Currant

Currant (Ribes nigrum L.) — Black Currant

1. Identity: Botanical Classification, Nomenclature, and Common Forms

1.1 Botanical and Chemical Identity

Ribes nigrum L., generally called blackcurrant, is a flowering plant that contains deep purple, bittersweet, and seed-bearing berries that can attain a diameter of about 1 cm. Blackcurrant (Ribes nigrum) is a member of the Grossulariaceae family, native to Europe, Asia, and North America. In 1700, French botanist Joseph Pitton de Tournefort (1656–1708) named the genus Ribes and several Ribes species in his publication Institutiones Rei Herbariae. Swedish botanist Carl Linnaeus (1707–1778) assigned the Latin name Ribes nigrum in his 1753 work Species Plantarum. Ribes means "currant," and nigrum means "black." The common name "currant" stems from raisins of Corinth (Greece) but was later applied also to berries of the Ribes genus.

The plant is known by several common names, including Black currant, Blackcurrant, European black currant, Gichtbeerblaetter, Johannisbeere (German), Kurokarin, Quincy berries, and Schwarze (German). Because of its enhanced antioxidant capacity and significant anthocyanin properties relative to a variety of fruits, blackcurrant, a deep-pigmented berry native to northern and central Europe and northern Asia, has become planted in many US regions.

1.2 Plant Description

The Ribes nigrum shrub is 1–2 m in height, and can grow wide or compact. The stem is erect and glandular and does not have spines. Buds are scented and yellowish-reddish in color. Leaves are alternate and simple, 5–10 cm long and 3–5 cm broad, having one node; leaf edges have 3–5 lobes and are pale-green in color. It has racemose inflorescence, bearing about 10–12 flowers. It bears purplish, aromatic, and sweet edible berries having seeds. Berries are 12 mm in diameter and have a shiny appearance.

1.3 Common Forms and Preparations

The berries (skin, flesh, and seeds), leaves as well as other plant parts can all be useful. The fruits can sometimes be eaten directly or produced in the form of jams, juices, and jellies. They are commonly used to synthesize dark violet pigments. These tiny round berries with incredibly flavorful seeds are generally used in processed items such as juice, jams and preserves, pie fillings, dessert toppings, yogurt, ice cream, mineral waters, teas, confectionery, and perfumes.

The fruits and leaves of the blackcurrant have a long history as a traditional medicine in both Asia and Europe. Nowadays, blackcurrant extract capsules have been commercialized as a dietary supplement and marketed as an immunity booster. Blackcurrant leaf is the common name for the leaf of the plant Ribes nigrum L. Preparations are obtained by drying and either comminuting or powdering the leaves, or by putting the plant material in water to dissolve compounds and form a liquid extract; the water is then evaporated to obtain a dry extract. Herbal medicines containing these blackcurrant leaf preparations are usually available as herbal tea to be drunk and in solid forms to be taken by mouth.

Black currant seed oil (BCSO) is an additional commercially important form. Black currant seed oil (BCSO), rich in both γ-linolenic (18:3n-6) and α-linolenic (18:3n-3) acids, has been shown to modulate membrane lipid composition and eicosanoid production.

2. Traditional and Historical Use

2.1 European Traditions

Archaeobotanical evidence of black currant cultivation dating back to the 15th century or earlier has been uncovered at medieval West Slavic settlements and castles in present-day Poland. An ethnobotanical review of wild plants of Estonia from the 1770s until the mid-20th century found that black currant fruits, leaves, and twigs were used as spices in the making of beer-like beverages, birch sap preparations, breads, pickles, and tea infusions.

It is native to the temperate regions of Eurasia and northern Asia and was cultivated for more than 400 years, but was described by herbalists only in the 17th century. In the 17th century, a herbalist and trained English surgeon John Gerard referred to the use of black currant for making tea and medical potions. Due to its anti-inflammatory qualities, black currant leaves have been used in European traditional medicine to treat a variety of diseases, including rheumatism, arthritis, and respiratory issues.

2.2 Asian and Other Traditional Systems

Blackcurrant is particularly valued for its anti-inflammatory, astringent, and bitter actions, and has a long history of use in European herbal medicine, Native American herbal medicine, and Japanese Kampo medicine. It was widely used in Chinese folk medicine. Black currants and the leaves from the shrub have been used in traditional medicine in Asia and Europe to treat a variety of ailments.

