Carnosine for Cataracts: Evidence Assessment
There is currently no convincing evidence that carnosine or N-acetylcarnosine (NAC) effectively prevents or reverses cataracts. 1
Current Evidence Overview
The Cochrane systematic review from 2017, which represents the highest quality evidence available, found insufficient data to support the use of N-acetylcarnosine for age-related cataracts. The review identified only two potentially eligible studies but could not obtain sufficient information to reliably determine how these studies were designed and conducted 1.
Proposed Mechanisms of Action
Several mechanisms have been proposed for how carnosine might theoretically help with cataracts:
- Anti-glycation properties: Carnosine appears to be a potent inhibitor of advanced glycation end product formation, which may be particularly relevant for diabetic cataracts 2
- Antioxidant effects: Some studies suggest carnosine may protect lens proteins from oxidative damage, though its direct antioxidant properties are described as weak 2
- Protection against lipid peroxidation: Cataracts are associated with increased lipid peroxidation products in lens tissue, and carnosine may potentially protect against this damage 3, 4
Laboratory and Animal Studies
Laboratory research has shown some promising results:
- In vitro studies demonstrated that L-carnosine has anti-glycation properties that could theoretically inhibit cataract formation 2
- Porcine lens studies showed that treatment with 20 mM L-carnosine dramatically inhibited advanced glycation end product formation in high galactose media 2
- Some animal studies have suggested preventive effects of carnosine on cataract development 5
Clinical Evidence
Despite theoretical promise, clinical evidence is severely lacking:
- The 2017 Cochrane review could not find sufficient reliable evidence to support NAC use 1
- While some researchers have claimed that NAC eye drops produce "effective, safe and long-term improvement in sight" 3, these claims have not been validated by high-quality clinical trials
- There are no well-designed randomized controlled trials with standardized outcomes to support efficacy claims
Important Considerations
Safety Profile
The available evidence does not suggest significant toxicity concerns:
- MTT cytotoxicity assays on human lens epithelial cells did not show significant decreases in cell viability compared to negative controls 2
- However, long-term safety data from well-designed clinical trials are lacking
Formulation Considerations
If considering NAC despite limited evidence:
- N-acetylcarnosine appears to have better corneal penetration than L-carnosine 4
- Some researchers suggest combining NAC with other compounds like carboxymethylcellulose to improve intraocular absorption 4
Recommendations for Clinical Practice
- Do not recommend carnosine or NAC as a primary treatment for cataracts
- Surgery remains the only proven effective treatment for cataracts
- If patients inquire about carnosine supplements:
- Inform them about the lack of convincing clinical evidence
- Emphasize that the Cochrane review found insufficient data to support its use
- Explain that high-quality clinical trials are needed before recommendations can be made
Common Pitfalls to Avoid
- Marketing claims vs. evidence: Many NAC products make bold claims about cataract reversal that are not supported by high-quality evidence
- Delayed surgical intervention: Patients may delay seeking proven surgical treatment while trying unproven alternatives
- Financial burden: Patients may spend significant money on products with unproven efficacy
Future studies on carnosine for cataracts should be randomized, double-masked, placebo-controlled trials with standardized quality of life outcomes and validated measures of visual acuity, contrast sensitivity, and glare 1.