted dietary interventions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-024-00850-8.

Introduction

Psoriasis is a chronic, relapsing, and immune-mediated skin disorder with an estimated prevalence of approximately 3% (over 7.5 million) among adults in the United States (U.S.) [1]. It was characterized by red, scaly plaques on the skin, which can be accompanied by itching, pain, and nail involvement [2]. Recent research has increasingly recognized psoriasis as a systemic inflammatory disease, exhibiting associations with a range of comorbidities, such as arthritis, cardiovascular conditions, metabolic syndrome, and mental health disorders [3–6]. These findings suggest an elevated risk of developing these additional health concerns among individuals with psoriasis, leading to substantial societal burdens and economic costs [7, 8]. The etiology of psoriasis is multifactorial, involving dysregulated interactions between the immune system, genetic components, and environmental triggers [2].

In recent years, there has been growing interest and some promising evidence regarding the role of nutrition and antioxidant supplementation in the treatment of psoriasis due to the recognition of associated comorbid conditions [9, 10]. Nutrition and dietary interventions have gained attention as potential adjunctive treatments for psoriasis due to their ability to modulate inflammation and oxidative stress. The Composite Dietary Antioxidant Index (CDAI) is a comprehensive scoring system designed to evaluate an individual’s overall dietary Total Antioxidant Capacity. It takes into account specific nutrients recognized for their antioxidant properties, including vitamins A, C, and E, as well as essential minerals like selenium and zinc, and phytochemicals such as carotenoids [11]. The CDAI has been widely employed in research studies to explore the correlation between dietary antioxidant intake and various health outcomes, particularly in chronic diseases like cardiovascular disease, diabetes, cancer, aging and depression [12–17].

Previous research has demonstrated that the association between the CDAI and pro-inflammatory mediators, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α, which are known to have substantial involvement in inflammatory conditions, including psoriasis [18]. Antioxidants supplementation exhibits promise in ameliorating oxidative stress and inflammation, offering a protective effect against diverse inflammatory conditions [19, 20]. Of note, psoriasis, a multifaceted condition influenced by genetic predisposition and immune system dysregulation has been linked to dietary patterns characterized by high-fat intake and inadequate consumption of essential vitamins and minerals [9, 10, 21]. Such dietary patterns have been linked to disease recurrence and activity in individuals with psoriasis. [10, 21] While some investigations propose a potential correlation between an antioxidant-rich diet, as measured by the CDAI, and psoriasis, further investigation is warranted to establish the precise relationship between the CDAI and psoriasis.

Currently, no studies have specifically examined the correlation between the CDAI and psoriasis, along with its individual components. Hence, this cross-sectional study aims to address this gap and investigate the potential relationship between the CDAI and psoriasis. By analyzing data from participants enrolled in the US National Health and Nutrition Examination Survey (NHANES), our objective is to contribute valuable insights into the association between the CDAI and psoriasis, thus enhancing our understanding of the influence of dietary antioxidant intake on this inflammatory skin disorder.

Materials and methods

Study design and population

This study employed a cross-sectional research design and obtained data from the NHANES, a comprehensive nationwide survey focusing on assessing overall health and nutritional status of the population [22, 23].

For this study, we analyzed data from the 1999–2020 cycles of NHANES, comprising a total of 11,876 individuals (Fig. 1). We excluded individuals with missing information on psoriasis status or dietary recall necessary for calculating the CDAI score. The final analytical sample included adults aged 18 years or older who participated in NHANES between 2005 and 2016. Psoriasis status was determined based on participants’ self-reported diagnosis by a healthcare professional. Dietary intake data were collected through 24-hour dietary recalls, providing information on food and beverage consumption. Participants were categorized into three groups based on their CDAI score tertiles.

Fig. 1.

Flow chart for inclusion and exclusion of the study population

Composite dietary antioxidant index

Dietary intake data in the NHANES dataset were collected through a 24-hour dietary recall interview, initially conducted in person and later followed up by a telephone interview within 3 to 10 days [24]. The United States Department of Agriculture’s Food and Nutrient Database for Dietary Studies was used to determine the intake of antioxidants, micronutrients, and total energy.

The CDAI comprises six standardized nutrients: carotenoids, selenium, zinc, and vitamins A, C, and E. Standardization involved subtracting the mean and dividing by the standard deviation for each nutrient. The CDAI score was calculated as the sum of these standardized nutrient intakes.

