Recent studies have revealed the biological effects of H2 in suppressing organ injuries due to acute inflammation and oxidative stress. Dahl salt-sensitive (SS) rats naturally develop elevated blood pressure (BP) and kidney injury with aging. The present study examined the effect of long-term supplementation of H2 in drinking water on age-related changes.Four-week-old male Dahl SS rats were fed 3 types of water (n = 30 each) for up to 48 weeks: filtered water (FW), water with a high H2 content (492.5 ppb) obtained with water electrolysis (EW), or dehydrogenated EW (DW). Animals were subjected to histological analysis at 16, 24, and 48 weeks.The FW group showed progressive BP elevation and increases in albuminuria and cardiac remodeling during the course of treatment. Histologically, there were significant changes as a function of aging, i.e., glomerular sclerosis with tubulointerstitial fibrosis in the kidney, and increased cardiomyocyte diameter with interstitial fibrosis in the heart at 48 weeks. These changes were related to the enhanced inflammation and oxidative stress in the respective organs. However, there were no striking differences in BP among the groups, despite histological alterations in the EW group being significantly decreased when compared to FW and DW in both organs, with concurrently lower oxidative stress and inflammatory markers at 48 weeks. Long-term ad libitum consumption of H2-enriched electrolyzed water can ameliorate the processes of kidney injury and cardiac remodeling with aging in Dahl SS rats by suppressing, at least partly, elevated inflammation and oxidative stress.