The High Blood Sugar Connection to Eye Diseases

By Brenna Thompson, MS, RD, LD
February 1, 2017

article_other_eye.jpgBefore starting with Nutritional Weight & Wellness, I never would have guessed my morning bowl of Kashi cereal with skim milk and a banana could lead me down a road towards cataracts, glaucoma or macular degeneration.

But now I know that these "healthy" foods were actually setting me up for a blood sugar rollercoaster. Each of these foods (cereal, skim milk and even the banana) is high in carbohydrates, which break down into sugar in the bloodstream. When carbohydrates are eaten in the right amounts and come from unprocessed foods (fruits, veggies and beans), just the right amount of insulin is released.

However, when too much carbohydrate or sugar is consumed, the body releases too much insulin. Excess sugar and insulin cause inflammation and are very damaging to blood vessels—including the tiny blood vessels in our eyes. Read on to learn more about the high blood sugar connection to eye diseases.


A cataract is a clouding of the lens in the eye. The lens is normally clear and used to bring objects into focus by changing their shape from very flat to round. There are several different types of cataracts, but the most common is age related. Just like hair and nails, the lens of the eye continually breaks down and regenerates, and over time its ability to do so diminishes. High blood sugars can lead to swelling within the lens, creating bubble-like pockets known as vacuoles. Imagine trying to look through a pair of binoculars with water spots on it; you will never be able to focus enough to see clearly. 

Surgery is often the go-to solution for people with advanced cataracts. However, according to Dr. Richard Bernstein, author of Dr. Bernstein’s Diabetes Solution, many of his diabetic clients with cataracts have improved their eyesight simply by eating a low-carbohydrate diet that results in normal blood sugar levels. This does not mean that high sugar foods should be replaced with “sugar free” alternatives. In Your Body’s Sign Language, Certified Clinical Nutritionist James McAfee writes that sorbitol, a sugar alcohol used in many sugar free foods, has been shown to increase blood vessel damage in people with diabetes. Just one more reason to focus on eating real foods!

Macular Degeneration

The leading cause of blindness in older adults is age-related macular degeneration (AMD). The macula is located at the back of the eye and works to bring images into focus. If the macula becomes damaged, people may find it difficult to recognize faces, read small print, or participate in activities such as sewing or fixing small objects. Family history, smoking, and high blood pressure are known causes of macular degeneration.

The first symptom of macular degeneration is a blurry spot in the center of a person's vision. Objects may also appear dull. Sometimes people feel as though they need more light to read a book than they did previously. While there is no cure for macular degeneration, high dose supplements of vitamins C, E, A, and zinc have been shown to slow the progression from the initial dry macular degeneration to the advanced wet macular degeneration. Approximately 10 percent of people progress from dry to wet macular degeneration. Wet macular degeneration occurs as damaged blood vessels begin to leak into the macula causing increased inflammation and swelling.

Studies have shown that people who eat diets high in leafy green vegetables and fatty fish are less likely to develop macular degeneration. To keep my blood sugars balanced between meals, I eat tasty snacks such as tuna salad served in a lettuce cup, or salmon deviled eggs with a side of broccoli salad.


Glaucoma is the second leading cause of blindness in the United States. A small study found that people with diabetes were at higher risk for optic neuropathy (damage to the optic nerve) and glaucoma. The most common form is known as open-angle or chronic glaucoma and is caused by increased pressure within the eye which damages the optic nerve that connects the eyes to the brain. Inside the eye, a clear fluid called aqueous humor needs to leave through a small channel in the front of they eye as more is made. If it cannot drain, the fluid will build up causing an increase in pressure within the eye. At first, most people have no symptoms, but over time they begin to experience tunnel vision as the nerves are damaged. Treatment typically consists of eye drops which decrease pressure in the eye.

How does glaucoma relate back to blood sugar? High blood sugars and excess insulin constrict blood vessels. The smaller the vessel, the higher the pressure exerted by the blood pushing through. Constricted blood vessels in the drainage channel make it difficult for the aqueous humor to drain. This chain of events leads to increased pressure within the eye, ultimately damaging the optic nerve.

Prevention is the prescription

Instead of waiting for your eyesight to deteriorate, take charge of your health and begin to eat foods that can prevent these age-related diseases. If you have elevated blood sugars or high blood pressure, begin eating a lower carbohydrate diet that focuses on vegetable carbs instead of processed carbs. Vegetables are naturally high in eye-protecting nutrients, including Vitamins A, C, and E. These important antioxidants can reduce inflammation and help preserve your sight. Instead of a big bowl of cereal for breakfast, try one of my new favorites, a big bowl of leftover stir-fry.

Many of my clients use a variety of supplements to preserve good eyesight. Nutrients that I recommend include alpha lipoic acid, lutein, lycopene and bilberry. All of these are found in the supplement 4Sight by Ortho Molecular. Just two capsules per day provide all of these antioxidants and other nutrients to protect your vision.  I also recommend that my clients take Omega 3-DHA. This Omega-3 fatty acid is identical to the fats that are found in your eyes.

Other steps towards better eye health include not smoking, limiting alcohol intake and wearing UV-blocking sunglasses.

Have you tried to give up sugar in the past without success?  Curb the cravings and improve health with our online class Breaking the Sugar Habit!

Enroll Today

For more information on the topic of eye health, listen to our Dishing Up Nutrition podcast: Dry Eye and Macular Degeneration.

About the author

Brenna loves nutrition and its life-changing effects. With an active lifestyle, she knows firsthand how to use the power of good nutrition to stay energized. She is a registered dietitian and licensed dietitian through the Minnesota Board of Dietetics and Nutrition. She received her B.S. in dietetics from Minnesota State University, Mankato, and completed her dietetic internship at West Virginia University Hospital, Morgantown. Brenna also received a M.S. in applied nutrition, with an emphasis on education, from Northeastern University. She worked as a clinical and wellness dietitian for the Phoebe Putney Memorial Health System in Albany, Georgia.

View all posts by Brenna Thompson, MS, RD, LD

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