Does eating garlic help your gut health?

Garlic contains allicin, an active compound that, in a small human study, lowered the production of TMAO. TMAO is a substance produced by gut bacteria from red meat and is associated with cardiovascular disease at high levels. In people with naturally high TMAO levels, one week of raw garlic juice also improved the diversity of gut bacteria and increased the proportion of beneficial bacterial species. This is the most direct finding in humans, but the study was small and lasted only one week.

Garlic also contains indigestible sugars that serve as food for beneficial gut bacteria, thereby stimulating the production of short-chain fatty acids. This makes garlic a prebiotic food on paper. In a laboratory experiment, cooked (roasted) garlic promoted the growth of Faecalibacterium, a gut bacterium associated with good gut health. Whether you can achieve this effect simply by eating garlic has not been tested in clinical studies.

Most other research has been conducted in mice or test tubes. For example, small particles that garlic naturally produces reduced gut inflammation in mice, restored the gut lining, and rebalanced the bacterial composition. Allicin also improved a fatty liver condition in mice and restored beneficial bacteria. These are interesting mechanisms, but not proof that simply eating garlic has the same effect in humans.

There is also a downside. For people with irritable bowel syndrome, garlic is in fact a well-known trigger of symptoms, because it is rich in certain fermentable carbohydrates. Raw garlic can also cause stomach complaints. In short: the potential benefits for the gut microbiome are promising but have not yet been demonstrated firmly enough to say that garlic is good for everyone's gut.