Gut Health and Diet: What to Eat for a Better Microbiome
The gut microbiome — the roughly 38 trillion bacteria living in your digestive tract — has attracted more scientific attention in the past decade than almost any other area of nutrition research. What has emerged is clear enough to act on: diet is the single most powerful lever for improving microbiome diversity and function.
Why the Microbiome Matters
The gut microbiome isn't just about digestion. It produces neurotransmitters (including about 95% of the body's serotonin), regulates immune function, influences inflammation levels, affects nutrient absorption, and communicates with the brain via the vagus nerve — the gut-brain axis. Low microbiome diversity is consistently associated with obesity, inflammatory conditions, depression, and metabolic disease.
The Most Impactful Thing You Can Do: Eat More Plants
The American Gut Project, one of the largest microbiome studies ever conducted, found that people who ate 30 or more different plant foods per week had significantly more diverse microbiomes than those eating 10 or fewer. The number was consistent regardless of whether people also ate meat.
Diversity of plants matters more than quantity of any single plant. A diet with spinach, carrots, lentils, apple, oats, walnuts, broccoli, garlic, onion, and berries is far better for microbiome diversity than eating large amounts of just two or three plant foods.
Prebiotic Foods
Prebiotics are the fibre types that feed beneficial gut bacteria. Best sources:
- Garlic and onions — high in fructooligosaccharides and inulin
- Jerusalem artichokes — exceptionally high in inulin
- Leeks, asparagus, bananas
- Oats — beta-glucan, also beneficial for blood sugar and cholesterol
- Legumes — lentils, chickpeas, black beans
Fermented Foods
A Stanford study found that a diet high in fermented foods increased microbiome diversity and reduced inflammatory markers more effectively than a high-fibre diet alone. Daily consumption of fermented foods appears to deliver live bacteria that influence the existing microbiome environment:
- Yogurt with live cultures
- Kefir — more bacteria than yogurt, also contains yeast
- Sauerkraut and kimchi (unpasteurised)
- Kombucha
- Miso and tempeh
What Harms the Microbiome
Antibiotics cause the most dramatic short-term disruption — necessary when needed medically, but microbiome recovery can take months. Beyond antibiotics: high consumption of ultra-processed foods, artificial sweeteners (particularly sucralose and saccharin have shown effects on glucose metabolism via microbiome disruption), chronic stress, and low fibre intake all negatively affect microbiome composition.
Probiotics Supplements vs Food
Probiotic supplements can be useful in specific situations (post-antibiotic recovery, certain IBS symptoms) but consistently have weaker evidence than fermented food consumption for general microbiome health. The diversity of bacteria in a varied fermented food diet exceeds what any capsule delivers.
Our Stress Relief plan incorporates fermented foods (kefir, yogurt) and prebiotic-rich vegetables throughout the week — reflecting the evidence that gut health directly affects stress resilience via the gut-brain axis.
Get the Stress Relief Plan →If you have inflammatory bowel disease or IBS, consult a dietitian before significantly increasing fibre intake — rapid changes can worsen symptoms initially.