For Patients With Diabetes, Dietary Changes May Preserve Vision

While patients may not expect to receive dietary advice during a visit to their ophthalmologist, the topic is highly relevant to visual health, especially for individuals with diabetes. Substantial research has established the critical importance of maintaining a healthy diet, regular exercise, and other lifestyle measures in preventing or delaying the onset of diabetes as well as related ocular conditions, such as diabetic retinopathy, which affects one-third of people with diabetes, and represents the main cause of blindness among working-age adults.¹ 

The estimated lifetime risk for diabetic retinopathy is 50% to 60% for patients with type 2 diabetes, and up to 90% for those with type 1 diabetes.¹ The increasing global prevalence of diabetes underscores the need for clinicians to understand the role of diet in diabetic retinopathy and adequately advise patients. 

“Education about diabetes and diabetic eye disease can be sight-saving, as diabetic retinopathy and diabetic macular edema can progress to irreversible vision loss if not treated,” says Aleksandra Rachitskaya, MD, an ophthalmologist at Cleveland Clinic Cole Eye Institute in Ohio.

The Mechanism of Diabetic Eye Disease

“The main drivers for diabetic retinopathy are glycemic control and duration of diabetes,” explains Kristen Nwanyanwu, MD, MBA, MHS, assistant professor of ophthalmology and visual science at Yale School of Medicine in New Haven, Connecticut.² “Glycemic control is modifiable, so diet along with the proper pharmacological support is paramount.” 

According to Abdhish Bhavsar, MD, president and director of clinical research at the Retina Center of Minnesota in Minneapolis, and clinical spokesperson for the American Academy of Ophthalmology, “Blood glucose control is the main indicator of progression risk in diabetic retinopathy.” In a 2019 study, investigators reported that mean hemoglobin A1C was “by far the strongest risk factor” for progression from nonproliferative diabetic retinopathy (NPDR) to proliferative diabetic retinopathy (PDR), followed by duration of diabetes, albumin excretion rate, and mean diastolic blood pressure. 

With high hemoglobin A1C and poor glycemic control, diabetic retinopathy can progress much more rapidly, Dr Bhavsar adds. Conversely, with low A1C and good glycemic control, progression may be substantially delayed or even halted for some period of time. 

“The damage of diabetes on the eye is cumulative — a patient who has severe NPDR is at risk of progression to PDR and developing such complications as vitreous hemorrhage and tractional retinal detachment,” Dr Rachitskaya notes. These risks further highlight the need for timely discussion between providers and patients regarding the preventive role of diet with patients. 

Key findings

Research findings increasingly support the protective effects of specific foods and dietary patterns in diabetic retinopathy. In a 2018 meta-analysis of 31 studies, a research team examined the link between dietary intake and diabetic retinopathy. Their results showed that greater consumption of dietary fiber and oily fish, and adherence to a Mediterranean diet, was protective against diabetic retinopathy. High caloric intake was linked to an elevated risk of diabetic retinopathy.³

One prospective study (n=3482) included in that analysis found a lower risk in patients consuming oily fish 2 or more times per week (HR, 0.41; 95% CI, 0.23–0.72), and an interventional study of 3614 patients demonstrated a protective effect of the Mediterranean diet compared to a low-fat control diet (HR, 0.60; 95% CI, 0.37–0.96).³

In a 2021 cohort study based on self-reported data from 261 patients in an outpatient ophthalmology clinic, researchers observed a lower risk of developing diabetic retinopathy in those who consumed fish more than 2 times per week (OR, 0.42; 95% CI, 0.18–0.94) and greater risk in those who consumed rice (OR, 3.19; 95% CI, 1.17–8.69).⁴ 

Results of a study published in 2018 revealed a significant association between increasing frequency of fish consumption and lower odds of severe diabetic retinopathy in those who had already developed the disease (OR, 0.91; 95% CI, 0.84–0.99 per 1-unit increase of fish intake; P =.038).⁵

Findings regarding the association between antioxidant intake and diabetic retinopathy have been mixed and inconclusive overall.³ While “AREDS2 has been studied in age-related macular degeneration and not in diabetes, I haven’t seen any data on supplements for diabetic retinopathy,” Dr Nwanyanwu says. Additionally, associations between diabetic retinopathy and other dietary components such as proteins, fatty acids, alcohol, and other beverages remain unclear.³

In terms of emerging research, a study published in 2021 in Scientific Reports found dysbiosis in the gut microbiomes of participants with diabetic retinopathy compared with healthy controls.⁶ This connection has implications for novel therapies to treat the disease and requires additional investigation.

