I heard that putting prepared rice, steamed buns, bread and other staple foods cold will produce resistant starch, the calories of food will be reduced, and eating such staple foods can lose weight! How many friends have tried such a "cold rice diet"?
Can you still eat such a fragrant hot rice? | Figureworm creative
Is this method of weight loss reliable? Is there a scientific basis for that?
First of all, the conclusion, in principle, cooling the staple food to produce resistant starch has a positive effect on weight loss, but the effect is limited and should not be used as the main way to lose weight.
Let's talk about it in detail.
01
What is resistant starch?
Starch is a carbohydrate formed by the polymerization of glucose molecules, one of the important forms of plant storage energy, and an important source of carbohydrate nutrients for us humans.
Starch is a relatively large family, if according to the difficulty of digestion, it can be divided into three categories:[1]
Fast digestion of starch: it can be digested and absorbed within 20 minutes in the small intestine, such as roasted potatoes, ripe bananas, etc.
Slow digestion of starch: In the small intestine for 20 to 120 minutes can be digested and absorbed, such as natural corn starch.
Resistant starch: Cannot be digested and absorbed in the small intestine, and is found in seeds, grains, and certain staple foods after cooling. Cold rice, for example, is because the content of resistant starch is increased after the rice is cooled.
The starch we usually use for stir-frying is | Figureworm creative
Resistant starch is also a kind of dietary fiber, although it can not be absorbed and utilized in the small intestine, but after 2 hours can reach the colon and be fermented by the microbial flora in the colon, which helps to increase the level of short-chain fatty acids, reduce the intestinal pH, reduce the number of pathogens in the intestine and increase the number of probiotics, which is conducive to the prevention of colon disease.
In addition, resistant starch also has the benefits of lowering blood cholesterol, reducing the risk of obesity, and helping to control blood sugar.
02
Cold rice helps with weight loss because of resistant starch
Under normal circumstances, the starch structure contained in rice is amylose, in the process of cooking rice, amylose will absorb water and expand and gelatinize, at this time the starch in rice belongs to fast digestion starch, amylase can freely decompose them, into glucose is used by the human body.
However, if the rice is prepared and not eaten, but puts it in the refrigerator and refrigerates, then there will be "aging and rejuvenation" at low temperatures. At this time, the content of resistant starch in rice, that is, this part of the starch that is not digested by the small intestine, increases, and it cannot be broken down into glucose for use.
Experiments have shown that after the prepared ordinary japonica rice was refrigerated and stored for 24 hours, the resistant starch content increased from 4% to 14%, an increase of 10%. [2]
Since the caloric value of resistant starch is only about half of the fast digestion starch, the content of resistant starch increases, which will lead to a decrease in the amount of calories absorbed by the rice eaten, which will also help to lose weight.
03
Some staple foods, it is useless to let cool!
Since rice may lose weight after putting it in the refrigerator and refrigerating, is it not true that all staple foods have the same effect when they are cold?
Not really!
Whether the content of resistant starch will increase after the staple food is cooled has a lot to do with the composition of food starch. The effect on foods with high amylose content will be greater, and the effect on foods with higher amylopectin content will be smaller.
Because low temperature refrigeration for a long time will make the amylose molecules re-tend to be ordered, forming a crystalline region, appearing regeneration effect, and having resistance to amylase. But for foods with higher amylopectin, such as glutinous rice, refrigeration has little effect on its digestion speed and blood sugar response, and even the blood sugar response is stronger. [2、3]
The difference between amylose (left) and amylopectin (right) shows | Figureworm creative
Therefore, for rice, steamed buns, and bread with high amylose content, the content of resistant starch after refrigeration will increase significantly; but for glutinous rice foods with high amylopectin content, such as tangyuan, Lantern, Zongzi, etc., don't expect it, even if it is cold to eat, it will not help to lose weight and control blood sugar.
04
These factors can also affect resistant starch
In addition to the structure of starch that affects the production of resistant starch, it is also related to the following four factors:[4]
The longer rice is heated, the more it promotes the content of resistant starch produced by its aging and rejuvenation.
Slow cooling is more conducive to the production of resistant starch than rapid cooling. Because the linear-chain molecules in the rapidly cooling starch gel are too late to recrystallize and aggregate, it is not easy to form resistant starch. So, don't freeze, keep it refrigerated.
The most suitable refrigeration temperature is 0 ~ 4 ° C, at this temperature the crystal growth is faster, which is conducive to aging and rejuvenation. Moreover, the entire process of resistance starch generation is generally completed within 24 hours.
Food water content is too high is not conducive to aging rejuvenation, usually the water content of more than 60% is not conducive to the production of resistant starch, such as thin porridge.
Some people may have such a question: what if it is cooled and then reheated? Will there still be resistant starch?
Unfortunately, if cold rice is reheated and eaten, the resistance starch content will be reduced, and it will be reduced a lot, and finally the resistance starch content is not even as good as when the rice is just out of the pot, eat this reheated rice, the weight loss effect is naturally more than think.
summary:
Although in principle, eating cold rice is helpful for weight loss, but after all, weight loss depends on the overall calorie intake level, even if you eat cold rice every day, but the total calorie intake is still high, it is still difficult to lose weight. Therefore, eating cold rice does not play a decisive role in weight loss.
In addition, long-term adherence to cold rice and cold steamed buns may lead to gastrointestinal discomfort, and this weight loss method needs to be carefully chosen. With the perseverance to eat cold rice, it is not as good as a reasonable diet and enhanced exercise, and the weight loss effect will be better!
Author | Xue Qingxin Member of Chinese Nutrition Society Registered Dietitian Health Manager Public Dietitian
Review | Song Shuang, Associate Researcher, Institute of Nutrition and Health, Chinese Center for Disease Control and Prevention
Editor-in-charge | Ding Song
bibliography:
[1] Zhu Ping, Kong Xiangli, Bao Jinsong, etc. Research progress on the application and efficacy of resistant starch in food[J].Journal of Nuclear Agriculture,2015,29(2):327-336.DOI:10.11869/j.issn.100-8551.2015.02.0327.
Wang Lu, Fan Zhihong, Shi Haiyan, etc. Starch digestion characteristics of several waxy foods[J].Food Science,2010,31(17):359-363.
Yu Shifeng,Zheng Xiqun. Research Progress on Influencing Factors and Formation Mechanism of RS3 Resistant Starch in Rice[J].Food Industry Science and Technology,2012,33(8):431-435.
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