Nutrition Action
Many people with weak gastrointestinal function have such an experience: after eating more fruits, the stomach is uncomfortable, it is very easy to diarrhea, and even lead to the onset of acute intestinal inflammation. In addition to the reasons why dietary fiber in fruits promotes excessive intestinal movement, it is likely to be related to the inflammatory response of the intestine caused by excessive fructose intake. The damaged intestinal barrier and the decline in digestion and absorption function are entangled with the imbalance of the intestinal flora, causing the human body to become weak and intolerant to a variety of foods.
Large amounts of fructose also cause fatty deposits in the liver, the appearance of fatty liver, but also produce metabolic disorders, reduce insulin sensitivity, increase the risk of diabetes. Excessive fructose intake can also lead to increased endogenous purines (suggesting increased catabolism in the body), increased uric acid, and increased risk of gout. These are the results of previously confirmed studies. In short, it is true that a lot of fructose is harmful to health.
So why did everyone say that fruits are good for health? Then we have to popularize six knowledge points with everyone.
Knowledge point 1: Does fructose mean "sugar in fruit"?
The sugar in the fruit consists of three parts: glucose, fructose and sucrose, of which fructose is only one. Fructose, the English name of fructose, is not a vague concept of "sugar in fruit", but a monosaccharide with a definite structure, a sugar that is different from glucose, sucrose, and maltose.
Knowledge point 2: Which fruits have a high proportion of fructose in sugar?
Some fruits have a larger proportion of sucrose, such as dates and peaches; some fruits have a larger proportion of glucose and fructose, such as watermelon and grapes. In general, the amount of glucose and fructose in fruits is basically equivalent.
Fructose gives people a fresh and refreshing sweetness, and it has the characteristic of sweetening at low temperatures. Sucrose does not have this property, and the sweetness is similar at any temperature. Fruits that feel sweeter when icy, and fruits that taste particularly sweet, are almost all fruits with a high proportion of fructose.
Knowledge point 3: Eating white sugar and honey will also increase the fructose in the body
From the perspective of plant metabolism, photosynthesis first synthesizes glucose, and then glucose can be isomerized as fructose. A molecule of glucose and a molecule of fructose combine to produce a molecule of sucrose, that is, the daily consumption of white sugar, and a molecule of sucrose in the intestine after being hydrolyzed by sucrase, and then produce a molecule of glucose and a molecule of fructose.
The sugar eaten daily at home, including cotton sugar, white sugar, brown sugar, rock sugar, brown sugar, etc., is mainly composed of sucrose. Therefore, after being digested and absorbed in the intestine, sugar-sweets bring both glucose and fructose.
Honey also contains three kinds of sugars: sucrose, fructose and glucose. In general, the more likely it is to crystallize the precipitated honey, the greater the proportion of glucose in it; the less likely it is to crystallize the precipitated honey in winter, the greater the proportion of fructose. This is because fructose has the highest solubility, followed by sucrose and the lowest glucose.
Knowledge point 4: How did the "industrially produced fructose" come about?
In the modern starch sugar industry, corn is first processed and starch extracted; then corn starch is used to hydrolyze glucose, and then glucose fructose isomerase isotarase is used to partially turn glucose into sugar to obtain high fructose glucose syrup. Industrially produced fructose glucose syrup, the proportion of fructose can reach up to 90%.
Fructose syrup is sweet and refreshing when chilled, so it is the main source of sweetness in various sweet drinks such as Coke Sprite. It is also used in many dessert shops to prepare drinks. Therefore, among the people who like to drink sweet drinks, sweet drinks are the biggest source of fructose.
A 500 ml bottle of sweet drinks will have about 50 grams of added sugar (sucrose or fructose syrup). If you count half of the fructose, there are about 25 grams of fructose. Therefore, drinking sweet drinks will inevitably make the body get too much sugar, and it will get quite a lot of fructose.
The fructose obtained by drinking drinks, the small amount of sugar obtained when drinking yogurt, the small amount of sugar put in when cooking, and the fructose obtained when eating fruits normally, the added fructose intake is inevitably excessive.
Knowledge point 5: How much sugar is in the fruit?
Tradition says that a certain fruit has less sugar, but it may not be accurate. Because the data in the food composition table are the results of a long time ago, they do not cover all new varieties of fruit, and often do not represent the sugar content of the fruit on the market. Some fruits are naturally high in sugar. For example, the sugar content of sweet grapes can reach 16% to 20%, of which 40% to 50% fructose. According to this calculation, eating 500 grams of grapes with 18% sugar content can get 90 grams of sugar, of which 36 to 45 grams of fructose.
There are also tropical fruits that Chinese people love to eat, and the sugar is also very impressive. Take a look at the sugar content of local fruits measured by Thai scholars: mangosteen 17.5%, rambutan 18.5%, mango 13.9%, lychee 17.9%, jackfruit 19.2%, senchi 17.2%.
However, those fruits that were not so high in sugar are now gradually being replaced by high-sugar varieties, so the sugar intake from fruits is getting higher and higher. Rock sugar oranges, granulated sugar oranges, rock sugar heart apples, etc., all take "sugar and sweetness" as the selling point. Because the fructose taste is sweet and delicious, fruit varieties with high fructose content will also be more popular, which makes more and more fructose eaten from fruits.
For example, our study last year found that a certain Fuji apple contains 8.3% fructose and 6.7% glucose. According to this sugar content, apples really can't be called low-sugar fruits. Speaking of this, everyone must have understood: eating a small amount of fruit is beneficial, not equal to eating a lot of fruit is beneficial. Eating a lot of fruit, or willfully drinking fruit juice, will also lead to excessive fructose!
Knowledge point 6: Eating more fructose is harmful, will eating less harmful?
Small amounts of fructose intake may be beneficial to health, such as glucose metabolism in the liver. In combination with starchy foods, a small amount of fructose without increasing the total amount of carbohydrates can help reduce glycosylated hemoglobin levels. But large intake is counterproductive.
Studies have suggested that as far as the prevention of diabetes is concerned, too much or too little fruit is not good, and two or three hundred grams is the appropriate amount.
There are several ways to reduce the harm of fructose
1. Avoid any sweet drinks.
2. Add less sugar in daily family meals, drink porridge and soup as much as possible without sugar, including honey should also be strictly limited.
3. Choose foods such as yogurt with low sugar content.
4. The number of fruits is 200 to 350 grams per day (peeling and kernelizing), do not often eat more than 1 pound.
5. When eating fruit, do not be overly obsessed with the strong sweetness, and the amount of fruit with high sweetness should be reduced as appropriate.
6. Don't drink a lot of juice, even if it's 100% juice. The same goes for self-squeezed juices.
7. Fruit can be used instead of sweets, or instead of some cold dishes, eat a small amount during meals, which can not only avoid excess, but also play a small amount of fructose on the promotion of glucose metabolism.
8. Don't buy fructose products on the market because of low fructose blood sugar metabolism.
Text/Fan Zhihong
(Director of Chinese Nutrition Society, Chief Expert of Science Communication hired by China Association for Science and Technology)
Source: Beijing Youth Daily