Psoriasis definition

Psoriasis status was determined through self-report by participants in response to the question, “Have you ever been diagnosed with psoriasis by a healthcare professional?“. Additionally, in the NHANES cycles of 2003–2004, a specific dermatology questionnaire was administered, which involved capturing digital images of four specific skin sites from the participants. These images were later evaluated by two dermatologists [25]. Among the 116,876 participants included in the NHANES dataset from 1999 to 2020, psoriasis data were accessible for 26,049 individuals.

Covariates

The collected information included various covariates such as age, gender, race ethnicity (non-Hispanic black, non-Hispanic white, Mexican American, and other races), poverty status, education level, smoking habits, alcohol consumption, presence of hypertension, diabetes mellitus, cardiovascular disease, stroke, heart attack, as well as the CDAI and its individual components. Trained interviewers employed a Computer-Assisted Personal Interview system for data collection, ensuring efficient and accurate data capture.

Education level was categorized into four groups: College or above, high school or equivalent, less than high school, and more than high school. Hypertension was determined by meeting specific criteria: systolic blood pressure (SBP) of 140 mmHg or higher and/or diastolic blood pressure (DBP) of 90 mmHg or higher, or the use of anti-hypertensive medication. Smoking status was divided into three categories: non-smokers, former smokers, and current smokers. Non-smokers included individuals who had never smoked or had smoked fewer than 100 cigarettes in their lifetime. Former smokers had smoked at least 100 cigarettes but were not currently smoking. Current smokers were participants who had smoked at least 100 cigarettes and reported smoking in the past 30 days. Alcohol consumption status was classified into five groups: Never drinkers, former drinkers, mild current drinkers, moderate current drinkers, and heavy current drinkers. Never drinkers had consumed fewer than 12 drinks in their lifetime. Former drinkers had consumed more than 12 drinks in their lifetime but had not consumed alcohol in the past year. Current drinkers were further categorized based on their drinking patterns. Heavy current drinkers were women who consumed three or more drinks per day or men who consumed four or more drinks per day, along with at least five instances of binge drinking per month. Moderate current drinkers included women who consumed two or more drinks per day or men who consumed three or more drinks per day. Body mass index (BMI) was calculated by dividing body weight by the square of height (kg/m²). Diabetes mellitus (DM) was defined using various criteria, including fasting plasma glucose levels, HbA1c levels, current use of antidiabetic medications, or self-reported history of diabetes.

Statistical analysis

We summarized and compared the baseline characteristics of participants, comparing individuals with psoriasis to those without the condition. Continuous variables were analyzed by reporting their mean (± standard deviation) or median (quartile range). Statistical tests, such as t-tests or Wilcoxon rank-sum tests, were utilized to compare these variables. Before conducting the analysis, the normality of the data was assessed using the Kolmogorov-Smirnov test. Categorical variables were reported as frequency (percentage) and compared using the Chi-square test. We conducted multivariable-adjusted logistic regression to assess the association between the CDAI and psoriasis. Odds ratios (OR) with 95% confidence intervals (CI) were calculated. The CDAI was categorized into tertiles, with the lowest tertile considered as the reference group. In Model 1, adjustments were made for age, sex, and total energy intake. Model 2 included additional adjustments for education level, smoking status, and BMI. Model 3 further adjusted for high blood pressure and diabetes. To examine potential nonlinear relationships, restricted cubic spline (RCS) curves were employed. These curves were based on four specific percentiles (5%, 35%, 65%, and 95%) of the CDAI distribution. Statistical significance was defined as a two-sided p-value less than 0.05. All statistical analyses were performed using SAS 9.4 and R 4.2.2.

Results

Study participants and baseline characteristics

The study included a total of 23,311 participants, out of which 621 were diagnosed with psoriasis. The baseline characteristics of the cohort are summarized in Table 1. The average age of the participants was 43.6 years, with 51.6% being female. Among the participants, 43.6% were Caucasian individuals. The average CDAI score was 0.59 ± 3.92. The sex ratio between the psoriatic and non-psoriatic populations was comparable. Individuals with psoriasis had a higher proportion of college degree or above education levels, higher BMI, and higher rates of smoking and drinking. Additionally, these individuals were also found to have a higher risk of cardiometabolic diseases such as diabetes, hypertension, and heart attacks.

Table 1.

