Benefits
Supports low-light vision and dark adaptation
Blackcurrant anthocyanins are studied for the eye's ability to adjust to dim light. In a small double-blind crossover study in 12 healthy adults, doses of 12.5, 20 and 50 mg appeared to lower the dark-adaptation threshold in a dose-dependent way. Only the 50 mg dose was significant, and that comparison was before versus after intake rather than against placebo. It used generic blackcurrant anthocyanins, not VitaCurrant.
Screen-related eye fatigue
In the same small crossover study, 21 healthy adults took 50 mg of blackcurrant anthocyanins or placebo before intensive computer screen work. The focusing shift seen after placebo did not appear after anthocyanins, but the difference was only borderline and not statistically significant. Eye-related symptoms on a fatigue questionnaire did improve significantly. It used generic blackcurrant anthocyanins, not VitaCurrant.
Supports circulation in forearm and shoulder muscles
In a small crossover study, a single dose raised resting forearm blood flow two hours later in 9 healthy men. In a second part, 11 adults took it daily for 2 weeks; during 30 minutes of typing, the shoulder muscle did not show the drop in oxygenated blood seen with placebo, while stiffness only trended lower and typing performance did not improve. Heart or artery health was not measured.
Mechanism of action
Rhodopsin regeneration in the retina
In frog retinal rod membranes, cyanidin glycosides from blackcurrant sped up the regeneration of rhodopsin, the light-sensitive pigment in rod cells, while the delphinidin glycosides had no significant effect. Faster rhodopsin regeneration is a proposed explanation for the dark-adaptation findings, but it has not been confirmed in people.
Ciliary muscle relaxation and focusing
Delphinidin-3-rutinoside, the main anthocyanin in blackcurrant, relaxed bovine ciliary muscle in laboratory tests, apparently through endothelin B receptors and nitric oxide signaling. Because the ciliary muscle controls the lens's focusing power, this is a proposed mechanism for the screen-work findings, not one shown in people.
Blood flow and nitric oxide signaling
In laboratory tests on eye muscle, delphinidin-3-rutinoside acted through nitric oxide signaling, a pathway that also relaxes blood vessels; whether this explains blood flow changes in people is not known. In people, a single dose raised resting forearm blood flow in healthy men, and eye blood flow rose in the two-year trial in glaucoma patients who stayed on prescription drops.
Clinical trials
Double-blind, placebo-controlled crossover study of blackcurrant anthocyanosides: doses of 12.5, 20 and 50 mg for dark adaptation and 50 mg for screen work. Generic blackcurrant anthocyanins, not VitaCurrant. (Nakaishi et al. 2000, Alternative Medicine Review)
Healthy adult volunteers (12 in the dark-adaptation test, 21 in the screen-work test)
The dark-adaptation threshold appeared to fall with dose, but only the 50 mg dose was significant (p = 0.011), in a before-versus-after comparison. After screen work, focus did not shift on anthocyanins but dropped on placebo, a borderline difference (p = 0.064). Eye-related symptoms on a fatigue questionnaire improved significantly. An erratum was later published (Altern Med Rev 2001;6(1):60). A small study.
Two parts: a double-masked, placebo-controlled crossover study of blackcurrant anthocyanins 50 mg/day for 4 weeks in healthy adults, and a re-analysis of glaucoma patients from the earlier two-year trial. Generic blackcurrant anthocyanins, not VitaCurrant. (Ohguro et al. 2013, Journal of Ocular Pharmacology and Therapeutics)
12 healthy volunteers, plus 21 glaucoma patients (12 anthocyanins, 9 placebo) on one antiglaucoma medication, selected from the two-year trial
In healthy volunteers, eye pressure fell from baseline at 2 and 4 weeks on anthocyanins and differed from placebo at 2 weeks. In the 21-patient subset, eye pressure was lower at 24 months, yet the full 38-patient trial these patients came from reported no significant change in eye pressure. Very small and partly a re-analysis, so this is not an established effect. Nothing here replaces prescribed glaucoma treatment; anyone with eye-pressure concerns needs an ophthalmologist.
Randomized, placebo-controlled, double-masked trial, blackcurrant anthocyanins 50 mg/day for 24 months, added to prescribed eye drops. Generic blackcurrant anthocyanins, not VitaCurrant. (Ohguro et al. 2012, Ophthalmologica)
38 people with open-angle glaucoma, 19 per group, who were already using prescription antiglaucoma eye drops
Over two years, the anthocyanin group showed less visual-field deterioration than placebo, but the difference was marginal (p=0.039) in a trial of only 38 people, 19 per group. Eye blood flow increased. There was no significant change in eye pressure. The supplement was given in addition to prescribed antiglaucoma medication, never instead of it. This is a report of a trial in people with an eye disease, not a benefit a healthy person should expect, and no one should change glaucoma treatment because of it.
Double-blind, placebo-controlled crossover study in two parts: a single dose of about 17 mg/kg of a blackcurrant anthocyanin concentrate at rest, and 7.7 mg/kg daily for 2 weeks before a typing task. Generic blackcurrant anthocyanins, not VitaCurrant. (Matsumoto et al. 2005, European Journal of Applied Physiology)
9 healthy men (resting part) and 11 healthy adults (typing part)
At rest, forearm blood flow rose significantly 2 hours after the single dose compared with placebo, with only a non-significant trend later; muscle oxygen use did not change. In the typing part, anthocyanins prevented the drop in oxygenated blood in the trapezius (shoulder) muscle, while muscle electrical activity and stiffness only trended lower, and typing performance did not improve. The lead author worked for a food company (Meiji Seika). Small study that says nothing about heart or artery health.