Why plant-forward diets consistently show the highest microbiome diversity—and how to do it right
Here’s what research consistently shows: The more plants you eat, the more diverse your microbiome becomes.
Studies comparing different dietary patterns find that people eating predominantly plant-based diets have:
This isn’t about moral arguments or environmental concerns (though those are valid). This is about what decades of research reveal about diet and human health: plants contain compounds—fiber, polyphenols, prebiotics—that your microbiome needs to thrive.
This page covers plant-based eating from a gut health perspective. We’ll explore:
Important clarification: “Plant-based” doesn’t necessarily mean 100% vegan. For many people, it means making plants the foundation of their diet while potentially including smaller amounts of animal products. Both approaches can benefit gut health—it depends on your goals and values.
“Plant-based” is an umbrella term that encompasses various approaches. Understanding the spectrum helps you choose what works for you:
Research shows that all plant-forward approaches benefit the microbiome compared to Western diets. The key factor is plant volume and diversity, not necessarily 100% elimination of animal products. A flexitarian eating 35+ different plants weekly may have better microbiome diversity than a vegan eating the same 10 foods repeatedly.
Research has identified multiple mechanisms through which plant-rich diets enhance gut health:
Studies of vegans and vegetarians consistently show fiber intake of 40-60+ grams daily—2-4 times what most omnivores consume.
Why this matters:
Learn more: Fiber: The Essential Nutrient
When animal products occupy less plate space, plant variety naturally increases. Research shows plant-based eaters typically consume 40-50+ different plants weekly compared to 10-15 for typical omnivores.
Impact:
Learn more: The 30 Plants Challenge
Plant foods are the exclusive source of polyphenols. Plant-based diets deliver 3,000-5,000mg daily—3-5 times typical Western intake.
Why this matters:
Learn more: Polyphenols & Phytonutrients
Research comparing omnivores to vegetarians and vegans finds distinct microbiome patterns:
Plant-based diets favor:
Lower levels of:
Plant-based diets avoid or minimize compounds associated with inflammation:
Learn more: Inflammation Explained
Studies consistently show vegans and vegetarians have:
Studies comparing the microbiomes of vegans, vegetarians, and omnivores found vegans had the highest bacterial diversity, followed by vegetarians, then omnivores. Vegans also showed significantly lower levels of inflammatory markers (CRP, IL-6) and higher levels of beneficial metabolites produced by gut bacteria.
The most common concern about plant-based eating: getting adequate nutrition. When done thoughtfully, plant-based diets can meet all nutritional needs. Here’s what requires attention:
Myth: Plant protein is insufficient or incomplete.
Reality: Plant foods contain all essential amino acids. While individual plants may be lower in specific amino acids, eating a variety throughout the day provides complete protein. You don’t need to combine foods at each meal.
Excellent plant protein sources:
Daily target: 0.8-1.0g protein per kg body weight (same as omnivores). Easily achievable with varied plant-based diet.
The situation: B12 is produced by bacteria, not plants or animals. Animals get B12 from bacteria in soil and water or supplements in feed. Vegans must supplement.
What to do:
Important: B12 deficiency can cause neurological damage. Don’t skip this supplement.
The difference: Plant foods contain non-heme iron (less readily absorbed than heme iron from meat).
Iron-rich plant foods: Lentils, chickpeas, beans, tofu, tempeh, spinach, Swiss chard, beet greens, quinoa, fortified cereals, pumpkin seeds, hemp seeds, dried apricots, prunes
Enhance absorption:
Note: Vegans and vegetarians don’t show higher rates of iron deficiency anemia than omnivores when eating varied diets.
The situation: Fish provide EPA and DHA directly. Plants provide ALA, which the body converts to EPA and DHA (though conversion rate is low, 5-15%).
Best plant sources of ALA: Flaxseeds (2.4g per tablespoon ground), chia seeds (2.5g per tablespoon), walnuts (2.5g per quarter cup), hemp seeds (1g per tablespoon), canola oil (1.3g per tablespoon)
For vegans: Consider algae-based EPA and DHA supplements (250-500mg daily) for optimal levels.
