Spices as influencers of body metabolism: an overview of three decades of research

The safety of the consumption of spices - turmeric, red pepper and black pepper and their respective active principles was established in animal studies by observing the influence on growth, organ weights, nitrogen balance and blood constituents upon feeding at levels close to human intake as well as upto 100-times the normal human intake. Exhaustive animal studies documented the beneficial influence of turmeric/curcumin, red pepper/capsaicin, and garlic on lipid metabolism, especially anti-hypercholesterolemic effect of the three spices and anti-lithogenic effect of curcumin and capsaicin. The anti-diabetic effects of turmeric/curcumin, onion and cumin seeds were also evidenced with particular ameliorative influence of curcumin and onion on diabetic nephropathy. The antioxidant effects of curcumin (of turmeric), capsaicin (of red pepper) and eugenol (of clove) were evidenced both in in vitro and in vivo systems and the consequential health beneficial anti-inflammatory influence in experimentally induced arthritis was documented. The mechanism of digestive stimulant action of common spices examined in experimental animals revealed to be mediated through phenomenal stimulation of bile secretion with an enhanced bile acid concentration (ingredients essential for fat digestion and absorption) and an appropriate stimulation of the activities of digestive enzymes of pancreas and small intestine. The protective influence of hypolipidemic spices - curcumin, capsaicin and garlic on the altered fluidity of erythrocytes under hypercholesterolemic situation was evidenced in experimental animal models. Antioxidant spices were also shown to greatly reduce LDL-oxidation and also modulate the synthesis of prostaglandins and leukotrienes. Several spices or their extracts were also found to beneficially inhibit platelet aggregation. All these observations strongly indicate that many spices and their active principles are excellent nutraceuticals. (C) 2004 Elsevier Ltd. All rights reserved.