​Long-term high fat diets linked to increased risk of COVID, finds study​

A team of researchers at the University of California - Riverside (UCR), US have recently examined and found that three high-fat diets heighten the expression of ACE2 and other host proteins, used by spike proteins of COVID-causing viruses to gain entry into the body. The team had previously linked soybean oil-based diets to obesity and diabetes, both of which have been studied to be major risk factors for COVID.

The researchers fed mice three different diets over the course of 24 weeks where at least 40 per cent of the calories came from fat. These groups were made to consume diets based on saturated fat from coconut oil, monounsaturated, modified soybean oil and unmodified soybean oil high in polyunsaturated fat. They then looked at all four parts of the mice's intestines, along with their microbiome. A fourth control group of mice was fed a low-fat diet.

"Word on the street is that plant-based diets are better for you, and in many cases that's true. However, a diet high in fat, even from a plant, is one case where it's just not true," said Frances Sladek, a UCR cell biology professor and senior author of the study published in the journal Scientific Reports. Further, it may not be possible to "just exercise away these effects", according to UCR microbiologist Poonamjot Deol, the study's co-first author.

"These diets impair immune system genes in the host, and they also create an environment in which harmful gut bacteria can thrive," said Sladek. These diets brought major changes in genes related to fat metabolism and the composition of gut bacteria. However, other observations were more surprising, such as changes in genes regulating susceptibility to infectious diseases, including those recognising infectious bacteria and those controlling inflammation, they said.

The coconut oil diets were found to impact gene expression the most, followed by the unmodified soybean oil diets, suggesting that polyunsaturated fatty acids in unmodified soybean oil play a role in altering gene expression. Microbiome changes, on the other hand, were observed to be more pronounced in mice fed with diets based on soybean oil, which the researchers said was the most commonly consumed oil in the US, and is increasingly being used in other countries, including Brazil, China, and India. They also noted that the findings applied only to soybean oil and not to other soy products, tofu, or soybeans.

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The researchers found that this effect was observed when the mice were fed these high-fat diets for 24 weeks was like "starting from childhood and continuing until middle age". "One night of indulgence is not what these mice ate. It's more like a lifetime of the food," said Deol.