Blueberries and blackberries reduce inflammatory response in artificial gut

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. 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.

Because palm oil triggered such a strong response, Casademont Roca investigated whether fruit could counteract it. This choice was not arbitrary: berries are part of the MIND diet, a dietary pattern aimed at supporting brain health. Previous research has also suggested that berries may have anti-inflammatory effects. The PhD candidate therefore focused on blueberries, and in addition on blackberries and bananas. She freeze-dried the fruits and digested them using stomach and intestinal juices and bile, before adding the resulting mixture, together with palm oil, to the artificial intestine. The result was striking: all three types of fruit reduced the measured inflammatory response. Blueberries had the strongest effect, reducing it by 46 per cent.

This effect may occur because the fruits suppress genes involved in the transport process. This suggests that blueberries, blackberries and bananas may reduce the amount of bacterial LPS entering the body, resulting in a lower immune response. Exactly how this works remains unknown. ‘The high levels of fibre and polyphenols in the fruit may have something to do with it,’ the PhD candidate speculates.

Does this mean that eating a portion of blueberries can neutralise the harmful effects of a fatty meal? The researcher cannot say for certain yet. The experiments were conducted in an artificial environment rather than in humans. Although the model consists of human intestinal and immune cells, a real human intestine is much more complex. It contains many cell types, blood flows alongside the intestinal wall, and thousands of species of microorganisms interact with each other and their host.

Therefore, the next step includes more advanced models, such as organoids: miniature organs that mimic the structure and properties of the human intestine. Animal studies could then help to unravel the underlying mechanisms further. Only after that can researchers investigate whether a similar effect also occurs in humans.

Casademont Roca’s research is part of the larger MOCIA research programme (Maintaining Optimal Cognitive function In Ageing). The programme investigates how lifestyle factors, including diet, can contribute to maintaining cognitive function as people age.