Effects of Black Currant Anthocyanoside Intake on Dark Adaptation and VDT Work-induced Transient Refractive Alteration in Healthy Humans

Alternative Medicine Review, Dec, 2000 by Hitoshi Nakaishi, Hitoshi Matsumoto, Shigeru Tominaga, Masao Hirayama

0:00 Measurement of [M.sub.tra], [M.sub.cff], and [M.sub.vas]1 (before the task)

0:10 Intake of juice (BCA or placebo)

2:10 Start of visual task

4:10 Completion of visual task

Measurement of [M.sub.tra]2, [M.sub.cff]2, and [M.sub.vas] 2 (after the task)

Variables Measured

The experimental near visual task consisted of a simple calculation test on a VDT, modifying the Kraepelin test method.[15] The task was loaded for two hours without a pause, and measurements were carried out for three items. First, the spherical (R) and cylindrical (C) refraction of the dominant eye was measured by means of an autorefractometer (Nidek AR-600A, Japan) according to the method of Nakamura and Uosato.[16] The refraction value for the dominant eye was evaluated in terms of the spherical equivalent of (S C/2). Second, the [M.sub.cff] value (flicker value) was measured using critical flicker fusion (CFF) determined via a Flicker 501 (Takei Kiki Kogyo, Japan) according to the method reported by Ogasawara et al.[17] This measurement was carried out five times with the signal frequency in UP mode and the mean of the five fusing values was determined. Third, subjective fatigue symptoms were assessed by a questionnaire consisting of five statements concerning the fatigue symptoms of the head and/or neck, arm, eye, shoulder, and lower back. The magnitude of each symptom was expressed in terms of VAS by having the subject place a mark on a 100 mm horizontal line indicating a continuum from no fatigue (left end) to strong fatigue (right end). The subject's response to each statement was defined as the distance (in millimeters) from the left end of the line to the mark.

Statistical Analyses

All measurements were performed before and after intake of the test samples (BCA concentrate or placebo). Comparison was made by means of a paired-t test.

Results

BCA Test Sample

The anthocyanoside content of the BCA concentrate used in this study was 9.2 percent by HPLC analysis.[12] As shown in Figure 1, the concentrate consisted of four components: D3G, D3R, C3G, and C3R. Each component was quantified by HPLC. The results of analysis of the BCA test samples (capsules and juice) are shown in Table 1. In preparation of the juice-type test samples, sucrose, citric acid, and coloring pigments were added to make the placebo's taste and color identical to the BCA.

Dark Adaptation Study

Dark adaptation values for twelve healthy volunteers were measured as the visual threshold after 30 minutes of dark adaptation, before and two hours after intake of BCA (at three dose levels: 50, 25, and 12.5 mg/subject) or placebo. The results are summarized in Table 3. Figure 2 shows the typical profile of dark adaptation threshold values during the 30-minute period before and after BCA intake in the case of one subject. The mean standard deviation before intake ranged from 2.056 [ or -] 0.209 (placebo) to 2.016 [ or -] 0.170 (BCA, 25 mg/subject). No significant difference was found among the four groups as a matter of course. Comparison of the mean standard deviation after intake among the four groups showed a decrease from 2.018 [ or -] 0.218 (placebo) to 1.923 [ or -] 0.167 (BCA, 50 mg/subject) with increasing doses of BCA. This dose-dependent decrease of the threshold was associated with expansion of the change in the refraction values for the dominant eye ([M.sub.da]) from -0.038 [ or -] 0.106 (placebo) to -0.115 [ or -] 0.131 (BCA, 50 mg/subject), comparing the values before and after intake. At the BCA dose level of 50 mg/subject, compared to the placebo, there was a significant difference (p = 0.014) in the threshold values after intake, but no significant difference in [M.sub.DA] (p = 0.171). In comparing the statistical p values obtained in analysis of the data after intake versus before intake among four dose levels of BCA, a significant difference (p = 0.011) was evident at only one dose level of BCA (50 mg/subject).