Consumption of essential nutrients in amounts generally considered adequate does not ensure maximal antioxidant capacities. Three week consumption of any of three semipurified, liquid formulas, as a sole nutrition source, depressed values for plasma total antioxidant status (TAS) in renal dialysis patients. Each formula contained the essential nutrients in amounts generally considered adequate, but did not contain major sources of phytonutrients. The fall in TAS values could not be attributed to altered plasma values for vitamin E, B-carotene or uric acid. Therefore, these results suggest that low phytonutrient intake adversely affects antixidant capacities.