GI 19: Lactose Intolerance + Abdominal Gas

💨 Abdominal Gas (Flatulence, Bloating, Belching)

(based on your slides + EOB emphasis)

🧬 1. Pathophysiology

Abdominal gas = normal biological process

Gas composition: N₂, O₂, CO₂, H₂, CH₄
Average daily expulsion: ~500–700 mL/day
Normally removed through eructation (burping) and flatulence

Symptoms: belching, flatulence, bloating, cramping, discomfort.
➡ Usually transient and benign but can overlap with other GI disorders: IBS, IBD, GERD, PUD, dyspepsia, constipation, diarrhea.

💭 2. Etiology & Pathophysiology

Three main mechanisms:

Mechanism	Description	Example
Aerophagia	Excessive swallowing of air during eating/drinking/speaking	Eating too fast, chewing gum, smoking, drinking through straws
Increased gas production in bowel	From incomplete digestion or malabsorption → undigested carbs/sugars fermented by colonic bacteria	Beans, lentils, lactose intolerance, high FODMAP foods
Other medical causes	IBS, celiac disease, diabetic gastroparesis	Slowed motility or malabsorption disorders

🧠 Fermentation = bacterial breakdown → CO₂ + H₂ + CH₄ → bloating + cramping.

💊 3. Common Medication Causes

Meds that increase gas or bloating:

Mechanism	Example Drugs
Alter gut microbiome	Antibiotics, lactulose
Alter food metabolism	Acarbose, metformin
Slow GI motility	Narcotics, anticholinergics, CCBs
Release gas	Effervescent tablets, carbonated beverages
Contain poorly absorbed polymers/fibres	Psyllium, polystyrene resins (cholestyramine)

💡 Quick test trick: “Anything that slows the gut or ferments in it = gas.”

🚩 4. Alarm / Referral Criteria

Refer if red flags present:

Persistent or frequent symptoms (several times a month or days at a time)
Severe intensity or sudden change in pattern
Age of onset >40 years
Unexplained changes in bowel habits
Systemic symptoms → GI bleeding, fatigue, fever, chills, weight loss
Associated pathology → IBS, celiac, diabetes, gastroparesis, dysphagia, odynophagia

🩸 Rationale: persistent gas may indicate partial obstruction, motility disorder, or malignancy.

🧘‍♀ 5. Non-Pharmacologic Management

Start here for mild, transient cases.

✅ Do:

Eat & drink slowly, chew thoroughly
Eat smaller meals
Try fermented dairy products (e.g. yogurt, kefir — contain probiotics)
Keep a food diary to identify trigger foods

❌ Avoid:

Carbonated drinks, FODMAP-rich foods (beans, onions, broccoli, wheat)
Washing food down with liquid
Smoking, gum, or hard candies (increase air swallowing)
Tight clothing
Lying down soon after meals

💊 6. Pharmacologic Therapy

Category	Example	Mechanism	Notes / Onset
Anti-flatulents	Simethicone	Defoaming agent ↓ surface tension → coalesces small gas bubbles into larger ones, easier to expel	Fast onset; safe for all ages (even infants). Dosed PRN (80–125 mg q6h).
Adsorbent	Bismuth subsalicylate	Binds H₂S → reduces odor and gas	May cause black stool/tongue; short-term use only. Avoid in kids or aspirin allergy.
Digestive enzymes	Lactase, α-galactosidase	Break down lactose or complex carbs before fermentation	Take with first bite of trigger food. Useful for lactose intolerance or beans.
Probiotics	e.g. Lactobacillus, Bifidobacterium	Restore gut flora balance; may reduce gas & bloating in chronic IBS	Evidence modest; takes weeks for benefit.

🧠 High-yield tip: Simethicone = symptomatic relief only; enzyme supplements = preventive relief.

🎯 7. Goals of Therapy

Relieve gas, bloating, and discomfort
Identify and eliminate triggers (food, medication)
Educate on lifestyle strategies
Rule out serious disease
Improve overall QoL

✅ Summary Snapshot

Step	Management Focus
1⃣	Rule out red flags (refer if present)
2⃣	Non-pharm (slow eating, smaller meals, avoid carbonated/FODMAP foods)
3⃣	Pharmacologic if needed: Simethicone → enzyme supplement → probiotic
4⃣	Reassess; if persistent or >40 yrs onset → refer

🧬 Abdominal Gas Related to Specific Foods & Beverages

🥛 1. Lactase Enzyme Deficiency → Lactose Intolerance

Pathophysiology:
Lactose (milk sugar) = disaccharide → normally broken down by lactase into glucose + galactose for absorption.
When lactase enzyme is deficient, lactose remains in the gut → fermented by bacteria → gas, bloating, cramping, diarrhea.

