Inflammation and glucose levels: How high blood sugar can turn a good system bad

Inflammation helps heal your body, but chronic inflammation can cause serious damage. Here’s how a healthy lifestyle—including a low-sugar diet—can help keep it in check.

Article highlights

  • Inflammation is a natural defense system in which your body attacks something it sees as a harm, such as a cut, an infection or even stress.
  • That response produces symptoms like redness, pain, swelling, warmth, and loss of function.
  • Chronic inflammation can increase your risk of heart attack, obesity, cancer and diabetes, among other conditions.
  • High blood sugar, or hyperglycemia, and the insulin resistance that often accompanies it, can be proinflammatory.
  • A healthy diet and lifestyle can greatly reduce your chance of chronic inflammation.

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Inflammation is your body’s way of protecting you from things that can cause harm. You can get an inflammatory response to an injury (like a cut or a splinter), to an infection from bacteria or a virus, or from other exposures that the body may see as a threat, such as stress, dietary sugar, and environmental toxins.

Inflammation is usually divided into two types: acute and chronic. Acute is the type that most people think of when they hear inflammation. This is what happens right after you cut yourself, brush up against poison ivy, or get an infection like the “common cold” or the flu. Your body sends out white blood cells that assess the situation and signal for reinforcements to attack the problem via chemical mediators, such as histamine, that can trigger specific cellular changes. As a result of this assault, you may experience one or more of the five most common symptoms of acute inflammation: redness, pain, swelling, warmth, and loss of function (e.g., difficulty bending an inflamed joint).

Inflammation is also responsible for most of the symptoms you have when you “feel sick,” like fever, chills and fatigue. While these can be annoying or uncomfortable, they are an indication that the body is doing its job protecting you. Without inflammation, even simple infections could become deadly. In most cases, once the harm is dealt with, the body can heal and return to normal—this usually takes somewhere between hours and days.

However, sometimes the inflammation never gets better and instead turns into a process that lasts for months or years—this is chronic inflammation. It may occur in response to an abnormality in the body, like cholesterol plaques in your arteries (atherosclerosis) or toxins from smoking. In many cases, chronic inflammation does not have a definitive cause. Sometimes the body attacks itself even though there is no injury or harmful agent floating around; this leads to auto-immune diseases, like rheumatoid arthritis and inflammatory bowel disease. Symptoms can range from very mild to severe, and even people with the same condition can have varying degrees of symptoms. Over time, chronic inflammation can cause permanent damage to cells and tissues.

How Do We Measure Inflammation? 

Sometimes blood tests can help confirm the presence of chronic inflammation by measuring for particular markers. Erythrocyte sedimentation rate (ESR) is a common test. It looks at how fast red blood cells settle to the bottom of a tube of blood. Normally, the cells settle slowly, but if you have inflammation they sink faster. This is a non-specific test, meaning that it only tells you if you have inflammation, not the cause. Another blood test measures your C-reactive protein (CRP) levels. During an inflammatory response, the liver makes CRP and releases it into the bloodstream. In general, higher levels of CRP indicate the presence of inflammation, but this test also does not identify the root cause.

Another potential marker of inflammation is uric acid (UA). Uric acid is usually a byproduct of DNA/RNA breakdown or the metabolism of ATP, the energy currency of your cells. High levels of uric acid may be present in and contribute to proinflammatory medical conditions like heart disease and diabetes. Research is still needed in this area, but some studies suggest that not only do uric acid levels potentially correlate with inflammation, but they may also precede insulin resistance, which can then lead to diabetes. 

Inflammation is important regardless of whether you feel it happening. Chronic inflammation has been linked to cardiovascular disease, diabetes, dementia and depression, among other conditions. Knowing you have inflammation can encourage you to identify risk factors that you can control and change, like sugar intake, that could lower chronic inflammation.

How does excess sugar affect inflammatory markers?

It is important to make a distinction between the different types of sugars in our food. One way that food sugars can be categorized is based on how they affect your blood glucose levels—this is called the glycemic index. Foods that cause a spike in blood glucose levels after a meal are said to have a high glycemic index. These include the refined carbohydrates that you have probably been told to avoid. Refined carbohydrates have had their fiber removed (along with other nutrients) and are found in bread, white sugar, cakes, cookies, crackers, tortillas, white rice, and many cereals. Foods that raise your blood glucose levels quickly have been associated with elevated levels of inflammatory markers, like CRP.

You may have heard that different types of sugar like fructose, high-fructose corn syrup, and sucrose (table sugar) can cause more or less inflammation, but so far studies have not shown a difference in the levels of inflammatory markers among kinds of sugars. That is not to say that they don’t affect your body in different ways, as we’ll address next, but there does not seem to be a difference in how they affect blood tests like CRP. 

