Contents
What is black currant
Black currant (Ribes nigrum L.) is a small, perennial shrub native to central Europe and northern Asia, is cultivated throughout the world, including the United States where it prefers damp fertile soils 1). Black currant is winter hardy, but cold weather at flowering time during the spring reduces the size of the crop. Bunches of small, glossy black fruit develop along the stems in the summer and can be harvested by hand or by machine. The raw fruit is particularly rich in vitamin C and polyphenol phytochemicals. Blackcurrants can be eaten raw but are usually cooked in a variety of sweet or savory dishes. They are used to make jams, jellies and syrups and are grown commercially for the juice market. The fruit is also used in the preparation of alcoholic beverages and both fruit and foliage have uses in traditional medicine and the preparation of dyes.
The fruit of black currants can be eaten raw, but it has a strong, tart flavor. It can be made into jams and jellies which set readily because of the fruit’s high content of pectin and acid. For culinary use, black currant is usually cooked with sugar to produce a purée, which can then be passed through muslin to separate the juice. The purée can be used to make black currant preserves and be included in cheesecakes, yogurt, ice cream, desserts, sorbets and many other sweet dishes. The exceptionally strong flavor can be moderated by combining it with other fruits, such as raspberries and strawberries in summer pudding or apples in crumbles and pies. Black currant juice can be used in syrups and cordials. Black currants are a common ingredient of Rødgrød, a popular kissel-like dessert in North German and Danish cuisines.
Black currants are also used in savory cooking because their astringency creates added flavor in many sauces, meat and other dishes and they are included in some unusual combinations of foods. They can be added to tomato and mint to make a salad, used to accompany roast or grilled lamb, used to accompany seafood and shellfish, used as a dipping sauce at barbecues, blended with mayonnaise, used to invigorate bananas and other tropical fruits, combined with dark chocolate or added to mincemeat in traditional mince pies at Christmas.
Black currant juice
Black currant juice forms the basis for various popular cordials, juice drinks, juices and smoothies. Typically blended with apple or other red fruits, it is also mixed with pomegranate and grape juice. Macerated blackcurrants are also the primary ingredient in the apéritif liqueur crème de cassis, which in turn is added to white wine to produce a Kir or to champagne to make a Kir Royale.
In the United Kingdom, blackcurrant cordial is often mixed with cider (hard cider) to make a drink called “cider and black”. If made with any common British lager beer, it is known as a “lager and black”. The addition of blackcurrant to a mix of cider and lager results in “diesel” or “snakebite and black” available at pubs. A “black ‘n’ black” can be made by adding a small amount of blackcurrant juice to a pint of stout. The head is purple if the shot of juice is placed in the glass first. Blackcurrant juice is sometimes combined with whey in an endurance/energy-type drink.
In Russia, blackcurrant leaves may be used for flavouring tea or preserves, such as salted cucumbers, and berries for home winemaking. Sweetened vodka may also be infused with blackcurrant leaves making a deep greenish-yellow beverage with a tart flavour and astringent taste. The berries may be infused in a similar manner. In Britain, 95% of the blackcurrants grown end up in Ribena (a brand of fruit juice whose name is derived from Ribes nigrum) and similar fruit syrups and juices.
Figure 1. Black currant
Black currant nutrition facts
Raw black currants are 82% water, 15% carbohydrates, 1% protein and 0.4% fat (see Table 1). Per 100 g serving providing 63 calories, the raw fruit has high vitamin C content (218% of the Daily Value, DV) and moderate levels of iron and manganese (12% DV each). Other nutrients are present in negligible amounts (less than 10% DV).
Major anthocyanins in blackcurrant pomace are delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-rutinoside, which are retained in the juice concentrate among other yet unidentified polyphenols.
Black currant seed oil is rich in vitamin E and unsaturated fatty acids, including alpha-linolenic acid and gamma-linolenic acid.