The baseline characteristics of the study population based on the presence of psoriasis

	All (N = 23311)	Psoriasis (N = 621)	No Psoriasis (N = 22690)	P value
Age (years)	43.6 (18.0)	48.3 (16.7)	43.5 (18.0)	< 0.001
Sex/Gender				1
Female	12,035 (51.6%)	321 (51.7%)	11,714 (51.6%)
Male	11,276 (48.4%)	300 (48.3%)	10,976 (48.4%)
Race				< 0.001
Mexican American	3864 (16.6%)	52 (8.37%)	3812 (16.8%)
Non-Hispanic Black	5129 (22.0%)	82 (13.2%)	5047 (22.2%)
Non-Hispanic White	10,157 (43.6%)	380 (61.2%)	9777 (43.1%)
Other Races	4161 (17.8%)	107 (17.2%)	4054 (17.9%)
Poverty	2.50 (1.65)	2.62 (1.71)	2.49 (1.65)	0.066
Education				0.001
College or above	11,461 (49.2%)	351 (56.5%)	11,110 (49.0%)
High school or equivalent	7399 (31.8%)	179 (28.8%)	7220 (31.8%)
Less than high school	4172 (17.9%)	89 (14.3%)	4083 (18.0%)
More than high school	258 (1.11%)	2 (0.32%)	256 (1.13%)
Smoke				< 0.001
Former	4783 (22.0%)	196 (32.3%)	4587 (21.7%)
Never	12,144 (55.7%)	264 (43.5%)	11,880 (56.1%)
Now	4857 (22.3%)	147 (24.2%)	4710 (22.2%)
Alcohol drinking				0.045
Never	2915 (14.1%)	64 (11.1%)	2851 (14.2%)
Former	3489 (16.9%)	111 (19.3%)	3378 (16.9%)
Mild	6414 (31.1%)	188 (32.7%)	6226 (31.1%)
Moderate	3235 (15.7%)	101 (17.6%)	3134 (15.6%)
Heavy	4565 (22.1%)	111 (19.3%)	4454 (22.2%)
Diabetes Mellitus	3292 (14.6%)	116 (18.9%)	3176 (14.4%)	0.002
Hypertension	8120 (34.8%)	292 (47.0%)	7828 (34.5%)	< 0.001
BMI (kg/m2)	28.7 (6.99)	30.0 (7.16)	28.7 (6.98)	< 0.001
Kcal	2176.0(1023)	2138.0(976)	2177.0(1024)	0.3486
CDAI	0.59 (3.92)	0.68 (4.05)	0.59 (3.91)	0.592
Vitamin _A	591 (587)	620 (584)	591 (587)	0.221
Vitamin _C	86.1 (101)	85.2 (112)	86.1 (101)	0.841
Vitamin _E	7.92 (6.20)	8.17 (6.49)	7.91 (6.19)	0.34
Zinc	11.5 (7.31)	11.3 (6.71)	11.5 (7.33)	0.515
Se	114 (64.7)	111 (58.2)	114 (64.9)	0.136
carotenoid	9150 (11842)	10,225 (13676)	9120 (11786)	0.047

Abbreviation: BMI: body mass index, CDAI: Composite Dietary Antioxidant Index, Se: selenium

Associations between CDAI and psoriasis

The association between psoriasis and the CDAI, along with its individual components, was examined using RCS in Fig. 2. We found a significant non-linear relationship between CDAI and psoriasis, as indicated by a statistically significant P-value of 0.015 for nonlinearity. To further examine this association, we conducted multivariate logistic regression models. The study participants were stratified into three distinct groups based on their CDAI scores. Tertile 1 referred to the group with the lowest CDAI scores, while tertile 3 represented the group with the highest CDAI scores. This categorization allowed for the investigation of the relationship between CDAI and psoriasis across varying levels of dietary antioxidant intake. Our findings indicate a significant association between CDAI and psoriasis, wherein individuals in tertile 3 exhibit a lower OR of having psoriasis when compared to those in tertile 1 (OR = 0.72, 95% CI 0.56–0.92, P = 0.009 in Model 3). This association persists consistently across all models, indicating a robust relationship between higher CDAI scores and a diminished likelihood of psoriasis occurrence.

Fig. 2.

Restricted cubic spline curves (RCS) for the association of psoriasis with composite dietary antioxidant index and its components

Furthermore, we conducted an analysis to examine the relationship between each component of the CDAI and psoriasis. Our findings revealed a significant inverse correlation between Vitamin E and psoriasis. Specifically, individuals in the highest tertile (tertile 3) of Vitamin E intake exhibited a reduced OR of developing psoriasis compared to those in the lowest tertile (tertile 1) (OR = 0.76, 95% CI 0.60–0.96, P = 0.039 in Model 3). However, no statistically significant associations were observed between other CDAI components and psoriasis. A summary of all logistic regression analyses can be found in Table 2.

Table 2.

