The humble goji berry – an increasingly popular ingredient in soups and teas – could hold the key to better eye health and vision.
A newly released study has found that eating a just handful of dried goji berries five times a week could increase the density of ‘sunblock’ pigments in the eyes.
Researchers from the University of California (Davis) say this helps to prevent some eye disease, specifically macular degeneration, in middle-aged people.
The pigments – lutein and zeaxanthin – filter out harmful blue light and “provide antioxidant protection”.
“Lutein and zeaxanthin are like sunscreen for your eyes,” said lead author Xiang Li, a doctoral candidate in the university’s Nutritional Biology Program.
“The higher the lutein and zeaxanthin in your retina, the more protection you have. Our study found that even in normal healthy eyes, these optical pigments can be increased with a small daily serving of goji berries.”
Australia and macular degeneration
According to the Macular Disease Foundation, about one in seven Australians over the age of 50 years have some evidence of age-related macular degeneration (AMD).
That’s 1.4 million people.
About 17 per cent or 240,000 of these people will experience vision impairment.
“AMD affects your central field of vision and can affect your ability to read or recognise faces,” said Dr Glenn Yiu, a co-author of the study and an associate professor in the Department of Ophthalmology and Vision Sciences.
The cause of AMD is complex: A mix of genetic risks, age-associated changes, and environmental factors like smoking, diet and sun exposure.
Early stages of AMD don’t have symptoms; however, physicians can detect AMD and other eye problems during a regular comprehensive eye exam.
This was a small study
According to a statement from the university, the researchers found that 13 healthy participants aged 45 to 65 who consumed 28 grams (about one ounce, or a handful) of goji berries five times a week for 90 days increased the density of protective pigments in their eyes.
In contrast (rather than strict control), 14 participants consumed a commercial supplement for eye health over the same period. They showed no increase in these pigments.
“Our study shows goji berries, which are a natural food source, can improve macular pigments of healthy participants beyond taking high-dose nutritional supplements,” Dr Yiu said.
What are Goji berries?
Goji berries are the fruit of two species of shrubby bushes (Lycium chinense and Lycium barbarum) found in north-west China.
The dried berries are a common ingredient in Chinese soups and are popular as herbal tea. They are similar to raisins and eaten as a snack.
In Chinese medicine, goji berries are said to have “eye brightening” qualities.
Ms Li grew up in northern China and became curious whether there were any physiological properties to “eye brightening”.
She researched the bioactive compounds in goji berries and found they contain high quantities of lutein and zeaxanthin, which are known to reduce the risk of eye diseases related to AMD.
The form of zeaxanthin in goji berries is readily absorbed in the digestive system so the body can use it.
The current treatment for intermediate stages of AMD uses special dietary supplements, called AREDS, that contain vitamins C, E, zinc, copper and lutein and zeaxanthin.
No known therapy has yet been shown to affect early stages of AMD.
“The next step for our research will be to examine goji berries in patients with early-stage AMD,” said Dr Yiu.