2.3 European Medicines Agency Recognition of Traditional Use

The European Medicines Agency (EMA) Committee on Herbal Medicinal Products (HMPC) concluded that, on the basis of its long-standing use, blackcurrant leaf preparations can be used for minor joint pain and for minor complaints affecting the urinary tract. This assessment represents a formal regulatory acknowledgment of traditional-use evidence, rather than a finding of clinical efficacy established by controlled trials.

3. Key Constituents and Active Compounds

3.1 Overview of Phytochemical Composition

Various bioactives present in blackcurrants have different functional and pharmacological aspects including anti-inflammatory, antioxidant, and antimicrobial properties. The most dominant and important bioactives include anthocyanins, flavonols, phenolic acids, and polyunsaturated fatty acids. The blackcurrant berries are an excellent source of various phytochemical and aromatic constituents, such as minerals, polyphenols, vitamins, polyunsaturated fatty acids (PUFA), soluble and insoluble dietary fiber, tannins, soluble sugars, organic acids and vitamins C and E.

Earlier findings have demonstrated that blackcurrants are a rich source of bioactive compounds (500–1342 mg/100 g of total polyphenols), predominately anthocyanins (160–411 mg/100 g). The fruits are a rich source of vitamin C and other health-beneficial substances such as rutin, organic acids, pectins, micro- and macronutrients, and essential oils.

3.2 Anthocyanins

Anthocyanins are the most studied and most abundant class of bioactive in blackcurrant berries. Blackcurrants (Ribes nigrum) contain four major anthocyanins: cyanidin-3-glucoside, cyanidin-3-rutinoside, delphinidin-3-glucoside, and delphinidin-3-rutinoside. The typical profile of blackcurrant anthocyanin (BCA) is 47% delphinidin-3-rutinoside (D3R), 13% delphinidin-3-glucoside (D3G), 35% cyanidin-3-rutinoside (C3R), and 5% cyanidin-3-glucoside (C3G). Cyanidin-3-rutinoside and delphinidin-3-rutinoside are the major components in blackcurrants.

The anthocyanin composition of the berries gives blackcurrant its rich purplish color. Anthocyanins belong to the flavonoid class of polyphenols. A standardized BC gemmotherapy extract (BC-GTE) prepared from fresh buds was found to contain approximately 133 phytonutrients. Furthermore, the first report to quantify the presence of significant flavonoids such as luteolin, quercetin, apigenin, and kaempferol was made in this extract.

3.3 Seed Oil Fatty Acid Composition

Supplemental oil sources of gamma-linolenic acid (GLA) include borage oil (Borago officinalis), 20–26% GLA; black currant (Ribes nigrum), 15–18%; and evening primrose (Oenothera biennis), 8–12%. According to Tufts researchers, black currant seed oil is a preferred source because it also contains 13–16% of the omega-3 fatty acid alpha-linolenic acid (ALA) as well as GLA. Black currant seed oil has one of the highest concentrations of the omega-6 fatty acid gamma-linolenic acid (GLA) found in any plant source. It is also a rich source of alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid precursor, and stearidonic acid (SDA), which the body converts into EPA more efficiently than ALA alone.

3.4 Other Notable Phenolics

The plant contains phenolic compounds such as anthocyanins, flavonoids, polyunsaturated fatty acids (PUFA), tannins, carbohydrates, and organic acids. Blackcurrant fruits contain polyphenolic substances with antioxidant, antimicrobial, antiviral, and antibacterial properties. Owing to these properties, polyphenols protect and support many functions of organs and systems, and in particular the digestive, nervous, and circulatory systems.

4. Established and Proposed Mechanisms of Action

4.1 Antioxidant Activity

The blackcurrant has been used as a traditional medicine in both Asia and European countries. It is known as a rich source of antioxidants, largely due to its high content of phenolic compounds, especially anthocyanins. The anthocyanins and other polyphenols in blackcurrant are well-characterized free-radical scavengers. Blackcurrants are now considered "super fruits" since they are supposed to have numerous therapeutic benefits, such as the capacity to treat chronic illnesses associated with oxidative stress.