The association of composite dietary antioxidant index and its components with psoriasis

Nutrients	Tertile 1	Tertile 2	Tertile 3	P for difference
		OR (95% CI)	OR (95% CI)
CADI
Model 1	Ref.	1.02(0.83–1.26)	0.78(0.61–0.99)	0.027
Model 2	Ref.	1.03(0.83–1.27)	0.75(0.59–0.96)	0.012
Model 3	Ref.	0.97(0.79–1.20)	0.72(0.56–0.92)	0.009
Vitamins A
Model 1	Ref.	0.90(0.74–1.11)	0.95(0.77–1.17)	0.619
Model 2	Ref.	0.94(0.77–1.16)	1.01(0.81–1.26)	0.734
Model 3	Ref.	0.93(0.76–1.15)	1.01(0.81–1.27)	0.660
Vitamins C
Model 1	Ref.	1.02(0.84–1.24)	1.09(0.89–1.33)	0.711
Model 2	Ref.	0.99(0.81–1.21)	0.98(0.80–1.20)	0.979
Model 3	Ref.	1.00(0.81–1.22)	0.97(0.79–1.19)	0.938
Vitamins E
Model 1	Ref.	0.98(0.79–1.21)	0.79(0.63-1.00)	0.054
Model 2	Ref.	0.96(0.78–1.19)	0.75(0.60–0.95)	0.029
Model 3	Ref.	0.96(0.78–1.19)	0.76(0.60–0.96)	0.039
Zinc
Model 1	Ref.	1.04(0.84–1.28)	0.96(0.75–1.23)	0.785
Model 2	Ref.	1.03(0.83–1.27)	0.94(0.73–1.20)	0.710
Model 3	Ref.	1.01(0.81–1.24)	0.93(0.73–1.19)	0.756
Selenium
Model 1	Ref.	0.96(0.78–1.17)	1.05(0.81–1.35)	0.715
Model 2	Ref.	0.96(0.78–1.18)	1.04(0.81–1.34)	0.758
Model 3	Ref.	0.95(0.78–1.17)	1.05(0.81–1.36)	0.672
Carotenoid
Model 1	Ref.	1.19(0.97–1.46)	0.94(0.77–1.14)	0.058
Model 2	Ref.	1.17(0.95–1.44)	0.93(0.76–1.13)	0.065
Model 3	Ref.	1.17(0.95–1.44)	0.92(0.75–1.13)	0.066

Note:

Model 1, adjusted for age, gender, and energy intake;

Model 2, adjusted for age, gender, energy intake, body mass index, smoking status, and education level;

Model 3, adjusted for age, gender, energy intake, body mass index, smoking status, education level, hypertension, and diabetes

Ref, reference (OR = 1)

Discussion

In this cross-sectional study, we aimed to assess the relationship between psoriasis and dietary antioxidant intake, as quantified by the CDAI, utilizing data obtained from the NHANES. We present the first large-scale analysis of this relationship in the US population. Our findings indicate a significant inverse association between dietary antioxidant intake, as measured by the CDAI, and the prevalence of psoriasis (The main findings are summarized in Figure S1). After controlling for potential confounding variables, the association between higher CDAI scores and a lower likelihood of psoriasis remains statistically significant. While limited evidence exists regarding the association between psoriasis and the CDAI, the role of specific dietary antioxidants in managing chronic inflammatory disorders, including psoriasis, has been extensively discussed [26–28]. Past research has primarily focused on the impact of individual antioxidant nutrients or food intake on psoriasis, yielding conflicting results [21, 26, 29, 30]. However, these studies often fail to consider the complex interrelationships and interactions among different antioxidants, potentially leading to biased conclusions.

In this study, we also investigated the association between individual components of the CDAI and psoriasis. Specifically, our findings revealed a significant inverse relationship between vitamin E intake and the risk of psoriasis. After controlling for potential confounding variables, individuals in the highest tertile of vitamin E intake displayed a significantly reduced risk of psoriasis compared to those in the lowest tertile. These results suggest that specific dietary antioxidants, such as vitamin E, may have a role in modulating the risk of psoriasis. Our study addresses this research gap and underscores the significance of overall dietary antioxidant intake, as quantified by the CDAI, in reducing the risk of psoriasis. These findings suggest that the combined antioxidant capacity of the diet may have a more substantial impact on reducing the incidence of psoriasis than individual antioxidants alone.

