With the onslaught of electronic devices, we are becoming a culture that is dependent on video display terminals (VDTs). As a result, there is a steady increase of vision stress, fatigue and even a condition known as “false nearsightedness.” A human placebo-controlled, double-blind, crossover study was conducted (Nakaishi et al., 2000) to determine the effects of black currant anthocyanins on eye fatigue, as indicated by the amount of lens refraction following prolonged computer work (this detects the amount of “false nearsightedness” by overworked ciliary muscles in the eye). The ciliary muscle is believed to be involved in the development of refractive myopia by becoming spastic as a result of excessive contraction during close-up work, thereby not relaxing enough to allow the lens to focus on distant images. The researchers concluded that ingestion of 50mg of black currant anthocyanins caused improvement in VDT-induced visual fatigue as well as dark adaptation. In another study the specific delphinidin anthocyanins in black currant were shown to relax bovine ciliary smooth muscle by inducing nitric oxide (NO) production (Matsumoto et al., 2005). Another mechanism of action that was explored by Matsumoto et al. (2003) involves rhodopsin. Rhodopsin is a key element of healthy vision, and the cyanidin anthocyanins in black currant, cyanidin-3-glucoside and cyanidin-3-rutinoside, stimulated the regeneration of rhodopsin in rod photoreceptors. An additional study by Matsumoto and his team of researchers (2006) demonstrated that black currant anthocyanins were absorbed, passed through the blood aqueous barrier and the blood-retinal barrier, and were distributed in ocular tissues as intact forms. The antioxidant properties of black currant anthocyanins can also help to curb free radical-induced vision deterioration.
Inflammation responses are tied to numerous other aspects of the body like the immune system and the balance between free radicals and antioxidants. A study by Lyall et al. (2009) used human exercise and cellular models to determine that the consumption of Artemis’ New Zealand black currant anthocyanins alleviates exercise-induced oxidative stress and inflammation, and may complement the ability of exercise to enhance immune responsiveness to potential pathogens. Other research groups have begun using New Zealand black currants in in vitro models of asthma. The encouraging preliminary studies show that the black currant attenuates eosinophilic inflammation in lung epithelium by modulating Th2 cytokines, which can have implications for alleviating airway inflammation.
Several preliminary studies have identified antiviral and immune-stimulating properties of black currants. After previously determining that black currants exhibited antiviral activity against influenza A and B viruses, Knox et al. (2001) took their research a step further by examining the antiviral activity of specific anthocyanin fractions from black currants and studied the mechanism of action. Specific anthocyanin fractions showed potent antiviral activity against influenza A and B viruses and likely, by means of inhibiting virus adsorption to cells and inhibiting viral release from infected cells. Similar results were reported by this same team of researchers in 2003. The growth of influenza in cells treated with black currant extract was completely suppressed and an inhibition of viral release from the infected cells was observed. Black currant also exhibited antiherpes virus activity in a 2003 study by Suzutani et al. by inhibiting herpes simplex virus type 1 attachment on cell membranes and by inhibiting protein synthesis in infected cells from the early stage of infection. In an animal study (Takata et al., 2005) black currant juice had a stimulatory effect on macrophages as well as several immune-modulating cytokines.
Black currant, in addition to possessing potent antioxidant benefits (Ghosh et al., 2006; Matsumoto et al., 2002), also appears to play a role in improving circulation and vasorelaxation. A 2002 study by Nakamura et al. reported that black currant enhanced synthesis of NO, which subsequently induced the endothelium-dependent vasorelaxation via the H1-receptors on smooth muscle endothelium. A double-blind, placebo-controlled, crossover, human pilot study suggested that black currant anthocyanins may improve shoulder stiffness caused by typing work by increasing peripheral blood flow and reducing muscle fatigue (Matsumoto et al., 2005). Preliminary human data also suggests that black currant juice could support the treatment and metaphylaxis of uric acid stone disease because of its alkalizing effect (Kessler et al., 2002).