4.2 Vascular and Endothelial Mechanisms

Ribes nigrum L. is a potent stimulator of the endothelial formation of nitric oxide (NO) in cultured endothelial cells and porcine coronary arteries. Immunohistochemical staining indicated that the score of endothelial nitric oxide synthase (eNOS) staining intensity was significantly higher in blackcurrant extract-treated groups compared to controls. Peripheral blood flow is improved following blackcurrant intake, which is attributed to anthocyanins increasing vasodilation.

4.3 Anti-inflammatory Mechanisms

Several health-promoting characteristics of blackcurrant compounds have been recognized, comprising immunomodulatory, antimicrobial, and anti-inflammatory properties, reduction of low-density lipoprotein, and a decline in cardiovascular disorders. The cytokine TNF-α (tumor necrosis factor alpha) is a pro-inflammatory molecule of the Th1-class and is known to play a crucial role in brain development by affecting the development and function of the hippocampus. However, elevated levels of TNF-α can indicate the presence of inflammation.

4.4 GLA and Prostaglandin Pathways

GLA is converted in the body to dihomo-gamma-linolenic acid (DGLA), which then produces series-1 prostaglandins, particularly prostaglandin E1 (PGE1). The body converts GLA to substances that have anti-inflammatory and anticancer effects. The mechanism of action of PUFA probably involves the metabolism of linoleic acid (LA) to arachidonic acid (AA) and thence to the myocardial eicosanoids; an age effect on the conversion of LA to gamma-linolenic acid (GLA) by Δ6-desaturase may be involved.

4.5 Ocular Microvascular Mechanisms

Vasorelaxant properties of anthocyanin-rich extracts derived from blackcurrant (Ribes nigrum L.) have been shown to improve retinal microcirculation in normal tension glaucoma. Anthocyanins have been widely used in traditional medicine specifically for improving scotopic vision and alleviating eye fatigue in older adults. These phytochemicals demonstrate remarkable anti-oxidative, anti-inflammatory, and immunomodulating properties.

5. Scientific Evidence by Area of Use

5.1 Cardiovascular Health and Vascular Function

Recent cell and animal studies suggest the potential of blackcurrants (Ribes nigrum) as a dietary agent that may reduce the risk of cardiovascular disease (CVD) by improving dyslipidemia, oxidative stress, and inflammation.

Flow-mediated dilation (FMD) and platelet aggregation (human RCT): A randomized, double-blind, placebo-controlled crossover trial investigated the acute effects of an anthocyanin-rich blackcurrant beverage, compared with a matched placebo, on selected markers of CVD risk in healthy middle-aged subjects in response to a high-fat meal. Twenty-three volunteers aged 39.9 ± 8.1 years completed the trial. Volunteers consumed either a 200 mL blackcurrant beverage (744 mg polyphenols comprising 711 mg anthocyanins and 32 mg procyanidins) or a placebo, together with a high-fat breakfast followed by a lunch. There was a significant cumulative improvement in FMD following consumption of the anthocyanin-rich blackcurrant beverage compared with the matched placebo over a 6-hour postprandial period. There was a trend for an inhibitory effect of the blackcurrant beverage on agonist-induced platelet aggregation, and significant effects were observed on systolic blood pressure and the inflammatory marker IL-8, although these were exploratory and not adjusted for multiple testing.

Blood lipids and inflammation in peri/postmenopausal women (pilot RCT): The effects of BC anthocyanin (ACN) supplementation on body composition, fasting blood lipids, and biomarkers of inflammation and oxidative stress were evaluated in a pilot randomized controlled clinical trial in peri- and early postmenopausal women. Thirty-eight eligible women aged 45–60 completed the trial, in which they were randomly assigned to one of three treatment groups: placebo (control group), 392 mg/day (low BC group), or 784 mg/day (high BC group) for six months. This trial is notable as one of the first clinical trials of its duration in this population; the pilot scale limits broad generalization.

Forearm blood flow and sedentary sitting (human crossover): A study examined the acute effects of anthocyanin-rich New Zealand blackcurrant extract and a placebo on hemodynamics during 120 minutes of sedentary sitting in healthy males. Additionally, researchers investigated whether changes in resting hemodynamics altered repeated isometric hand-grip exercise performance and post-exercise forearm blood flow. Ten healthy males completed two trials during which they ingested either blackcurrant extract (1.87 mg total anthocyanins/kg bodyweight) or placebo powder. Heart rate, blood pressure, and forearm blood flow were measured prior to and at 30, 60, 90, and 120 min post-ingestion. Heart rate, blood pressure, and mean arterial pressure changed over time but did not differ between treatments. This negative finding for these specific endpoints highlights the variability in outcomes across different study designs.

