Complementary Therapies in Medicine (2014) 22, 159—165

Available online at www.sciencedirect.com

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jo ur nal home p ag e: www.elsev ierhea l th .com/ journa ls /c t im

Is dietary supplementation more commonamong adults with psoriasis? Results fromthe National Health and NutritionExamination Survey

Patrick B. Wilson ∗

School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States

Received 7 October 2013; received in revised form 2 December 2013; accepted 13 December 2013Available online 22 December 2013

SummaryObjectives: Individuals with psoriasis are often unsatisfied with traditional medical treatmentsand may be more likely to use dietary supplements as alternative or complementary treatment.Limited data is available on the prevalence of dietary supplement use amongst individualswith psoriasis in the general population. The aim was to utilize a representative sample of theUnited States to estimate the prevalence of dietary supplement use among adults self-reportingpsoriasis.Design and setting: Cross-sectional data analysis from the 2009 to 2010 National Health andNutrition Examination Survey. Dietary supplementation over the past 30 days was ascertainedand population weights were used to obtain estimates representative of the general population.Logistic regression was used to determine whether psoriasis was associated with higher odds ofsupplement use.Results: This study consisted of 6211 participants aged ≥20 years (representing 219 millionAmericans). Among the 184 participants reporting psoriasis (representing 6.9 million Amer-icans), 53% reported using at least one dietary supplement, which was not different fromparticipants without psoriasis (49.5%, P = 0.416). Participants with psoriasis did not have higherodds of supplement use after adjusting for covariates. Multivitamin/mineral supplements werethe most common dietary supplements used by participants with psoriasis (29.6%), and the most

common reasons for taking them were to maintain and improve health. Only 12 supplementstaken by participants with psoriasis were intended to improve skin health.Conclusions: Dietary supplementation over the past 30 days was repopsoriasis amongst the United States general population. Few indivdietary supplements specifically to improve skin health.© 2013 Elsevier Ltd. All rights reserved.

∗ Correspondence to: 220 Cooke Hall, 1900 University Avenue SE, MinnE-mail address: wilso733@umn.edu

0965-2299/$ — see front matter © 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.ctim.2013.12.007

rted by half of adults with

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eapolis, MN 55455, United States. Tel.: +1 612 625 5300.

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soriasis is a chronic, immune-mediated skin disease thatan significantly impact quality of life.1,2 Although estimatesary with the population studied, approximately 2—3% ofmericans have psoriasis,3,4 and this amounted to approxi-ately $2 billion in health care costs in the United States

or 2004.5 Although there has been immense progress insoriasis treatment over the past several decades, manyreatments remain expensive and/or limited in access. Bio-ogics, which will continue to gain more widespread use foroderate-to-severe psoriasis because of their efficacy, typ-

cally cost more than $20,000 per year without insuranceoverage.6 Cost considerations may ultimately contributeo some psoriasis patients seeking alternative treatments,ncluding dietary supplements. Beyond cost and access bar-iers, perception of under-treatment may contribute toatients seeking alternative or complementary treatments.ne large survey from the general population found that only0% of individuals with psoriasis were highly satisfied withheir current treatment and 25% were clearly dissatisfied.4

oreover, discordance often exists between practitionersnd patients regarding the severity of a patient’s psori-sis, and patients frequently believe that those aroundhem—–even their attending physicians—–under-appreciatehe severity of their condition.7

A dietary supplement is defined by the Food and Drugdministration (FDA) as, ‘‘a product taken by mouth thatontains a dietary ingredient intended to supplement theiet.’’8 The FDA considers dietary supplements to bender the umbrella of foods since the passage the Dietaryupplement Health and Education Act.8 Because of theirlassification under foods, most dietary supplements can beold without prior FDA approval. In addition, the efficacy andafety of any given dietary supplement does not generallyeed to be shown prior to its marketing.8 Dietary supple-ent use in the United States has been estimated to be

round 50%.9 Given that a substantial proportion of psoriasisatients remain untreated or under-treated, it is plausiblehat individuals with psoriasis are more likely to rely onupplements as alternative or complementary treatment.ltimately, this may result in the prevalence of dietary sup-lement use being higher among individuals with psoriasis.hile some clinical trials have shown potential benefits of

ietary supplementation for psoriasis,10—12 interactions withommon anti-psoriatic drugs are a concern. For example,erbal supplements can increase or decrease the concentra-ion of cyclosporine13 and modify the risk of hepatotoxicityith methotrexate use.14