What does high blood sugar do to your body?

Eating too much of any type of sugar can lead to spikes in your blood glucose levels, also called hyperglycemia. In most healthy people, the body responds to these spikes by releasing insulin, a hormone that works to bring glucose levels back down to normal. If, however, you repeatedly have too much glucose in your body, over time the cells become “numb” to insulin, causing blood sugar to rise. This state is known as insulin resistance and it is proinflammatory, potentially causing damage throughout your body. 

One target of these harmful effects is your endothelial cells, the cells that line your blood vessels. Repeated levels of high blood sugar can cause your blood vessels to produce damaging reactive molecules called free radicals, via compounds called advanced glycation end products (AGEs). Too much free radical activity generates oxidative stress, damage to endothelial cell function, and inflammation in the blood vessels. Hyperglycemia can also cause oxidation of free fatty acids stored in your fat cells, which contributes to inflammation.

In addition, glucose causes the oxidation of low-density lipoprotein (LDL), increasing your risk of plaque build-up in your blood vessels. Another negative effect is that high blood sugar levels promote blood vessel constriction and platelet clumping, which can promote blood clots.

Lastly, we all know that excess sugar leads to weight gain, which in turn increases your risk of other medical problems like obesity, high blood pressure, and many more. What’s more, excess fat tissue—particularly around the waist—promotes immune cell activation and secretes large quantities of proinflammatory chemicals. Diabetes, which is fundamentally a disease of glucose dysregulation, is itself a severe proinflammatory state

What long-term health problems can inflammation cause?

In light of the detrimental effects that high blood glucose levels can have on the body, it should not come as a surprise that many health problems are related to hyperglycemia and inflammation. Long-term inflammatory diseases are the most significant cause of death worldwide. While chronic inflammation may be present without symptoms or only mild findings initially, it contributes to many long-term health problems, including:

  • Cardiovascular diseases, including heart attacks and strokes: There is a relationship between inflammatory markers, like high-sensitivity CRP (hsCRP), and risk of cardiovascular disease. Also, atherosclerosis (plaque buildup in your blood vessels) involves chronic low-grade inflammation and is the main culprit in heart attacks and strokes.
  • Obesity: Fat tissues secrete inflammatory chemicals; the higher your body mass index (BMI) the more pro-inflammatory compounds you have circulating in your body. This may partially explain why obesity increases your risk of heart diseases, diabetes, and cancers.
  • Cancers: Inflammation seems to play a role in cancers, including kidney, prostate, ovarian, hepatocellular, pancreatic, and colorectal.
  • Diabetes: Immune cells affect your pancreas, which produces insulin, and the presence of inflammatory markers further highlight diabetes’ relationship with chronic inflammation. This inflammation also leads to many of the complications associated with diabetes, like diabetic retinopathy, neuropathy, and nephropathy, as well as the increased risk of heart attacks and strokes.
  • Rheumatoid arthritis: Chronic inflammation in your joints that can lead to permanent damage and loss of function.
  • Lung diseases like asthma and chronic obstructive pulmonary disease: Inflammation from irritants lead to lung problems.
  • Alzheimer’s disease: Chronic inflammation is linked to cognitive decline and dementia.

What can you do to limit inflammation?

While it may seem like inflammation is everywhere, there are steps that you can take to limit it.

Changes in your diet are among the easiest ways to decrease inflammation. Avoid refined carbohydrates, sugary beverages, and other foods that cause spikes in your blood glucose levels. Instead, increase your consumption of fiber, fruits, vegetables, nuts, seeds, and other low-glycemic-index foods, all of which may help lower your risks of cardiovascular disease and diabetes. The plant chemicals called polyphenols in green and black teas have been shown to lower levels of inflammatory markers, like CRP. Curcumin, present in turmeric, has been shown to help with inflammation in animal studies.

You already know that exercise, especially moderate intensity exercise, can help with weight loss—but it may also decrease the levels of proinflammatory chemicals in your body, regardless of how much weight you lose. And exercise decreases your risk of heart disease, diabetes, obesity and other medical problems, so it’s an all-around winner when it comes to improving your health.

Smoking and stress are two other factors that can increase inflammation. Similarly, people with sleep disorders, or who simply don’t get enough sleep on a regular basis, are at higher risk of having chronic inflammation.

Inflammation is an important part of your body’s defense systems, especially when it comes to fighting infections. However, it can also wreak havoc in your body if left unchecked, especially over the long run. Positive lifestyle choices that limit inflammation can go a long way toward keeping your body healthy.