The Effects of Fructose on Your Immune System

The science of sugars and their effects toward our immune system

Quarantine can take a real toll on our mental sanity. Some may find themselves excessively worrying about the virus and how to keep their loved ones safe and cared for. Others find the lack of physical human connection quite unbearable, which robs their sense of inspiration and motivation to continue performing in their usual levels of productivity, and that can be quite frustrating.

These stressful times may subconsciously push us to wander towards sweet treat lane in an attempt to find solace and peace of mind in the safeguard of comfort foods that are usually high in fats or sugars.

One explanation involves the stress hormone cortisol. Normally, when someone is stressed, the adrenal glands secrete a hormone called cortisol, with the intention of reducing stress, but concomitantly ramp up appetite. Over longer periods, the body can start desensitising cortisol, which disrupts the pathway, causing the regulatory cortisol button to stay ‘on’ most of the time.

A Harvard Mental Health Letter quotes that fat- and sugar-rich foods appears to have a feedback effect that dampens stress-related responses and emotions. Researchers hypothesise that most of this has to do with the increased insulin release with cortisol, which induces hunger and the propensity to gravitate towards sweeter treats. It makes sense that they’re called comfort foods, both consciously and subconsciously.

It doesn’t help that most of us are psychologically programmed to favour foods that are high in sugars. Most parents reward their children with candy or cookies, and I don’t blame them, but this inadvertently strengthens the reward pathway in the brain, associating the sense of achievement with the feeling of joy and pride from sugary treats. It’s thought that most addictions are derived indirectly from these cemented neural pathways.

You can probably guess the direction this is leading towards. Fructose is a terrible sugar. They are found amply in table sugar, syrups, sugary drinks, honey, dried fruits, and in all your favourite desserts.

In the body, they are metabolised exclusively by the liver, where they are converted to fat, unlike glucose which can be metabolised by every cell in the body. The liver is an effective fat synthesiser. Other carbohydrates such as galactose and maltose do not follow the same pathway as fructose does. This helps explain why elevated fructose consumption can lead to weight gain and is a major risk factor for obesity.

Because fructose is metabolised in the liver, excessive consumption may overwork our liver cells, causing fatty liver disease, and in the process also suppress immune function. A 2014 paper published by Miriam Vos in the Journal of Hepatology (AASLD) outline that fat intake — which causes a rise in metabolic toxin formation in the blood— when coupled with increased fructose feeding causes metabolic dysregulation and loss of TLR-4 function.

Fat intake Toll-like receptors, often abbreviated to TLR play a critical role in the innate immune system, and endotoxins are the best studied TLR-4 complement. The endotoxin stimulates an inflammatory response and causes an elevation in levels of free fatty acids as well as impairing insulin sensitivity, which cycles back to increase insulin production and triggers a desire for eating sweet foods. Fructose does ultimately take a Toll.

Another paper that was published to the British Society of Immunology theorises that fructose induces the release of interferon (IFN-γ), an inflammatory cytokine, through recruitment of dendritic cells, which are part of the innate immune system. The rise in interferon secretion causes an increase in free radicals (AGEs), which further dampens the immune system. The study also outlines that “the AGEs formed by fructose induced increased levels of inflammatory cytokines in dendritic cells compared to AGEs from glucose”.

These findings may be striking, but they do not directly suggest that the immune changes are acute, which is where most current concerns are confined to. The SARS-CoV-2 outbreak has lasted over 5 months now, with some countries yet to see a decrease in case or death counts. Chronic suppression in immunity is probably the most likely outcome, since it takes time and barrels of fructose for potential metabolic dysregulation to occur.

A controversial study in 1970 took the blood of subjects after consuming a large dose of sugar. The blood was then placed in a petri dish and inoculated with a common strain of bacteria. Under a microscope, researchers could see that after a dose of sugar, certain white blood cells called neutrophils were far less aggressive in gobbling up the bacteria, demonstrating a perceived lack in optimal immune functioning.

The study has since never been replicated, and experts have stipulated that concluding sugar suppresses acute immune system functioning based on a sugar-injected petri dish full of neutrophils is an unjust oversimplification. However, an interesting study in 2016 showed an impressive benefit to starving a bacterial infection, but conversely feeding a viral infection.

“Fasting has opposite consequences in different types of inflammation”, says Ruslan Medzhitov, who was one of the few researchers involved in that paper. “Consuming sugar seemed to help the animals recover from viral infections but hinder their ability to fight off bacterial ones.”

Mind you, this finding was based on an animal study and focuses on entire fasts rather than removal of particular food groups. Nonetheless, it sheds an interesting light in the midst of the COVID-19 situation. If it’s true, then eat you must. Hit pause on fasting routines, but I’d still recommend skipping the fructose for other healthier, lower glycemic index options such as fruits, oatmeal, rice, and other complex carbohydrates.

It’s all very confusing stuff. The current consensus holds stance in the idea that overwhelming amounts of fructose and ensuing spike in blood sugar levels derails our body’s metabolism and immune system in ways we don’t fully understand yet.

The occasional cake or cookie might even be beneficial to our mental sanity, for which I’m sure the pandemic has bitten a chunk off from all of us. But as with any form of doing, be mindful and intentional. Acknowledge that we are still in full control of our actions, even if the things going on around may give us the illusion of helplessness.

Be wise in your decisions and actions, and you will come out of this pandemic on top.

Written by

Junior doctor, writer, photographer, and part-time social media strategist. Receive weekly updates from me ⤵

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