Sugar (4) – The immune system:
It is known that a diet high in sugar is related to type 2 diabetes and obesity (1) and also, that the high blood sugar levels that accompany diabetes, can cause malfunctions of the immune system (2).
Many health professionals continue to deny the link between sugar consumption and a weaker immune system, even if decades of experimentation seem to suggest otherwise.
In 1973 (3), a blood sample was taken from subjects after consuming a large dose of sugar and then inoculated with a common strain of bacteria.
Once under the microscope, the researchers were able to observe that neutrophils (white blood cells) were much less aggressive at eating bacteria, which suggests a decrease in the immune response after consuming sugar.
Almost four decades later (4), a study expanded on this research and found that sugar (especially fructose) negatively affected the immune response to viruses and bacteria.
In this case, it was observed that fructose down-regulated innate immune mechanisms mediated by MBL against viruses and bacteria (influenza A and Staphylococcus Aureus).
(Note: MLB (mannose-binding lectin), is a lectin that is synthesized in mammals, which binds to the structures of sugars present in a wide variety of bacteria and other microorganisms to eliminate them.)
Seven years later, in a study conducted on fruit flies (1); it was observed that in the presence of sugar, white blood cells could not effectively do their job of destroying harmful bacteria or viruses.
Innate immunity is the first line of defense against invading pathogens and parasites, and a high sugar diet, induced abnormal activation of the innate immune system, including inflammation.
The following year, an article that was published for the British Society for Immunology (5), theorized that fructose induces the release of interferon (IFN-γ), an inflammatory cytokine, through the recruitment of dendritic cells, which are part of the innate immune system. The increased secretion of interferon caused an increase in free radicals, further weakening the immune system.
“Our results provide evidence for the possible mechanism of immune deterioration on high fructose consumption”
N Jaiswal et al. Clin Exp Immunol. 2019 Aug (5)
In addition, it was also highlighted that the AGEs formed by fructose induced an increase in the levels of inflammatory cytokines in dendritic cells higher than the AGEs resulting from glucose.
To conclude, in a very recent study published in the journal Nature Communications (6), they demonstrated that fructose reprograms cellular metabolic pathways, increasing the production of inflammatory cytokines both in human monocytes treated with lipopolysaccharides (endotoxins) and in mouse macrophages.
“Taken together, our work underpins a pro-inflammatory role for dietary fructose in LPS-stimulated mononuclear phagocytes which occurs at the expense of metabolic flexibility”
Nicholas Jones et al. Nat Commun. 2021 (6)
Inflammation of this type can damage cells and tissues and contribute to the organs and systems of the body not working as they should, which has the potential to cause disease.
In summary, sugar in the diet has the potential to decrease the response to microorganisms (1,3,4) and promote inflammation through different mechanisms (1,5,7), all factors that negatively affect the immune system.
References:
1 – A high-sugar diet affects cellular and humoral immune responses in Drosophila.
2 – High blood sugar of diabetes can cause immune system malfunction, triggering infection.
3 – Role of sugars in human neutrophilic phagocytosis.
4 – Dietary sugars inhibit biologic functions of the pattern
5 – High fructose‐induced metabolic changes enhance inflammation in human dendritic cells.
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