Although a fair number of investigations have examinedhe prevalence of complementary and alternative treat-ent use in psoriasis, most of these investigations have used

ighly-selective samples, did not report specific dietary sup-lements taken, and/or did not compare the prevalence ofietary supplement use to a control population.15—22 Theational Health and Nutrition Examination Survey (NHANES)

s a program of studies that utilizes interviews and physi-al examinations to assess the health of adults and childrenn the United States on a continual basis. For 2009—2010,

elf-reported psoriasis diagnosis and detailed information onietary supplement use over the past 30 days were assessed.herefore, the purpose of this investigation was to estimate

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P.B. Wilson

he prevalence of dietary supplement use among individualself-reporting psoriasis in the general population, comparese to individuals without psoriasis, and characterize whichpecific supplements were used and why.

ethods

articipants

his analysis includes individuals aged ≥20 years par-icipating in the 2009—2010 NHANES. NHANES usesomplex, multistage, probability sampling to achieve

representative sample of the non-institutionalized,ivilian population of the United States. Oversamplingf racial/ethnic minorities, low-income persons, andlderly is done to increase the reliability and preci-ion of estimates. NHANES sampling procedure uses fourtages—–counties, segments, households, and individuals.ouseholds are mailed a letter informing residents thatn interviewer will visit their home, and individuals withn households are randomly selected based on designatedge-sex-race/ethnicity screening subdomains. If eligiblendividuals are identified, interviewers attempt to recruithese individuals. After the household interview is con-ucted, participants are invited to receive an examinationt a mobile examination center. The age cut-off of 20 yearsas selected to ensure that participants had complete datan covariates and to limit the study inferences to adults. Theational Center for Health Statistics Ethics Review Boardpproved the protocols and informed consent was obtainedrom participants.

soriasis

elf-reported psoriasis diagnosis was assessed in the homey trained interviewers using a Computer-Assisted Personalnterviewing system. Participants were asked if they hadver been diagnosed with psoriasis by a healthcare provider.articipants were not asked to report psoriasis clinical sub-ype or the severity of their psoriasis.

ietary supplement use

HANES collects information about the use of prescrip-ion and nonprescription dietary supplements and antacidsuring the preceding 30 days. A dietary supplementuestionnaire was conducted during the home interview.articipants were asked if they had taken a dietary sup-lement over the past 30 days and were shown a cardisting examples of dietary supplements, such as multivi-amins/minerals (MVM), herbals, and fish oil. Participantshat answered ‘‘yes’’ were asked to show the interviewerhe dietary supplement container(s) or report the detailsf unavailable (about 20—25% of cases). Participants werelso asked if they had taken any non-prescription antacids.ntacids used as medication were not counted as dietary

list of potential reasons for taking each dietary supple-ent (e.g. improve health, maintain health, improve skin

ealth/dry skin) and could also generate their own reasons.

161

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Participants were allowed to select multiple reasons for tak-ing each dietary supplement. Dietary supplement nonuserswere considered as those who did not report taking a dietarysupplement over the past 30 days. MVM, omega-3 fattyacid, and herbal supplement use among participants withpsoriasis were also specifically quantified since these cat-egories of supplements have been frequently reported inother populations.9,23,24 Supplements labeled as B-vitamincomplexes were considered MVM supplements and thoselabeled as fish oil, flaxseed oil, or krill oil were consideredomega-3 fatty acid supplements.

Other variables

Age, education, gender, race/ethnicity, smoking status, andmedical co-morbidities (arthritis, coronary heart disease,cancer) were self-reported at the home interview. Edu-cation was recoded into a dichotomous variable (≤highschool vs. >high school). Participants were asked if they hadsmoked at least 100 cigarettes in their life (to establish ever-smoker) and about current smoking habits. Participants wereconsidered smokers if they reported currently smoking atleast on some days. Height and weight were used to calcu-late body mass index (BMI). For participants with psoriasisreporting herbal supplement use, prescription drug data fileswere reviewed to identify medications that could potentiallyinteract with herbals.

Statistical analysis

Analyses were conducted using SPSS Complex Samples (ver-sion 21, IBM, Armonk, NY). NHANES-supplied interviewpopulation-weights were used to account for the complexsampling design and interview nonresponse. Frequency ofdietary supplement use is reported as both unweightedcounts and population-weighted prevalences. Reasons fortaking dietary supplements are reported as unweightedcounts because multiple reasons can be given for eachdietary supplement, complicating population weighting.

Means and standard errors (via the Taylor lineariza-tion method) were calculated for the continuous variablesBMI and age and were compared between those with andwithout psoriasis. The general linear model function wasused to compare continuous variables by entering them asdependent variables and psoriasis diagnosis as a factor. Inunadjusted analyses, differences between proportions forcategorical variables were compared using the Rao—Scottlikelihood Chi-square test. Logistic regression was used toassess whether psoriasis was associated with higher odds ofdietary supplement use while controlling for age, gender,education, and race/ethnicity.9 Statistical significance wasset at P < 0.05.

Results

A total of 13,272 individuals were invited to participate dur-

ing recruitment, of which 8397 were aged ≥20 years. Amongthese adults, 6218 agreed to be interviewed, representing aresponse rate of 74%. After excluding individuals with incom-plete data, 6211 participants aged ≥20 years comprised

apop

igure 1 Prevalence of dietary supplementation for gender,ducation, and age by psoriasis diagnosis.

he analytical sample, representing 219 million Americans.f the analytical sample, 184 participants—–representing.9 million Americans—–reported a diagnosis of psoriasis.he population-weighted prevalence of psoriasis was 3.2%.he characteristics of the participants by self-reportedsoriasis diagnosis are reported in Table 1. Participantsith psoriasis were more likely to be non-Hispanic white,e a current smoker, and report a previous diagnosis ofancer.

Overall, there was no significant difference in the preva-ence of dietary supplement use by psoriasis diagnosis, as3.0% and 49.5% of those with and without psoriasis reportedse over the past 30 days (P = 0.416; Table 2). Further-ore, the distribution of total supplements used was similaretween those with and without psoriasis, with the vastajority of participants taking 0—3 dietary supplements.nly 7.8% of participants took ≥4 dietary supplements overhe past 30 days. Dietary supplement use among partici-ants reporting arthritis did not vary by psoriasis diagnosis.mong participants reporting arthritis, 59.3% of participantsith psoriasis compared to 62.2% of participants withoutsoriasis reported dietary supplement use. Analysis of sup-lement use by other co-morbdities was not completedecause of low counts among participants with psoria-is.

Fig. 1 shows the prevalence of dietary supplement useor gender, education, and age by psoriasis diagnosis. Moreomen reported taking dietary supplements compared toen (P < 0.001), as did those who had greater than a high

chool education (P < 0.001). The prevalence of dietaryupplement use also increased with age (P < 0.001), with7.8% of those aged ≥60 years reporting dietary supple-ent use. In the logistic regression model, psoriasis was

ot associated with significantly higher odds of dietary sup-lement use after adjusting for age, gender, education,nd race/ethnicity (odds ratio 1.13, 95% confidence interval.81—1.56; P = 0.450).

Table 3 shows the prevalence of MVM, omega-3 fatty

cid, and herbal supplement use among participants withsoriasis. MVM supplements were the most common typef dietary supplement reported, with approximately 30% ofarticipants with psoriasis taking them. The most common

162 P.B. Wilson

Table 1 Demographic characteristics and co-morbidities of the participants by psoriasis diagnosis.

Psoriasis Na = 184 (%)b No psoriasis Na = 6027 (%)b P-value

Age (years) 48.8 ± 1.6 46.9 ± 0.5 0.248BMI (kg/m2) (N = 174; 5815)c 29.4 ± 0.4 28.7 ± 0.1 0.143Gender, female 89 (44.7%) 3122 (52.0%) 0.103Race/ethnicity 0.001

Mexican American 21 (4.7%) 1116 (8.7%)Other Hispanic 17 (3.2%) 615 (5.1%)Non-Hispanic white 121 (81.9%) 2854 (67.5%)Non-Hispanic black 17 (6.0%) 1103 (11.6%)Other race/ethnicity 8 (4.3%) 339 (7.2%)

Education 0.169High school or less 100 (47.9%) 3098 (41.6%)Current smoker 60 (29.5%) 1285 (20.0%) 0.003

Co-morbiditiesArthritis 78 (34.4%) 1595 (23.5%) 0.072

RA 21 (26.1%)d 295 (15.6%)d

OA 18 (23.7%)d 496 (36.5%)d

PsA 3 (7.1%)d 5 (0.6%)d

Cancer 35 (19.5%) 585 (9.6%) 0.014CHD 15 (5.6%) 239 (3.0%) 0.258

BMI, body mass index; CHD, coronary heart disease; OA, osteoarthritis; PsA, psoriatic arthritis; RA, rheumatoid arthritis.a N represents unweighted counts.b Percentages are weighted to U.S. population.c BMI not available for some participants.

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easons for taking MVM supplements were to maintain andmprove health, and only one of the MVM supplements wasntended to improve skin health/dry skin. The prevalencesf omega-3 fatty acid and herbal supplement use were.2% and 3.8%, respectively. The most common reason givenor taking omega-3 fatty acid supplements was to improveeart health, while herbals were taken for a variety ofeasons.

