The Good and Bad of Sugars

The Good and Bad of Sugars
We already know that sugar is not a healthy option for most people, but new information suggests there are those industries that want to hide its negative health effects. (Shutterstock)
Yuhong Dong
Known as “the sweetest killer” and “a poison more addictive than drugs,” sugar is consumed by virtually everyone. According to Dr. Heather Moday, a U.S. immunologist, during the COVID-19 pandemic, sugar is the worst food for your immune system.

What Exactly Is Sugar?

Sugar is a food that everyone is very familiar with, and it’s ubiquitous in our lives. We need sugars to maintain our health, and they can also bring us relaxation and pleasure. However, sugar is like a double-edged sword that can also damage our health if left unchecked. So, what exactly is sugar?
Sugar is an umbrella term for a large group of carbohydrates. They’re naturally occurring in many foods, but are added in substantial quantities in many processed foods.


Glucose is one of the body’s two key energy sources. The other is fat. Glucose is sometimes known as blood sugar when it’s measured inside the body. It’s an energy-supplying substance that the human body and brain can directly utilize. Excess glucose is stored in the body in different ways. It can be converted into liver glycogen and muscle glycogen and then released into the blood to supply energy when needed. It can also be converted to fat.
Glucose is relatively rare in nature. Honey, for example, has a high amount of glucose and fructose. For the most part, glucose is created inside the body when we digest carbohydrates or starch.


Fructose is a sugar that’s abundantly present in fruits, honey, and sweet vegetables, such as beets, potatoes, carrots, and onions. It’s the “sweetest” of all sugars. It’s 1.7 times sweeter than sucrose.

Fructose can’t be directly used for energy in the body, and excess fructose can’t be converted to glycogen storage like glucose, so it’s mainly converted to fat. Fatty livers, obesity, and some other problems are mainly related to fructose. In addition, fructose reduces the body’s sensitivity to insulin and its ability to process fat, thus increasing the risk of diseases, such as heart disease and fatty liver disease.

However, eating fruits in appropriate moderation is beneficial and harmless to the human body, because the sugar in fruit isn’t like free sugars, such as granulated sugar, but it’s encapsulated inside the cells, as the cell walls of plants prevent fructose from being absorbed by the body too quickly.

What we need to be more vigilant about isn’t the natural sugars in fruits and vegetables, but the added sugars, especially high-fructose corn syrup. These “free sugars” can make blood sugar levels rise rapidly.


Sucrose is derived from sugar canes. Common sugars used in the food industry, such as white sugar, brown sugar, and rock sugar are all basically composed of sucrose.


Lactose, mainly derived from milk, is beneficial to the health of the intestines. However, some people lack lactase in their intestines and can’t digest lactose. For them, after drinking milk, they'll develop lactose intolerance, and this may cause diarrhea.


Polysaccharides are sugar chains composed of many glucose molecules. Starch and cellulose in rice and noodles are examples of polysaccharides. Cellulose comes from grains, fruits, and vegetables, and is very important to the human body’s health.

Is Sugar More Addictive Than Drugs?

Sugar is necessary to maintain our health, but we need to rationally face some of the health problems it also brings.

As mentioned, although fructose is high in sweetness, a moderate intake of fruits and vegetables is beneficial to the human body. What we really need to be wary of is artificially added free sugars, such as sweet chocolates, cakes, and other sweets that many people love.

We all know that children love to eat sugar. This is because children need a lot of energy when they’re growing up. Sugar can also activate the “pleasure centers” of our brain and trigger the release of dopamine, which brings a sense of pleasure.

However, this can lead to addiction. There’s even a saying that sugar is more addictive than drugs.

In 2007, a study by researchers at the University of Bordeaux in France conducted a particular reward experiment with rats. In this experiment, two levers were placed in front of the rats for them to choose freely. Choosing Lever C would give them the “reward” of cocaine (an addictive drug); choosing S would give them some water with saccharin, which has no calories—just a sweet taste. The rats chose sweetness over cocaine, even when the dose of cocaine was increased. They did another experiment with sucrose and found the same results.

“Our findings clearly demonstrate that intense sweetness can surpass cocaine reward, even in drug-sensitized and -addicted individuals. We speculate that the addictive potential of intense sweetness results from an inborn hypersensitivity to sweet tastants,” the researchers wrote.

Other scientists looking at previous research found that sugar had potent effects on the brains of rats.

“Sugar is noteworthy as a substance that releases opioids and dopamine and thus might be expected to have addictive potential,” researchers wrote in a 2008 review published in Neuroscience & Behavioral Reviews.

“Neural adaptations include changes in dopamine and opioid receptor binding, enkephalin mRNA expression and dopamine and acetylcholine release in the nucleus accumbens. The evidence supports the hypothesis that under certain circumstances rats can become sugar dependent. This may translate to some human conditions as suggested by the literature on eating disorders and obesity.”

Another later research review came to similar conclusions.