Diabetic vascular protection (animal model): Results from a diabetic mouse model suggest that the intake of anthocyanin-rich blackcurrant extract could have beneficial effects on the blood vessels of diabetic patients. This remains preclinical evidence only.

5.2 Eye Health and Glaucoma

Open-angle glaucoma — visual field and ocular blood flow (2-year RCT): To examine the influence of black currant anthocyanins (BCACs) on the disease progression of open-angle glaucoma (OAG), a randomized, placebo-controlled, double-masked trial was conducted in 38 patients with OAG treated with antiglaucoma drops. BCACs (50 mg/day, n = 19) or placebos (n = 19) were orally administered once daily for a 24-month period. Systemic blood pressure, pulse rates, intraocular pressure (IOP), ocular blood circulation by laser-speckle flowgraphy, and Humphrey visual field mean deviation (MD) were measured during the 24-month period. The trial results showed that the BCAC-treated group exhibited a significant improvement in ocular blood flow and in the visual field, whereas no significant changes were observed in systemic and ocular conditions, including IOP. The authors suggest that oral administration of BCACs may be a safe and promising supplement for patients with OAG in addition to antiglaucoma medication. The very small sample size (n = 19 per arm) is a significant limitation, and these results require replication in larger trials.

Retinal microcirculation and digital eye strain: Vasorelaxant properties of anthocyanin-rich extracts derived from blackcurrant have been shown to improve retinal microcirculation in normal tension glaucoma. Prospective interventional studies containing anthocyanin extracts in formulation seem to demonstrate therapeutic protection against several asthenopic symptoms in patients with heavy screen time behaviors. Overall, the ophthalmological evidence base for blackcurrant anthocyanins is promising but limited to small trials from a narrow group of Japanese investigators, and independent replication is needed.

5.3 Exercise Performance and Recovery

Systematic review and meta-analysis: One systematic review and meta-analysis found an improvement in sport performance when supplementing with blackcurrant (standardized mean difference 0.45, 95% CI 0.09–0.81, p = 0.01). The effective dose appears to be between 105 and 210 mg of total blackcurrant anthocyanins prior to exercise. There were insufficient studies reporting oxidative markers, cognitive effects, or biomarkers to comment on the mechanism of action. The review concluded that blackcurrant has a small, but significant, effect on sport performance, with no known detrimental side effects.

Narrative review (2024): A 2024 narrative review focused on observations with intake of anthocyanin-rich blackcurrant supplements on whole-body exercise performance and exercise recovery. This review included 17 studies with a randomized placebo-controlled crossover design (10 studies on performance and 8 on recovery effects) and 1 with a randomized placebo-controlled parallel group design.

Null findings in cycling: Investigations examining the effects of acute blackcurrant extract supplementation on exercise performance are limited. No performance benefits were found after an acute dose of blackcurrant extract on 16.1 km cycling time trial performance. Previous research examining the ergogenic benefits of blackcurrant supplementation on exercise performance is contradictory. However, 5-km running performance was improved following acute supplementation of 900 mg blackcurrant extract in a study by Moss et al. (2023). In summary, the evidence on exercise performance is mixed; effects may depend on exercise modality, dose, and timing of supplementation.

5.4 Bone Health

Postmenopausal bone mineral density (pilot double-blind RCT): Blackcurrant supplementation decreased the loss of whole-body bone mineral density (BMD) compared to the control group (p < 0.05), though the improvement of whole-body BMD remained significant only in the high BC group (p < 0.05). Blackcurrant supplementation also led to a significant increase in serum amino-terminal propeptide of type 1 procollagen (P1NP), a marker of bone formation (p < 0.05). These findings suggest that daily consumption of 784 mg of blackcurrant powder for six months mitigates the risk of postmenopausal bone loss, potentially through enhancing bone formation. Further studies of larger samples with various skeletal conditions are warranted to confirm these findings. This is a pilot study and the evidence should be considered preliminary.

