Does Vinegar-Stir-fried Potato Shreds contain Slow-Digesting Starch? How to Eat Potatoes Without Surges in Blood Sugar?

Everyone knows that potatoes (scientific name Solanum tuberosum) are a kind of food rich in starch and a cheap ingredient. But the magic of potatoes is that they have a variety of shapes and are versatile, and can fully penetrate into human diet.

Everyone eats potatoes, but there are many concerns , such as worrying about getting fat or worrying about blood sugar rising too quickly after a meal. Today we will discuss three common problems:

1 How much starch does a potato contain? Can it be substituted with rice in equal amounts?

2 How to eat potatoes without taking in too much starch and gaining weight?

3 Will eating potatoes with rice cause blood sugar to rise? How to eat them to help lower blood sugar?

Let's start with the first question: How much starch do potatoes have? Do steamed potatoes have more starch, or do cooked rice have more starch?

The starch content of various potato varieties varies greatly, ranging from 11% to 25%. Usually, potatoes with high starch content are used to extract starch, make products such as starch and vermicelli, or as raw materials for brewing. Potatoes used for cooking and stewing have a slightly lower starch content, usually less than 20%.

How to convert potatoes and rice? It should be calculated according to the starch content.

Below we calculate based on a starch content of 18% [1].

The starch content of 1 jin of Northeastern rice (japonica rice) is 75%. After being cooked into rice, its weight becomes 2.3 jin, containing about 33% starch.

After 1 pound of potatoes are steamed, the weight changes very little and the starch content is still 18%.

Therefore, 1 jin of steamed potatoes ≈ 0.24 jin of raw rice ≈ 0.55 jin of cooked rice

Or we can say that, based on starch content, 1 catties of raw rice ≈ 4 catties of steamed potatoes

Because the so-called 2 liang of rice in the cafeteria is 100 grams of rice, so——

1 liang of rice (50g raw rice, 115g cooked rice) ≈ 200g steamed potatoes.

Therefore, potatoes and rice cannot be converted in equal amounts. If you use potatoes to replace the same amount of rice, the starch you eat will not increase, but decrease.

Now let’s talk about the second question. How can we eat potatoes without gaining weight?

As mentioned earlier, the starch content of steamed potatoes is not as high as that of rice. If you use the same amount of cooked potatoes and cooked rice, then you are eating less starch .

At the same time, potatoes without oil or salt not only have less fat and starch, but also have a lower energy density. They also have a higher satiety level than foods such as rice and bread[2]. In terms of the satiety index, with white bread as 100, rice is 138, and potatoes are 343.

In other words, when eating the same calorie value, plain potatoes are more filling than rice and bread.

That is to say, if you replace rice with potatoes, you should eat more, but you can't eat more because potatoes are too filling. You feel full before you eat the same amount of potatoes as rice...

Many girls found that their periods were delayed after replacing rice with potatoes, sweet potatoes and other foods.

One of the reasons is that after they switched to potatoes and sweet potatoes as their staple food, they actually ate much less calories. If they increase exercise, eat less meat, and reduce snacks...the calories in a day will be too low.

But why do potatoes still have the bad reputation of being "high in starch" and "a fattening food"? Should potatoes protest this injustice?

This is because people often face a problem: because they love potatoes, they will eat too much extra starch, and at the same time eat the fat used for fried potatoes, stewed potatoes, and fried potatoes.

For example, eat rice with a plate of fried potato shreds; eat pancakes with a plate of fried potato shreds.

For example, eat rice with a bowl of potato and chicken; eat steamed buns with a bowl of potato vermicelli stewed meat. Perfect.

Also, after dinner, have a bag of potato chips; between meals, have a bag of chips .

Potatoes + cooking oil, the calories may reach or even exceed the same amount of rice.

For example, French fries contain 15% fat and have a calorie value of 298 kcal/100 g, which is much higher than cooked rice.

Therefore, when eating potatoes, you should use steaming and boiling to eat them in their original flavor, and remember to reduce some staple foods such as rice and steamed buns. Especially those potatoes that are fried or stewed with ribs or pork belly and soaked in oil, they really can't be enjoyed often.

3. Will replacing part of the rice with potatoes increase blood sugar levels after a meal?

There is a possibility that it will remain basically unchanged, or there is a possibility that it will decrease.

There are several things to consider when substituting potatoes for rice.

First, how many potatoes were eaten? How much rice was replaced? Was the total amount of starch in the meal increased or decreased? Second, how were the potatoes cooked? Was the starch a fast-digesting type?

If potatoes and rice are eaten together, the total amount of starch is reduced, so blood sugar levels after a meal will usually not be higher than when rice is eaten alone.

For example, the fried shredded potatoes that Chinese people often eat are made by cutting the potatoes into shreds and soaking them in water, which washes away some of the starch.

This dish is usually fried to a crispy texture, and the starch gelatinization degree is not that high, so it is not a high GI type.

Especially for shredded potatoes with vinegar, vinegar can enhance the heat resistance of the potato cell wall, which can convert some of the potato starch into resistant starch or slowly digestible starch. Adding vinegar itself can also help delay the rise in blood sugar after a meal [3].

Chinese people like this kind of crispy fried potato shreds, or non-fried stewed potatoes; while Westerners mainly eat floury baked potatoes, greasy French fries, or mashed potatoes with a super high glycemic index.

For this reason, existing research results show that eating potatoes does not increase the risk of diabetes and cardiovascular disease in Chinese people. There are even epidemiological studies that have found that compared with those who do not eat potatoes, those who eat small to moderate amounts of potatoes have a significantly lower risk of death [4].

Let’s get back to the topic of replacing rice with potatoes and postprandial blood sugar.

A study found that if 30% of white rice is replaced with cooked potatoes, and potatoes and rice are eaten together, then the blood sugar level after a meal is basically the same, provided that the same amount of carbohydrates is consumed . This is true for both soft high-GI cooked potatoes (GI=83, equivalent to the texture of stewed potatoes) and chewy medium-GI potatoes (GI=56, equivalent to the texture of fried potato shreds). Therefore, replacing part of the rice with potatoes will not lower the blood sugar level after a meal.

However, if you eat potatoes 30 minutes before eating rice, the effect is slightly different. Both types of potatoes can slightly reduce the peak blood sugar level, but the medium GI potato is more effective. Not only can it reduce the peak blood sugar level after a meal by 22%, it can also reduce the area under the blood sugar curve by 7%[5]. In other words, the glycemic index is reduced.

Therefore, if we stew the potatoes less soft or fry them less soft, then eating potatoes first and then rice may be beneficial to blood sugar control, provided that the amount of starch remains unchanged.

For potato lovers, this may be good news. But there are two things to remind you: if there is too much oil in the fried potato shreds, it is recommended to rinse the oil with hot water; and don't add extra rice just because the potatoes are so delicious...

Related Literature:

1 Yang Yuexin, ed. Chinese Food Composition Table (Standard Edition) Volume 1. Peking University Medical Press, 2018

2 Anderson GH, et al. White vegetables: glycemia and satiety.[J]. Advances in Nutrition (Bethesda, Md.), 2013,4(3): 356S-67S.

3 Li Shuang et al., Regulatory effect of vinegar on postprandial blood glucose. Chinese Condiment, 2017, 42(1): 153-156

4 Chen X, et al. Current intake levels of potatoes and all-cause mortality in China: a population-based nationwide study[J]. Nutrition, 2020: 110902.

5 Zhao W, et al. Potato Preload Mitigated Postprandial Glycemic Excursion in Healthy Subjects: An Acute Randomized Trial. Nutrients. 2020; 12, 2759

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