The implications of our study extend to the potential role of dietary antioxidants in the management of psoriasis. If a significant association between the CDAI and psoriasis is established, it would indicate that a higher antioxidant intake through diet may have a protective effect against psoriasis or contribute to its management. Conversely, if no significant association is found, it would suggest that factors other than dietary antioxidant intake, as measured by the CDAI, exert greater influence on the development or severity of psoriasis. Our study also offers a rationale and valuable population cohort information for future research aimed at investigating individual antioxidant components or combined antioxidant agents in relation to the pathogenesis of psoriasis, particularly in terms of inflammation regulation. Additionally, it highlights the potential for dietary nutrition strategies to serve as adjunctive treatments for alleviating psoriasis symptoms and associated comorbidities.

Investigating the mechanistic basis of the observed negative association between the CDAI and psoriasis is crucial, given the likely involvement of oxidative stress and inflammation in this relationship. Oxidative stress can lead to an imbalance of reactive oxygen species and endothelial dysfunction, while inflammation can trigger neutrophil release and elevate reactive oxygen species levels [31, 32]. These mechanisms contribute not only to psoriasis but also to other conditions such as atherosclerosis and chronic kidney disease [33, 34]. Therefore, gaining a deeper understanding of these underlying mechanisms is essential, as it can pave the way for the development of novel treatments and dietary interventions aimed at managing psoriasis. In addition, prior research has indicated that biological agents can enhance hematological parameters associated with cardiometabolic disease in patients with psoriasis, suggesting their potential value in treating cardiovascular and metabolic comorbidities linked to this condition [35]. Furthermore, the effects of dietary antioxidant interventions on specific blood parameters related to cardiometabolic diseases, as well as their potential to simultaneously improve or reverse the progression of these conditions in psoriasis, warrant further investigation.

In conclusion, our study sheds light on the relationship between dietary antioxidants and the risk of psoriasis. Our findings highlight the significance of overall dietary antioxidant intake and the potential mechanistic links involving oxidative stress, inflammation, and psoriasis. These findings have implications for the development of dietary interventions in managing psoriasis. Future research should focus on confirming the causal relationship between dietary antioxidants and psoriasis, exploring targeted dietary interventions, and investigating potential interactions among different antioxidants to gain a more comprehensive understanding of their impact on psoriasis risk.

Limitations

Nevertheless, it is crucial to acknowledge the limitations of our study. While NHANES offers a substantial and diverse sample of the US population, it is susceptible to potential biases and limitations inherent in survey data. The cross-sectional design of the NHANES dataset restricts our ability to establish a causal relationship between CDAI and psoriasis. The unequal sample sizes, particularly the smaller number of psoriasis patients in our study, may affect statistical power and limit the reliability of comparison. Additionally, relying on self-reported diagnosis of psoriasis introduces the possibility of misclassification errors, a common concern in population-based epidemiological studies. To address these limitations and further explore the association, longitudinal studies or randomized controlled trials including more balanced sample sizes are necessary. Such studies would enable us to investigate the relationship over time and evaluate the impact of changes in antioxidant intake through diet on psoriasis outcomes more accurately.

Conclusions

Our investigation addresses the knowledge gap surrounding the association between the CDAI and psoriasis by analyzing data from NHANES. The results of our study have the potential to enhance our comprehension of the role that dietary antioxidants may play in psoriasis and provide guidance for future investigations in this area. The findings may have implications for dietary interventions as adjunct therapies for psoriasis prevention or management. Ultimately, by understanding the relationship between the CDAI and psoriasis, we can potentially improve the overall management and quality of life for individuals affected by this chronic inflammatory condition.

Electronic supplementary material

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Abbreviations

BMI

Body mass index

CDAI

Composite Dietary Antioxidant Index

DM

Diabetes mellitus

IL

Interleukin

NHANES

National Health and Nutrition Examination Survey

OR

Odds ratio

RCS

Restricted cubic spline

Se

Selenium

TNF

Tumor necrosis factor

Author contributions

WDL, LLD and XCL participated in research design, the writing of the paper, the performance of the research and data analysis. BS participated in research design, the writing and revising of the paper. YD participated the revising of the paper. The authors have no conflict of interest. All authors read and approved the final manuscript.

Funding

No funding.

Data availability

The data used in this study can be obtained upon reasonable request to the corresponding author. Additionally, the raw data can also be accessed on the website of the National Center for Health Statistics (NCHS) at https://www.cdc.gov/nchs/nhanes/.

Declarations

Ethics approval and consent to participate

The study adhered to the ethical principles outlined in the Declaration of Helsinki. Informed consent was obtained from all participants, and the NHANES study protocol received approval from the ethics committee of the National Center for Health Statistics (NCHS) under Protocol #2011-17.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.