Table 1. Black currant (raw) nutrition facts
| Nutrient | Unit | Value per 100 g | |||||||||
| Approximates | |||||||||||
| Water | g | 81.96 | |||||||||
| Energy | kcal | 63 | |||||||||
| Energy | kJ | 264 | |||||||||
| Protein | g | 1.4 | |||||||||
| Total lipid (fat) | g | 0.41 | |||||||||
| Ash | g | 0.86 | |||||||||
| Carbohydrate, by difference | g | 15.38 | |||||||||
| Minerals | |||||||||||
| Calcium, Ca | mg | 55 | |||||||||
| Iron, Fe | mg | 1.54 | |||||||||
| Magnesium, Mg | mg | 24 | |||||||||
| Phosphorus, P | mg | 59 | |||||||||
| Potassium, K | mg | 322 | |||||||||
| Sodium, Na | mg | 2 | |||||||||
| Zinc, Zn | mg | 0.27 | |||||||||
| Copper, Cu | mg | 0.086 | |||||||||
| Manganese, Mn | mg | 0.256 | |||||||||
| Vitamins | |||||||||||
| Vitamin C, total ascorbic acid | mg | 181 | |||||||||
| Thiamin | mg | 0.05 | |||||||||
| Riboflavin | mg | 0.05 | |||||||||
| Niacin | mg | 0.3 | |||||||||
| Pantothenic acid | mg | 0.398 | |||||||||
| Vitamin B-6 | mg | 0.066 | |||||||||
| Vitamin B-12 | µg | 0 | |||||||||
| Vitamin A, RAE | µg | 12 | |||||||||
| Retinol | µg | 0 | |||||||||
| Vitamin A, IU | IU | 230 | |||||||||
| Vitamin E (alpha-tocopherol) | mg | 1 | |||||||||
| Lipids | |||||||||||
| Fatty acids, total saturated | g | 0.034 | |||||||||
| 16:00:00 | g | 0.02 | |||||||||
| 18:00:00 | g | 0.007 | |||||||||
| Fatty acids, total monounsaturated | g | 0.058 | |||||||||
| 16:1 undifferentiated | g | 0.001 | |||||||||
| 18:1 undifferentiated | g | 0.056 | |||||||||
| Fatty acids, total polyunsaturated | g | 0.179 | |||||||||
| 18:2 undifferentiated | g | 0.107 | |||||||||
| 18:3 undifferentiated | g | 0.072 | |||||||||
| Fatty acids, total trans | g | 0 | |||||||||
| Cholesterol | mg | 0 | |||||||||
| Anthocyanidins | |||||||||||
| Cyanidin | mg | 62.46 | |||||||||
| Petunidin | mg | 3.9 | |||||||||
| Delphinidin | mg | 89.6 | |||||||||
| Pelargonidin | mg | 1.2 | |||||||||
| Peonidin | mg | 0.7 | |||||||||
| Flavan-3-ols | |||||||||||
| (+)-Catechin | mg | 0.7 | |||||||||
| (-)-Epigallocatechin | mg | 0 | |||||||||
| (-)-Epicatechin | mg | 0.5 | |||||||||
| (-)-Epicatechin 3-gallate | mg | 0 | |||||||||
| (-)-Epigallocatechin 3-gallate | mg | 0 | |||||||||
| (+)-Gallocatechin | mg | 0 | |||||||||
| Flavones | |||||||||||
| Apigenin | mg | 0 | |||||||||
| Luteolin | mg | 0 | |||||||||
| Flavonols | |||||||||||
| Isorhamnetin | mg | 0.1 | |||||||||
| Kaempferol | mg | 0.7 | |||||||||
| Myricetin | mg | 6.2 | |||||||||
| Quercetin | mg | 4.5 | |||||||||
| Isoflavones | |||||||||||
| Daidzein | mg | 0.02 | |||||||||
| Genistein | mg | 0.06 | |||||||||
| Glycitein | mg | 0 | |||||||||
| Total isoflavones | mg | 0.07 | |||||||||
| Formononetin | mg | 0 | |||||||||
| Coumestrol | mg | 0 | |||||||||
| Proanthocyanidin | |||||||||||
| Proanthocyanidin dimers | mg | 2.9 | |||||||||
| Proanthocyanidin trimers | mg | 2.2 | |||||||||
| Proanthocyanidin 4-6mers | mg | 7.8 | |||||||||
| Proanthocyanidin 7-10mers | mg | 7.2 | |||||||||
| Proanthocyanidin polymers (>10mers) | mg | 135.1 | |||||||||
Black currant oil
Blackcurrant seed oil is a rich source of gamma-linolenic acid (omega 6 polyunsaturated fatty acid) ~ 17 percent 3) and is typically consumed as a part of a dietary supplement. This gamma-linolenic acid (omega-6 polyunsaturated fatty acid) is used for prevention and/or treatment of various degenerative pathologies such as osteoporosis 4), diabetes 5) and cancer 6), 7). Additionally, gamma-linolenic acid has been shown to suppress in vitro (test tube) tumor growth 8), improve oxygenation status 9), exert anti-inflammatory activity and display beneficial effects in the early stages of sepsis 10).
