Study indicates high-fructose diets could harm immune system

The vilification of sugar in food and beverage is nothing new; consumer preferences have been trending toward natural, non-sugar sweeteners for years. Given the results of a recent study on fructose by researchers at Swansea University’s Medical School, the University of Bristol and the Francis Crick Institute in London, that is unlikely to change.

While fructose is a naturally occurring sugar that can be found in fruits and vegetables, it is also the basis of high fructose corn syrup (HFCS), a manufactured sweetener used in everything from soft drinks and candy to frozen meals and salad dressings.

The study, published in Nature Communications, sought to “investigate the metabolic response to fructose exposure in activated human monocytes”—specifically on the immune system, a topic of much interest as we pass the one-year mark of the COVID-19 pandemic.

The results indicated fructose “reprograms cellular metabolic pathways to favor glutaminolysis and oxidative metabolism, which are required to support increased inflammatory cytokine production in both LPS-treated human monocytes and mouse macrophages.”

Put more simply, the authors found fructose promotes production of inflammation-causing cytokines. This causes inflammation of the immune system, which causes production of even more inflammatory-associated molecules. This inflammation within the immune system, according to the authors, can damage cells and tissues and leave individuals more susceptible to illness—an especially prescient issue over the last 12 months.

The authors remarked on the importance of such studies on fructose consumption, noting, “a growing concern regarding high fructose corn syrup consumption globally—in some cases, accounting for 10% caloric intake in the [U.S.]—thus underscoring the need to understand the implications of fructose exposure.” They also noted prior research has linked fructose to “numerous metabolic disorders such as obesity, cancer and non-alcoholic fatty liver disease,” but that current research lacks in understanding its impact on the immune system.

The 2020-25 Dietary Guidelines for Americans, while not singling out HFCS, does recommend limiting intake of all added sugars, which includes HFCS.

“Our study is exciting because it takes us a step further toward understanding why some diets can lead to ill health,” said one of the study’s authors, Emma Vincent, Ph.D. “Research into different components of our diet can help us understand what might contribute to inflammation and disease and what could be best harnessed to improve health and well-being,” echoed fellow author Nick Jones, Ph.D.