Skip to main content

Prebiotics

Feeding your beneficial gut bacteria with the right fibers and compounds.

📖 The Story​

Click to expand

Dr. Justin Sonnenburg calls them "MAC": Microbiota Accessible Carbohydrates—the fibers your gut bacteria can actually eat. When he and his wife, also a microbiologist, analyzed modern Western diets, they found something alarming.

Traditional populations eating high-fiber diets have 30-50% more gut bacterial diversity than Westerners. More striking: when Western diets were given to African populations, their microbiome diversity dropped within weeks. When high-fiber African diets were given to Westerners, diversity improved—but not as much.

"It's like we've been starving an organ," Dr. Sonnenburg explained. "Except the organ isn't visible—it's our microbiome."

The solution wasn't probiotics. It was feeding the bacteria already there. Prebiotics. And the modern diet was providing only a fraction of what gut bacteria evolved to expect.

The lesson: You can take all the probiotics you want, but without prebiotics—the food for bacteria—they won't thrive. Feed the garden, not just plant seeds.

🚶 The Journey​

Understanding Prebiotics

The Basic Equation:

Prebiotics (food) + Bacteria (gut) → SCFAs (benefit)

Prebiotic Definition:

  • Selectively utilized by host microorganisms
  • Confers a health benefit
  • Must reach the colon intact (not digested earlier)
  • Feed beneficial bacteria preferentially

🧠 The Science​

How Prebiotics Work

The Fermentation Process​

What Happens:

Prebiotic fiber reaches colon
    ↓
Bacteria ferment it
    ↓
Short-chain fatty acids (SCFAs) produced
    ↓
Benefits throughout body

Short-Chain Fatty Acids (SCFAs):

SCFAMain Bacteria ProducingKey Benefits
ButyrateFaecalibacterium, RoseburiaColon cell fuel, anti-inflammatory, barrier support
PropionateBacteroidesLiver metabolism, glucose regulation
AcetateMany speciesEnergy, appetite regulation

Butyrate (Most Important):

  • Primary fuel for colonocytes (colon cells)
  • Strengthens tight junctions
  • Anti-inflammatory
  • May reduce cancer risk
  • Supports immune function
  • Affected by fiber intake directly

Types of Prebiotics​

Classic Prebiotics:

TypeSourcesBacteria Fed
InulinChicory root, Jerusalem artichoke, garlicBifidobacteria
FOS (fructooligosaccharides)Onion, banana, asparagusBifidobacteria, Lactobacilli
GOS (galactooligosaccharides)Legumes, breast milkBifidobacteria
LactuloseSynthetic (medication)Bifidobacteria

Emerging Prebiotics:

TypeSourcesBacteria Fed
Resistant starchCooled potato/rice, green bananaButyrate producers
PectinApples, citrusVarious beneficial
Beta-glucanOats, barley, mushroomsVarious beneficial
PolyphenolsBerries, tea, cocoaVarious (emerging research)

Why Different Fibers Matter​

Diversity of Fibers → Diversity of Bacteria

Different bacteria eat different fibers. Eating only one type of fiber feeds only some bacteria. Variety is key.

Fiber SourceTypeWhat It Feeds
Onion, garlicInulin, FOSBifidobacteria
OatsBeta-glucanDifferent set
LegumesGOS, resistant starchDifferent set
Cooled riceResistant starchButyrate producers
ApplesPectinDifferent set

Conclusion: Eat varied fiber sources, not just one.

Research Findings​

Well-Supported:

  • Prebiotics increase Bifidobacteria (multiple studies)
  • Increase SCFA production
  • May improve calcium absorption
  • May improve blood glucose regulation
  • Support immune function

Emerging:

  • Anxiety/mood (GOS study showed reduced cortisol)
  • Appetite regulation
  • Weight management
  • Skin health (gut-skin axis)
## đź‘€ Signs & Signals

Signs of Adequate Prebiotic Intake​

SignalWhat It Indicates
Regular, well-formed bowelsFiber + bacteria balance
Minimal bloatingAdapted microbiome
Good energySCFA production, absorption
Tolerates variety of foodsDiverse bacteria
Stable moodGut-brain axis supported