Table 4 shows the 12 dietary supplements that werepecifically intended to improve skin health/dry skin amongarticipants with psoriasis, with vitamin E being the mostommon supplement used for that reason. Finally, Table 5ists the specific herbal supplements taken amongst partic-

pants with psoriasis, along with prescription medicationsaken. Among the eight participants taking herbal sup-lements, five reported use of at least one prescriptionedication.

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Table 2 Prevalence of dietary supplement use among adults with

Psoriasis Na = 1

Any supplement use over the past 30 days 93 (53.0%)

Number of supplements used

0 91 (47.0%)

1 46 (29.0%)

2—3 31 (16.2%)

4—5 9 (5.5%)

6+ 7 (2.3%)

a N represents unweighted counts.b Percentages are weighted to U.S. population.

iscussion

his study indicates that dietary supplementation is notore common among adults self-reporting psoriasis in thenited States general population. Overall, approximatelyalf of all participants reported taking a dietary supple-ent over the past 30 days, which reaffirms estimates of

eneral population use from the 2003 to 2006 NHANES.9

urthermore, the frequency of individuals taking multi-le supplements (≥2) was not greater among individualsith psoriasis. Fleischer et al.17 provides data that isost directly comparable to this investigation. In total,

17 individuals with psoriasis presenting at the Wake For-

st University Department of Dermatology were asked toeport past or current alternative therapy use, includ-ng dietary supplementation. Overall, 23% of the sampleeported herbal use and 42% reported vitamin use. Of note,

and no psoriasis.

84 (%)b No psoriasis Na = 6027 (%)b P-value

2824 (49.5%) 0.4160.632

3203 (50.5%)1420 (24.1%)990 (17.5%)274 (5.1%)140 (2.7%)

Is dietary supplementation 163

Table 3 Prevalence of use for popular dietary supplements among adults with psoriasis and reasons given for use.

Prevalence Na = 184 (%)b Reasons given for takingc

Multivitamins/minerals 49 (29.6%)To maintain health 19Supplement diet 18To improve health 14Prevent health problems 7Prevent colds/boost immunity 5Get more energy 6Skin health/dry skin 1

Omega-3 fatty acid supplements (fish oil/flaxseed oil) 18 (9.2%)For heart health 11To improve health 4Prevent colds/boost immunity 3Skin health/dry skin 2To maintain health 2Prevent health problems 2

Herbals 8 (3.8%)To improve health 3Skin health/dry skin 2For mental health 2Prevent colds/boost immunity 2Improve sleep 2

a N represents unweighted counts.b Percentages are weighted to U.S. population.c Does not equal the number of participants reporting use because m

the use of those therapies was significantly more commonamong those with severe disease.17 Another investigationof approximately 500 psoriasis patients from a Norwe-gian dermatology department found that 19% and 25% hadtried or currently used herbal remedies and health foodpreparations.15 More recently, a study of Korean outpatientswith psoriasis indicated that 33/189 (17.5%) had or cur-rently used health supplements and 60/189 (31.7%) had orcurrently used herbal remedies.22

High-quality evidence regarding the efficacy and safetyof specific dietary supplements for psoriasis is generallylacking. The most extensive clinical trial data exists forfish oil, with some studies showing positive results whileothers have not.25 Interestingly, only two of the omega-3fatty acid supplements used among individuals with psori-asis in this population were being taken to improve skinhealth/dry skin, with the majority being taken for heart

Table 4 Dietary supplements taken to improve skinhealth/dry skin among adults with psoriasis (N = 12).

Supplement taken Count

Vitamin E 4Fish oil/flaxseed oil/omega-3 2Vitamin A 2Turmeric 1Biotin 1Multivitamin/mineral 1Burdock 1

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ultiple reasons can be given for each supplement.

ealth. While the benefits of omega-3 fatty acid supple-ents for cardiovascular disease are intensely debated,

here appears to be a modest benefit in terms of car-iovascular events and mortality.26 These cardiovascularvent benefits, however, have not been directly examined inndividuals with psoriasis. Given that growing evidence indi-ates that moderate-to-severe psoriasis may increase theisk for cardiovascular events,27,28 future research shouldvaluate the effects of omega-3 fatty acid supplemen-ation on cardiovascular disease risk factors and events insoriasis.