5.5 Rheumatoid Arthritis and Joint Conditions

Evidence is conflicting regarding the benefits of black currant as an antioxidant source. Two small published trials showed some benefit in rheumatoid arthritis, but black currant was not compared to a gold standard. Long-term safety and efficacy have not been studied for any of the above potential uses. The EMA's HMPC recognition of blackcurrant leaf for minor joint pain is based on traditional use rather than controlled clinical evidence.

With respect to black currant seed oil specifically, NCCIH says oils containing GLA may have some benefit for relieving RA symptoms, but only a few studies have been done on each oil. Another NCCIH review says the evidence is preliminary, while omega-3s remain the only nutritional approach with clear benefit signals for RA.

5.6 Immune Function

Examining the effects of black currant seed oil (vs. placebo) in healthy elderly subjects, researchers from Tufts found that GLA reduced levels of PGE2 and improved immune function. Anthocyanin-rich blackcurrant extract was discovered to possess antioxidant, anti-inflammatory, and immunostimulatory impacts in clinical research. The immune data remain preliminary, with most human evidence based on surrogate biomarkers rather than clinical disease endpoints.

5.7 Blood Glucose and Postprandial Glycemia

A randomized crossover trial (Lappi et al., Br J Nutr 2020) investigated whether blackcurrant (Ribes nigrum) lowers sugar-induced postprandial glycaemia independently and in a product with fermented quinoa. An animal study (Kim et al.) evaluated the effect of a treatment (10 weeks) with blackcurrant in mice with type 2 diabetes (T2DM). The authors found that the intervention significantly improved the homeostatic model evaluation of glucose, insulin, and insulin resistance (HOMA-IR) indices, diabetic blood markers, cardiac function markers and cardiac thickening, and elevated levels of inflammatory cytokines in cardiac tissue of T2DM mice. Animal findings do not automatically translate to clinical benefit in humans.

5.8 Neuroprotection

Flavonoids are an important class of natural phytonutrients and are well known for their protective effects against neurodegeneration and neuroinflammation. The neuroprotective effect of flavonoid-rich foods or drinks has been linked to enhanced neuronal connection and communication, including an ability to suppress neuroinflammation. These effects have the potential to promote memory, learning, and cognitive function in the hippocampus. Data in this area derive primarily from animal/cell models and a small pilot study; no substantial human clinical trials of blackcurrant anthocyanins for cognitive outcomes have been completed as of current literature.

5.9 Chemoprevention (Preclinical Only)

Anthocyanins are known to possess potent anticarcinogenic properties against several cancers, demonstrating potential for cancer prevention. Black currant (Ribes nigrum L., Grossulariaceae) fruits have a high anthocyanin content. This "superfruit" is known to possess various pharmacological effects including alleviation of chronic oxidative stress and inflammation. In contrast to a large volume of literature on the health benefits of black currant, limited evidence on antitumor effects of black currant exists with virtually no data on the prevention of experimental carcinogenesis. Blackcurrant juice and extract have been demonstrated to significantly slow the growth of Ehrlich carcinoma in vivo and also to dramatically reduce the proliferation of prostate, stomach, intestine, colon, and breast cancer cells in vitro. All chemoprevention data are from animal and cell-based experiments. No human clinical trials for cancer prevention have been reported to date.

6. Body Systems and Health Areas of Association

• Cardiovascular system: Vascular function (FMD), platelet aggregation, blood lipid profiles, blood pressure modulation, endothelial nitric oxide production.
• Visual/ophthalmological system: Retinal microcirculation, ocular blood flow in glaucoma, visual field, dark adaptation, digital eye strain.
• Musculoskeletal system: Bone mineral density (postmenopausal), joint pain and rheumatoid arthritis (leaf preparations, seed oil GLA).
• Immune system: Modulation of eicosanoids, cytokines, and inflammatory biomarkers; immune function in elderly subjects (seed oil).
• Metabolic/endocrine system: Postprandial glycemia, insulin sensitivity, lipid metabolism.
• Neurological system: Anti-neuroinflammatory activity, TNF-α suppression (preclinical and pilot).
• Urinary tract: Traditional use for minor urinary complaints (EMA leaf assessment).
• Sport/exercise physiology: Exercise performance, oxidative stress during exercise, exercise recovery.

Owing to these properties, polyphenols in blackcurrant protect and support many functions of organs and systems, in particular the digestive, nervous, and circulatory systems.

