Palm oil may increase the uptake of bacterial molecules through the gut wall, a process that scientists have linked to inflammatory responses in the body. Blueberries and blackberries, by contrast, appear to temper this process. PhD candidate Aina Casademont Roca discovered this in a laboratory study using artificial intestines.
The gut does more than absorb nutrients: it also forms a barrier and sometimes allows microbial molecules to pass into the bloodstream. Excessive amounts of such bacterial substances in the blood have been linked to low-grade inflammation, which in turn may adversely affect processes such as brain health. To investigate how food influences this transmission process, Casademont Roca built a simplified model of the human small intestine in the laboratory, consisting of intestinal cells and immune cells. She exposed these artificial guts to different types of dietary fat, including fish oil, olive oil, peanut oil and palm oil. She then examined how each type of fat impacted the uptake of the bacterial molecule lipopolysaccharide (LPS), a process that previous studies have linked to inflammatory processes in the body.
Of the fats tested, palm oil triggered the strongest response: the gut wall allowed the most bacterial LPS to pass through. The activity of an important inflammatory pathway, NF-κB, doubled compared to the situation without added fat. When Casademont Roca tested if eating fruit could counter this, she discovered that blueberries tampered the inflammatory activity, by as much as 46 percent.
Not all fats cause the same response
Not every dietary fat caused Casademont Roca's artificial intestine to react the same way. Fish oil and peanut oil, by contrast, reduced its activity, while olive oil had no effect. According to Casademont Roca, this may be related to the composition of the fats: palm oil consists largely of saturated fatty acids, while fish, peanut and olive oils are rich in unsaturated fatty acids.
In the artificial guts, the PhD candidate found that palm oil led to more LPS transport through the intestine compared to the other fats. Interestingly, this was not only because the bacterial molecules leaked between intestinal cells. The researchers therefore focused on another mechanism: transcellular transport. In this process, a substance passes through an intestinal cell, from one side to the other. ‘We suspect that some fats, such as palm oil, activate mechanisms that actively transport specific substances through intestinal cells,’ explains Casademont Roca. When bacterial molecules, such as LPS, reach tissues beyond the gut, immune cells respond to them. Researchers suspect that this can trigger low-grade inflammation in the body.
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