A GI surgeon highlights 4 foods for better gut health—here's what the evidence says
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[This fruit] is particularly rich in soluble fiber, which promotes softer stool and increases stool frequency without the associated side effects of some laxatives.
—Karan Rajan, GI surgeon
Many of your patients likely think gut health is all about probiotics in a pill or bland high‑fiber diets, but some everyday foods—from juicy fruits to that necessary morning coffee—can meaningfully support digestion, stool regularity, and even microbial diversity.
In a TikTok video, Rajan Karan, MBBS, a gastrointestinal surgeon, breaks down four surprising staples that science shows may help your patients’ guts, and what the evidence really says about each.
1. Kiwi
"[It's] one of my all time favorites and has been shown in research studies to be as effective as psyllium husk and prunes to improve the symptoms of bloating and constipation," Dr. Rajan said. "Kiwi is particularly rich in soluble fiber, which promotes softer stool and increases stool frequency without the associated side effects of some laxatives."
What the evidence says
A randomized controlled trial compared two green kiwifruits daily (approximately 6 g dietary fiber) with psyllium (7.5 g) in subjects with functional constipation or irritable bowel syndrome with predominant constipation. The kiwifruit improved complete spontaneous bowel movements (CSBMs) compared to psyllium.[]
Research has also found that kiwifruit increased bowel movement frequency and improved GI comfort in patients with constipation.[]
A 2024 systematic review and meta‑analysis reconfirmed that kiwifruit is an effective treatment for functional constipation.[]
2. Coffee
"Coffee has been consistently linked with a reduced risk of fatty liver disease and the development of liver cirrhosis and chronic liver disease," Dr. Rajan said. "Coffee contains the double whammy of soluble fibers and polyphenols."
Polyphenols, he explained, act as prebiotics to feed your good gut bacteria. "Coffee may also improve gut motility, making it beneficial for reducing constipation," he added.
What the evidence says
A recent study found that coffee consumption is strongly associated with altered gut microbiota composition, including increased abundance of Lawsonibacter asaccharolyticus, independent of caffeine content.[]
A narrative review of coffee and the microbiota described how polyphenols and melanoidins in coffee may modulate microbiota, and some human trials have shown an increase in Bifidobacterium after coffee consumption.[]
Regarding motility and constipation, a 2024 literature review noted that moderate coffee consumption (< 4 cups per day) may enhance gut motility and may help prevent constipation.[]
3. Mixed nuts (almonds, walnuts, pistachios)
"Having a mixture of nuts gives you a diverse range of prebiotic fibers, which promotes microbial biodiversity in your gut," Dr. Rajan said. "There are studies suggesting that regular nut consumption—around 20 to 30 grams—a day is associated with a reduction in colorectal cancer risk, possibly by reducing inflammation and improving microbial biodiversity."
What the evidence says
A 2020 systematic review and meta-analysis found that nut consumption may affect gut microbiota and gut function, but the evidence in randomized controlled trials is limited, there were no effects of nut consumption on stool output, and results were heterogeneous.[]
A meta‑analysis of 38 studies found that nut intake was inversely associated with all‑cancer risk (RR = 0.90). Specifically, the colorectal cancer (CRC) sub‐analysis found RR = 0.77 (95% CI, 0.63–0.94) for the highest vs the lowest nut intake.[]
Another meta‑analysis on the consumption of nuts and legumes and the risk of CRC showed an incremental benefit: Each 28 g of nuts per day is associated with a 33% lower risk of CRC (RR = 0.67, CI 0.45–0.98).[]
4. Yogurt (live active cultures)
"Look for yogurt containing live active cultures like Lactobacillus and Bifidobacterium, which can help to add to your good microbial load," Dr. Rajan said. "Yogurt has been shown to alleviate symptoms of IBS and can even improve lactose digestion in those who are lactose intolerant."
What the evidence says