Effect of Omega-3 Fatty Acids, Lutein/Zeaxanthin, or Other Nutrient Supplementation on Cognitive Function: The AREDS2 Randomized Clinical Trial

Importance  Observational data have suggested that high dietary intake of saturated fat and low intake of vegetables may be associated with increased risk of Alzheimer disease.

Objective  To test the effects of oral supplementation with nutrients on cognitive function.

Design, Setting, and Participants  In a double-masked randomized clinical trial (the Age-Related Eye Disease Study 2 [AREDS2]), retinal specialists in 82 US academic and community medical centers enrolled and observed participants who were at risk for developing late age-related macular degeneration (AMD) from October 2006 to December 2012. In addition to annual eye examinations, several validated cognitive function tests were administered via telephone by trained personnel at baseline and every 2 years during the 5-year study.

Interventions  Long-chain polyunsaturated fatty acids (LCPUFAs) (1 g) and/or lutein (10 mg)/zeaxanthin (2 mg) vs placebo were tested in a factorial design. All participants were also given varying combinations of vitamins C, E, beta carotene, and zinc.

Main Outcomes and Measures  The main outcome was the yearly change in composite scores determined from a battery of cognitive function tests from baseline. The analyses, which were adjusted for baseline age, sex, race, history of hypertension, education, cognitive score, and depression score, evaluated the differences in the composite score between the treated vs untreated groups. The composite score provided an overall score for the battery, ranging from −22 to 17, with higher scores representing better function.

Results  A total of 89% (3741/4203) of AREDS2 participants consented to the ancillary cognitive function study and 93.6% (3501/3741) underwent cognitive function testing. The mean (SD) age of the participants was 72.7 (7.7) years and 57.5% were women. There were no statistically significant differences in change of scores for participants randomized to receive supplements vs those who were not. The yearly change in the composite cognitive function score was −0.19 (99% CI, −0.25 to −0.13) for participants randomized to receive LCPUFAs vs −0.18 (99% CI, −0.24 to −0.12) for those randomized to no LCPUFAs (difference in yearly change, −0.03 [99% CI, −0.20 to 0.13]; P = .63). Similarly, the yearly change in the composite cognitive function score was −0.18 (99% CI, −0.24 to −0.11) for participants randomized to receive lutein/zeaxanthin vs −0.19 (99% CI, −0.25 to −0.13) for those randomized to not receive lutein/zeaxanthin (difference in yearly change, 0.03 [99% CI, −0.14 to 0.19]; P = .66). Analyses were also conducted to assess for potential interactions between LCPUFAs and lutein/zeaxanthin and none were found to be significant.

Conclusions and Relevance  Among older persons with AMD, oral supplementation with LCPUFAs or lutein/zeaxanthin had no statistically significant effect on cognitive function.

Trial Registration  clinicaltrials.gov Identifier: NCT00345176

The prevalence of Alzheimer disease, estimated to have affected 5.2 million people in the United States in 2013, may triple in the next 4 decades.¹ Epidemiologic studies have suggested that diets high in omega-3 long-chain polyunsaturated fatty acids (LCPUFAs) have a protective role in maintaining cognitive function.² Docosahexaenoic acid (DHA), a component of omega-3 LCPUFA, is an essential structural component of the brain cells, and low levels of DHA have also been found in persons with Alzheimer disease.³ For these reasons, omega-3 LCPUFAs were tested for the treatment of dementia. However, numerous randomized clinical trials (RCTs) failed to show omega-3 LCPUFAs to be effective in treating dementia.^4,5

Similarly, observational data suggested that high dietary intake or high plasma levels of antioxidants may also be associated with better cognitive performance,^6-8 but RCTs did not support this hypothesis.^9,10 Results of an RCT of beta carotene suggested that this carotenoid might be important in the treatment of dementia, depending on the duration of supplementation.¹¹ A possible role for lutein and zeaxanthin in the treatment of cognitive impairment in older adults has also been raised in a small RCT of lutein combined with omega-3 LCPUFAs in 49 women with limited follow-up.¹²

Quiz Ref IDThe Age-Related Eye Disease Study 2 (AREDS2),¹³ an RCT¹⁴ of omega-3 fatty acids and/or lutein/zeaxanthin supplements for the treatment of age-related macular degeneration (AMD) and cataract, provided an opportunity to evaluate the role of these oral supplements in preventing cognitive decline. AREDS2 enrolled one of the largest numbers of study participants for cognitive function testing at baseline and every 2 years, in a study with long-term follow-up periods (median of 5 years), providing a more definitive result showing the effects of oral nutritional supplementation on cognition.

