Resilience of small intestinal beneficial bacteria to the toxicity of soybean oil fatty acids

Abstract

Over the past century, soybean oil (SBO) consumption in the United States increased dramatically. The main SBO fatty acid, linoleic acid (18:2), inhibits in vitro the growth of lactobacilli, beneficial members of the small intestinal microbiota. Human-associated lactobacilli have declined in prevalence in Western microbiomes, but how dietary changes may have impacted their ecology is unclear. Here, we compared the in vitro and in vivo effects of 18:2 on Lactobacillus reuteri and L. johnsonii. Directed evolution in vitro in both species led to strong 18:2 resistance with mutations in genes for lipid biosynthesis, acid stress, and the cell membrane or wall. Small-intestinal Lactobacillus populations in mice were unaffected by chronic and acute 18:2 exposure, yet harbored both 18:2- sensitive and resistant strains. This work shows that extant small intestinal lactobacilli are protected from toxic dietary components via the gut environment as well as their own capacity to evolve resistance.

Linoleic acid inhibits Lactobacillus activity by destroying cell membrane and affecting normal metabolism

“…The human intestinal flora in different generations was previously analyzed, and findings showed that several intestinal strains are lost during the evolutionary process, thereby decreasing the diversity of the intestinal flora. 4 Under the increasing annual global consumption of vegetable oil, this situation may possibly be related to excessive PUFAs intake. 18 High omega-6 PUFA doses negatively affect the intestinal microecological balance.…”

“…However, exposure to high PUFA concentration inhibits the growth and adhesion of Lactobacillus ( Lactobacillus casei and Lactobacillus bulgaricus ), thereby reducing the amount of Lactobacillus in the body. Linoleic acid, which is the main fatty acid in soybean oil, inhibits the growth of an important probiotic Lactobacillus reuteri . However, the mechanism underlying the effect of linoleic acid on Lactobacillus activity is unclear.…”

“…Linoleic acid, which is the main fatty acid in soybean oil, inhibits the growth of an important probiotic Lactobacillus reuteri. 4 However, the mechanism underlying the effect of linoleic acid on Lactobacillus activity is unclear.…”

The Western diet: a blind spot of eating disorder research?—a narrative review and recommendations for treatment and research

“… 124 Until the turn of the 20th century, the ratio of omega-6:omega-3 intake was 1:1, and this has increased to 20:1 in the Western diet in parallel with the obesity epidemic. 125 Experimental work shows that linoleic acid is toxic to beneficial bacteria in the gut, 126 which may explain why the increased ratio of omega-6 to omega-3 has been linked with inflammation and metabolic disorders as well as depression and eating disorders. 125 , 127 , 128 Disappointingly, interventions aimed at improving omega-6:omega-3 ratios by using fish oil supplements have yielded conflicting results.…”

Critique of the Chinese dietary guidelines on the consumption of cooking oils

“…Soybean oil is more obesogenic than coconut oil and fructose (Deol et al., 2015). Linoleic acid rich in soybean oil was proved inhibited Lactobacillus reuteri , and a beneficial bacterium has become less common in Western population (Di Rienzi et al., 2018). A recent randomized controlled trial found evidence that with increased proportion of soybean oil in the Chinese diet, gut microbiota diversity was decreased, and content of indole and arachidonic acid that positively correlated to proinflammatory markers was increased (Wan et al., 2019).…”