Signs of Insufficient Prebiotic Intake​

SymptomPossible Connection
ConstipationLow fiber, reduced motility
Needing laxativesFiber gap
Frequent infectionsImmune function from SCFAs
Hard, infrequent stoolsLow fiber, low butyrate
Carb cravingsMay relate to gut bacteria signaling

Signs You're Increasing Too Fast​

SymptomWhat It Means
Significant bloatingBacteria adjusting (or SIBO)
Excessive gasToo much fermentation too fast
CrampingGI tract adapting
UrgencyToo much too soon

Solution: Slow down, increase gradually over weeks

🎯 Practical Application​

Using Prebiotics Effectively

Prebiotic Foods​

Top Prebiotic Foods:

FoodPrebiotic TypeServing
Chicory rootInulin (highest)Coffee substitute, powder
Jerusalem artichokeInulinRoasted, soups
GarlicInulin, FOSRaw or cooked
OnionFOSRaw or cooked
LeeksInulinCooked
AsparagusInulinCooked
Bananas (green)Resistant starch, FOSRaw
OatsBeta-glucanCooked
BarleyBeta-glucanCooked
LegumesGOS, resistant starchCooked
ApplesPectinRaw with skin
FlaxseedMucilage, lignansGround

Resistant Starch Trick:

  • Cook rice, potatoes, or pasta
  • Cool completely (refrigerate overnight)
  • Reheating is fine—resistant starch remains
  • Cooling increases resistant starch by 2-3x

How Much:

  • No RDA for prebiotics specifically
  • General fiber: 25-38g/day
  • Include prebiotic-rich foods daily
  • Variety matters as much as amount
## 📸 What It Looks Like

Sample Day: High-Prebiotic Diet​

Breakfast:

  • Oatmeal with ground flax and banana
  • Total: beta-glucan + mucilage + FOS/RS

Mid-morning:

  • Apple with almond butter
  • Total: pectin

Lunch:

  • Large salad with chickpeas and onion
  • Olive oil dressing
  • Total: GOS + FOS + polyphenols

Afternoon:

  • Carrots and hummus
  • Total: legume-based (GOS)

Dinner:

  • Protein with garlic
  • Roasted asparagus and leeks
  • Cooled potato (from day before) reheated
  • Total: inulin + FOS + resistant starch

Daily Prebiotic Total:

  • 5+ different prebiotic sources
  • Multiple fiber types
  • Feeds diverse bacteria

30-Plant Week with Prebiotics​

DayPrebiotic Highlights
MondayGarlic + onion + oats + apple
TuesdayLeeks + legumes + banana
WednesdayAsparagus + barley + berries
ThursdayJerusalem artichoke + flax + apple
FridayChicory + garlic + legumes
SaturdayAll the above variety
SundayMeal prep different prebiotic foods
## 🚀 Getting Started

Week 1: Baseline​

  • Assess current fiber intake (most people low)
  • Identify prebiotic foods you already eat
  • Note digestive baseline (bloating, regularity)
  • Pick 2-3 prebiotic foods to add

Week 2: Begin Adding​

  • Add one prebiotic food daily (garlic, onion, or oats)
  • Note tolerance
  • Keep amounts moderate
  • Stay hydrated (fiber needs water)

Week 3-4: Expand​

  • Add second prebiotic type
  • Try resistant starch (cool then reheat)
  • Increase portions slightly
  • Note changes in digestion

Month 2+: Optimize​

  • Aim for 5+ prebiotic sources daily
  • Variety of fiber types
  • Consider supplement if desired
  • Build sustainable habits
## 🔧 Troubleshooting

Common Prebiotic Challenges​

"I bloat terribly with fiber"

  • Start much smaller amounts
  • Try cooked vs raw (easier)
  • May indicate SIBO (investigate)
  • Increase very slowly (weeks)
  • Try PHGG or acacia (low gas)

"I don't like most high-fiber foods"

  • Start with what you do like
  • Cooking changes texture
  • Blend into smoothies
  • Try supplements as bridge
  • Taste adapts over time

"My gas is unbearable"

  • Too much too fast
  • Scale back, go slower
  • Cooked foods often easier
  • May need to address underlying issue
  • Some gas is normal during adaptation

"I'm on low-FODMAP and can't eat prebiotics"

  • Low-FODMAP is temporary
  • Work on reintroduction phase
  • Some prebiotics tolerated (PHGG)
  • Goal is to eat them eventually
  • See dietitian

"I don't notice any difference"

  • Changes are often internal (SCFA production)
  • Look for subtle signs (regularity, energy)
  • Give it 4-8 weeks
  • Combine with overall gut support
## 🤖 For Mo

AI Coach Guidance​

Assessment:

  1. "How much fiber do you estimate you eat daily?"
  2. "Which prebiotic foods do you currently eat?"
  3. "Any bloating or digestive issues?"
  4. "Are you on a restricted diet (low-FODMAP, etc.)?"