“At the neurobiological level, the neural substrates of sugar and sweet reward appear to be more robust than those of cocaine (i.e., more resistant to functional failures), possibly reflecting past selective evolutionary pressures for seeking and taking foods high in sugar and calories,” a 2013 review published in Current Opinion in Clinical Nutrition and Metabolic Care reads.

Worst Food for the Immune System

Compared with other addictive substances, sugar addiction affects our body in a more subtle way, like a chronic poison.

Moday pointed out that during the COVID-19 pandemic, sugar is the worst food we can eat for the health and effectiveness of the immune system.

The American Journal of Clinical Nutrition conducted an experiment. After a group of subjects fasted overnight, they took 100 grams of free sugar orally on an empty stomach. As a comparison, another group of subjects took the same amount of starch orally on an empty stomach. The experiment found ingesting free sugars cut the “combat power” of phagocytes by nearly half. Phagocytes are important immunity cells that protect us by ingesting harmful foreign particles, bacteria, and dead or dying cells.

The maximum reduction occurred between one and two hours after ingesting sugar. Even after five hours, immunity was still affected.

In contrast, the control group that ingested starch didn’t show a decline in immunity. Therefore, eating a moderate amount of rice, noodles, and steamed bread won’t harm the immune system the way that sugar will.

However, the negative effect of excessive intake of sugar on the immune system isn’t limited to inhibiting the functions of phagocytes.

A high-sugar environment can also cause chronic inflammation and inhibit all aspects of the immune system, including white blood cells, natural killer cells, macrophages, and T cells, resulting in a decrease in the comprehensive ability of the human body to recognize and kill germs. Also, another study found that 50 percent of patients hospitalized with COVID-19 in the United States have diabetes or obesity.

Therefore, to improve our bodies’ natural immunity, we must pay more attention to eating less added sugar.

Eating Less Sugar Is Anti-Aging

Eating too much sugar is known to have several common health effects, such as tooth decay, weight gain, obesity, and diabetes. The increase in blood sugar caused by consuming sugar will also soak the body’s cells in a high-sugar environment, which will produce advanced glycation end products (AGEs).

AGEs are normally produced by the body’s metabolism, and the ability to remove AGEs decreases with age. It has been shown that AGEs contribute to increased oxidative stress and inflammatory responses. They also accelerate aging and lead to many chronic degenerative diseases, such as diabetes, atherosclerosis, osteoporosis, kidney diseases, neurodegenerative diseases, cancer, and skin degeneration.

You can also ingest AGEs through dry heat cooking meats or baked goods. Beef and other red meats contain more AGEs than white meats. Therefore, for our own health, we can try to eat less roasted, fried beef and eat more beef stew instead, and the amount of AGEs will significantly decrease.

Back to the issue of sugar, a good question may be how much sugar we should eat every day?

Although an excessive intake of sugar is unhealthy, sugar is also essential for maintaining our bodies.

“Sugar is such an important element that scientists refer to it as the third building block of life—after DNA and protein,” a 2021 article in Science Daily reads.

So, what amount of sugar should we consume daily?

According to the World Health Organization’s latest dietary guidelines released in 2015, the amount of free sugar should be reduced to less than 5 percent of the total daily calorie intake and no more than 25 grams (six teaspoons) in order to avoid obesity, tooth decay, diabetes, heart disease, vascular diseases, and even cancer.

Best Way to Cut Sugar

In order to improve health and the effectiveness of our immune system, people who are accustomed to eating sweets can consider reducing sugar. To reduce sugar, we must learn to read nutrition labels on food packaging. Sugar can go by many names, including agave nectar, brown sugar, cane crystal, cane sugar, corn sweetener, corn syrup, crystalline fructose, dextrose, evaporated cane juice, organic evaporated cane juice, fructose, fruit juice concentrates, glucose, high-fructose corn syrup, honey, invert sugar, lactose, maltose, malt syrup, molasses, raw sugar, sucrose, and syrup.

Check the sugar content of every item in your pantry. Also, eat fewer processed foods and more carbohydrates in the form of vegetables, beans, fruits, nuts, or seeds.

We often eat sugar for emotional reasons rather than for the needs of the body. Part of the reason they’re so addictive is because they temporarily satisfy an emotional desire. They do this, we’ve learned, by increasing dopamine levels in a similar way to drugs, such as cocaine. If you refrain from consuming too much sugar, the desire to eat sugar will weaken; but if you indulge in eating sugar, then the desire will increase, and the next time will be even more difficult.

Part of the problem with the dopamine-triggering effects of sugar is how it compels us to overeat.

Scientists conducted an experiment in which one group of rats was fed to be 100 percent full, whereas another group was 70 fed to be percent full. Guess which group of rats lived longer? The rats that were fed to 70 percent full lived 20 percent longer than the first group.

Sugary foods provide an overpowering flavor that can denature our taste preferences. A normal flavor profile can satisfy us with good food that we don’t feel compelled to overeat. Instead, we can savor and enjoy its taste. To be a person with good taste, literally and figuratively, we might as well start with how we eat and savor nuanced flavors while we hold excessive desires in check. This will also bring many benefits to our health.