for people ages 50-95 (full criteria)
Healthy Volunteers
healthy people welcome
at UC Davis
study started
completion around
Principal Investigator
by Robert M Hackman, PhD (ucdavis)Glenn Yiu, MD, PhD (ucdavis)



The goal of this project is to conduct a clinical trial in 60 participants ranging from age 50-95 with small drusen who are at risk for age-related macular degeneration (AMD). The study will evaluate the effects of 28g of goji berry intake or an equivalent amount and type of fiber, five days a week for six months, on visual health, gut microbiome profiles, skin carotenoid measures, and lipoprotein profiles.

Official Title

Effects of Goji Berry Intake on Risk of Age-related Macular Degeneration: A Randomized Clinical Trial


Age-related macular degeneration (AMD) is the third leading cause of blindness worldwide. The disease occurs when the macula in the central retina develops lesions due, in part, to the loss of the protection of macular pigments zeaxanthin, lutein, and meso-zeaxanthin, which are responsible for light filtering and oxidative defense. The major risk factor for AMD is aging, and currently, no definitive prevention for AMD exists.

Goji berry (Lycium Barbarum) is a fruit that has been used as traditional medicine in Asian countries for more than 2,000 years. Modern science has identified potential benefits of the berry in oxidant defense, immune regulation, diabetes, and vision in animal and cell models. Nonetheless, evidence regarding the effects of goji berries on human health is scarce. The bioactive components of goji berries include zeaxanthin, lutein, Lycium Barbarum polysaccharides-protein complex, betaine, cerebroside, minerals, and vitamins. Importantly, goji berries contain the highest concentration of zeaxanthin among all commonly consumed foods.

Previous clinical studies have shown that goji berries have a high bioavailability of zeaxanthin, and that macular pigment optical density (MPOD) was increased after supplementation. This study uses macular pigment optical volume (MPOV; a measure that integrates MPOD across multiple macular eccentricities) as the primary outcome measure. It is unknown if the changes in MPOV will be associated with other functional changes or anatomic conditions in the eye among a population with small drusen, a risk factor for AMD. In addition, the impact of goji berry intake on the gut microbiome profile and associated metabolites is unknown, and potentially important in understanding the mechanism(s) of action.

Participants who meet the eligibility criteria will be enrolled and will be randomized 1:1 to the goji berry arm or fiber arm of the study. Over the course of approximately 180 days, participants will consume the assigned food item five days per week and attend three study visits.

Study visits will include ophthalmic imaging and testing, skin carotenoid measurements, completion of a food record, height, weight, handgrip strength, blood pressure measurement, and fasting blood collection. At 2 timepoints participants will be asked to provide a stool sample (collected within 24 hours of visit).


Age-Related Macular Degeneration, Goji Berry, Lutein, Zeaxanthin, Fiber, Carotenoids, Gut Microbiome, HDL, Cholesterol Efflux Capacity, Eye Health, Macular Degeneration


You can join if…

Open to people ages 50-95

  • Diagnosis of small drusen by a retinal specialist
  • Willingness and ability to comply with the study protocol
  • 50 - 95 years of age

You CAN'T join if...

  • Dislike of, or allergy to, goji berries or any of the ingredients in the fiber-rich wafers and gummies (wheat, corn, oats, soy, natural orange flavor, xylitol, annatto, pectin, or other food ingredients)
  • Consumption of > 2 alcoholic drinks per day
  • Indications of substance or alcohol abuse
  • Current or planned use of a blood thinner (e.g., Coumadin, Warfarin) at any time during study
  • Use of multi-vitamin or any other supplements that contain lutein and/or zeaxanthin (if willing to stop the supplement, subject can be enrolled 6 months from stop date)
  • Taking any new medications started within the past 6 months, or changes in medication regimen planned in the next 6 months (stable use greater than 6 months is not exclusionary)
  • Any planned international travel during the study
  • Consuming >3 servings/day of a combination of spinach, kale, lettuce, orange bell peppers, corn, parsley, squash, broccoli, pumpkin, edamame
  • Regularly consuming >3 eggs/day
  • Currently participating in any other interventional research study
  • Diagnosed with inflammatory bowel disease, irritable bowel syndrome, other gastrointestinal disorder, undergoing cancer therapy or immunocompromised, or diagnosis of another condition where lutein, zeaxanthin and/or fiber supplementation would be contraindicated or would interfere with ability to participate in the study
  • Any physical characteristic or condition that precludes ability to perform study procedures
  • Medical or psychiatric condition that, in the opinion of the Investigator, would compromise study findings or prevent the participant from completing the study


  • UC Davis Eye Center, Tschannen Eye Institute accepting new patients
    Sacramento California 95817 United States

Lead Scientists at University of California Health

  • Robert M Hackman, PhD (ucdavis)
    Researcher, Nutrition, College of Agricultural and Environmental Sciences. Authored (or co-authored) 34 research publications
  • Glenn Yiu, MD, PhD (ucdavis)
    Associate Professor, Ophthalmology, School of Medicine. Authored (or co-authored) 120 research publications


accepting new patients
Start Date
Completion Date
University of California, Davis
Study Type
Expecting 60 study participants
Last Updated