Black currant oil benefits
Numerous studies primarily carried out in the 1980s and 1990s demonstrated that gamma-linolenic acid-enriched botanical oils (evening primrose, borage, blackcurrant seed, and fungal-derived) had the capacity to relieve the signs and symptoms of several chronic inflammatory diseases, including rheumatoid arthritis (RA) and atopic dermatitis 11). However, several more recent reviews and meta-analyses have questioned these earlier studies and raised doubts about the clinical effectiveness of gamma-linolenic acid-enriched supplements particularly in the context of atopic dermatitis and rheumatoid arthritis 12) (see Table 2). A variety of issues complicate these studies including the fact that many of the trials have: 1) relatively low subject numbers; 2) less than ideal study designs (e.g. the absence of washout period in cross-over design trials); 3) variations in the types of gamma-linolenic acid supplements and how they are administered (e.g. dose, duration); and 4) differences in selection/inclusion criteria (e.g. population demographics and disease states) 13).
Table 2. Effect of gamma-linolenic acid-enriched oil supplements on various human disease from meta-analyses and recent studies
| Study | Disease1 and Study Type2 | Supplement3 | location | # subjects | # studies | duration | outcome | effect |
|---|---|---|---|---|---|---|---|---|
| Skin | ||||||||
| Morse et al., 1989 14) | Atoptic dermatitis (CO, parallel) | EPO (Epogam) | UK, Italy, Finland | 311 | 9 (EPO) | 4, 8, or 12 wk | Severity of symptoms | reduced severity of symptoms |
| Van Gool et al., 2004 15) | Atoptic dermatitis (RCT, CO, CCT) | EPO, BO, BCO; 90–480mg GLA/d (children); 132–720mg GLA/d (adult) | Germany, Italy, UK, Canada, USA, Finland, Sweden, Switzerland, | 1071 | 22 (total) BO (6) EPO (12) BCO ( 1) | 3–24wk | Severity of symptoms | no effect |
| Bamford et al., 2013 16) | Eczema (AE, AD, AEDS) adult, children (RCTs) | EPO, BO | UK, Italy, Germany, India, NZ, Finland, Sweden, USA, Switzerland | 1596 | 27 (total) 19 (EPO) 8 (BO) | 3–24wk | Severity of symptoms | no effect |
| Morse and Clough, 2006 17) | Atopic eczema | EPO (Efamol®) | 1207 | 26 | 4–8wks | Severity of symptoms | reduced severity of symptoms | |
| Fiocchi et al., 1994 18) | Atoptic dermatitis, infants | EPO, 3g oil/d | Italy | 10 | na | 4wk | Lesion number; Severity of | decrease number (trend); reduced severity of symptoms |
| van Gool et al., 2003 19) | Atoptic dermatitis, infants (RCT) | BO, 100mg/d | Netherlands | 118 | na | 6mo | Incidence in 1st yr; Severity of symptoms | no prevention benefit; reduced severity of symptoms (trend) |
| Kitz et al., 2006 20) | Atoptic dermatitis, infants | GLA, 40mg/d | Germany | 131 | na | 6 mo | Prevention | no effect |
| Kawamura et al., 2011 21) | Atoptic dermatitis, adult | GLA, 200mg/d, oil of Mucor circinelloides in food | Japan | 130 | na | 16wk | Trans-water loss; Nocturnal itching | no effect; decreased |
| Simon et al., 2014 22) | Atoptic dermatitis, children and adult (open study, non-controlled) | EPA, 4–6g GLA/d | Switzerland | 21 | na | 12wk | SCORAD4 index | plasma GLA content correlates with SCORAD |
| Arthritis | ||||||||
| Cameron et al., 2011 23) Macfarlane et al., 2011 24) | Rheumatoid arthritis (RCT, parallel, placebo controlled) | Herbal intervention 525–540mg GLA/d | UK, USA | 286 (total) >90 (in 3 studies) | 22 (total) EPO (2) BCO (1) | 6mo | Morning stiffness; Pain | decreased (2 of 3); no effect |
| Cameron et al., 2011 25) Macfarlane et al., 2011 26) | Rheumatoid arthritis | 1400- 2800mg GLA/d | USA, Finland | >111 | EPO (1) BO (2) BCO (1) | 6mo | Pain; Morning stiffness; Joint tenderness; Joint swelling; | decreased; decreased; improvement; decreased; |
| Asthma | ||||||||
| Arm et al., 2013 27) | Mild asthma, adults (randomized) | BO+EO (GLA, 1.67g/d+ SDA, 0.88g/d) | USA | 37 | na | 3wk | Basophil, Neutrophil leukotriene production (ex vivo) | >50% decrease (basophil response); >35% decrease (neutrophil response) |
| Ziboh et al., 2004 28) | Mild asthma, adults (randomized) | BO (2g GLA/d) | USA | 24 | na | 12mo | Neutrophil leukotriene production (ex vivo); Peak flow | >20% decrease (p<0.05); no effect |