🧠 Types of Lactose Intolerance

Type	Cause	Notes
Primary	Gradual, natural decline in lactase activity with age	Most common; tolerance varies
Secondary	Secondary to illness (e.g. gastroenteritis, celiac, surgery)	Usually transient
Congenital	Genetic absence of lactase	Rare (e.g. galactosemia)

💡 Remember: lactose intolerance = enzyme deficiency, not milk allergy (no immune response).

🧀 Typical Tolerance Levels

Most people can ingest:

Up to 12 g lactose (~1 cup milk), or
15–18 g when taken with meals — fewer symptoms.

🩺 Treatment Options

Dietary modification
- Limit or avoid high-lactose foods (milk, soft cheeses, ice cream).
- Choose lactose-free or lactase-treated products (e.g. Lactaid milk).
- Replace with fortified substitutes: soy, almond, oat milk.
- Ensure Ca & Vit D supplementation.
Lactase enzyme supplements
- e.g. Lactaid®, Lacteeze®
- MOA: supplies lactase enzyme → breaks down lactose before digestion.
- Dose: 9000 FCC units at first bite of lactose-containing food or immediately before.
- Advantages: Well tolerated, no drug interactions.
- Limitations: Large lactose loads may still cause symptoms.

🧠 Exam hint: “Take with first bite” and “still incomplete breakdown with large lactose amounts” are key phrases.

🥦 2. Oligosaccharide-Related Gas (Beano Section)

Pathophysiology:
Oligosaccharides = short carbohydrate chains (3–10 sugars).
→ Only partially digested in small intestine; rest reach colon → bacterial fermentation → gas.

Foods high in oligosaccharides:

Vegetables: onions, leeks, cauliflower, cabbage, broccoli, beansprouts.
Beans/Legumes: chickpeas, lentils, black beans, peanuts, soy.
Grains: rye, wheat, barley, cereals, granola, pasta, rice bran.

🧠 Mnemonic: “Beans, Broccoli, Bread.”

💊 Treatment — α-Galactosidase Enzyme (Beano®)

Aspect	Details
MOA	Breaks down oligosaccharides into absorbable sugars before they reach colon.
Dose	150–450 GalU (≈ 1 tablet) with first bite of meal (max ~1200 GalU/day).
Notes	Do not use on hot foods (heat inactivates enzyme).
Advantages	Reduces gas from beans, veggies, high-fibre foods.
Disadvantages	Effectiveness varies; rare allergic reactions (rash, itching).

🧠 Tip: take with first bite of beans or fibre-rich meals — it’s preventive, not treatment for existing gas.

🍶 3. Summary Table — OTC Enzyme Products

Feature	Lactase	α-Galactosidase (Beano)
Use	Lactose intolerance	Gas from oligosaccharides (beans, veggies)
MOA	Breaks down lactose → glucose + galactose	Breaks down complex carbs → simple sugars
Dose	9000 FCC units with first bite of dairy	150–450 GalU with first bite of food
Advantages	Safe, no DDIs	Effective for high-fibre diets
Disadvantages	Doesn’t fully digest large lactose loads	Questionable efficacy, rare allergy
Onset	Immediate (works with meal)	Immediate (works with meal)

⏱ Monitoring

Reassess in 1–2 weeks
- If symptoms improve → continue enzyme use as needed before trigger meals.
- If no improvement despite enzyme + avoidance → refer (possible IBS, celiac, pancreatic insufficiency, etc.)

✅ Quick Summary

Step	What to Remember
1⃣	Most tolerate small lactose doses, especially with meals.
2⃣	Lactase deficiency → bloating, diarrhea, gas.
3⃣	Take lactase enzyme or Beano with first bite of trigger food.
4⃣	Avoid hot foods (Beano) & high lactose loads.
5⃣	Reassess in 1–2 weeks → refer if persistent.