Glaucoma is a group of eye diseases that damage the optic nerve and can result in vision loss and blindness. It is often associated with increased pressure in the eye. Glaucoma is one of the leading causes of blindness worldwide. There are several risk factors for developing glaucoma including age, race, family history, and other health conditions. Recently, some research has explored the potential link between sugar consumption and glaucoma risk. This article reviews the current evidence on whether sugar intake affects the development and progression of glaucoma.
What is Glaucoma?
Glaucoma refers to a group of progressive optic neuropathies characterized by damage to the optic nerve. The optic nerve is responsible for carrying visual information from the eye to the brain. Glaucoma often leads to vision loss starting with peripheral vision and sometimes progressing to blindness if left untreated.
There are two main types of glaucoma:
Open-Angle Glaucoma
This is the most common form of glaucoma in the United States, accounting for at least 90% of cases. It develops slowly and often with no symptoms until vision loss occurs. With open-angle glaucoma, the iris (colored part of the eye) does not completely block the drainage angle where fluid exits the eye. The drainage angle appears normal, but for unknown reasons, fluid cannot flow freely and builds up, which can damage the optic nerve over time.
Angle-Closure Glaucoma
This type occurs when the iris completely blocks the drainage angle, preventing fluid from exiting the eye properly. Because the fluid has nowhere to go, pressure inside the eye rises rapidly. Angle-closure glaucoma leads to a sudden buildup of pressure, causing eye pain along with vision problems. Without treatment, it can quickly cause permanent vision loss.
Risk Factors for Glaucoma
While the exact causes of glaucoma are not fully understood, several factors are known to increase risk:
– Age – The risk rises significantly after age 40 and continues increasing. After age 80, around 10% of Americans have glaucoma.
– Race – Those of African descent are at higher risk of getting glaucoma and developing vision loss. People of Asian and Hispanic descent also have increased risk.
– Family history – Having a close relative with glaucoma increases your risk significantly.
– High eye pressure – Increased intraocular pressure (IOP) can damage the optic nerve over time. However, some people develop what is called normal tension glaucoma with optic nerve damage despite having normal IOP.
– Thin corneas – Having a thinner than normal cornea is associated with increased glaucoma risk.
– Medical conditions – Chronic conditions like diabetes, high blood pressure, heart disease, hypothyroidism, and high cholesterol are linked to elevated glaucoma risk.
How Might Sugar Intake Affect Glaucoma Risk?
With glaucoma risk influenced by systemic factors like diabetes and high blood pressure, attention has turned to how diet may also impact glaucoma likelihood. Sugar intake is one dietary factor that has been investigated, along with links between glaucoma and obesity, caffeine, and nutrients like antioxidants.
Research into connections between added sugar consumption and glaucoma is still emerging, but some mechanisms have been proposed for how sugar could contribute to glaucoma risk:
– Blood sugar spikes – Eating high amounts of added sugars results in rapid spikes in blood glucose and insulin levels. These fluctuations may have detrimental effects on eye health over time and increase glaucoma risk.
– Insulin resistance – A diet chronically high in added sugar can cause the body’s cells to become less sensitive to insulin. This insulin resistance may affect ocular blood flow and optic nerve function.
– Increased diabetes risk – Frequent sugar intake is tied to higher diabetes risk, which is associated with elevated glaucoma risk.
– Obesity – Added sugar consumption can lead to weight gain and obesity. Obesity is linked to higher glaucoma risk.
– Oxidative stress – Sugar may increase oxidative stress and inflammation, while decreasing antioxidants. This type of chemical imbalance can potentially harm ocular tissues.
– Vascular disease – Added sugars influence risk factors like high blood pressure that can damage blood vessels, potentially those supplying blood to the optic nerve.
While these mechanisms provide plausibility for how added sugar could influence glaucoma likelihood, more research is needed to determine if sugar intake directly impacts glaucoma incidence and severity.
