Gut health and GLP-1s: Summary
- GLP-1s can boost certain beneficial gut bacteria as foods containing prebiotics and probiotics can
- Semaglutide boosts beneficial gut bacteria but may reduce diversity
- Liraglutide, exenatide, and dulaglutide also boost beneficial bacteria
- All GLP-1s boost Akkermansia muciniphila, which is associated with cardiovascular and intestinal health
- It is important for GLP-1 users to pay attention to gut health
As GLP-1 weight-loss drugs grow in popularity, they are beginning to change the food sector.
Reducing food intakes, changing taste, and even influencing appetite for alcohol, the drugs have taken the food world by storm.
But as our understanding of gut health grows, it begs the question: how much do GLP-1 drugs affect the microbiome?
Are GLP-1s beneficial to the gut?
GLP-1 drugs “can change the gut environment in a few ways,” explains nutritionist and British Dietetic Association (BDA) spokesperson Nichola Ludlam-Raine.
These include slowing down digestion, changing bile acids, and reducing how much food (and fibre) reaches the gut microbiota.
“Early studies suggest they can shift the balance of gut bacteria, but findings in humans are still mixed, with more research being needed in this area as we don’t know if the effects are positive or negative!”
GLP-1s can boost beneficial gut bacteria
A review of available studies explored the specific effects of different GLP-1 receptor agonists on the gut. Many can boost populations of positive gut bacteria, much as probiotics and prebiotics in food can.
Semaglutide, the GLP-1 used for popular products including Wegovy and Ozempic, saw mixed results.
On the one hand, some beneficial gut bacteria saw an increase, such as A. muciphila (known for positive metabolic effects on human health, and boosted by the consumption of polyphenols in food).
However, other studies linked semaglutide to a decrease in microbial diversity.
Liraglutide, sold commercially as Victoza and Saxenda, was also linked to positives for metabolic health, leading to the increase of gut bacteria such as Lactobacillus (which can be increased by the consumption of probiotics such as yoghurt and prebiotics such as onions and bananas) and Allobaculum (which can be increased by foods like wasabi).
According to animal studies, the administration of exenatide, known by its commercial name of Bydureon, leads to the increase in genera for Barnesiella, and Ruminococcus (which can be increased by nuts such as walnuts). In human studies, exenatide increased Coprococcus (the increase of which has been linked to mental health, and is increased by a high fibre diet) and Bifidobacterium.
Dulaglutide, known by its commercial name Trulicity, was connected to increases in Bacteroides and Ruminococcus genera in animals and Lactobacillus in humans.
Akkermansia muciniphila, which is linked to improved cardiovascular health, better weight management and intestinal health, was increased by all GLP-1s.
Do GLP-1-induced dietary changes affect the gut?
As well as the drugs themselves, the dietary changes incurred by GLP-1 drugs can also affect the gut.
“Eating smaller amounts, especially if it means less fibre, can reduce the fuel that good gut bacteria thrive on. This can lower beneficial compounds like short-chain fatty acids (SCFAs), which influence everything from weight to mood and immunity, and make constipation worse if fibre and fluids aren’t kept up,” explains BDA’s Ludlam-Raine.
Much like with nutrients such as protein, the intake of which those on GLP-1s need to pay attention to, gut health is an important factor for users of the drugs to consider.
“My advice to patients on GLP-1s is to remember your gut still needs looking after – and it isn’t the less food the better!” says Ludlam-Raine.