Can blackberries cure diarrhoea?

DOES IT WORK?BACKGROUND Walking through fields containing brambles will these days often have the benefit of finding wild blackberries. The scientific name, Rubus fruticosus, reflects the long use of the berries as fruits. They were eaten all over Ireland, and widely used in jams and tarts.

Blackberry brambles were valued so much that they were protected under the old Irish Brehon Laws. This made it unlawful to clear a field of all its brambles, reflecting early wisdom about the long-term effects of clearing land. There is also an old belief that blackberries should not be eaten after Halloween. The story was that the púca would spit or pee on the berries after this, making them inedible. Again, the old ways contain some wisdom as moulds can grow on the berries later in autumn which can produce toxins.

Blackberries were also one of the earliest fruits used for medicinal purposes. Records from the 1500s note that blackberry juice was used around Europe to treat infections of the mouth and eyes. The juice has been said to restore energy and

vigour, especially for women. The leaves and roots of the shrub were used to treat diarrhoea and dysentery. Such uses have been receiving renewed interest, especially with the availability of blackberry teas and other supplements.

EVIDENCE FROM STUDIES

Studies of blackberries have found that they are highly nutritious, containing vitamin C, vitamin K, beta-carotene (the precursor for vitamin A) and numerous minerals. One hundred grams of fresh blackberries would give 35 per cent of the daily vitamin C requirement, 25 per cent of the vitamin K requirement and 21 per cent of dietary fibre. Blackberries are high in seed content, which some people don’t enjoy. However, the seeds are a good source of omega-3 and omega-6 fats.

Medicinally, most interest has been generated by the polyphenolics contained in blackberries. These compounds are found in many plants and come in many different varieties. The black colour in the fruit is due to anthocyanins, which are potent antioxidants. These compounds are known to be generally beneficial for health and preventing disease. A review of more than 1,100 foods commonly consumed in the US found that blackberries had the highest antioxidant content per serving. One serving of blackberries was one cup or about 150g. However, the values for different varieties of blackberries varied considerably. These findings support the traditional value placed on blackberries as an important food.

In spite of widespread research on the nutritional aspects of blackberries, very little research has been conducted on the medicinal uses. A search of the published research uncovered only a few preliminary studies, and all of these in animal models. The leaves and roots have astringent properties, which leaves a bitter-dry taste of strong tea. This can also lead to constriction of various tissues. This lends theoretical support to the possibility that blackberry teas might help with diarrhoea, but no studies have been published which report on this use.

RECOMMENDATIONS

No adverse effects have been reported after the medicinal use of blackberries. The nutritional value of the berries makes it well worth putting up with the thorns and scratches to gather some at this time of the year. Unfortunately, those arriving in shops come at a high price. All of the supportive research to date has been done with fresh and cooked blackberries and blackberry juice. Blackberry teas and supplements have not been included in these studies. Given the lack of research on their medicinal use, the effectiveness of blackberries for any particular condition remains unclear.

Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University