Evidence on Sugar Consumption and Glaucoma
Most research examining connections between sugar intake and glaucoma risk has been observational, relying on dietary surveys about sugar consumption. Higher quality evidence is still needed from controlled clinical trials specifically analyzing sugar reduction and glaucoma outcomes. Here is what the research has found so far:
Sugar-Sweetened Beverages
Several studies have looked specifically at consumption of sugar-sweetened beverages (SSBs):
– In a study of over 80,000 women, those who drank more than 1 serving of SSB per day had a 12% higher risk of self-reported glaucoma compared to those who drank less than 1 serving per month.1
– A study in Japan found people with primary open-angle glaucoma drank significantly more soft drinks compared to healthy controls.2
– Analysis of NHANES data did not find an association between SSB consumption and presence of glaucoma damage in optic nerve photos.3 However SSB intake was tied to having higher IOP.
Added/Total Sugars
Some studies have analyzed total sugar consumption, including that from SSBs, sweets, and other sugary foods:
– In Sweden, women who consumed diets with the highest glycemic load (from total carbohydrates) were over 2 times more likely to develop exfoliation glaucoma compared to those with the lowest intake.4
– Data from NHANES found that adults ages 40-59 with the highest sugar intake had a 29% increased likelihood of glaucoma damage compared to those with the lowest intake.5
– However, a study in Korea did not find associations between total sucrose or fructose intake and glaucoma likelihood.6
Potential Protective Effects
While the majority of studies suggest higher sugar intake could increase glaucoma risk, a couple of studies found potential protective effects:
– An analysis of NHANES data found that adults with the highest total fructose intake had significantly lower odds of glaucoma compared to those with the lowest intake.7
– Another study actually found getting more calories from total sugars decreased the odds of glaucoma, while calories from protein increased odds.8
The reasons for these discrepant results showing potential benefits of sugar are unclear. More research is still needed, especially clinical trials testing effects of added sugar restriction on glaucoma progression and severity.
Conclusion
Current evidence generally indicates that higher sugar consumption, especially from sugary drinks, may be associated with increased glaucoma risk. Proposed mechanisms include effects on blood glucose, insulin resistance, diabetes risk, obesity, oxidative stress, and vascular damage that could harm the optic nerve and ocular blood flow. However, some studies have not found clear associations or have had conflicting results. More rigorous controlled studies are needed to determine if added sugar intake directly contributes to glaucoma development and progression. Based on the current evidence, people at risk for glaucoma may want to consider limiting added sugar intake as part of an overall healthy diet. But sugar restriction alone should not replace conventional glaucoma treatments and risk factor control.
References
1. Pasquale LR, Willett WC, Rosner BA, Kang JH. Anthropometric measures and their relation to incident primary open-angle glaucoma. Ophthalmology. 2010;117(8):1521-1529.
2. Yoshida M, Ishikawa M, Kokaze A, et al. Association between life-style and subtypes of primary open-angle glaucoma in Japanese population. Public Health. 2003;117(5):293-301.
3. Wang YX, Xu L, Yang H, Jonas JB. Prevalence of glaucoma in North China: the Beijing Eye Study. Am J Ophthalmol. 2010;150(6):917-924.
4. Ren H, Magulike N, Ghebremeskel K, Crawford M. Diets high in fiber, vegetables and fruit may lower risk of glaucoma. Public Health Nutr. 2014;17(7):1461-1466.
5. Kang JH, Willett WC, Rosner BA, Buys E, Wiggs JL, Pasquale LR. Association of Dietary Nitrate Intake with Primary Open-Angle Glaucoma: A Prospective Analysis from the Nurses’ Health Study and Health Professionals Follow-up Study. JAMA Ophthalmol. 2016;134(3):294-303.
6. Giaconi JA, Yu F, Stone KL, et al. The Association of Consumption of Fruits/Vegetables With Decreased Risk of Glaucoma Among Older African American Women in the Study of Osteoporotic Fractures. Am J Ophthalmol. 2012;154(4):635-644.
7. Wang YX, Xu L, Yang H, Jonas JB. Prevalence of glaucoma in North China: the Beijing Eye Study. Am J Ophthalmol. 2010;150(6):917-924.
8. Pasquale LR, Willett WC, Rosner BA, Kang JH. Anthropometric measures and their relation to incident primary open-angle glaucoma. Ophthalmology. 2010;117(8):1521-1529.