Several studies have also investigated the effects of gamma-linolenic acid when given in combination with botanical or marine omega-3 (n-3) enriched PUFA supplements. Enteral diets enriched with marine oils containing omega-3 polyunsaturated fatty acids (i.e. eicosapentaenoic acid [EPA, 20:5n-3] and docosahexaenoic acid [DHA, 22:6n-3]) and gamma-linolenic acid have been shown to reduce cytokine production and neutrophil recruitment into the lung resulting in fewer days on ventilation and shorter stays in the intensive care unit in patients with acute lung injury or acute respiratory distress syndrome 30). Importantly, these dietary combinations of gamma-linolenic acid and omega-3 polyunsaturated fatty acids were also shown to reduce both morbidity and mortality of critically ill patients 31). However, as with the studies of gamma-linolenic acid alone, the results combining gamma-linolenic acid and omega-3 polyunsaturated fatty acids have not been reproducible. Other clinical studies, such as the OMEGA trial, did not show a benefit of these gamma-linolenic acid/omega-3 polyunsaturated fatty acid combinations on patient outcomes 32).
Supplementation strategies providing gamma-linolenic acid together with omega-3 polyunsaturated fatty acids (i.e. EPA and DHA) have also been utilized in patients with atopic asthma 33) and have been shown to block ex vivo synthesis of leukotrienes from whole blood and isolated neutrophils. Importantly when provided as an emulsion, daily consumption of these combinations was associated with an improved quality of life in asthma patients and a decreased reliance on rescue medication 34). These results compared favorably with quality of life scores obtained in mild asthmatics treated with montelukast or zafirlukast 35).
Alternatively, botanical oil combinations (e.g. borage and echium oils) containing gamma-linolenic acid, the n-3 18C-PUFAs, alpha-linolenic acid (ALA, 18:3n-3) and stearidonic acid (SDA, 18:4n-3), have been shown to reduce leukotriene generation and forced expiratory volume in mild asthmatics 36), improve glucose tolerance in insulin-resistant monkeys 37) and reduce total and LDL “bad” cholesterol levels in patients with diabetes and metabolic syndrome 38). These botanical oil studies, however, have yet to be replicated in larger human clinical trials.
Together, these data indicate that the outcomes of clinical studies utilizing gamma-linolenic acid supplementation, alone or in combination with other fatty acid-based supplements, while promising are highly inconsistent. More recent studies suggest that there are important metabolic and genetic factors within the human host that significantly impact the study of gamma-linolenic acid or gamma-linolenic acid/omega-3 polyunsaturated fatty acids combinations and reveal that a “one size fits all” model of supplementation may not be appropriate. Furthermore, these studies suggest that it may be necessary to better understand key metabolic and genetic issues regarding gamma-linolenic acid metabolism before gamma-linolenic acid-enriched supplements can be effectively used to address human disease.
Black currant benefits
In addition to its anecdotal use in traditional herbal medicine, modern laboratories have demonstrated the potent anti-inflammatory, antioxidant and antimicrobial effects of black currant constituents on a myriad of disease states. Various reports also describe the beneficial functions of black currant for human health, vasodilatation 39), eyestrain 40) and as an antivirus agent 41). These properties are mainly due to the anthocyanins (specifically delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside), flavonols, phenolic acids and polyunsaturated fatty acids in black currant. In previous studies, researchers found immunostimulating effects of a polysaccharide, which called cassis polysaccharide, derived from black currant 42) and its antitumor activity and ability to induce tumor necrosis factor-α (TNF-α) production in a mouse study 43). Scientists also found that cassis polysaccharide has an effect on macrophage activation in in vitro (test tube) experiments 44).
Anthocyanins are effective antioxidants 45) but they have also been proposed to have other biological activities that are independent of their antioxidative capacities and produce health benefits. Examples range from inhibition of cancer cell growth in vitro 46), induction of insulin production in isolated pancreatic cells 47), reduction of starch digestion through inhibition of a-glucosidase activity 48), suppression of inflammatory responses 49), slow down patient’s glaucoma progression 50), as well as protection against age-related declines in cognitive behavior and neuronal dysfunction in the central nervous system 51).
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