Broaching the Topic

Since the topic of dietary choices may elicit shame or defensiveness in some patients, it is important for clinicians to broach the topic in a tactful way. Dr Nwanyanwu usually leads with questions such as, “How does your diabetes team think you’re doing?” and “What’s a typical breakfast for you?” 

“These questions signal that you want the best for your patients and let them know that you’re working together, not preaching to them,” Dr Nwanyanwu explains. 

Dr Bhavsar approaches the topic by focusing on the need to optimize hemoglobin A1C. “Aiming for a 6% to 7% range is a good goal for most patients,” and these levels are associated with a “very high chance of slowing progression,” he advises. “There are also other benefits to eating well and staying active, including a lower risk of heart disease and stroke, which are tied to overall health and eye health.” 

He generally recommends that patients eat well, including adequate consumption of leafy greens, fruits, vegetables, nuts, and whole grains, and limited intake of saturated fat. He directs patients to information provided by the American Academy of Ophthalmology regarding dietary recommendations for optimal visual health disease prevention.⁷ 

While it is necessary to discuss the role of diet in eye health and the risk of progression in diabetic retinopathy, Dr Bhavsar notes the limits of ophthalmologists in recommending specific dietary changes in-depth. “The main downside is that clinicians rarely have the opportunity to evaluate the patient’s diet, so I encourage them to consult with a dietitian in addition to their endocrinologist,” he explains. 

Dr Rachitskaya adds that consultation with a dietitian can be especially helpful for patients who experience challenges in maintaining healthy eating habits. Dr Nwanyanwu also emphasizes the impact of social determinants of health, including food insecurity, on glycemic control. Providers should aim to connect affected patients with local community resources and aid programs that can facilitate access to nutritious foods.⁸

References

1. Wong TY, Sabanayagam C. Strategies to tackle the global burden of diabetic retinopathy: from epidemiology to artificial intelligence. Ophthalmologica. 2020;243(1):9-20. doi:10.1159/000502387
2. Hainsworth DP, Bebu I, Aiello LP, et al; Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) Research Group. Risk factors for retinopathy in type 1 diabetes: the DCCT/EDIC study. Diabetes Care. 2019;42(5):875-882. doi:10.2337/dc18-2308
3. Wong MYZ, Man REK, Fenwick EK, et al. Dietary intake and diabetic retinopathy: A systematic review. PLoS One. 2018;13(1):e0186582. doi:10.1371/journal.pone.0186582
4. Kadri R, Vishwanath P, Parameshwar D, Hegde S, Kudva AA. Dietary associations with diabetic retinopathy-A cohort study. Indian J Ophthalmol. 2021;69(3):661-665. doi:10.4103/ijo.IJO_253_20
5. Chua J, Chia AR, Chee ML, et al. The relationship of dietary fish intake to diabetic retinopathy and retinal vascular caliber in patients with type 2 diabetes. Sci Rep. 2018;8(1):730. doi:10.1038/s41598-017-18930-6
6. Das T, Jayasudha R, Chakravarthy S, et al. Alterations in the gut bacterial microbiome in people with type 2 diabetes mellitus and diabetic retinopathy. Sci Rep. 2021;11(1):2738. doi:10.1038/s41598-021-82538-0
7. American Academy of Ophthalmology. Diet and Nutrition. Accessed online December 10, 2021.
8. American Diabetes Association. 1. Promoting health and reducing disparities in populations. Diabetes Care. 2017;40(Suppl1):S6-S10. doi:10.2337/dc17-S004