7. Dosage Forms and Dosages Reported in Studies

Dosages vary considerably by application and preparation type. The following represent only doses reported in primary studies or authoritative databases:

• Glaucoma/visual field (oral anthocyanins): 50 mg/day of black currant anthocyanin concentrate (BCACs), orally administered once daily for a 24-month period (n = 19).
• Cardiovascular/FMD (single acute dose): 200 mL blackcurrant beverage containing 711 mg anthocyanins (and 32 mg procyanidins), consumed with a high-fat meal in a postprandial crossover design.
• Bone health / blood lipids in postmenopausal women: 784 mg of blackcurrant powder per day for six months. The same study also used a low-dose arm of 392 mg/day (low BC group) for six months.
• Exercise performance: The effective dose appears to be between 105 and 210 mg of total blackcurrant anthocyanins, administered prior to exercise. A dose of 900 mg blackcurrant extract (acute) improved 5-km running performance in one study.
• Sedentary vascular study (forearm blood flow): 1.87 mg total anthocyanins per kg body weight (acute dose) in healthy males.
• Black currant seed oil (BCSO) — general GLA dosing range: Variable depending on the type of oil being used: black currant seed oil, 2 to 10 grams/day.

It should be noted that dosage standardization across studies is inconsistent. Some studies dose by total anthocyanin content, others by total extract weight, and others by body weight. This variability hampers cross-study comparison.

8. Safety, Tolerability, and Drug Interactions

8.1 General Safety Profile

Blackcurrant has a small, but significant, effect on sport performance, with no known detrimental side effects. Long-term safety and efficacy have not been studied for any of the major potential uses of black currant. The short-duration studies that exist have not reported significant adverse events, but systematic safety surveillance data are lacking.

8.2 Platelet Aggregation and Anticoagulant Interactions

The cardiovascular case for black currant seed oil rests primarily on GLA's prostaglandin-related mechanisms rather than direct endpoint studies. Black currant seed oil may theoretically affect platelet aggregation based on its fatty acid activity. This is a precautionary consideration rather than a firmly established clinical interaction. The anthocyanin fraction of blackcurrant berry preparations has also been shown to trend toward inhibition of platelet aggregation in acute postprandial studies, as noted above, which is relevant for individuals taking anticoagulant or antiplatelet medications.

8.3 Blood Pressure Effects

No effects on blood pressure and pulse were noted in one clinical glaucoma study involving oral BCAC administration. However, the short-duration vascular study demonstrated that heart rate, blood pressure, and mean arterial pressure changed over time but did not differ between treatments with blackcurrant extract vs. placebo in an acute sitting paradigm, suggesting that hemodynamic effects at tested doses are limited in healthy males.

8.4 Interactions with Antiglaucoma Medications

A randomized, placebo-controlled, double-masked 24-month trial revealed that oral administration of black currant anthocyanins (BCACs) slowed down the visual field deterioration and elevation of ocular blood flow of open-angle glaucoma (OAG) in patients already using antiglaucoma drops, suggesting no apparent antagonism with standard topical therapy, although this was not formally assessed as an interaction study.

8.5 US Regulatory Status

Black currants (Ribes nigrum) have been called "the forbidden fruit" in the United States. They help spread a fungus that infects white pine trees. For this reason, black currants were once removed from many areas, leaving many Americans to miss out on these nutritious berries. Federal restrictions were largely lifted by the early 21st century, and blackcurrant supplements are now commercially available in the US, though cultivation restrictions remain in some states.

8.6 Herb–Drug Interaction Considerations

The possibility of drug interactions, direct toxicities, and contamination with active pharmaceutical agents are among the safety concerns about dietary and herbal supplements. Although there is a widespread public perception that herbs and botanical products in dietary supplements are safe, research has demonstrated that these products carry the same dangers as other pharmacologically active compounds. Interactions may occur between prescription drugs, over-the-counter drugs, dietary supplements, and even small molecules in food — making it a daunting challenge to identify all interactions that are of clinical concern.

Specific documented interactions for blackcurrant fruit or seed oil are not well characterized in the published clinical literature. The theoretical concern most relevant to this ingredient is the combination of GLA-derived antiplatelet effects with anticoagulant drugs (e.g., warfarin) or antiplatelet agents (e.g., aspirin, clopidogrel), but this has not been formally studied in humans for blackcurrant specifically.

