How sugar is making us sick (and 8 reasons to avoid it)

Obesity, diabetes, leaky gut, heart disease, cancer, dementia… These health problems don’t have just one cause—they’re multifactorial. But if we could eliminate one thing from the modern diet to reduce the risk of developing these conditions, one could make a strong case to eliminate refined sugar.

Even organizations like the American Heart Association and the CDC, typically behind the curve on nutrition, caution against sugar. For example, the CDC advises we limit added sugars to less than 10% of daily calories. However, on a 2000 calorie diet, that’s 12 teaspoons of added sugar! Imagine spooning that down.

There is much gnashing of teeth about whether or not sugar is actually addictive. What’s not controversial is that it’s easy to overconsume. An estimated 17% of the average American adult’s daily calories come from added sugar, and drinks in particular. Sodas, fruit juices, and so-called “sports” drinks are hyperpalatable, but they’re not satiating. Overconsumption of these sugar-loaded beverages is a major driver of the US “diabesity” (obesity + diabetes) epidemic.

You probably already know that sugar is bad for you, but I wrote this article to really dive into why. We’ll define what sugar is, cover how its overconsumption is linked to specific consequences, and I’ll wrap up by recommending a great alternative to sugar. Stick with it—I think you’ll learn something new!

What is Sugar?

When most people talk about sugar, they’re talking about sucrose, aka table sugar. Sucrose is a disaccharide, meaning it’s composed of two simple sugars, or monosaccharides—namely, glucose and fructose, the two natural forms of sugar found in plants.

Other sugars include galactose, lactose, and maltose, but when I discuss the problems with sugar, I’m mostly referring to added sugar—the sucrose, fructose, and high fructose corn syrup added to processed foods to make them easy to overeat. High fructose corn syrup is a liquid sweetener similar to sucrose, and it’s what you’ll find in many modern beverages.

Sugar, Insulin Resistance, and Inflammation

Eating too much sugar has been linked to nearly every chronic disease. But before exploring these links, we need to talk about insulin resistance and inflammation. Understanding this will lay the foundation for why sugar is harmful.

Sugar Drives Insulin Resistance

When you eat sugar, that sugar ends up in your blood. And the more sugar you eat, the higher your blood sugar gets. High blood sugar is a dangerous, inflammatory state—and your body knows it. So when blood sugar gets high, your pancreas releases insulin to clean up the mess.

Insulin commands your blood sugar. It tells glucose to kick rocks, shuttling it out of your bloodstream and into the cells of your liver and muscle tissue. It’s there that glucose stored in the form of glycogen, which can be called upon for later use.

But glycogen stores are not infinite. They fill up quickly, and when they do, insulin is forced to store excess blood sugar as body fat instead. On a high-sugar diet, this gets out of hand FAST. With nowhere to put the excess blood sugar, fat stores can accumulate pretty rapidly. It’s a vicious cycle, particularly when we consider how easy it is to overconsume candy, dessert, and soda.

Take it too far, and you’ll fundamentally alter your cells’ ability to listen to insulin. It becomes difficult to store glucose as glycogen, and so glucose builds up in your blood instead. This is known as insulin resistance, and it’s the hallmark of type 2 diabetes and many other conditions.

Sugar Drives Inflammation

Inflammation is a low-grade immune response in the absence of specific disease. Think of it as a harmful effect of immune system confusion. It’s good to keep chronic inflammation low if you’d like to live a long, healthy life.

Where does sugar come in? High sugar diets have been correlated with chronic inflammation—specifically, with high circulating levels of an inflammatory particle called C-reactive protein, or CRP.

Sugar consumption is always a few steps removed from inflammation. Consider the following:

• Sugar causes excess fat storage, which leads to inflammation.
• Sugar increases blood sugar levels (hyperglycemia is an inflammatory state).
• Sugar feeds pathogenic gut bacteria and increases gut permeability (leaky gut).
• Sugar decreases the production of ketones, which have anti-inflammatory effects.

The takeaway is: Eating sugar increases inflammation, and inflammation drives chronic disease.

8 Reasons to Avoid Sugar

Now that we’ve laid the framework, let’s look at some specific issues linked to excess sugar intake:

#1: Obesity

In the United States, obesity has reached epidemic proportions. Over 30% of US Americans are obese, and hundreds of thousands die each year from obesity-related diseases like diabetes, heart disease, cancer, and neurodegenerative disease. Obesity, it’s clear, is a significant risk factor on a patient’s chart.

Sugar deserves a large chunk of the blame. Study after study indicates that the more sugar someone consumes, the more weight they gain. But what drives sugar-induced weight gain?

First, a bit of common sense: added sugar increases your calorie intake. There’s a couple of factors contributing here. For one, sugar isn’t satiating—100 calories of high fructose corn syrup simply won’t fill you up like 100 calories of fat or protein. Second, sugar provides your brain with a nice hit of dopamine. So it’s easy to want more, and it’s easy to eat more without getting full.

