The importance of low carbohydrate diet (LCD) has been emphasized across the world, in which Dr. Bernstein has contributed much for continuous glucose monitoring (CGM) [1]. LCD seems to be adequate diet therapy for diabetes, obesity and metabolic syndrome (Met-S) associated with the benefits of ketone bodies [2]. We have to consider the background and practical aspects of LCD in different situations [3].

In Western countries, they usually have bread for years. In contrast, people in Eastern or Asian countries have rice or noodle for traditional habit. Generally, 75g of carbohydrate is equally to 196g of cooked rice with 62% water ratio, and 409g of porridge with same calorie of 82% moisture. For the protocol of the clinical research, participants were asked to eat cooked rice 196g vs porridge 409g in the morning on an empty stomach [4]. Compared to the former, the latter was more quickly digested and absorbed, causing a rapid rise in postprandial blood glucose levels. This is thought to be due to the rate of starch digestion. When the glycemic index (GI) was measured, the former was set at 100, while the latter showed a very high value of 146.

From these results, porridege with higher moisture seems to show higher GI value. Then, the rice with less moisture (harder rice, or brown rice) is probably show lower GI. However, related research has shown the opposite results. As usual rice showed 100 of GI, hard rice with 54% moisture has 122 of GI. The reason would be the misunderstanding for the moisture of the rice. One of the probable answer would be the number of chews. Alpha-amylase, a starch-digesting enzyme, is less able to break down hard rice than regular cooked rice. Then, it theoretically results in a lower blood glucose rise. As a study, the chewing rate of rice was controlled, varying between 15 and 30 times per mouthful. Chewing 30 times resulted in a significantly higher post-prandial blood glucose response and increased peak blood glucose levels. As a result, the GI value also increased from 68 to 88 [5]. The number of chews observed in this study was higher in participants who unconsciously ate hard rice. The results were 10 chews per 10g mouthful for porridge, 20 chews for rice, and 35 chews for hard rice.

From these results, the following inference can be made [6]. The more times chewing develops, the longer the time the food comes into contact with alpha-amylase in the mouth. This is thought to have led to the conclusion that hard rice develops hyperglycemia than regular rice. Therefore, making rice hard is not very effective for blood glucose control. On the other hand, it is thought that swallowing rice without chewing would be the best way to prevent hyperglycemia after eating. Our diabetes team has collected valuable data from clinical practice and research until now. Among our medical staff, a 59-year-old female with type 2 diabetes (T2D) as a registered nurse, underwent CGM. Various hyperglycemic conditions were investigated depending on the food intake a day, as shown in Figure 1.

Figure 1: CGM Data with Post-Prandial Hyperglycemia.

It has long been said that brown rice, rather than white rice, is more effective in controlling post-prandial hyperglycemia. Indeed, brown rice contains more dietary fiber and lipids, and theoretically has a greater effect in controlling blood glucose than white rice, which contains only starch. Comparing previously published data, the GI value is 67.4 for white rice and 61.5 for brown rice [7]. Furthermore, germinated brown rice has a lower GI value of 56.9. However, this argument is not so simple. To continue chewing corn, potatoes, and apples more frequently will increase post-prandial hyperglycemia. In other words, it has been stated that a simple way to reduce post-prandial hyperglycemia would be to swallow without chewing [8]. Consequently, the benefits of chewing thoroughly are extremely important rather than just considering hyperglycemia.

Comparative study was performed between white rice (WR) and rice cake (RC) [9]. The participants felt that RC as more springy and sticky than WR. The RC was chewed more per bite and consumed faster than WR. The glucose response for RC was significantly higher for 0-30 min and lower in the later (30-120 min) postprandial period compared to WR. The brown rice has been a whole-grain food which is often assumed to show lower glycemic index (GI) compared to WR [10]. Some studies objectively confirmed clinical effect of a brown-rice diet on glycemic control and metabolic parameters in comparison with the WR diet.

Even brown rice, once mashed, has the same hyperglycemic effect as WR [11]. It has been shown that cooking brown rice with twice the amount of water has the same hyperglycemic effect as WR. Furthermore, multigrain rice cooked with barley (rolled barley) and other grains can be expected to have the effect of slowing post-prandial hyperglycemia due to the action of water-soluble dietary fiber such as beta-glucan. The relationship among chewing, GLP-1 secretion, postprandial blood glucose and insulin levels, was examined. Chewing a single bite 30 times did not affect blood glucose or serum insulin levels, but increased plasma active GLP-1 levels [12].

Cooking rice with oil can also be beneficial, because the oil coats the starch and slows its digestion. Adding oils, especially coconut oil and ghee (clarified butter), can increase the amount of starch that is difficult to digest [13]. Fried rice coats the rice grains with oil, making it harder for enzymes to access the starch, resulting in slower digestion [14]. This has led to studies showing that fried rice is digested more slowly and has a lower GI than regular cooked rice [15].

Recently, clinical importance of hyperglycemia has been known [16]. Lots of consumers are interested in food with lower GI and higher indigestible carbohydrate content. The research was carried out to investigate the effect of digestibility on cooked WR with turmeric and garlic powders [17]. As a result, rice with turmeric power revealed reduced digestibility with lowered rapidly digestible starch (RDS) as 41.5 % vs 57.6 % in WR. Furthermore, elevated slowly digestible starch as 36.1 vs 29.4% in WR, and resistant starch (RS) fraction as 22.6% as WR 14% were observed. Generally, both spices could inhibit starch digestion as a potential ingredient for lowering starch digestibility.

Certain food ingredients can be added to rice to decrease post-prandial hyperglycemia. For example, adding turmeric as a spice when cooking rice reduces starch digestibility. Compared to regular rice, turmeric-added rice had a significantly lower proportion of RDS, while the proportions of slowly digestible starch (SDS) and resistant starch (RS) increased [18]. By applying self-emulsifying delivery systems (SEDSs), curcumin instant rice (CIR) can be produced. CIR can increase slowly digestible starch to 26.4-28% following steamer steaming (SST) associated with elevated anti-oxidant activity [19]. The comparison among RDS, SDS, and RS is summarized in Figure 2.

Figure 2: The comparison among RDS, SDS, and RS.

Similarly to turmeric, saffron has also produces yellow rice such as paella in Spanish dishes, and it has the effect of suppressing blood glucose. Saffron includes physiologically active elements as safranal, crocin and crocetin [20]. Then, saffron has been known for its clinical efficacy of anti-diabetic properties [21]. For the diabetic environment, much reactive oxygen species (ROS) are produced in the tissue and organs, where such type of ROS may cause severe damage to DNA, cell membranes, and proteins. Most effective measurement for oxidative damage and inflammation would be the modulation of signaling pathway. As natural substances, saffron can be used for treatment for the signaling system [22]. Recently, saffron (Crocus sativus L.) has attracted attention for its wide-ranging therapeutic potential and phytochemical profile [23].

In summary, some perspectives and topics were described in this article, including LCD, post-prandial hyperglycemia, GI, WR, brown rice, RDS, SDS, RS, turmeric, saffron and so on. Authors and collaborators have continued medical and social movement of LCD method. Current article will become useful reference in the future diabetic practice and research.

Conflict of Interest

The authors declare no conflict of interest.

Funding

There was no funding received for this paper.

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