High-fat diets linked to unexpected health risks

Researchers at UC Riverside have found new evidence that may help motivate you to ditch a high-fat diet in the new year. 

According to the study, diets that are high in fat affect genes linked to obesity, colon cancer, the immune system, and brain function. The team found that high fat intake may also elevate the risk of COVID-19 infection.

Focus of the research 

For the investigation, the researchers fed mice three different high-fat diets (with at least 40% of calories from fat) over 24 weeks. These diets included saturated fat from coconut oil, monounsaturated fat from modified soybean oil, and polyunsaturated fat from unmodified soybean oil. 

The experts analyzed genetic changes in all four parts of the intestines, alongside examining the microbiome.

Surprising genetic alterations

The study revealed significant changes in gene expression across all diets when compared to a low-fat control 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 study senior author Professor Frances Sladek.

The research highlights the extensive impacts of these diets, including major shifts in gut bacteria and fat metabolism genes.

Alarming findings

One of the more alarming discoveries was the detrimental effect of high-fat diets on genes regulating immunity and infectious diseases. 

“We saw pattern recognition genes, ones that recognize infectious bacteria, take a hit. We saw cytokine signaling genes take a hit, which help the body control inflammation,” said Sladek. 

‘So, it’s a double whammy. These diets impair immune system genes in the host, and they also create an environment in which harmful gut bacteria can thrive.”

Additional insights 

The study revealed an association between high-fat diets and increased expression of ACE2 and other proteins, which facilitate COVID-19 entry into the body.

Furthermore, the team observed that high-fat food increased signs of stem cells in the colon. “You’d think that would be a good thing, but actually they can be precursors to cancer,” explained Sladek.  

Changes in gene expression 

Coconut oil showed the greatest number of changes in gene expression, followed by the unmodified soybean oil. The researchers noted that negative changes to the microbiome in this study were more pronounced in mice fed the soybean oil diet. 

The experts had previously documented negative health effects of high soybean oil consumption. In 2015, they found that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice. 

In 2020, the researchers demonstrated that soybean oil can also affect genes in the brain related to conditions like autism, Alzheimer’s disease, anxiety, and depression. 

In the current study, the team found that the expression of several neurotransmitter genes were changed by the high-fat diets, confirming that diet can impact the gut-brain axis.

Concerning results

The researchers emphasized that these findings only apply to soybean oil, and not to other soy products, tofu, or soybeans themselves. “There are some really good things about soybeans. But too much of that oil is just not good for you,” said UCR microbiologist Poonamjot Deol.

While the findings are based on mouse studies and may not fully translate to humans, the similarities in working DNA between the two species make the results concerning. The high consumption of soybean oil in the United States is particularly alarming. 

“Some fat is necessary in the diet, perhaps 10 to 15%. Most people though, at least in this country, are getting at least three times the amount that they need,” said Deol. 

Study implications 

The experts noted that there is no need to panic over one or two meals, considering it was the long-term effects of a high-fat diet (24 weeks) that caused the observed changes in mice.

“In human terms, that is 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. 

Still, the researchers hope the study will cause people to closely examine their eating habits. “Some people think, ‘Oh, I’ll just exercise more and be okay. But regularly eating this way could be impacting your immune system and how your brain functions,” said Deol. “You may not be able to just exercise away these effects.”

The study is published in the journal Scientific Reports.

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