Diabetes is a metabolic disease that can lead to multiple organ dysfunction and failure. And it can have a particularly detrimental effect on the eyes, including an increased risk of cataract formation. Diabetic cataracts are a main cause of low vision and blindness among hyperglycemia sufferers today — and as instances of diabetes are increasing globally, so too is the prevalence of diabetic cataract disease.
Diabetics have a significantly higher chance of cataract development than non-diabetics. Although surgery is currently the only real treatment option for diabetic cataracts, complications associated with such procedures can cause problems.
To that end, prevention and/or the delay of cataract development is key in managing diabetic eye health. And although multiple factors are involved in the development of diabetic cataracts, it is believed that oxidative stress caused by a hyperglycemic environment is a major contributor to cataract induced lens deterioration.
The Beneficial Properties of Coconut Water
Coconut water is well known for its beneficial health properties. Rich in antioxidants, you don’t have to look far to find products espousing its thirst-quenching and mind and body-nourishing properties. It is one of the fastest growing beverage categories on the planet.
Historically, coconut water has long been used as a medicinal treatment for a multitude of ailments and prescribed for everything from burning pain during urination, to dysuria, gastritis, burning eyes, indigestion and hiccups. It’s even been said to help expel a retained placenta. It was administered intravenously during WWII as a hydration/resuscitation liquid, and is still used for emergency situations in remote areas to this day.
But it’s the active biological ingredients in coconut water that could potentially provide protection from diabetic complications like cataracts. Studies conducted on diabetic rats have shown it can reduce levels of blood glucose and blood lipids, as well as regulate metabolism. Research also indicates that coconut water has antioxidant and anti-thrombotic properties, which can help protect the pancreas, kidney, heart and other organs.
Anti-cataract Effects of Coconut Water on Rats
A recent (2021) study out of China examined the effects of coconut water on cataract development in diabetic rats. It also sought to clarify the anti-diabetic pathogenic mechanism in coconut water.*
Forty-eight laboratory rats were divided randomly into four groups of 12. One group was left as the control, while the others were given a single intraperitoneal injection of 1% streptozotocin in order to induce diabetes. After 72 hours, blood glucose levels were measured and 33 (n=11 in each group) of the injected rats modeled diabetic characteristics.
The control and one of the induced diabetic groups were given a normal rodent chow diet and water. The third (diabetic) group was given a normal rodent chow diet plus coconut water. The final (diabetic) group was given rodent chow, water, and glibenclamide (a commonly prescribed anti-diabetic agent) orally at a dose of 0.6 mg/kg daily.
It should be noted liquids, including coconut water, were available ad libitum, meaning that doses were not regulated in vivo.
A slit lamp was used to monitor lens deterioration bi-weekly and the severity of cataract development was measured using a 5-grade scoring system: 0, clear normal lens; 1, peripheral vesicle; 2, peripheral vesicle plus cortical opacity; 3, diffused central opacity; and 4, mature cataract.
At 16-20 weeks, all lenses in the diabetic control group were graded either 3 or 4. However, diabetic rats treated with glibenclamide or consuming coconut water showed reduced lens opacity (from grade 1-4). Cells cultured simultaneously in vitro showed similar results. Although there was no significant difference in effectiveness between treatment with coconut water and glibenclamide, coconut water appeared to outperform on some measures.
It seems to work, but how?
In vitro observations showed cells treated with 5-10% coconut water resulted in significantly mitigated elevations of MDA (malondialdehyde, a frequently assessed marker of oxidative damage) levels. Coconut water also limited the reduction in the activity of beneficial enzymes SOD (superoxide dismutase) and GSH-Px ( glutathione peroxidase) which are inhibited by a high glucose (hyperglycemic) environment.
Coconut water’s effectiveness against hyperglycemia appears to be due to the presence of certain biologically active compounds. These include ascorbic acid, cysteine, phenolic compounds and L-arginine. These are excellent free radical scavengers and their antioxidant abilities can reduce oxidative stress and help to protect organs.
Given that oxidative stress is a known cause of diabetic cataract progression, this would tend to suggest that coconut water’s antioxidant properties are key to its diabetic disease related preventative prowess.
More Research is Still Needed
Despite such promising results in this first-of-its-kind study, more work must be done to determine the exact mechanism behind coconut water’s apparent success in the fight against diabetic cataract development.
While a 5-10% dose of coconut water proved to have a protective effect on LECs (lens epithelial cells) in an in vitro high glucose environment, further study is required to determine at what concentration coconut water works best, or loses effectiveness (especially in vivo). Higher doses could even result in toxic outcomes, we simply don’t know yet. Additional concentration gradient experiments are required.
*Zhang X, Peng L, Dai Y, et al. Anti-cataract effects of coconut water in vivo and in vitro. Biomed Pharmacother. 2021;143:112032.