Antioxidant supplementation, particularly with vitamin E, was found to reduce the amount of albumin in DKD patients’ urine, according to a recent review and meta-analysis published in PLOS One.
“In this meta-analysis, the researchers found that antioxidant supplementation was associated with significant reductions in albumin excretion,” concluded the researchers from the Institute of Clinical Physiology, Reggio Calabria and the University of Messina.
“This finding is encouraging because pathological urinary albumin excretion (UAE) is an early sign of DKD,” wrote lead author, Davide Bolignano.
However, the overall effect of antioxidant supplements on slowing diabetic kidney disease (DKD) is still little clearer. The researchers defined the primary study outcome as the number of patients needing to start chronic dialysis due to worsening of DKD. Results found no significant difference between intervention and control groups on this measure.
The review’s objective was to see if antioxidant supplementation could slow progression of DKD to end stage kidney disease (ESKD). DKD is recognised as the prime cause of ESKD with around half of long-term diabetics developing some level of renal damage during their lifetime.
Most trials included in the study employed vitamin C and/or vitamin E. However others included vitamin B6, zinc, lipoic acid, reduced glutathione and silymarin. Antioxidants were used either singly or in combination.
None of the antioxidants appeared to make a difference to the primary outcome as explained above. However, researchers had difficulty reaching firm conclusions due to the diversity of outcome measures, study designs, trial sizes and data robustness of the individual trials. Secondary endpoints were more consistently defined and therefore easier to evaluate.
Secondary outcomes in the meta-analysis were changes in UAE and kidney function, which was measured by glomerular filtration rate (GFR). Although antioxidants reduced the amount of albumin in DKD patients’ urine, they did not induce a significant improvement on kidney function.
Most antioxidants showed some degree of benefit in reducing UAE, with vitamin E showing the most consistent effect. Nevertheless, results are far too inconclusive to form the basis of therapy recommendations. Conclusions are further limited by inability to identify individual effects of each component in multi-supplement interventions.
The researchers commented, “Despite cumulative findings point at some benefits of antioxidant therapy (particularly vitamin E) on early signs of renal damage, there is still no robust evidence supporting a widespread use of any of these agents as an alternative (or additive) therapy for retarding diabetic kidney disease progression.”
Source: PLOS One
Volume 12 Issue 6 published online, doi: 10.1371/journal.pone.0178699
“Antioxidant agents for delaying diabetic kidney disease progression: A systematic review and meta-analysis”
Authors: Davide Bolignaro et al