As we all work to build immune function and reduce our risk of COVID-19, it’s important to know what may hurt your immune system.  Some lifestyle habits, conditions, and foods can reduce your body’s ability to stay healthy. Does sugar weaken your immune system?

Based on the evidence, sugar does impose a threat to your immune system. Here’s what it does, and how it can impact the immune system both directly and indirectly.

Does Sugar Weaken Your Immune System?

Sugar’s Direct Impact on Your Immune System

First, researchers have long noted that large amounts of sugar directly weaken your immune system.

In fact, studies have found that consuming 75-100 grams of sugar in one sitting (given as a sugar solution in research) suppresses the body’s immune responses. This amount of sugar caused a 50% drop in the ability of immune white blood cells to engulf bacteria in lab studies. Interestingly, when complex starches were ingested, the white blood cells were not weakened in this same way.

This effect lasted hours in the studies. The white blood cells were weakened most 2 hours after the sugar ingestion, but the effect lasted for 5 hours.

Discussion of the Study

First, 75-100 grams of sugar is a very large amount. But, if you imagine the amount one might eat at a party or celebration, with pizza, soda, and cake, it’s easy to see how 100 grams of sugar can be ingested.

Or, imagine college students staying up late studying for exams. They may consume sodas to stay awake plus high-sugar foods, and easily consume this large amount of sugar.

Secondly, this study shows that the immune cells were specifically weakened towards their fight of bacteria, but not necessarily viruses. Still, sugar had a direct and negative effect on the immune system.

Sugar’s Indirect Impact on Your Immune System

Sugar also plays a role in indirectly weakening your immune system.


It causes many conditions associated with poor immune function. Many of these conditions can make you more susceptible to COVID-19, other viruses, and chronic diseases.

Sugar Increases Inflammation

One key to boosting your immune function is to reduce inflammation in the body. To do so, it’s important to consume anti-inflammatory nutrients such as omega-3 fats, anti-inflammatory spices like turmeric and ginger, maintain a healthy weight, and more. On the other hand, one must reduce their intake of processed foods and sugars.

In many studies, researchers have found that added sugars (added to teas, sweets, etc.) and natural sugars in fruit juices are associated with increased inflammatory markers (1).

Chronic inflammation is associated with immunosuppression and illness.

High Sugar, Obesity, and Immune System

The Standard American Diet, high in processed foods and sugars, has contributed to the sky-rocketing obesity epidemic in our country. High sugar intakes also contribute to insulin resistance, high triglycerides, and weight gain.

What does this have to do with the immune system?

Obesity impairs and weakens the immune system. In fact, we know it diminishes its ability to fight viruses such as influenza and other respiratory viruses (2). What’s more, obesity can put your body in a state of chronic high blood glucose (due to insulin resistance) which is also associated with a higher risk of infection.

High Sugar Intake, Cardiovascular Disease, and Diabetes Risk

Type 2 Diabetes and cardiovascular disease are also associated with diets high in processed foods and sugars (3). And unfortunately, the immune system is weakened in both conditions.

In fact, diabetes mellitus is a major risk factor for the development of tuberculosis. Why? Patients with diabetes display defects in bacterial recognition, phagocytic activity, and cellular activation which results in impaired production of immune cells that fight disease (4).

What’s more, metabolic syndrome, cardiovascular disease, and diabetes are all associated with a chronic inflammatory state, which weakens the immune system (5).

Bottom Line

Whether directly or indirectly, whether against viruses, bacteria, or chronic disease, we can conclude that diets high in sugar weaken your immune system. As you work to build your health and immune function, do your best to omit the sugar in your diet. If you need help, start the Keto Zone diet today. You can even sign up for the Keto Zone 21-Day-Challenge now, for free!