Interestingly, vitamin E was the most common dietaryupplement taken to improve skin health/dry skin amongarticipants with psoriasis. Vitamin E was not effective atmproving psoriasis severity in one study,29 and importantly,wo meta-analyses have found an increased risk of mortalityith high-dose vitamin E supplementation.30,31 The aver-ge dose of vitamin E in this study was 423 IU/day, whichquals the threshold for mortality risk in the meta-analysisrom Miller et al.30 Herbal use was relatively uncommonmong individuals with psoriasis in this population (3.8%).he greater herbal use reported in past studies may stemrom differences in the populations sampled and surveyuestion methodology.15,17,22 The previous studies inquireds to whether individuals had ever tried herbal supplemen-ation (as opposed to over the past 30 days) and representedlinical populations actively seeking treatment for psoriasis.

mong the eight participants with psoriasis reporting herbalse, five reported taking at least one prescription medica-ion. Several of the herbals being taken—–echinacea, sawalmetto, garlic—–have documented drug interactions,32—34

164 P.B. Wilson

Table 5 Prescription drugs used among adults with psoriasis using herbal supplements (N = 8).

Participant characteristics (sex, age,race/ethnicity)

Herbal supplement(s) taken Prescription drug(s) taken

Male, 25 years, Mexican American Valerian root extract, echinacea NoneMale, 29 years, Mexican American Milk thistle AlbuterolFemale, 70 years, non-Hispanic white Cinnamon Allopurinol, esomeprazole,

simvastatin, furosemide, lisinopril,potassium chloride

Male, 74 years, non-Hispanic white Turmeric, saw palmetto Glipizide, lovastatin, metformin,metoprolol, ramipril

Female, 48 years, non-Hispanic white Dandelion root, Xiao Yao Wan,myrrh gum, burdock

None

Male, 63 years, non-Hispanic white Valerian root Duloxetine, exenatide, lansoprazole,losartan, metformin, oxaprozin,tamsulosin, trazodone, valacyclovir

Male, 60 years, non-Hispanic white Blend containing garlic, guggul,Jiaogulan, and artichoke

None

Male, 50 years, non-Hispanic white Milk thistle extract Clonazepam, cyclobenzaprine,

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lthough extensive research from clinical trials is not avail-ble for many herbals.35

Strengths of this study include the use of a representativeample of the United States population with oversamplingf minority groups and the methodology used to assessietary supplementation. The sample represented approxi-ately 219 million Americans, and compared to the previous

tudies on this topic, it more accurately reflects the distri-ution of population factors such as age, education, andace/ethnicity. While there was nonresponse among indi-iduals invited to participate, NHANES-provided samplingeights were used to adjust for survey nonresponse. Fur-

hermore, since the dietary supplementation interviewsere conducted in participants’ homes, interviewers wereble to visually confirm most dietary supplements reported75—80%), which is an improvement upon purely self-eported data. This level of detail on the supplementssed is a clear strength, as previous investigations simplyeported alternative therapy use by broad categories.15,17

lso, the use of a Computer-Assisted Personal Interviewingystem and standardized protocols ensured that interviewerariability was minimized. Despite these strengths, someimitations must be acknowledged, such as the lack of pso-iasis diagnosis confirmation and the lack of informationn psoriasis severity. Although no data on the accuracyf psoriasis self-report is available, self-reports of otherhronic diseases have been shown to be accurate.36 Fur-hermore, data on psoriasis severity was not availableo examine if supplementation use varied with diseaseeverity. Despite this, a previous report indicates thatHANES reflects typical psoriasis severity distributions, aspproximately one-third of those reporting psoriasis had—2% body surface area involvement, while 15—20% hadody surface area involvement greater than 3%.37 Addi-ionally, it cannot be guaranteed that the list of reasons

or taking supplements available to participants capturedotivations related to improving psoriasis. Participants withsoriasis taking dietary supplements intended to improveealth may have considered their psoriasis as a major

lithium, sertraline

ontributor to overall health. Finally, these data should note extrapolated to populations actively seeking treatmentt dermatology clinics and other clinical facilities, since theyay perceive their psoriasis to be significantly worse than

ndividuals with psoriasis in the general population.In conclusion, dietary supplement use does not appear

o be more prevalent among adults self-reporting psoria-is in the United States general population. Approximatelyalf of adults with psoriasis reported taking a dietary sup-lement over the past 30 days, with MVM supplements beinghe most frequently used dietary supplement. Generally, theost common reasons given for taking dietary supplementsere to improve and maintain health, and use of dietary

upplements specifically for skin health was relatively infre-uent. Additional clinical trials are needed to evaluate theafety and efficacy of specific dietary supplements on pso-iasis severity and its related co-morbidities.

unding

one declared.

onflicts of interest

one declared.

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