Inhibitory effects of spices and herbs on iron availability.

Spices and herbs are extensively used in indigenous diets in tropical regions where prevalence of iron deficiency is still high. They are rich in polyphenolic compounds that are expected to inhibit iron absorption by forming iron complexes in the intestine, making dietary iron less available for absorption. The effects of six spices and herbs (chili pepper, garlic, 'Pak kyheng' (Thai leafy vegetable), shallot, tamarind, turmeric) and one mixture of spices (curry paste) on iron availability were determined by measuring the percentage dialyzable iron after addition of spices and herbs to a rice meal after simulated digestion. All tested spices and herbs contained from 0.5 to 33 mg polyphenol per meal and were potent inhibitors of iron availability (20-90%), reducing iron availability in a dose-dependent manner--with the exception of tamarind, which at 11 mg polyphenol per meal enhanced iron availability. Our findings demonstrate that culinary spices and herbs can play an important role in iron nutrition.