Tasty and nutrient-packed, Goji berries might a have a role in preventing retinal damage associated with diabetes.
Also known as Wolfberries, Goji berries are the fruits of the shrubs, Lycium barbarum and Lycium chinense. These two closely related species are native to both Asia and areas surrounding the Mediterranean Sea.
For over two thousand years, the fruit and root bark of the plant have been used in Traditional Chinese Medicine. The orange-red berries, which are oblong and shriveled like raisins, can be eaten fresh but are more commonly found in a dried form.
Sweet but tangy, Goji berries contain protein, including all of the essential amino acids, iron, and Vitamins B1, B2 and C. They are also a good source of carotenoids, especially zeaxanthin, flavonoids and polysaccharides.
It is the carotenoid content that gives the berries a potential role in preventing diabetic retinopathy, one of the most common and serious complications of both Type I and Type II diabetes.
Over time, high blood sugar levels can damage retinal blood vessels. As the disease progresses, vision can become impaired and the most severe cases can ultimately result in vision loss.
Dr. Daniel Lin, Assistant Professor of nutritional science, and his fellow researchers at Oklahoma State University of Human Sciences looked to the humble Goji berry to ascertain whether it could play a role in preserving healthy retinal tissue.
In a preliminary rodent study, Dr. Lin and his fellow researchers explored the impact of two of the carotenoids found in Gojis: zeaxanthin and lutein, both of which are highly concentrated in the macula of the eyes of humans as well as rodents.
Reversing Mitochondrial Damage
For eight weeks, the researchers fed one group of mice a diet including 1% Goji berries. A second group of similar mice got the same diet minus the Gojis. Using high performance liquid chromatography, the investigators measured the carotenoid content of the retinal and liver tissue obtained from the two groups of mice.
The mice fed the diet containing Goji berries had a 13.7% increased concentration of zeaxanthin and lutein in both types of tissue.
To ascertain the effect these carotenoids might have on diabetic retinopathy, Lin’s group also examined the retinas of the mice.
Just as in humans, hyperglycemia, such as can be found in poorly controlled diabetes, can lead to oxidative stress and mitochondrial dysfunction, a primary marker of diabetic retinal degeneration.
After eight weeks, the retinas of the mice in the Goji berry group showed marked improvement, with a complete reversal of mitochondrial damage and improvements in both mitochondrial dispersion and retinal epithelial pigment granules. As Dr. Lin observed, “the mitochondria get damaged and need to be recycled to prevent downstream damage” and the goji berries appeared to do just that.
Dr. Lin believes his research is the first to show that, “Wolfberry bioactive constituents prevented or delayed the onset of the disease of diabetic retinopathy in an animal model.”
The researchers also found reduced hypoxia in retinal blood vessels of the mice fed the Goji berries. Since hyperglycemia can cause hypoxia and subsequent vascular dysfunction in people with diabetes, these intriguing findings will hopefully encourage further research to determine if the berries will have the same protective effects against diabetic retinopathy in humans.
While the scientists work all of that out, there are plenty of other reasons to become familiar with this nutrient-dense fruit.
US Cultivation on the Rise
Chewier than raisins, and naturally sweet but not too-sweet, these orange-red berries are delicious eaten out of hand or included in a trail mix of nut and some pieces of dark chocolate. They can be used in place of dried cherries or cranberries to top a salad.
The orange-red berries can be added to smoothies, used to top smoothie bowls, sprinkled over oatmeal, or baked into muffins.
Because they also have a tart quality, Goji berries are also a tasty addition to rice, quinoa or grain dishes.
The only slight downside is cost; since they have been dubbed a “super food” in much of the popular press, Goji berries have become quite expensive. Recently, a 16oz. package of organic Gojis was listed for $16.79 on Amazon.com.
However, they can be purchased for significantly less at Asian grocery stores. The bulk of the Goji berries sold in the United States are imported from China but now farmers in California, Nevada and New Mexico and beginning to grow them.
Although Goji berries have been safely eaten for thousands of years, Dr. Lin notes that a few case reports indicate that they may interact with blood thinning drugs. Patients using these drugs should exercise caution before consuming Goji berries. Also be aware that the Lycium genus is part of the Nightshade family, so people with Nightshade allergies or sensitivities may also want to be careful with Goji berries.
Researchers have yet to establish whether Gojis will be as efficacious in mitigating the effects of diabetic retinopathy in humans as they were in mice. In the meantime they make a delicious and nutritious addition to most peoples’ diet.
Julia Powers is a nutrition consultant and writer based in Hingham, MA. After earning her masters in nutrition at the University of Bridgeport, she opted to further her education at the Maryland University for Integrative Health, where she is enrolled in the nutrition internship program. She also completed a ten-month mentorship program in Functional Medicine & Clinical Nutrition, with Dr. Liz Lipski. In addition to her private consultancy, Julia Powers Nutrition, she is a frequent contributor to Edible South Shore, and South Coast magazines.