According to a small, randomized trial conducted at the University of California, Davis, eating a small serving of dried goji berries on a regular basis may help prevent or delay the development of age-related macular degeneration (AMD) in healthy middle-aged people.
AMD is the main cause of vision loss in the elderly, affecting more than 11 million people in the United States and 170 million worldwide.
"AMD affects your central field of vision and can affect your ability to read or recognize faces," said Glenn Yiu, a co-author of the study and an associate professor in the Department of Ophthalmology and Vision Sciences.
The researchers discovered that eating 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 the eyes of 13 healthy volunteers aged 45 to 65.
In comparison, 14 study participants who consumed a commercial eye health supplement during the same time period showed no improvement.
"Lutein and zeaxanthin are like sunscreen for your eyes," said lead author Xiang Li, a doctoral candidate in the 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," said Li.
The study was published in the journal Nutrients.
Importance of Goji Berries in Chinese Medicine
Goji berries are the fruit of two shrubby bushes found in northwest China, Lycium chinense and Lycium barbarum. The dried berries are used in Chinese soups and are also used to make herbal tea. They are similar to raisins and eaten as a snack.
In Chinese medicine, goji berries are said to have "eye brightening" qualities. Li was raised in northern China and became interested in whether "eye lightening" had any physiological properties.
"Many types of eye diseases exist, so it is not clear which disease 'eye brightening' is targeting," said Li.
Li looked into the bioactive chemicals in goji berries and discovered that they contain a lot of lutein and zeaxanthin, which are known to lessen the risk of AMD-related eye diseases.
According to Li, the type of zeaxanthin found in goji berries is also a highly bioavailable form, meaning it is easily absorbed in the digestive system so the body can üşe it.
The current treatment for intermediate stages of AMD is dietary supplements containing vitamins C, E, zinc, copper, lutein, and zeaxanthin, known as AREDS. There is no recognized therapy that has been shown to affect AMD in its early stages.
According to Yiu, the cause of AMD is complicated and multifactorial, involving a combination of inherited risks, age-related changes, and environmental variables such as smoking, food, and sun exposure.
"Our study shows goji berries, which are a natural food source, can improve macular pigments of healthy participants beyond taking high-dose nutritional supplements," said Yiu. "The next step for our research will be to examine goji berries in patients with early-stage AMD."
Although the findings are promising, the researchers point out that the study size was small and that more research is required.