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Surprising Side Effects Sugar Has on Your Immune System, Says Science

A new study on fructose shows the damage it may do to your immune system and more.

Looking for more reasons to cut your sugar intake? There's a lot of research out there about what the various kinds of sugar can do to your health—which will likely be more than enough incentive to watch how much of the sweet stuff you eat.

Table sugar is made up of two molecules: glucose and fructose. Fructose occurs naturally in honey, and in small quantities in a number of fruit and vegetables (squash, beets, sugar cane, and corn, to name a few). It tastes sweeter than glucose, which is why it's used in High Fructose Corn Syrup and a number of processed foods.

Up until the early 1900s, the average American would eat about 15 grams of fructose per day, mostly from fruits and vegetables, as Harvard Health points out. But now that number has skyrocketed, and today, the average person eats about 55 grams of fructose daily. We've known for some time that eating excess sugar can have many adverse effects on our health, and experts believe that fructose may be even more harmful to us than glucose, as more studies come out associating it with a number of serious health conditions.

The latest research backs this up. Most recently, a new study published in the journal Nature Communications found that fructose can increase inflammation, which implies that it could even negatively impact our immune response.

"This research by no means says people should stop eating fruit, as I have seen some people suggest online, but more reducing the consumption of high fructose corn syrup that is found in certain beverages," Dr. Nick Jones, the lead author of the study, tells Eat This, Not That!

Read on to learn more about what kind of effects fructose can have on the body, according to research.


Sugar in bowl and spoon

"We find that a certain type of white blood cell called monocytes become more inflamed when cultured in fructose," explained Dr. Jones. "What that means is, when we give them fructose instead of glucose, they produce more proteins associated with inflammation called cytokines."

In other words, fructose can cause cells in our body to become inflamed. This kind of inflammation can damage cells and tissues, which in turn can lead to systems in our bodies—like white blood cells in the immune system—not working as they should.

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Potential Immune System Damage

honey coffee

A 2019 study found that dendritic cells, which are also critical to immune response, also became inflamed when exposed to fructose as opposed to when they were exposed to glucose. However, more research is needed to determine if and exactly how fructose might affect our immune system's response to a virus.

"We don't know yet how fructose would affect the body's response to viruses," said Dr. Jones. "As this work has just been released, there is certainly more [research] to do, especially when considering viruses that target the liver, where fructose will be more abundant."

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All cells are able to metabolize glucose, but only the liver can break down fructose in high amounts. When you eat too much fructose, the liver turns it into fat, which can lead to weight gain and obesity.

The new study connecting fructose and inflammation could also explain the link between fructose and obesity, as chronic low-grade inflammation is also associated with obesity.

Type 2 Diabetes

dessert assortment on blue table

When you eat large amounts of fructose, you may also be increasing your risk of type 2 diabetes. Plenty of research, like this 2013 study and this 2009 study, has found that drinking fructose-sweetened beverages (like soda) can decrease your insulin sensitivity, which is a risk factor for developing type 2 diabetes. There's not enough research to definitively show that the increased risk of type 2 diabetes is because of the fructose itself, or because of the increased caloric intake—but either way, managing the amount of sugary beverages you drink will decrease your risk of developing type 2 diabetes.

What's more, some rat and mouse studies are finding that fructose may impair insulin-signaling even cause insulin resistance, although more research and human studies are needed to confirm these findings.

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Non Alcoholic Fatty Liver Disease


Non Alcoholic Fatty Liver Disease (NAFLD) is a relatively new condition that is associated with the rise in obesity and type 2 diabetes. Fatty liver develops when your liver produces too much fat or doesn't break the fat down efficiently enough. In turn, NAFLD can lead to more serious conditions like liver cancer or even liver failure.

According to a research paper published in 2018, evidence suggests that NAFLD is linked to fructose consumption, which causes fat to accumulate in the liver when the liver goes to break it down. Although more research is needed to confirm this link, the study's authors wrote that reducing fructose intake "may have a significant benefit" in preventing fat from building up in the liver.

For more healthy eating news, check out these 8 ways to support your immune system now, according to Harvard.

Urvija Banerji
Urvija Banerji has written about food for publications like Atlas Obscura, Eater, and The Swaddle. Read more about Urvija
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