The study design is reported in Supplement 1.¹³ AREDS2 limited enrollment to people at high risk of progressing to late AMD, those with either bilateral large drusen, or large drusen in one eye and late AMD in the fellow eye. The clinical research was conducted according to the Declaration of Helsinki and all institutional review boards approved the AREDS2 research protocol. All participants provided written informed consent for AREDS2. At the time of randomization, study participants were asked whether they agreed to be contacted for the ancillary study. Within 3 months following randomization, verbal informed consent was obtained and written materials regarding the AREDS2 Cognitive Function Study were provided to the study participants.

This study, supported by the National Institutes of Health (NIH), was required to gather information on race and ethnicity. Using guidelines from the NIH Health Policy on Reporting Race and Ethnicity Data: Subjects in Clinical Research, self-reported race and ethnicity of the AREDS2 participants were collected with 2 ethnic categories (Hispanic or Latino and not Hispanic or Latino) and 5 racial categories (American Indian or Alaska Native, Asian, black or African American, Native Hawaiian or other Pacific Islander, and white). Participants were able to select more than 1 racial category.

AREDS2 was a randomized, double-masked, placebo-controlled, 2 × 2 factorial trial evaluating the risks and benefits of adding omega-3 LCPUFAs (specifically docosahexaenoic acid [DHA], 350 mg, and eicosapentaenoic acid [EPA], 650 mg, and/or lutein/zeaxanthin, 10 mg/2 mg) to the original AREDS formulation, or one of the variations of the AREDS formulation for the treatment of AMD. Study participants were randomly assigned in a 1:1:1:1 allocation to take one of the following study supplements daily: (1) placebo; (2) DHA/EPA; (3) lutein/zeaxanthin; or (4) DHA/EPA and lutein/zeaxanthin. The investigational products matched the placebos in size, shape, and taste. The original randomization scheme is displayed in eFigure 1 in Supplement 2.¹⁵

Because they are known to be at high risk for developing late AMD, all AREDS2 participants were also offered the original or a modified version of the AREDS formulation. A second randomization was conducted to evaluate the effect of eliminating beta carotene from the AREDS supplements (beta carotene vs no beta carotene) and the effect of comparing 80 mg of zinc vs 25 mg of zinc. Participants who consented to the optional secondary randomization were randomly assigned to receive: (1) AREDS formulation (vitamins C, 500 mg; E, 400 IU; beta carotene, 15 mg; zinc oxide, 80 mg; and cupric oxide, 2 mg); (2) AREDS formulation minus beta carotene; (3) AREDS formulation with low zinc (25 mg); or (4) AREDS formulation minus beta carotene and low zinc. Current smokers and former smokers who had quit within 1 year before randomization and who agreed to this secondary randomization were randomized to 1 of the 2 groups without beta carotene because beta carotene supplementation has been shown to increase the risk of lung cancers in cigarette smokers.^16,17 Participants who did not consent to this secondary randomization were provided with the original AREDS supplements if they were not current smokers or had not smoked within the past year. The flow diagram for the secondary randomization is available in a previously published report.¹⁵

The primary and secondary randomizations were stratified by clinical center and AMD category (bilateral large drusen or large drusen in one eye and advanced AMD in the fellow eye) using randomly permuted blocks of varying sizes. Each treatment was assigned 5 bottle numbers. Bottle numbers were issued via an electronic randomization system for each participant once study eligibility was verified. The assigned bottle number was used to distribute the study treatment(s). AREDS2 Coordinating center personnel involved in creating the randomization system had access to the bottle number/treatment assignments. Participants and study personnel were masked to treatment assignment. Participants received their study supplements or matching placebos at each annual visit. Adherence with the study supplements was measured with annual pill counts. In a subset of participants, the serum levels were also evaluated for adherence at baseline and years 1, 3, and 5. Follow-up study visits were scheduled annually with telephone contacts by study coordinators at 6 months between study visits and at 3 months postrandomization to collect information on AMD treatment and adverse events. Investigators, also masked to all medical data and treatment assignments, conducted the analyses.

