Poison for some, preserves for others

(Visual China/Photo)

Poison of youth

Researchers at the Institute of Medical Sciences at the University of Tokyo in Japan found that adolescents had higher sugar intake and the incidence of mental disorders than other age groups, and that schizophrenic patients who consumed more sucrose had more severe symptoms. There are a variety of behaviors associated with sugar-induced mental illness, including hyperactivity, memory loss, and sensory dullness.

Past studies have shown that most chronic mental illnesses, such as schizophrenia and bipolar disorder, have multiple causes, including genetic and environmental risk factors, with most developing before the age of 30. But the researchers also found that some people with schizophrenia and bipolar disorder consumed about twice as much sugar as healthy people of the same age, and the more people with schizophrenia consumed more sugar, the more severe the symptoms.

To do this, researchers at the University of Tokyo experimented with mice, first feeding young mice two diets, one normal and the other high-sugar diet, mainly starch or sucrose. After 50 days of feeding, the mice were tested on 8 different behaviors, including movement, sonic startle response, object position test, and maze behavior. The results showed that the sucrose-fed mice had significantly lower performance in object position testing, working memory, and getting out of the maze. This suggests that a diet high in sucrose may have induced mental illness in mice.

Further discussions showed that glycosylated end products (AGEs) can induce the production of inflammation and oxidative stress in various tissues and lead to a positive feedback loop that further increases glycosylated end products. However, another substance, glyoxalase I. (GLO1, a zinc metallose), protects cells from glycosylated end products. Previously observed in patients with schizophrenia and bipolar disorder, a decrease in the level of glyoxalase I. may be the cause of increased inflammation and oxidative stress manifested in the symptoms of these diseases, if coupled with increased sugar intake.

To this end, researchers have explored and demonstrated it from gene knockout. The researchers constructed model mice that were knocked out of glycosalase I and fed them on a high-sugar diet. As a result, the high-sugar diet induced microcapillary damage and reduced brain glucose uptake in glyoxalase I. knockout mice. Meanwhile, the researchers found similar vascular damage in brain samples of schizophrenia and bipolar disorder.

These results suggest that a high-sugar diet may affect the brain's uptake of glucose through glyoxalase I-related metabolic pathways, and cause brain capillary damage and brain dysfunction, ultimately causing psychiatric disorders. Therefore, limiting sugar intake can avoid the development of mental illness, and the use of chronic anti-inflammatory drugs such as aspirin can prevent the harm caused by a high-sugar diet.

The World Health Organization's recommendation for sugar is that adults and children should consume free sugars to less than 10% of their total energy intake per day. And a further reduction to less than 5 percent or about 25 grams (6 teaspoons) per day will have more health benefits. Free sugars are simple sugars (e.g., glucose, fructose) and disaccharides (e.g., sucrose or granulated sugar) added to food and beverages by manufacturers, chefs or consumers, as well as sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates. That is, in addition to eating, eat a variety of free sugars every day should not exceed 25 grams.

The preserves of others

For the average person, too much sugar becomes poison, but for others it is a tonic, they are Greenlanders. As a result of their long-term life in the North Pole of the Earth, Greenlanders have evolved a mutant gene that makes them absorb sugar differently from others on Earth. And, because of this gene, Greenlanders have lower body mass index (BMI), body weight, fat percentage, and cholesterol levels, and are generally healthier. They have less belly fat and are more likely to have 6-pack abs. The World Health Organization defines "overweight" as having a body mass index equal to or greater than 25 and "obesity" as having a body mass index equal to or greater than 30.

Research teams from the University of Copenhagen, the University of Southern Denmark and a number of research institutes in Greenland analyzed data from 6,551 adult greenland residents and conducted trials on mice, and recently published the results. The results showed that Greenlanders generally carry a sucrase-isomalase variant gene (c.273_274delAG) that causes congenital sucrase-isomalase deficiency and isomeltase incapable of breaking down and absorbing sucrose and isomaltose as people elsewhere on the planet do.

But Greenlanders have a different way of metabolizing sugar than people elsewhere on Earth. They don't absorb ordinary sugars from the blood like people without genetic variants. Instead, sugar enters the intestines of Greenlanders directly. In the gut, gut bacteria convert sugar into a short-chain fatty acid called acetate. Previous studies have shown that acetate reduces appetite, boosts metabolism, and boosts immunity. It is in this way that Greenlanders are not afraid of diseases such as gaining weight, diabetes and cancer, even if they eat more sugar.

Greenlanders have a mutated gene for another way of metabolizing sugar that is determined by the environment in which they live and the lifestyle they have adapted to this unique environment for thousands of years. The eating habits of Greenlanders are very different from those of the rest of the world. In the icy Arctic, Greenlanders feed on the meat and fats of fish, whales, seals and reindeer for many years, and although there are plant foods in the area, they are few, the most common of which is a plant-based food called crowberry, so their diet contains very little sugar. This condition makes it unnecessary for them to absorb sugar quickly in the blood and also causes mutations in their genes that metabolize sugar.

The environment determines genes, which in turn determine the way sugar is absorbed and metabolized. For Greenlanders, initial sugar intake can lead to diarrhea, abdominal pain and bloating. However, as they age, greenlander gut bacteria become accustomed to sugar and learn how to convert it into energy.

In addition to deriving from 6551 Greenlanders that their genetic variants cause different ways of sugar metabolism, the researchers demonstrated this mechanism with mouse experiments. The researchers tested two groups of mice, one of which was a mouse model of sucrose-isomaltase knockout (Sis-KO), which inhibited their ability to absorb sugar, similar to the genetic variants found in Greenlanders. But the second group of mice had normal sugar absorption and metabolism.

The results showed that knockout mice gained only half as much weight as another group of normal mice when they had free access to fat and sugary foods. This also circumstantially demonstrates that greenlanders' genetic variants are not only not harmful to their health due to sugar intake, but also have other benefits such as weight loss and BMI.

Therefore, danish studies may also provide new ideas for people to limit their sugar intake and thus reduce obesity and treat cardiovascular disease, or to study new drugs. If a drug can be developed that inhibits the sucrase-isomaltase gene, it is possible for people to eat sugar without causing obesity and diabetes.

Zhang Tiankan