Nitrates and nitrites in selected vegetables purchased at supermarkets in Siedlce, Poland.

BACKGROUND Vegetables constitute a vital part of the human diet, being the main source of minerals, vitamins, dietary fibre and phytochemicals. They however, also contain nitrates and nitrites, which adversely affect human health. OBJECTIVE To determine nitrate and nitrite content in selected vegetables purchased at supermarket chains in Siedlce and to assess their impact on consumer health. MATERIAL AND METHODS Vegetable samples were purchased from local supermarkets in Siedlce, town situated in the Mazovian province (Voivodeship) of Poland. These consisted of 116 samples of nine vegetables types including butterhead and iceberg lettuce, beetroot, white cabbage, carrot, cucumber, radish, tomato and potato collected between April and September 2011. Concentrations of nitrate and nitrite were determined by standard colorimetric methods used in Poland, with results expressed as mg per kg fresh weight of vegetables. RESULTS Nitrate concentrations varied between 10 mg x kg(-1) to 4800 mg x kg(-1). The highest mean nitrate concentrations were found in radishes (2132 mgkg(-1)), butterhead lettuce (1725 mg x kg(-1)), beetroots (1306 mg x kg(-1)) and iceberg lettuce (890 mg x kg(-1)), whereas the lowest were found in cucumber (32 mg x kg(-1)) and tomato (35 mg x kg(-1)). Nitrite levels were also variable; the highest concentrations measured were in beetroot (mean 9.19 mg x kg(-1)) whilst much smaller amounts were present in carrot, cucumbers, iceberg lettuce, white cabbage, tomatoes and potatoes. The daily adult consumption of 100 g amounts of the studied vegetables were found not exceed the ADI for both nitrates and nitrites. CONCLUSIONS Findings indicated the need for monitoring nitrate and nitrite content in radishes, butterhead lettuce and beetroot due to consumer health concerns.