Phytic acid content may affect starch digestibility and glycemic index value of rice (Oryza sativa L.).

BACKGROUND: Phytic acid (PA) is an anti-nutrient present in cereals and pulses. It is known to reduce mineral bioavailability and inhibit starch-digesting α-amylase (which requires calcium for activity) in the human gut. In principle, the greater the amount of PA, the lower is the rate of starch hydrolysis. It is reflected in the lower glycemic index (GI) value of food. People leading sedentary lifestyles and consuming rice as a staple food are likely to develop type 2 diabetes. Hence, this study was planned to understand how PA content of different rice varieties affects the GI. RESULTS: Rice Khira and Mugai which had very low PA (0.30 and 0.36 g kg-1 , respectively) had higher GI values and α-amylase activity, while Nua Dhusara and the pigmented rice Manipuri black rice (MBR) which had high PA (2.13 and 2.98 g kg-1 , respectively) showed low α-amylase activity and GI values. This relationship was statistically significant, though a weak relationship was found for the pigmented rice. Expression levels of MIPSI, IPKI and GBSSI markedly increased in the middle stage of grain development in all of the six genotypes having contrasting PA and GI. Maximum expression of MIPSI and IPKI was observed in Nua Dhusara and MBR (which had high PA) while that of GBSSI was observed in Khira and Mugai (with higher GI) at middle stage showing a negative correlation between PA and GI. CONCLUSIONS: The data indicate that high PA content in rice might have an adverse effect on starch digestibility resulting in slower starch digestion in the human gut and consequently low glycemic response. © 2019 Society of Chemical Industry.

Phytic acid: Blessing in disguise, a prime compound required for both plant and human nutrition.

Phytic acid (PA), [myo-inositol 1,2,3,4,5,6-hexakisphosphate] is the principal storage compound of phosphorus (P) and account for 65%-85% of the seeds total P. The negative charge on PA attracts and chelates metal cations resulting in a mixed insoluble salt, phytate. Phytate contains six negatively charged ions, chelates divalent cations such as Fe2+, Zn2+, Mg2+, and Ca2+ rendering them unavailable for absorption by monogastric animals. This may lead to micronutrient deficiencies in humans since they lack the enzyme phytase that hydrolyzes phytate and releases the bound micronutrients. There are two main concerns about the presence of PA in human diet. The first is its negative impact on the bioavailability of several minerals and the second is the evidence of PA inhibiting various proteases essential for protein degradation and the subsequent digestion in stomach and small intestine. The beneficial role of PA has been underestimated due to its distinct negative consequences. PA is reported to be a potent natural plant antioxidant which plays a protective role against oxidative stress in seeds and preventive role in various human diseases. Recently beneficial roles of PA as an antidiabetic and antibacterial agent has been reported. Thus, the development of grains with low-PA and modified distribution pattern can be achieved through fine-tuning of its content in the seeds.