Paul M. Gross, PhD
One of China's oldest stories about the health benefits of consuming natural foods is goji berry's reputation (“wolfberry”, Lycium barbarum L.) for preserving vision well into old age, even for many centenarians. Traditional Chinese medicine has been using goji for this purpose over some 20 centuries (3,6)
Goji, an English contraction of the Mandarin name, gǒuqǐ (pronounced “goo-chee” for wolfberry), is renowned for its nutrient density, containing numerous essential vitamins, minerals and phytochemicals that may support ocular health. Among them are nutrients sufficiently established as valuable to vision that they have been assessed in NIH-sponsored clinical trials and now are ingredients of commercial supplements – essential vitamins A, C and E, the essential mineral zinc, and carotenoids, beta-carotene, lutein and zeaxanthin (1,5)
A nutritional wonder of nature, the goji berry contains all of these eye health nutrients and more. In this essay, we'll cover a dozen goji nutrients, where modern scientists are just beginning to verify what ancient Chinese shamans have practiced for centuries – goji may be nature's most complete eye healthfood.
You may have noticed the increasing public interest in goji berry. Pay a visit to http://google.com/trends and enter “goji” as a search word to see how this berry is rapidly capturing public attention around the world.
Where can you buy goji berries? There are numerous websites selling products under the goji or wolfberry name (7). If available to you, go to your nearest Chinatown where you can buy them at a fair price ($3-5 per lb). Choose dried berries that are the largest and reddest, have moisture content similar to raisins, and come from the goji berry capital of China, Ningxia (7).
Eye health nutrients
Most of what we know about specific nutrients that affect eye health comes from clinical trials on patients with age-related eye diseases, given the acronym AREDs. This ongoing series of clinical trials is sponsored by the US National Eye Institute, a division of NIH, and conducted by ophthalmologists across the United States and Canada (1).
The main nutrients identified in the first AREDs reports were the antioxidant vitamins A, C and E combined with high doses of zinc and the carotenoid, beta-carotene (a pro-vitamin A compound converted to vitamin A upon digestion). Since then, further research not yet completed is considering food-derived carotenoid pigments found in the human retina – zeaxanthin and lutein – and other essential nutrients and antioxidant chemicals ingested via plant foods. (The term “essential” has two meanings: 1) the nutrient is essential to health, and 2) it is not made by the body so is essential that we obtain it via food intake.)
A Dozen Friends of Eye Health
All the following nutrients are present in goji berries. Data sources are from two recently published books (3,6).
1-3. Antioxidant vitamins A-C-E. Vitamin A, formed from precursors called retinol (from dairy products) or retinal (from plant carotenoids like beta-carotene present in goji), serves antioxidant, filtering and immune functions in the eye. Vitamins C and E are, respectively, water-soluble and lipid-soluble antioxidants that become resident in the eye with a variety of protective functions against oxidative and intense light stress. Goji berries are an exceptionally good source of vitamin C (29 mg/100 g dried fruit, approx. 30% of the US Dietary Reference Intake, DRI) (3).
4. Zinc. As a cofactor for numerous enzymes, some of which play antioxidant roles, zinc can be viewed as a complementary element guarding eye health. Its precise role especially in age-related macular degeneration is not yet defined, but it is nonetheless included as one of the AREDs nutrients currently under clinical study. Zinc content per gram in goji berries (2 mg/100 g, 20% DRI) is high among edible plants (3).
5-6. Zeaxanthin and lutein. Almost identical in chemical structure, these two carotenoids present in green, orange, red and yellow plant foods are selectively absorbed from the blood by the retina. They are deposited in a retinal compartment called the macula lutea where scientific studies have proved a light-absorbing filter role against intense sunlight and an antioxidant role against reactive oxygen species. Goji berry is one of nature's richest sources of zeaxanthin (162 mg/100 g; there is no DRI for this nutrient) (3).
7-8. Beta-carotene and lycopene. Not only a precursor to vitamin A formation, beta-carotene also serves as a potent antioxidant source that seeks fat layers for storage. This has significance to eye protection, as the neural elements of the retina are lined with fatty sheaths where antioxidant protection is needed. Usually associated with tomatoes (a botanical relative of the goji berry), lycopene provides antioxidant functions. Beta-carotene and lycopene contents in goji berries are exceptional among edible plants (7.4 mg and 1.4 mg/100 g, respectively) (3,4,6).
9-10. Magnesium and selenium. Although the research is preliminary at present, there is evidence that magnesium and selenium, essential minerals with rich contents in goji berries (109 mg and 50 mcg/100 g; 30% and 97% DRI, respectively), participate as cofactors in retinal antioxidant reactions (3).
11. Riboflavin (vitamin B2). Like other B vitamins, riboflavin supports energy production by aiding the metabolism of carbohydrates, fats and proteins. It has not been conclusively proved that riboflavin serves a health function in the eye. Recent research has shown, however, that riboflavin is associated with nutrition of collagen fibrils affected by cataracts and keratoconus, a degenerative corneal disease. Goji berries have among the highest riboflavin content per gram in nature (1.3 mg/100 g or 100% DRI) (3).
12. Phenolics. These chemicals from colorful plants are pigments with a great diversity of chemical structures and names. They are the main dietary antioxidants in foods Americans eat, and so likely contribute to eye health in ways not yet clear from modern research. In goji berries, phenolic concentration is particularly enriched (total phenolics of 1309 mg/100 g), with preliminary evidence that the phenolic well-known in red raspberries – ellagic acid – is also localized in goji fruit (86 mg/100 g) (6).
Although it will take years for modern science to unravel the eye health nutrients in goji berries, we have enough evidence already by knowing that these dozen nutrients are involved in supporting vision and overall health (1,2,5).
Our choice is to involve plant foods containing these nutrients in our diets, whether by using goji berries or other colorful plants foods with similar nutrient characteristics (2,6).
1. Age-Related Eye Disease Study Research Group, A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss. Arch Ophthalmol. 2001 Oct;119(10):1417-36.
2. Bartlett H, Eperjesi F. An ideal ocular nutritional supplement? Ophthalmic Physiol Opt. 2004 Jul;24(4):339-49.
3. Gross PM, Zhang X, Zhang R, Wolfberry: Nature's Bounty of Nutrition and Health, Booksurge Publishing, 2006.
4. Gross PM, Exploring exotic antioxidant superfruits. Nat Prod Insider Oct 16, 2006, p 92-4.
5. Naguib Y, Eye Health Update, Nutraceuticals World, May 2005, 46-55.
6. Young G, Lawrence R, Schreuder M, Discovery of the Ultimate Superfood, Essential Science Publishing, 2005
7. Wolfberry (goji) site, http://wolfberry.org