The relationship of plasma concentration and intake of vitamin C was measured in a randomly selected group of 368 apparently healthy adult subjects of two nutritional regimens: traditional mixed diet (general population, n=187) and vegetarians (n=181). The condition of protective plasma concentration over 50 micromol/l (50.3-89.4 micromol/l), the value of which reduces the risk of free radical disease, was found in 87 subjects from the general population group, in whom the average vitamin C intake was 124.2 mg per day in range of 92-181. The recommended dietary allowance for this group in amount of 77 mg of vitamin C daily was calculated from current Slovak recommendations being in amount of 80 mg per day for men and 75 mg for women. Previous epidemiological studies as well as the presented results show that approximately a half of Slovak general population have vitamin C deficient (below 23 micromol/l) or suboptimal (23-50 micromol/l) plasma concentrations with insufficient antioxidative protection. Significantly higher plasma vitamin C concentrations in comparison to non-vegetarians were observed in the vegetarian group. Protective concentrations were noted in 88% of vegetarians vs 46% of non-vegetarians. The significantly reduced values of products of oxidative damage of DNA (DNA breaks with oxidised purines and oxidised pyrimidines), lipids (conjugated dienes of fatty acids, malondialdehyde) and proteins (carbonyls) were found in subjects with plasma vitamin C concentrations being over 50 micromol/l vs. below 50 micromol/l. The data emphasize the role of vitamin C in free radical disease prevention under the condition of protective, antioxidative concentrations. The results of general population group document the need to revise the recommended dietary allowance for vitamin C as well as to change the nutritional habits including regular consumption of fruit and vegetables several times daily (Tab. 3, Ref. 28).