Nutrient Composition and Heavy Metals Content of Three Leafy Vegetables ( Amaranthus Cruentus L., Lactuca Sativa L., Solanum Macrocarpon L.) in Porto-Novo, Republic of Benin

Abstract

The interest of leafy vegetables has increased in recent years, mainly because of health benefits due of their nutritional compounds. Knowledge of the nutrients of vegetables is necessary to better value them in the diet of the population. The aim of this study was to determine the nutrients of three green leafy vegetables cultivated and consumed at Porto-Novo. For this purpose, using standard methods, carbohydrates, protein, fat, crude fibre, ash, calcium, potassium, magnesium, iron and zinc were determined in 24 samples of Amaranthus cruentus L., Solanum macrocarpon L. and Lactuca sativa L. and were compared. Also, heavy metals (Pb, Cd) contents of these vegetables and of soils were compared. The significant difference between nutrients of leafy vegetables was tested by ANOVA. Lactuca sativa L. has the highest water content, Amaranthus cruentus L. has the highest content of proteins, ash, fibre, zinc, calcium and potassium while the Solanum macrocarpon L. has the highest content of fat and iron. Solanum macrocarpon L. has the highest lead content while Amaranthus cruentus L. has the highest cadmium content. These results show that leafy vegetables could provide an important part of nutritional requirements for the adequate protection against diseases. The results suggest that Amaranthus cruentus L. has the high content of nutrients followed by Solanum macrocarpon L. and Lactuca sativa L.. Cadmium and lead found in vegetables of this study in Porto-Novo must be monitored and managed to prevent adverse consequences on human health.