Gut Health Diversity Score

The Gut Health Diversity Score quantifies your gut microbiome diversity potential based on weekly intake of plant variety (the 30+ plant species per week threshold from the American Gut Project), daily fermented food servings (matching the Stanford Sonnenburg lab's fermented foods study), dietary fiber grams per day, probiotic supplementation, and processed food exposure. The score draws from peer-reviewed nutrition science to produce a 0–100 number that tracks your behaviors most strongly associated with diverse, resilient gut microbiomes. The scientific foundation comes from three landmark studies. The American Gut Project (McDonald et al., 2018) analyzed stool samples from 11,336 participants and identified plant species variety as the strongest dietary predictor of gut microbiome diversity — people eating 30+ different plant species per week had significantly more diverse microbiomes than those eating 10 or fewer. The Stanford fermented foods study (Wastyk et al., 2021) showed that 10 weeks of consuming 6 servings of fermented foods per day increased gut diversity and reduced inflammatory markers. The ZOE study at King's College London established dietary patterns associated with metabolic and inflammatory outcomes mediated through gut microbiome composition. Why does gut microbiome diversity matter? More diverse microbiomes are associated with reduced risk of inflammatory bowel disease, improved immune function, better mental health (via the gut-brain axis), more efficient nutrient absorption, and reduced all-cause mortality in observational studies. The mechanism: diverse microbiomes are more resilient to perturbations (antibiotics, infections, stress) and produce more diverse short-chain fatty acids (butyrate, propionate, acetate) that nourish the gut barrier and modulate systemic inflammation. This calculator scores five behaviors that drive diversity: plant variety (40 points max, scaling to 30+ plants/week), fermented foods (25 points max, scaling to 3+ servings/day), fiber intake (20 points max, scaling to 30g/day), probiotic supplementation (5 point bonus), and processed food intake (penalty up to 15 points for heavy intake). The total provides a single number to track gut health behavior over time and identify which lever (plants, fermented, fiber, or processed reduction) would most improve your gut health.

1. 1Step 1 — Count Plant Variety (Past 7 Days): List every distinct plant species you've consumed in the past week. Each species counts once regardless of quantity. Sources to include: fruits (apple, pear, banana, mango, kiwi), vegetables (broccoli, kale, spinach, carrot, onion, garlic), herbs (basil, parsley, oregano, mint), spices (cumin, turmeric, cinnamon, black pepper), nuts (almonds, walnuts, pecans), seeds (sunflower, sesame, chia, flax), legumes (lentils, chickpeas, kidney beans). Spice blends count as multiple plants based on ingredients.
2. 2Step 2 — Calculate Plant Score (Max 40 Points): Plants Score = min(40, plants/30 × 40). Hitting the 30-plants target gives full 40 points. Below 30, score scales proportionally: 15 plants = 20 points, 20 plants = 26.7 points, 25 plants = 33.3 points. The 30-plant threshold matches the American Gut Project's finding for measurable microbiome diversity gains.
3. 3Step 3 — Count Fermented Foods (Per Day): How many servings of fermented foods do you consume daily on average? Sources: yogurt with live cultures (½ cup = 1 serving), kefir (¼ cup = 1 serving), sauerkraut (¼ cup = 1 serving), kimchi (¼ cup = 1 serving), kombucha (½ cup = 1 serving), miso (1 tbsp = 1 serving), tempeh (¼ cup = 1 serving). Skip bread, wine, and pasteurized 'fermented' products without live cultures.
4. 4Step 4 — Calculate Fermented Score (Max 25 Points): Fermented Score = min(25, fermented/3 × 25). The Stanford Sonnenburg lab study used 6 servings/day for maximum effect, but most practitioners can achieve meaningful benefits at 3 servings/day. Below 3 servings scales proportionally: 1 serving = 8.3 points, 2 servings = 16.7 points, 3+ servings = 25 points.
5. 5Step 5 — Enter Daily Fiber Intake (Grams): Total daily fiber from all sources. Best estimate methods: tracking app (Cronometer, MyFitnessPal) for 1 week to establish baseline; nutrition label reading; rough estimation from food choices. Most Americans average 15g/day; ideal target is 30g/day. Fiber Score = min(20, fiber/30 × 20). Below 30g scales proportionally.
6. 6Step 6 — Indicate Probiotic Supplement Use: Daily probiotic supplement adds 5 points. Evidence for probiotic supplements is mixed — single-strain supplements are inferior to fermented food sources (which provide dozens of strains plus prebiotic substrates), but some specific strains have evidence for specific conditions (lactobacillus rhamnosus for diarrhea, bifidobacterium infantis for IBS-D, lactobacillus reuteri for infant colic).
7. 7Step 7 — Select Processed Food Intake: None (0 penalty), light 1–2x/week (−2 points), moderate daily (−5 points), heavy most meals (−15 points). Ultra-processed foods damage the gut barrier and microbiome through emulsifiers (polysorbate 80, carboxymethylcellulose), artificial sweeteners (sucralose, saccharin), preservatives, and refined sugars. Total Score = Plants + Fermented + Fiber + Probiotic Bonus − Processed Penalty, clamped 0–100.