Lastly, sugar consumption leads to insulin resistance, which activates fat-storage mode. Put it all together and you have a recipe for obesity.

#2: Type 2 Diabetes

Closely linked to obesity and insulin resistance is type 2 diabetes, a metabolic disorder defined by high blood sugar, high insulin, high blood pressure, and excess fat mass.

One study followed over 90,000 women over 8 years, comparing 2 groups. Those in the first group consumed more than one sugary beverage per day, and those in the second group consumed less than one sugary drink per month. The study showed that group 1 correlated with an 83% higher risk of developing Type 2 diabetes than group 2. Pretty significant!

#3: Heart disease

Everything we’ve talked about so far—insulin resistance, inflammation, obesity, and diabetes—also increases one’s risk of heart disease.

When I say heart disease, I’m talking about atherosclerosis, or the buildup of plaque on the arterial wall that eventually leads to stroke or heart attack. Globally, heart disease is the number one cause of death.

According to a review in the journal Nutrients, a person’s risk of heart disease rises by 10 to 20 percent for each additional sugary beverage consumed daily. Other data from The Framingham Heart Study found that drinking more than one sugary beverage per day was linked to high blood pressure and high triglycerides, both heart disease risk factors.

#4: Cognitive decline

Multiple lines of evidence point to high sugar diets impairing cognition. When you look at population data, for instance, you find more age-related cognitive decline at higher sugar intakes.

In animals, researchers have found that excess intake of fructose and sucrose—different forms of sugar—all appear to have negative effects on the hippocampus, a region of the brain involved in memory processing.

Sugar also impairs brain function in humans. In one study, drinking a glucose or sucrose solution caused declines in mental performance compared to placebo.

#5: Cancer

Compared to healthy cells, many cancer cells love metabolizing glucose for energy. This is called the Warburg effect, and it’s likely why the ketogenic diet (a low-carb diet which keeps blood glucose low) is therapeutic for certain cancers. In other words, it’s likely that eating sugar feeds cancer. And indirectly, sugar increases inflammation which also creates conditions ideal for cancer progression.

Fructose is a particularly bad actor here. In mice, the equivalent of one daily soda’s worth of high fructose corn syrup accelerated the progression of colon cancer.

To be clear, cancer is an extremely complex condition, and cutting out sugar certainly won’t cure it. But with the data we have, that seems like a solid move to slow its progression.

For more on the dangers of fructose, check out Peter Attia’s podcast with Rick Johnson. Both of these guys are very intelligent MDs, and they cover the topic brilliantly.

#6: Leaky gut

High sugar diets feed pathogenic bacteria and fungi in the gut. These bad bacteria, in turn, damage the fragile gut barrier, creating a condition called leaky gut.

When someone has leaky gut, food particles leak through the intestinal wall and into the blood. The immune system then attacks these food particles, creating more damage, more leaky gut, and the cycle continues.

The good news? Low-carb, low-sugar diets can starve bad bacteria to help heal your gut. If you want to go deep on this topic, I highly recommend reading Healthy Gut, Healthy You by Dr. Michael Ruscio.

#7: Cavities

Your dentist was right all along. Sugar is bad for your teeth. It feeds bacteria of the mouth (such as Streptococcus mutans) that cause tooth decay. Unsurprisingly, higher sugar consumption is linked to higher rates of cavities in children.

#8: Kidney disease

Imagine drinking two liters of Coke after four hours of heated exercise. That’s what twelve healthy adults did in a recent study published in the American Journal of Physiology. The results revealed a variety of poor biomarkers (like increased creatinine) suggesting the participants had sustained kidney injury.

To bolster this result, observational data on over 3,000 black Americans has linked higher consumption of sugary beverages to higher rates of chronic kidney disease.

Choosing a Sugar Alternative

A healthy diet is a low-sugar diet. But does that mean a healthy diet can’t be sweet? Not necessarily.

There are many sugar alternatives available: both high and low-carb varieties of natural sweeteners, and zero calorie artificial sweeteners. While most of the compounds are probably healthier than sugar, there’s a lot of debate to be had on that subject. Check out The pros and cons of 12 popular sugar substitutes to learn more.

My recommendation? Go with stevia, a zero-calorie sweetener derived from the leaves of the stevia rebaudiana plant. Compared to sugar and artificial sweeteners, stevia appears to blunt the post-meal rise in blood sugar and insulin levels.

It has also been shown to lower inflammation, improve oral health, exert antioxidant effects, lower blood pressure, and reduce liver damage. Like with almost anything, too much stevia may not be optimal (there’s much debate around whether it materially increases insulin)—but since stevia is about 300 times sweeter than sugar, you don’t need much to get the job done.

Lastly, if you’re having difficulty steering clear of sugar, check out my other article, 5 ways to reduce sugar cravings. And remember, the longer you steer clear of sugar, the easier it gets.