AREDS2 used a cognitive battery similar to the one used in AREDS, administered by certified personnel by telephone over a period of 30 minutes (eMethods in Supplement 2).⁹Quiz Ref ID The cognitive function test administrators, who were masked to the participant’s study supplement assignment and medical history, received extensive initial training as well as certification on interview techniques and scoring of responses. Subsequently, quarterly reviews of 3 randomly selected interviews on audiotape from each interviewer were centrally conducted to provide feedback regarding the interview and scoring techniques for quality assurance. The first administration of the AREDS2 telephone battery instruments was within 3 months after randomization to the primary AREDS2 protocol and approximately every 2 years thereafter.

The AREDS Telephone Battery was originally found to be an appropriate substitute for participants who were unable to complete an in-clinic assessment of cognitive function.¹⁸ All tests have been validated and used in previous studies with cognitive function testing. An abbreviated version of the cognitive battery consisting of the Hearing Handicap Inventory, CES-D (Center for Epidemiologic Studies’ Depression Scale), and TICS (Telephone Interview of Cognitive Status) (all of which took approximately 10-15 minutes to administer) was administered to participants who had time constraints or other concerns about undergoing the full-length battery. The AREDS2 cognitive battery consisted of 8 tests of cognitive function that were administered after each participant was tested for hearing and depression at each telephone call for cognitive function testing. The order of testing is listed in the Box. The ranges of the values for these individual tests are described in eAppendix in Supplement 2.

Box Section Ref ID

The primary outcome in the planned ancillary study of cognition evaluated the yearly change in the composite scores of the cognitive function tests (items 3-10 in the Box). A higher change in score indicated better cognition vs negative values, which represented worsening of the cognitive function testing. We assessed the difference in the yearly change of the scores by treatment main effects, focused mainly on omega-3 LCPUFAs vs no omega-3 LCPUFAs, as stated a priori. Secondary analyses included lutein/zeaxanthin vs no lutein/zeaxanthin, high zinc vs low zinc, and beta carotene vs no beta carotene, because these nutrients were previously explored in other studies. However, this ancillary study was not sufficiently powered to evaluate these additional nutrients.

The change in the TICS total score, a comprehensive testing of all the domains over the course of the study from baseline, was assessed.²⁵ A composite score was constructed by converting the test results of the 8 cognitive tests (Box) z scores and then adding the z scores. The composite score provided an overall score for the battery, ranging from −22 to 17, with higher scores representing better function.¹⁸ This methodology has been used in previously published studies of cognitive function testing.^26,27 We also individually evaluated the yearly change in the cognitive function scores for the 8 cognitive function tests from baseline to 2 and 4 years. Composite scores were analyzed only in those participants who completed the entire battery of cognitive function tests, while those who had a TICS score only were analyzed for all participants who had TICS scores available in the entire cohort.

The primary hypothesis, stated at the beginning of the AREDS2 ancillary cognitive function study, was to test whether omega-3 LCPUFAs (the main effects of those who were randomized to receive omega-3 LCPUFAs vs those not randomized to receive omega-3 LCPUFAs) would have any effect on cognitive function. It was estimated that 15% to 35% of the AREDS2 participants would have a score greater than the normal range for the TICS. We assumed that at least 3000 AREDS2 participants (1500 assigned to receive omega-3 LCPUFAs and 1500 assigned to receive no omega-3 LCPUFAs) would have at least 85% power to detect an odds ratio (OR) of 0.75, as measured by the TICS, assuming a 2-sided α = .05 and a control group (no omega-3 fatty acids) rate of participants with a score greater than the normal range. The study was powered to evaluate only the main effects of omega-3 LCPUFAs, but because this is a factorial design, studies of interaction were also conducted to assess for potential interactions between omega-3 LCPUFAs and lutein/zeaxanthin.

For each test of cognitive function, changes in score from baseline to time of study visits at 2 and 4 years were evaluated using a mixed-model regression. The models took into account the repeated measures of the participants, the unequal time spacing, and number of cognitive tests for each participant by using a spatial power covariance structure. The models provided estimates of yearly change in score that could be associated with the AREDS2 study supplement assignment and each covariate. The models were adjusted for baseline age, sex, race, history of hypertension, education, baseline cognitive score, and baseline depression score. Age, baseline score, and baseline depression score were treated as continuous variables, and the others were treated as categorical variables with race dichotomized to white vs nonwhite. A repeated-measures logistic regression was used to analyze the outcome of a TICS score of less than 30. To account for the correlation of multiple visits per participant, an autoregressive correlation structure was used. To account for multiplicity of analyses, we used 99% CIs rather than the conventional 95% CI. Because 36 models were conducted, to be statistically significant, the P value would need to be <.001.

