A gradual increase in blood pressure (BP), often attaining hypertensive levels, is common during aging--"age-related hypertension." Therefore, means to prevent or ameliorate this elevated BP safely are important. Although oral B-nicotinamide adenine dinucleotide (NADH), a natural coenzyme, is used principally to treat various neurologic disorders, we wished to investigate whether this agent had the same potential to lower BP and benefit the cardiovascular system as does coenzyme Q10, a similar-type agent. As a first approximation, spontaneously hypertensive rats (SHR) were used to determine effects of oral NADH. In a blinded, placebo-controlled study, ten rats received placebo; and ten, NADH for ten weeks. Systolic BP was measured by tail plethysmography. Blood was collected terminally, and chemistries were performed by routine methodologies. Thiobarbituric acid reactive species (TBARS) (an estimate of lipid peroxidation/free radical formation) was measured in renal and hepatic tissues. The following was noted: water and food intake were comparable, and the steady weight gain of young SHR were similar in the placebo and NADH groups. Although systolic BP did not differ between the two groups over the first month, it decreased and stayed markedly lower for the remainder of study in SHR receiving oral NADH. At the end of 60 days, SBP in NADH-treated SHR was 184 mm Hg +/- 2.8 (SEM) compared to 201 mm Hg +/- 2.1 (SEM) in control SHR (p < 0.001). No significant differences were seen in blood levels of glucose, insulin, triglyceride, and HDL levels but NADH intake lowered total cholesterol (p < 0.002) and LDL (p < 0.02). Renal TBARS were also significantly lower in SHR receiving NADH (P < 0.001). Accordingly, supplementation with the natural coenzyme NADH theoretically could prove to be useful in preventing age-related increases in BP and, thus, various cardiovascular maladies.