In July 2010, a group of New Zealand researchers reported that the berry fruit black currant showed promise in reducing airway inflammation in a human cell study. In particular, one of the chemical compounds present in black currant, proanthocyanidins, was shown to suppress certain proteins in the epithelial cells (the cells that make up the lining of lung tissue) that are responsible for triggering inflammation in response to the presence of allergens in the lungs. (Hurst SM, et al. Blackcurrant proanthocyandins augment IFN-gamma-induced suppression of IL-4 stimulated CCL26 secretion in alveolar epithelial cells. Mol Nutr Food Res. 2010 Jul,54 Suppl 2:S159-170)
The study focused primarily on the black currant’s effectiveness in reducing over-production of white blood cells that lead to inflammation and ultimately trigger asthma attacks, but given that the researchers speculated that black currant may help alleviate airway inflammation in general we thought the study was worthy of your attention.
As the research team explained, “The search for suitable foods as a natural alternative or as a complement to traditional therapies for the prevention and/or alleviation of inflammatory related diseases has become the focus of recent research. In particular, berry fruit consumption has been shown to alleviate lung inflammation in animal models. In this study we provide supportive evidence that blackcurrant-derived polyphenolic compounds, in particular proanthocyanidins, have the potential to modulate cellular events leading to the suppression of IL-4 and IL-13-stimulated CCL26 secretion, a primary eosinophilic chemokine that facilitates chronic lung inflammation in asthma patients.”
In the study, the researchers isolated human epithelial cells in culture. In one set of cell samples, they exposed the cells to black currant prior to introducing cell proteins known as cytokines (specifically, interleukin-4 otherwise known as IL-4, and interleukin-13, or IL-13) that signal secretion of certain white blood cells known as eosinophils (specifically CCL26) that in turn trigger lung inflammation. In effect, the researchers were trying to simulate the cell’s response to the presence of an allergen.
You see, when bacterial or fungal material is inhaled into the lungs, the cells of the lung lining detect their presence and begin secreting the proteins called cytokines that are responsible for signaling the body to produce white blood cells to attack and kill the invading bacteria or fungi.
In asthmatics, there is a miscommunication in the body between these proteins and the white blood cells which results in the production of way-too-many white blood cells. This in turn inflames the lung tissue (in effect hardening the cells due to the overload of the white blood cells crowding around). The hardening of the cells causes the cells themselves to enlarge and results in airways that constrict or narrow. This makes it extremely difficult to breathe. Scientists are not certain of the root cause that drives this miscommunication in asthmatics but suspect that the epithelial cells in asthmatics are damaged/altered by a yet-unknown source.
There is a similar mechanism in COPD patients that involves essentially the same process but typically different cytokines and different white blood cells. In the case of COPD, scientists believe the main reason for the miscommunication between the epithelial proteins and white blood cells is damage/alteration of epithelial cell structure caused by long-term exposure to cigarette smoke and other harmful airborne pollutants.
So, getting back to the study, the research team compared the black currant/cytokine exposed samples to cell samples that were exposed to cytokines alone. Then, the researchers counted the number of white blood cells (CCL26) generated in each set of cell samples. They determined that the black currant/cytokine exposed cell samples had notably fewer counts of the white blood cells compared to the cells exposed only to cytokines.
While the researchers speculated on a few reasons why black currant (and other berry fruits) may help reduce airway inflammation, there is no scientific consensus as to the precise mechanism. The article authors’ speculations included the possibility that the antioxidant properties of berry fruits such as black currant may cause certain fruit chemical compounds to bind to the cytokines thereby reducing the number of cytokines available to signal white blood cell production.
If you are interested in trying black currant, it is available in produce stores as raw fruit or juice. There are also a wide variety of black currant oil nutritional supplements available on the market. This particular study made no recommendations regarding consumption levels or dosage levels so we don’t have a dosage recommendation to offer but we did find the following dosage information on healthline.com, “As a dietary supplement, black currant is available in 500 milligram and 1,000 milligram capsules that typically contain black currant seed oil, vegetable glycerine, and gelatin. Black currant is likely safe when used at a maximum dose of 1,000 milligrams (500-1,000 milligrams are often used per day). Black currant juice is also commercially available and has been taken in doses up to 1.5 liters per day, when mixed with apple juice. Maximum doses of black currant seed oil used in clinical trials range from 4.5-6 grams per day up to eight weeks, although there is no proven effective dose, and safety has not been established. Black currant anthocyanins have been taken in doses of 7.7-50 milligrams for up to two months. Based on some herbal textbooks, there is a lack of reported toxicity concerns with black currant consumed as food or ingested in 500 milligram tablets three times a day.”
As we have counseled before regarding other nutritional supplements, please consult your physician prior to consuming black currant to ensure there are no counter-indications related to other medications you take or other aspects of your particular situation.
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