Participants were excluded from the analyses if they were missing baseline cognitive function tests, any follow-up test, an incomplete test, or missing baseline demographic data. All analyses were conducted under the principle of intention to treat and no data imputation was applied. All analyses were conducted using SAS version 9.3 (SAS Institute Inc).

A total of 4203 participants were enrolled between October 2006 and September 2008 at 82 clinical sites across the United States and followed up until December 2012 in AREDS2. Enrollees had to satisfy the specified inclusion and exclusion criteria.¹³ Of the 4203 AREDS2 participants enrolled, 3741 (89%) consented to the full Cognitive Function Study, 462 declined, and 3501/3741 (93.6%) underwent cognitive function testing (Figure 1). Of the 3501 who consented, 2991 (85%) participated in this study by completing at least 1 full interview and 510 (15%) had the shortened battery (eTable 1 in Supplement 2). Among those who consented for the present study, we excluded individuals with no baseline test, no follow-up test, or missing demographic data or incomplete tests, leaving us with 3073 participants for analyses. Of the 3 possible interviews for cognitive function during the course of the study (baseline, year 2, and year 4), 2831 of 3501 (81%) of study participants contributed to all 3 interviews, 410 (12%) had 2 interviews, and 260 (7%) had 1 interview only (eTable 1 in Supplement 2). The mean (SD) age of the participants in the Cognitive Function Study was 72.7 (7.7) years and 57.5% were women.

AREDS2 participants included in the analyses of the Cognitive Function Study were younger, more likely to be white, and more likely to have a higher level of education (eTable 2 in Supplement 2). Among those who participated, there was a fairly comparable distribution of the treatment assignments. However, among those who did not participate, there was a relatively greater proportion assigned to lutein/zeaxanthin (eTable 2 in Supplement 2). Baseline serum levels of the nutrients evaluated were comparable across treatment groups. Table 1 describes the comparable baseline characteristics of the participants who were randomly assigned to receive omega-3 LCPUFAs (DHA/EPA) or no omega-3 LCPUFAs (DHA/EPA).

Evaluation of adherence with the primary study supplements showed that 1439 of 1736 participants (82.9%) assigned to receive omega-3 LCPUFAs and 1419 of 1688 who were (84.1%) assigned to receive no omega-3 LCPUFAs were adherent to their study drugs at least 75% of the time and taking 75% or more of their study drugs. Similarly, 1432 of 1690 participants (84.7%) assigned to receive lutein/zeaxanthin and 1494 of 1724 (86.7%) who were assigned to not receive lutein/zeaxanthin took 75% or more of the study medications at least 75% of the time. In addition, serum levels of 545 AREDS2 participants who were randomized to the treatments showed a 2-fold or greater increase in the serum levels of omega-3 LCPUFAs and/or lutein/zeaxanthin, compared with those participants who were not assigned to receive the respective nutrients.

The baseline cognitive function scores for all the participants included in the various analyses are displayed in eTable 3 (in Supplement 2). The baseline scores from the cognitive function tests were comparable across the randomized groups of the main effects of omega-3 LCPUFAs vs no omega-3 LCPUFAs (Table 2). Similar balanced distribution was seen across all the randomized groups of all the other nutrients evaluated (eTable 4 in Supplement 2).

Table 3 reports the baseline demographics and risk factors for the participants included in the TICS scores analyses and/or the composite scores analyses. Higher cognitive function scores indicate better cognition. For the outcome of the change at years 2 and 4 from baseline, calculated as yearly change, negative values signal a decrease in cognitive function when compared with baseline (Table 4). In general, the cognitive function testing scores decreased over time for the AREDS2 participants.

AREDS2 participants who achieved higher scores at baseline on both the TICS and the composite score were more likely to be women and white. Participants with higher levels of education also achieved higher scores on testing. Persons without a history of hypertension, congestive heart failure, coronary heart disease, myocardial infarction, and stroke were more likely to score higher in both TICS and composite scores.

