What is the Role of Diet in Mitigating a Complication of Diabetes that Affects the Eyes?

— Dawn M. Sweet, Ph.D.

Diet may be a contributing factor to reducing the risk of developing diabetic retinopathy. 

Diabetic retinopathy, a microvascular complication that affects retinal capillaries, affects one third of patients with diabetes, and if left untreated, it could result in partial vision loss or complete blindness.¹ Diabetic retinopathy can negatively affect one’s quality of life as well as increase one’s risk for a cardiovascular event; it may also contribute to all-cause mortality.^2,3 Given the severe negative consequences of diabetic retinopathy, understanding its causes is critical. To date, little is known about what causes diabetic retinopathy, though poorly managed diabetes, hyperglycemia, and hypertension are suspected causes. ¹ Another less understood and less examined cause is believed to be diet. 

Diet and Diabetic Retinopathy

A recent review systematic review looked at 27 studies that investigated the role of diet in developing diabetic retinopathy.¹ The reviewed studies focused on the role of fruits and vegetables, fish, among other food items. 

The Mediterranean Diet

A 2015 study⁴ compared the Mediterranean diet, a diet enriched with extra virgin olive oil or nuts, to a low fat diet in a prospective study over six years. Results suggest that following a Mediterranean diet enriched with extra virgin olive oil can reduce the risk of diabetic retinopathy by as much as 40 percent. Those participants who were the most compliant with Mediterranean diet were found to decrease their risk by as much as 60 percent. The Mediterranean diet enriched with nuts also reduced the risk of diabetic retinopathy but the reduction in risk was not statistically significant. 

Food Groups

Fruit, vegetables, and fish have been found to be important foods to mitigate the risk of diabetic retinopathy. Diets fortified by fruits, vegetables, and fish have been shown to protect against diabetic retinopathy. In a Japanese cohort study that included participants with Type 2 diabetes,⁵ results suggest that diets high in fruit, ≥ 173.2 grams per day, yielded a 50 percent decrease in retinopathy compared to those participants who consumed ≤ 53.2 grams of fruit per day. 

Consuming oily fish twice per week was also found to decrease the risk of retinopathy by 60 percent⁶ while another study found that consuming 85–141 grams of dark fish (e.g., salmon, swordfish) weekly resulted in a nearly 70 percent decrease in retinopathy.⁷ The protective benefits of fish are evinced through its omega-3 and vitamin D levels while the protective effects of fruits and vegetables are evinced through their antioxidants, vitamins C and E, and carotenoids or polyphenols.¹ The protective effect of fruits and vegetables in reducing diabetic retinopathy is believed to be associated with polyphenols because they have been found to improve glucose homeostasis and insulin resistance

Low Calorie Diet Coupled with a Mediterranean Diet and Fruits, Vegetables, and Fish 

While there is still room to investigate the role of diet in reducing the risk of diabetic retinopathy, there is strong evidence to suggest one’s diet plays a critical role. Because of the high rate of retinopathy — one third of diabetic patients — it is important for clinicians to discuss diet modifications such as the increased inclusion of fruits, vegetables, fish, and swapping out less health oils with extra virgin olive oil as part of a Low Calorie (LCD) or Very Low Calorie Diet (VLCD). 

Sources:

1. Diet and risk of diabetic retinopathy: a systematic review
2. International Diabetes Federation
3. Diabetic retinopathy predicts all-cause mortality and cardiovascular events in both type 1 and 2 diabetes: meta-analysis of observational studies
4. Mediterranean diet, retinopathy, nephropathy, and microvascular diabetes complications: a post hoc analysis of a randomized trial
5. Fruit intake and incident diabetic retinopathy with type 2 diabetes
6. Dietary Marine omega-3 fatty acids and incident sight-threatening retinopathy in middle-aged and older individuals with type 2 diabetes: prospective investigation from the PREDIMED trial
7. Adequate vitamin D status is associated with the reduced odds of prevalent diabetic retinopathy in African Americans and Caucasians

About the Author: Dr. Dawn M. Sweet has over 20 years of experience in the field of communication. Dr. Sweet has given several invited talks to and workshops for academic and private sector audiences on the role of nonverbal and verbal communication in achieving positive outcomes and mitigating bias. Her research has been published in several top ranked peer-review journals, and it has been featured on NPR’s River to River / All Things Considered, Buzzfeed, and Science Daily. Her research has also been used to inform expert testimony.