Nitrogen fertilizers and the amount of vitamins in plants: A review

Effect of mineral fertilizers on the vitamin content of plants has received very little attention by scientists in English‐speaking countries, especially in recent years. A review of the literature, however, has revealed a rich source of information mostly published in non‐English journals. Based on these reports, nitrogen fertilizers, especially at high rates, seem to decrease the concentration of vitamin C in many different fruits and vegetables, among them potatoes, tomatoes and citrus fruits, the major sources of this vitamin in human nutrition in many societies. Nitrogen fertilizers are also shown to increase the concentrations of carotenes and vitamin B₁ in plants. Since excess use of nitrogen fertilizers increases the concentration of NO₃ in plant foods and simultaneously decreases that of ascorbic acid, a known inhibitor for the formation of carcinogenic N‐nitroso compounds from nitrite, it appears that the use of these fertilizers may have a double negative effect on the quality of food plants. Vitamin C and several carotenoids have antioxidant properties and reportedly reduce the risk of cardiovascular diseases and some forms of cancer. Whether long‐term consumption of food plants grown with excess use of nitrogen fertilizers would have an overall positive or negative effect on the total intake of antioxidative vitamins by consumers warrants investigation.