The yearly change in the composite cognitive function score was −0.19 (99% CI, −0.25 to −0.13) for participants randomized to receive LCPUFAs and −0.18 (99% CI, −0.24 to −0.12) for those randomized to receive no LCPUFAs (difference in yearly change, −0.03 [99% CI, −0.20 to 0.13]; P = .63; Figure 2A). The difference in the yearly change of the TICS between the omega-3 LCPUFA treatment groups was −0.10 (99% CI, −0.24 to 0.04; P = .07; Figure 2A). Further evaluation of the TICS score for the odds of having a score less than 30 was conducted using a binary outcome of TICS score of less than 30, which is considered to be less than normal. The odds of having a TICS score of less than 30 was 1.12 (99% CI, 0.91 to 1.39; P = .15; Figure 3). The yearly changes of the various tests that contributed to the composite scores ranged from −0.10 to 0.17; none of these changes were statistically significant (Figure 2A).

The yearly change in the composite cognitive function score was −0.18 (99% CI, −0.24 to −0.11) for participants randomized to receive lutein/zeaxanthin vs −0.19 (99% CI, −0.25 to −0.13) for those randomized to not receive lutein/zeaxanthin (difference in yearly change, 0.03 [99% CI, −0.14 to 0.19]; P = .66; Figure 2B). Similarly, the difference in the yearly TICS score change between the lutein/zeaxanthin treatment groups was −0.01 (99% CI, −0.16 to 0.13; P = .80; Figure 2B), and the odds of having TICS score of less than 30 was 1.08 (99% CI, 0.87 to 1.33; P = .35; Figure 3). The results of the tests ranged from −0.32 to 0.41 and none were statistically significant (Figure 2B).

We also evaluated the data stratified by the dietary intake of omega-3 LCPUFAs and lutein with zeaxanthin. We found no difference among participants with varying dietary intake.

Studies of interaction were conducted to assess for potential interactions between omega-3 LCPUFAs and lutein/zeaxanthin. We found no statistically significant interaction between omega-3 LCPUFAs and lutein/zeaxanthin (TICS score, P = .14; composite score, P = .98).

The yearly change in the composite cognitive function score was −0.20 (99% CI, −0.27 to −0.13) for participants randomized to receive high zinc vs −0.19 (99% CI, −0.27 to −0.12) for those randomized to receive low zinc (difference in yearly change, −0.02 [99% CI, −0.21 to 0.17]; P = .77; Figure 2C). Similarly, the difference in the yearly TICS score change between the high and low zinc groups was −0.01 (99% CI, −0.18 to 0.16, P = .89; Figure 2C), and the odds of having TICS score of less than 30 was 1.07 (99% CI, 0.84 to 1.36; P = .49; Figure 3). The results of the tests ranged from −0.23 to 0.12 and none were statistically significant (Figure 2C).

The yearly change in the composite cognitive function score was −0.24 (99% CI, −0.32 to −0.16) for participants randomized to receive beta carotene vs −0.18 (99% CI, −0.26 to −0.10) for those randomized to not receive beta carotene (difference in yearly change of −0.16 [99% CI, −0.36 to 0.04]; P = .04; Figure 2D). Similarly, the difference in the yearly TICS score change between the beta carotene treatment groups was −0.11 (99% CI, −0.28 to 0.07; P = .12; Figure 2D), and the odds of having TICS score of less than 30 was 1.14 (99% CI, 0.88 to 1.46; P = .19; Figure 3). The results of the substudies ranged from −0.48 to −0.01 and none were statistically significant (Figure 2D).

Quiz Ref IDAfter a 5-year RCT, supplementing with omega3-LCPUFAs, specifically DHA and EPA (total, 1 g), and/or lutein, 10 mg, and zeaxanthin, 2 mg, did not have a statistically significant effect on cognitive function in this population of persons with intermediate AMD (bilateral large drusen) or late AMD in one eye. The results of the randomization to high zinc vs low zinc or beta carotene vs no beta carotene also showed no statistically significant effect. However, worse cognitive function at study entry was associated with increasing age, lower education level, and the male sex in our baseline cross-sectional data. Other medical risk factors such as hypertension and other cardiovascular disease including stroke were associated with lower cognitive function testing scores. During the course of the study, these same risk factors, as well as a lower baseline cognitive function test score, were also associated with greater decline in the cognitive function test scores—both the TICS and the composite score (Table 3).

