Will gluttony for rich and delicious food make the liver become as sticky as dough?

Will gluttony for rich and delicious food make the liver become as sticky as dough?


Recently, “Nature” magazine published a rather unique article, talking about the relationship between the “viscoelasticity” of the liver and diabetes and cancer. Viscoelasticity is a term that many food professionals are familiar with because it is an important textural property of dough made from wheat flour (flour) and water.

The mixed dough is slightly sticky but very elastic. It can be stretched to make noodles or expanded and porous bread; it can be baked into crispy biscuits or made into sticky elastic dumpling wrappers. It can be said that it is precisely because of its viscoelasticity and the fact that the degree of viscoelasticity is easy to adjust. This unique property makes dough a favorite ingredient in the world and can be made into tens of thousands of different delicacies.

However, it is really rare for medical professionals to talk about the viscoelasticity of living animal livers.

Researchers have found that the “feel” of the livers of diabetic patients has changed. Although it has not yet hardened, it has stronger viscoelasticity than healthy people. Why does the liver of diabetics become more “sticky”?

The liver becomes “sticky”, which may be caused by food containing AGEs that damages the liver.

What is the difference between diabetics and healthy people? That is, there is more sugar in their blood, higher levels of glycated hemoglobin, and more “advanced glycation end products” in their bodies.

Research has long found that AGEs are a type of ingredients that promote aging. The amount of AGEs in the human body is closely related to the occurrence of serious diseases such as diabetes, chronic kidney disease, atherosclerosis, Alzheimer’s disease, and skin aging. Research in recent years has found that the risk of cardiovascular and cerebrovascular diseases and diabetes can be predicted by measuring the content of AGEs in the skin. At the same time, more than half of people with diabetes have fatty liver problems. High fat levels in the liver will also affect its texture.

AGEs in the human body come from two sources. On the one hand, it comes from the products of the Maillard reaction between blood sugar and proteins in the body, which are “self-made AGEs”; on the other hand, it comes from AGEs taken in from food, which can be called “exogenous AGEs”.

In order to verify the relationship between AGEs and liver viscoelasticity, the researchers of this new study conducted animal experiments and fed mice feed rich in AGEs to see what changes would happen to them.

The results really showed that the livers of mice eating high AGEs gradually underwent changes similar to those of people with type 2 diabetes – not only did the liver become insulin resistant, the texture of the liver also changed, and the viscoelasticity became stronger, which is very interesting. This is largely due to the cross-linking of collagen.

Worst of all, researchers found that this change in liver viscoelasticity is also accompanied by the activation of certain metabolic pathways, which can lead to an increased risk of cancer even if cirrhosis does not occur. And if AGEs are controlled, this risk can be reduced.

This study once again strongly reminds people that AGEs in food can really be absorbed by the human body, and harmful metabolic changes will occur after eating too much.

Four conditions for food to produce large amounts of AGEs need to be remembered

1. Contains rich protein

Although the protein quality of meat and chicken skin is not high enough and is mainly collagen, their ability to undergo Maillard reaction is very strong. This may be because collagen contains hydroxylysine, and this amino acid contains free amino groups, which initiates the Maillard reaction very quickly.

2. Contains more fat

There is abundant subcutaneous fat under animal skin, and the unsaturated fatty acids in it rapidly undergo fat oxidation when burned, grilled, or fried at high temperatures, which can provide more small-molecule carbonyl compounds for the Maillard reaction. The content of unsaturated fatty acids in chicken and duck is higher than that in pork, beef and mutton. Theoretically, it is more susceptible to oxidation at high temperatures.

3. Pickle foods with sugary condiments

Marinating, which is often done before cooking on the barbecue, provides the sugar that is lacking in meat. Before roasting chicken, roast duck, barbecue, or fish, sugary seasonings (such as cooking wine, oyster sauce) are often added to marinate, or honey or caramel is applied on the surface (such as roast duck, roast suckling pig, etc.) to promote cooking. The German reaction increases the aroma and at the same time increases the content of AGEs. Many chefs now like to add more sugar to dishes, taking advantage of the principle of promoting the Maillard reaction. Of course, this will also bring more AGEs. For example, Coke Chicken, Kung Pao Pork, etc.

4. After high temperature heating

After heating at high temperature, the water content is less and the color is brown, indicating that the Maillard reaction is particularly violent and thorough.

What foods are high in AGEs?Fried foods, processed meat products, high-temperature roasted nuts, etc.

Knowing a large number of conditions that produce AGEs, we can understand that in daily foods, fried foods, processed meat products, high-temperature roasted cereal foods, roasted or fried nut foods, high-temperature processed cooking oils, etc. , are important sources of AGEs.

A survey conducted among Chinese residents found that in a pure Chinese diet dominated by starchy foods, staple foods contribute the most to the intake of AGEs, followed by meat and meat products. In Western-style diet, in addition to cereal products and meat products, bread, pastries and biscuits are also important sources. A survey found that nut-roasted foods (fried or roasted peanuts, walnuts, almonds, etc.) and seasoning oils (sesame oil, chili oil made by frying and frying) are also important sources of AGEs in the diet. .

Is it particularly easy to “get angry” after eating roasted nuts? Rich in protein and fat, it is more likely to produce AGEs after heating

Another point that needs to be emphasized is that from the perspective of food composition, research has found that foods rich in protein and fat are particularly likely to produce AGEs after heating, and the production is even greater than foods rich in starch alone. For example, the CML content in roasted almonds and roasted cashews is as high as 6650kU/100g and 9807kU/100g respectively, which is much higher than that of roasted potatoes (218kU/100g) roasted for 45 minutes.