Target: 1,000-1,200mg daily
Plant sources: Fortified plant milks (300mg per cup, check labels), tofu calcium-set (350mg per 4 oz), collard greens and turnip greens (200-250mg per cup cooked), tahini (130mg per 2 tbsp), chia seeds (180mg per 2 tbsp), almonds (75mg per quarter cup), white beans (130mg per cup)
Note: Some vegetables (spinach, beet greens) contain calcium but also oxalates that reduce absorption. Focus on low-oxalate sources listed above.
Few foods naturally contain vitamin D (fatty fish, egg yolks, some mushrooms). Most omnivores are also deficient.
Recommendations:
Good sources: Legumes (chickpeas, lentils, beans), pumpkin seeds, hemp seeds, cashews, almonds, oats, quinoa, nutritional yeast (fortified)
Enhance absorption: Soaking, sprouting, or fermenting legumes and grains reduces phytates that inhibit zinc absorption.
Always: Vitamin B12
Strongly consider: Vitamin D, algae-based omega-3 (EPA and DHA)
Possibly: Iodine (use iodized salt or seaweed), iron (if low, especially menstruating women)
Vegetarians including dairy and eggs may need B12 and D, possibly omega-3.
Gradual transition is typically more sustainable than overnight change. Here’s a practical progression:
Instead of eliminating foods, add more plants. They naturally crowd out animal products.
Week 1-2: Add Without Removing
Week 3-4: Increase Plant Protein
Week 5-6: Shift Proportions
Week 7-8: Choose Your Level
Key principle: Progress, not perfection. Even increasing plants from 10% to 50% of your diet dramatically benefits your microbiome.
Here’s what a fully plant-based day might look like:
Nutritional highlights: Protein 70-80g (from legumes, grains, nuts, seeds, vegetables), Fiber 50-60g, Plant diversity 20+ different plants in one day, Complete nutrition (with B12 supplement)
The problem: Relying on processed vegan substitutes—vegan burgers, fake meats, vegan cheese, packaged snacks.
Why it’s an issue: Many vegan products are ultra-processed with similar gut-harming properties as their animal-based counterparts.
The solution: Emphasize whole plant foods—legumes, whole grains, vegetables, fruits, nuts, seeds. Use processed alternatives occasionally, not as staples.
Learn more: Foods to Limit or Avoid
The problem: Not eating enough legumes, tofu, tempeh, or other protein-rich plants.
The solution: Include protein-rich plants at every meal. Track protein for a few days to ensure adequacy (0.8-1.0g per kg body weight).
The problem: Assuming plant foods or “natural” eating provides B12.
The reality: No plant foods naturally contain B12 in bioavailable form. All vegans must supplement.
The solution: Take B12 supplement daily or weekly. Non-negotiable.
The problem: Finding 10 plant-based foods you like and eating only those.
Why it’s limiting: Microbiome diversity requires plant diversity. Eating rice, beans, and broccoli every day won’t optimize gut health.
The solution: Aim for 30+ different plants weekly. Try new vegetables, grains, legumes, nuts regularly.
Learn more: The 30 Plants Challenge
The problem: Winging it leads to inadequate nutrition or resorting to processed foods.
The solution: Meal prep on weekends. Batch cook grains, legumes, roast vegetables. Have quick staples ready.
The problem: All-or-nothing thinking leads to giving up after slip-ups.
The solution: Progress over perfection. Even 80% plant-based is dramatically better than typical Western diet. Focus on increasing plants, not achieving purity.
Use our free tools to track plant diversity and ensure complete nutrition
The 30 Plants Challenge →
Maximizing plant diversity
Fiber: The Essential Nutrient →
Why plant-based is high-fiber
Polyphenols & Phytonutrients →
Plant compounds and gut health
Mediterranean Diet →
Plant-forward eating pattern
The Anti-Inflammatory Plate →
Plant-based meal structure
Fermented Foods Guide →
Plant-based probiotic sources
Meet the Microbiomes →
Bacteria plant-based diets support
Inflammation Explained →
How plants reduce inflammation
Foods to Limit or Avoid →
Avoiding “junk food vegan” trap
Recipe Library →
Whole food plant-based meals