9. Summary of Evidence Strength

• Eye health/glaucoma: Preliminary positive signal from two small RCTs (Ohguro group, Japan; total n ≈ 38–40 per trial); requires independent replication in larger populations before conclusions can be drawn.
• Cardiovascular markers (FMD, blood lipids): Moderate preliminary evidence from small RCTs; epidemiological associations exist but causal inference limited.
• Exercise performance: Small, statistically significant positive effect in meta-analysis (small effect size); contradicted by several null individual cycling trials. Evidence is mixed and dose/modality-dependent.
• Bone mineral density: Single pilot RCT (peri/postmenopausal women, n = 38); promising but insufficient to support clinical recommendations.
• Rheumatoid arthritis (seed oil/leaf): Weak — two small trials, no comparison to standard of care; EMA recognition based only on traditional use.
• Immune modulation: Biomarker-level human evidence; clinical meaningfulness not established.
• Neuroprotection, cancer chemoprevention: Preclinical (animal/cell) only; no human clinical data.

References

• Biological activities, therapeutic potential, and pharmacological aspects of blackcurrants (Ribes nigrum L): A comprehensive review — PMC / Food Science & Nutrition (2023)
• Acute Effects of an Anthocyanin-Rich Blackcurrant Beverage on Markers of Cardiovascular Disease Risk in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial — PMC (2025)
• Blackcurrant Anthocyanins Improve Blood Lipids and Biomarkers of Inflammation and Oxidative Stress in Healthy Women in Menopause Transition — PMC (2023)
• Blackcurrants Reduce the Risk of Postmenopausal Osteoporosis: A Pilot Double-Blind, Randomized, Placebo-Controlled Clinical Trial — PMC (2022)
• Anthocyanin-Rich New Zealand Blackcurrant Extract Supports the Maintenance of Forearm Blood-Flow During Prolonged Sedentary Sitting — PMC (2020)
• Potential Vasculoprotective Effects of Blackcurrant (Ribes nigrum) Extract in Diabetic KK-Ay Mice — PMC (2021)
• The Flavonoid Rich Black Currant (Ribes nigrum) Ethanolic Gemmotherapy Extract Elicits Neuroprotective Effect — PMC (2023)
• Two-year randomized, placebo-controlled study of black currant anthocyanins on visual field in glaucoma — Ophthalmologica (2012), Ohguro et al., PubMed
• Black Currant Anthocyanins Normalized Abnormal Levels of Serum Concentrations of Endothelin-1 in Patients with Glaucoma — PMC (2013)
• Therapeutic Effects of Anthocyanins for Vision and Eye Health — PMC (2019)
• Can Nutrition Play a Role in Ameliorating Digital Eye Strain? — PMC (2022)
• The effect of New Zealand blackcurrant on sport performance and related biomarkers: a systematic review and meta-analysis — PMC (2020)
• Anthocyanin-Rich Blackcurrant Supplementation as a Nutraceutical Ergogenic Aid for Exercise Performance and Recovery: A Narrative Review — PMC (2025)
• No Effect of Acute or Chronic New Zealand Blackcurrant Extract on Cycling Performance or Physiological Responses in Trained Cyclists — PMC (2025)
• Biological Activity of Blackcurrant Extracts (Ribes nigrum L.) in Relation to Erythrocyte Membranes — PMC (2014)
• Anthocyanin-rich black currant (Ribes nigrum L.) extract affords chemoprevention against diethylnitrosamine-induced hepatocellular carcinogenesis in rats — PubMed (2011)
• Berries and Human Health: Mechanisms and Evidence — PMC (2023)
• Extraction, Identification, and Health Benefits of Anthocyanins in Blackcurrants (Ribes nigrum L.) — Applied Sciences, MDPI (2021)
• Ribis nigri folium — European Medicines Agency (EMA) Herbal Medicinal Product Page
• Black Currant Uses, Benefits & Dosage — Drugs.com Natural Products (reviewed Nov 2025)
• Effect of dietary supplementation with black currant seed oil on the immune response of healthy elderly subjects — American Journal of Clinical Nutrition (1999), ScienceDirect
• Black currant herb profile — HerbalGram / American Botanical Council
• Herb-Drug Interactions — NCCIH / NIH