Quiz Ref IDThe strengths of the study include the high adherence rates to the study supplements, as well as the high rates of cognitive function testing in a clinical trial with a relatively large study population. The interviewers underwent extensive training as well as periodic certification to ensure quality data. The battery of cognitive function tests in AREDS2, which was conducted over the telephone without visual input, is particularly appropriate for a population that has AMD. This battery of testing is similar to the battery used in other large-scale studies that used a similar telephone interview, especially using the TICS test, to evaluate cognitive function. These tests have been validated to give quality assessments.²⁸

The limitations of this trial include the limited generalizability of the results because the study was conducted in a select population of well-nourished and highly educated persons with at least intermediate AMD or advanced AMD in one eye. This condition is also a neurodegenerative disease with limited information on its pathogenesis. Another limitation of this study is the possibility that at nonphysiologic levels, the nutrients we tested have different biologic effects, different from those attained with dietary intake. It is possible that these supplements were started too late in the aging process since the mean age of the study population at baseline was 72.7 years. It is plausible that supplementation duration of 5 years may be insufficient, as suggested by the differential effects seen in the Physicians Health Study II (PHSYII) cognitive ancillary study in those participants who had 18 years of supplementation with beta carotene vs those with a much shorter duration of 1 year.¹¹ The process of cognitive decline may occur over decades, thus a short-term supplementation given too late in the disease may not be effective.

We attempted to evaluate the role of antioxidant vitamins and zinc in cognitive function testing in the original AREDS study, which was a placebo-controlled RCT.⁹ A limitation of the original AREDS results, however, was that cognitive testing was not conducted at baseline, which left researchers unable to determine whether antioxidant or copper and zinc treatment influenced the rate of cognitive decline (although baseline cognition was likely identical across assigned treatment groups).

Quiz Ref IDThe observational data regarding dietary intake of specific nutrients such as omega-3 LCPUFAs and antioxidants suggest strong inverse associations with dementia, yet the RCTs have failed to show beneficial effects. It is possible that eating foods rather than taking any specific single supplement may have an effect. Similarly, observational data suggested a protective association of high levels of dietary omega-3 LCPUFAs for AMD, but the overall primary effects of the AREDS2 study on AMD also demonstrated that DHA/EPA had no effect on the treatment of AMD¹⁵ while lutein/zeaxanthin had an incremental effect.^15,29 Similarly, we found that omega-3 LCPUFAs for the treatment of cardiovascular disease in AREDS2, another ancillary study, also did not result in a beneficial effect.³⁰ Studying dietary and food intake patterns rather than specific factors isolated with food source may better reflect nutritional benefits because we have no knowledge of the actual factor(s) that may make an effect or of the interactions between nutrients that influence the physiologic effects of any one nutrient that may target tissues or pathways.

Among older persons with AMD, oral supplementation with LCPUFAs or lutein/zeaxanthin had no statistically significant effect on cognitive function.

Corresponding Author: Emily Y. Chew, MD, BG 10-CRC Room 3-2531, 10 Center Dr MSC1204, Bethesda, MD 20892-1204 (echew@nei.nih.gov).

Author Contributions: Drs Chew and Clemons had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Chew, Grodstein.

Acquisition, analysis, or interpretation of data: Chew, Clemons, Agrón, Launer, Bernstein.

Drafting of the manuscript: Chew, Agrón.

Critical revision of the manuscript for important intellectual content: Chew, Clemons, Agrón, Launer, Grodstein, Bernstein.

Statistical analysis: Clemons, Agrón, Launer.

Obtained funding: Chew, Clemons.

Administrative, technical, or material support: Chew, Clemons, Grodstein.

Study supervision: Chew.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Bernstein reports serving as a consultant for Kemin Health, Kalsec, DSM, and ScienceBased Health. No additional disclosures were reported.

Funding/Support: This study was sponsored by the NIH; by the intramural program funds and contracts from the National Eye Institute (NEI)/NIH, Department of Health and Human Services, contract HHS-N-260-2005-00007-C. ADB and contract N01-EY-5-0007. Funds were generously contributed to these contracts by the following NIH institutes: Office of Dietary Supplements (ODS), National Center for Complementary and Alternative Medicine (NCCAM), National Institute on Aging (NIA), National Heart, Lung, and Blood Institute (NHLBI), and National Institute of Neurological Disorders and Stroke (NINDS).

Role of the Funder/Sponsor: Dr Chew is responsible for the management, analysis, and interpretation of the data as well as the preparation, review, and approval of the manuscript. The decision to submit the manuscript for publication was also determined by Dr Chew, a staff member of the funding agency.