DOES IT WORK?BACKGROUND Goji berries are one of several fruits which have been growing in popularity in recent years. Prior to recent marketing efforts they were known as wolfberries.
The bright red berries come from two closely related shrubs called Lycium barbarumand Lycium chinense. They are extensively cultivated on large plantations in China. The berries are shaken from the bush because they are so tender. They are then dried to give reddish-looking raisins which are usually cooked before being eaten. In England, the shrubs are known as Duke of Argyll's Tea Tree after the man who introduced them to the UK in 1730. They are typically found in hedgerows.
Goji berries have been used in the traditional medicine of Asia for millennia. They are recommended generally as a source of energy and vitality. In Tibet they have been nicknamed “happy berries” because of the sense of wellbeing they are said to give people. Many myths have been circulated about goji berries, including claims that a Chinese man who died in 1930 had lived for 252 years by consuming the berries daily.
Since 2002, goji berry juice has been aggressively marketed, especially on the internet. The berries are said to give people energy and, more specifically, to help slow vision and cognitive deterioration that often accompanies ageing. This has led to investigations into the accuracy of the claims in the UK and the US. A number of distributors have been warned by regulators about making exaggerated claims. At the same time, other producers have been funding research into the health effects of goji berries.
EVIDENCE FROM STUDIES
Extensive investigations of the berries and extracts have found numerous nutritional components, including vitamin C, carotenoids and several antioxidants. Most interest has focused on a group of unusual polysaccharides, which are complex sugars. However, exactly how these affect the body has yet to be determined.
The first controlled trial of goji juice examined its effect on general health and vitality and was published in 2008. Thirty-four healthy people were randomly assigned to either 120ml of commercial goji juice daily or a placebo juice. The study lasted two weeks with the participants who completed questionnaires at the start and finish. Over this time, those drinking goji increased their scores in 10 areas, including calmness, sleep quality, ability to focus and feelings of happiness. Those taking the placebo showed improvements in only two areas.
However, this sort of study has numerous limitations. It did not directly compare the two groups’ overall scores, but focused on 10 individual items. Twenty other items did not show improvements. Concerns have also been raised about potential biases. The goji juice manufacturer funded the study and employed the researchers and all the participants. All these factors point to the importance of independent research which has yet to be done.
The same manufacturer and researcher conducted another study on antioxidant levels. This double-
blind study was conducted in China with 50 healthy adults for a month. Those drinking 120ml of goji juice daily had raised antioxidant levels in their blood. How this might impact their health was not directly studied.
PROBLEMATIC ASPECTS
Goji berries are edible and safe, although some people can be allergic to them. Two cases have been reported where women taking warfarin (a blood-thinner) had excessive bleeding after regularly drinking a tea made from leaves of the plant. Subsequent studies suggest that goji can interfere with warfarin metabolism. People stabilised on warfarin should be monitored carefully and may require adjustments to their warfarin dose.
RECOMMENDATIONS
Goji juice is one of several new products marketed as “super juices”. The juice is nutritious and has a long tradition of providing health benefits. However, the research available to support any specific health benefit is very limited. Any claim that something can prevent or slow the effects of ageing would require much more substantial evidence than is currently available for goji berries. As a nutritious juice, it can help provide antioxidants that contribute to an overall healthy diet.
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
