Research
Mixed
Increased dietary fiber intake lowers colonic pH, which selectively suppresses Bacteroides spp. and promotes butyrate-producing gram-positive bacteria.
Eating more fiber not only feeds good bacteria directly but also creates an acidic environment in the gut that favors beneficial bacteria and suppresses others.
GoodSupportsHIGH confidence
A one-unit decrease in pH (from 6.5 to 5.5) has been shown to have a profound selective effect upon the colonic microbial community in fermentor simulations supplied with soluble polysaccharides, with a tendency to suppress Bacteroides spp. and to promote butyrate-producing gram-positive bacteria.
Why this rating
Supported by fermentor simulations and cited studies.
Source
The impact of nutrition on the human microbiome
Harry J. Flint · Nutrition Reviews · 2012
DOI 10.1111/j.1753-4887.2012.00499.x
narrative_reviewCited 282×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Dietary intake of nondigestible carbohydrates (resistant starch, prebiotics) directly influences the species composition and total numbers of the human colonic microbiota.Good
- Low-carbohydrate weight-loss diets decrease the concentration of microbially produced short-chain fatty acids and reduce the proportion of butyrate-producing bacteria.Good
Related findings · Mixed
- Bariatric surgery (VSG and RYGB) is the most effective and sustainable treatment for obesity, producing marked and sustained weight loss that non-surgical interventions cannot match.Strong
- Severely protein-deficient diets (2–3% energy) induce lean body mass loss and metabolic imbalance, whereas adequate protein intake (0.66 g/kg/d minimum) is a prerequisite for maintaining muscle, bone, and physiological function.Strong
- For patients with Class III obesity (BMI >39.9 kg/m2), metabolic bariatric surgery (MBS) is significantly more effective than any currently approved medication, with BilioPancreatic Diversion (BPD) showing the highest estimated weight loss.Strong
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →