Anti-nutritional factors, their adverse effects and need for adequate processing to reduce them in food

Abstract

Anti-nutritional factors are compounds found in most food substances which are poisonous to humans or in some ways limit the nutrient availability to the body thus preventing optimal exploitation of the nutrients present in food and decreasing its nutritive value. Anti-nutritional factors are present in different food substances in varying amounts depending on the kind of food. Many anti-nutrients (oxalate, phytate etc) and toxic substances (cyanide, nitrate, phenols etc) are present in many plants and vegetables. Cassava for example contains high levels of cyanide, a respiratory poison. Anti-nutrients in plant foods are responsible for deleterious effects related to the absorption of nutrients and micronutrients. For example phytic acid, lectins, tannins, saponins, amylase inhibitors and protease inhibitors have been shown to reduce the availability of nutrients and cause growth inhibition. However when used at low levels phytate, lectin, tannins, amylase inhibitors and saponins have also been shown to reduce the blood glucose and insulin responses to starchy foods and/or the plasma cholesterol and triglyceride. Anti-nutrients can be divided into two groups viz heat-stable group (phytic acid, tannins, alkaloids, saponins, non-protein amino acids etc) and heat labile group (lectins, cynogenic glycosides, protease inhibitors and toxic amino acids etc). Due to the presence of several anti-nutritional factors legumes possess low protein digestibility. Most of the toxic and anti-nutrient effects of these compounds in plant foods can be removed by several processing methods such as soaking, germination, boiling, autoclaving, fermentation, genetic manipulation and other processing methods without altering the nutritional value of food.