Fytáty

Phytic acid (myoinositol hexaphosphate)

Zdroje

• Unrefined cereals
• Seeds
• Nuts
• Legumes
• Some fruits
• Tubers [1]

Vlastnosti fytátů

• Complexes with divalent cations
• Insoluble compounds in the intestine
• Negative impact on the absorption of
• Zinc
• copper
• Manganese [1]
• Hexa- and penta-phosphate esters of inositol inhibuje absorbci:
• Zinc [1]
• Inositol esters with fewer phosphate groups
• Probably limited effect [1]

Degradace fytátů

• Endogenous phytases during fermentation
• Eg
• Leavened bread [1]
• Endogenous phytases during germination
• Eg
• Bean sprouts [1]
• Thermal processing
• Partial nonenzymatic hydrolysis of phytate in some foods [1]

Poměr fytátů / Zn absorpce

• Inhibitory effect of phytates on zinc absorption
• Quantified by the millimolar ratios of phytate / zinc in the diet
• Ratios < 12
• Little effect on zinc bioavailability
• 15- 20 critical molar ratios
• Ratios nad 20
• Associated with zinc deficiency [1]

Potenciace inhibičního vlivu fytátů na absorpci Zn

• Zinc-calcium-phytate complex
• In the intestinal lumen
• Even less soluble than are zinc-phytate complexes [1]
• Millimolar ratios of (phytate x calcium) / zinc
• May be a better predictor of zinc bioavailability
• Critical millimolar ratio > 22 may induce marginal zinc deficiency [1]

Literatura