This is because the Maillard reaction starts with a reaction between a carbonyl group and an amino group. The amino group comes from protein amino acids and their decomposition products, while the carbonyl group comes from carbohydrates (especially small molecule sugars) and the oxidation products of fats. . Under high temperature conditions, fat oxidizes very quickly, and even in the absence of sugar and starch, it can provide the carbonyl groups required for the Maillard reaction.

In a sense, these data can explain why eating roasted nuts and roasted seeds and nuts is particularly likely to increase the inflammatory response, causing “inflammation” problems such as sore throat, dry mouth, acne and blisters. Because although roasting increases the aroma and makes the taste crisper, it will produce a large amount of pro-inflammatory substances such as AGEs and acrylamide.

Delicious nuts such as peanuts, cashews, and almonds contain more than 20% protein, more than 40% fat, and about 20% carbohydrates. Together, they are an ideal matrix for the Maillard reaction to fully occur after heating.

Early studies have found that the content of AGEs will increase significantly in foods that have been processed at high temperatures, such as frying, roasting, or deep-frying until they are brown and fragrant. For example, brown, fragrant, and crispy foods such as roasted chicken skin, roasted duck skin, and fried pork skin have the highest content in theory.

AGEs are the end products of the Maillard reaction. If you increase the cooking temperature and time, more will be produced.

For example, the content of CML (a major AGEs compound) in raw chicken was measured to be only 769kU/100g; but after grilling, the content increased to 4848kU/100g.

The content in raw steak is 800kU/100g, while the content after frying in olive oil is 10058kU/100g.

Therefore, when cooking fish and eggs, if you can lower the heating temperature and make it tender, AGEs will be greatly reduced.

For example, if you fry an egg with olive oil for 2 minutes at medium-low heat, the CML content is only 97kU/100g; while frying it at high heat for 1 minute will increase to 243kU/100g.

Similarly, when eggs are scrambled over medium-low heat for 2 minutes, the CML content is only 63kU/100g; while frying over high heat for 1 minute will increase to 123kU/100g.

The same rule applies to cooking meat and barbecue. The higher the temperature and the longer the time, the greater the production of AGEs.

Why is this? Because AGEs are the end products of the Maillard reaction. The Maillard reaction speeds up as the temperature increases, and it also speeds up when the water content decreases. Therefore, in fresh foods such as milk, fresh eggs, raw fish, and raw meat, almost no Maillard reaction occurs, and the content of AGEs is very low. But after heating and cooking, the content will increase significantly. Moreover, as the heating temperature increases, the production speed becomes faster and faster.

How to adjust your diet to avoid excessive intake of AGEs?

The content of AGEs in fresh, natural, high-moisture-content vegetables, fruits, fish, meat, eggs, and milk is minimal, and the content in steamed foods is also very low. Because under the conditions of large amounts of water and low temperature treatment, the Maillard reaction occurs very slowly, and the production of AGEs will be very small.

Way 1 to reduce AGEs:

Avoid eating too much high-temperature processed food, eat more fresh and natural food, and lower the cooking temperature.

1. Specific operation methods

Do not use bread, fried dough sticks, fried cakes and other high-temperature cooked foods as staple food. Eat steamed buns, rice, boiled noodles, porridge, etc.

Eat less fried and grilled foods and increase the proportion of steamed and stewed dishes.

The oil temperature should be lower when cooking, and the eggs should be tender when frying. Use less oil.

Eat fresh meat and fish, and avoid eating cured meats, processed meat products, salted fish, dried fish, etc.

Eat less fried and roasted nuts. Try to eat fresh walnuts that have not been roasted. You can eat peanuts cooked with five spices.

Eat less baked biscuits, cookies, pastries, baked buns and other snacks.

Eat less fried or baked foods such as potato chips and crispy rice.

2. Long-term storage will also produce AGEs

For example, although cheese production does not go through high-temperature heating and most of the lactose is removed, it does go through long-term fermentation for several months. During this process, some fats and proteins are gradually decomposed. Reactive carbonyl compounds produced by the oxidation of fats and proteins react with amines produced by the degradation of amino acids. Maillard reaction products will also accumulate, increasing the number of AGEs.

Foods such as sausages, bacon, dried fish, and dried meat that have been pickled for a long time have similar patterns. During the storage process, the AGEs content increases. Adding lots of salt will speed up this process.

Way 2 to reduce AGEs:

Ensure the proportion of fruits, vegetables and grains, and consume sour condiments and natural spices appropriately.

Acidic substances such as lemon juice and vinegar have similar effects. Studies have reported that spices such as tea, pomegranate peels, garlic, and polyphenol extracts from some fruits, vegetables, and herbs are beneficial to reducing glycation reactions, thereby reducing AGEs produced during food cooking and processing.

Eating more fresh fruits and vegetables, whole grains and beans in your daily diet to diversify your food will help reduce the intake of AGEs in the diet, and will also help provide a variety of food ingredients that inhibit the formation of AGEs. At the same time, a healthy diet itself is beneficial to improving blood sugar and blood lipid levels, thereby reducing the formation of endogenous AGEs.

The last thing to emphasize is that any substance in food follows the rule of “dose determines toxicity.” Foods containing AGEs are not poisons, just like foods containing sugar and salt. They provide delicious taste and are good for the appetite. At the same time, the body’s inflammatory response is not as low as possible. Therefore, properly enjoying delicious food heated at high temperatures is part of a happy life.

However, don’t overdo anything, not even the delicious food. Barbecuing frequently, frying every day, and eating a lot of grilled food are not a healthy eating life. In addition to a large number of AGEs that promote aging, more pro-inflammatory substances and even carcinogens are also introduced.

Text/Fan Zhihong (Director of the Chinese Nutrition Society, chief scientific communication expert employed by the China Association for Science and Technology)



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