Key Coaching Points:

  • Food sources first, supplements if needed
  • Diversity matters as much as amount
  • Increase slowly (weeks, not days)
  • Some gas during adaptation is normal
  • Feeds existing bacteria—lasting change

Common Misconceptions:

  • "I need supplements" → Food sources often sufficient
  • "More is always better" → Gradual increase matters
  • "Gas means it's bad for me" → Some is normal adapting
  • "One type is enough" → Variety feeds diversity

Example Scenarios:

  1. "I want to improve my gut health":

    • Assess current fiber intake
    • Add prebiotic foods (garlic, onion, oats)
    • Increase slowly
    • Aim for 30+ plants weekly
    • Variety of fiber types

  2. "I get terrible bloating from fiber":

    • May indicate SIBO—investigate
    • Start very small
    • Try PHGG or acacia (low gas)
    • Cook foods (easier)
    • Consider testing

  3. "I'm on low-FODMAP—can I eat prebiotics?":

    • Low-FODMAP is temporary
    • Work on reintroduction
    • Some prebiotics tolerated
    • Goal is to eat them again
    • See dietitian for guidance
## âť“ Common Questions

Q: What's the difference between prebiotics and probiotics? A: Probiotics are live beneficial bacteria you consume. Prebiotics are the food that feeds bacteria (yours and probiotics). Both are important—prebiotics support the bacteria already in your gut.

Q: Can I take prebiotics if I have SIBO? A: Usually not recommended during active SIBO—they may feed bacteria in the wrong place. After SIBO treatment, gradual reintroduction is important. PHGG may be tolerated earlier.

Q: How long until prebiotics work? A: Microbiome changes can begin within days. Tolerance builds over 2-4 weeks. Full benefits develop over weeks to months of consistent intake.

Q: Do prebiotics cause weight gain? A: No—they're not absorbed for calories. The SCFAs produced provide minimal calories. Fiber actually supports healthy weight through satiety and metabolic effects.

Q: Can I get enough from food alone? A: Yes, most people can. A varied diet with vegetables, fruits, whole grains, and legumes provides abundant prebiotics. Supplements are convenient but not necessary.

## âś… Quick Reference

Prebiotic Foods Cheat Sheet​

FoodPrebiotic TypeEasy Way to Eat
GarlicInulinAdd to any savory dish
OnionFOSCooked in everything
OatsBeta-glucanBreakfast
BananasFOS, RSSnack or smoothie
LegumesGOS, RSSoups, salads, sides
ApplesPectinWith skin, snack
AsparagusInulinRoasted side
LeeksInulinSoups, roasted
FlaxseedMucilageGround in smoothies/oats

Starting Protocol​

  1. Week 1: Add one prebiotic food daily
  2. Week 2: Add second source
  3. Week 3-4: Increase amounts
  4. Month 2+: Aim for 5+ daily sources

💡 Key Takeaways​

Essential Insights
  1. Prebiotics feed your beneficial bacteria—as important as probiotics
  2. Variety matters—different fibers feed different bacteria
  3. Increase slowly—weeks, not days, to build tolerance
  4. Food sources work—supplements optional, not required
  5. SCFAs are the payoff—especially butyrate for colon health
  6. Resistant starch is a hack—cool cooked starches to create it
  7. Some gas is normal—adapting gut, but severe bloating investigate
## đź“š Sources
  • Sonnenburg & Sonnenburg - "The Good Gut" (2015) Tier C
  • Gibson et al. - "Expert consensus on prebiotic definition" (2017) Tier A
  • ISAPP prebiotic guidelines Tier A
  • Schmidt et al. - "GOS and cortisol response" (2015) Tier A

🔗 Connections​