Nutritional guidance during antibiotic therapy: what to eat and what to avoid

Antibiotics are essential tools in combating bacterial infections, yet they are also associated with significant gastrointestinal side effects.

The impact of antibiotics on the digestive system

Antibiotics act by destroying or inhibiting the proliferation of bacteria. However, in addition to targeting pathogenic organisms, they also disrupt beneficial gut flora, particularly within the colon.

This disruption—commonly referred to as dysbiosis—can lead to:

• Bloating, diarrhea, or constipation
• Abdominal pain
• Impaired nutrient absorption
• Increased susceptibility to opportunistic infections, such as Clostridioides difficile

In this context, nutrition plays a critical role in maintaining intestinal balance and promoting microbiota recovery.

Probiotics and prebiotics: alies for gut health

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (WHO/FAO). Fermented foods such as plain yogurt with live cultures, kefir, and brine-fermented vegetables (excluding vinegar-based products) may help preserve microbiota diversity.

Prebiotics, on the other hand, are non-digestible dietary fibers that nourish beneficial colonic bacteria. These are found in:

• Allium vegetables: onion, garlic, leeks, asparagus
• Slightly green bananas, apples, oats
• Root vegetables, especially Jerusalem artichoke and parsnip

A diet combining both probiotics and prebiotics can stimulate the recovery of the gut ecosystem during and after antibiotic treatment.

Foods to avoid during antibiotic therapy

Certain foods may interfere with antibiotic absorption or exacerbate gastrointestinal symptoms:

• High-fat dairy and aged cheeses – For antibiotics such as tetracyclines and fluoroquinolones, calcium can impair absorption. Avoid concurrent intake.
• Alcohol – May disrupt antibiotic metabolism (notably with metronidazole) and intensify gastrointestinal side effects.
• Ultra-processed, sugar-rich foods – Can promote the growth of pathogenic bacteria and worsen microbiota imbalance.
• Iron or calcium supplements – May interact with antibiotic absorption; administer at least two hours apart from the antibiotic dose.

The underrated importance of hydration

Antibiotic-associated diarrhea can result in significant fluid loss and dehydration.

Adequate fluid intake is essential and may include:

• Still water and herbal teas (e.g., chamomile, ginger)
• Clear vegetable broth
• Oral rehydration solutions, particularly in persistent diarrhea

Caffeinated beverages and carbonated soft drinks should be avoided if digestive symptoms occur.

Sample balanced daily menu during antibiotic treatment

A simple, gut-friendly dietary plan could include:

• Breakfast: Yogurt with oats and slices of slightly green banana
• Snack: An apple or a handful of raw almonds
• Lunch: Vegetable broth followed by brown rice with lean fish and steamed broccoli
• Snack: Kefir
• Dinner: Steamed vegetables with quinoa and a boiled egg

Meals should be easily digestible, fiber-rich, and nutritionally balanced without overburdening the digestive system.

Post-treatment: supporting microbiota recovery

Restoration of gut microbiota may take several weeks or even months, depending on antibiotic type and duration. Recommendations include:

• Continued consumption of probiotic- and prebiotic-rich foods
• A diverse, plant-forward diet
• Optional administration of standardized probiotic supplements, upon medical or pharmaceutical guidance

A study published in Cell (Suez et al., 2018) found that probiotic supplementation may, in some cases, delay the natural recolonization process, highlighting that nutritional strategies are preferable for most individuals.

Antibiotics are life-saving agents, yet their metabolic toll on the gut should not be overlooked. A well-balanced diet rich in fibers, probiotics, and prebiotics not only supports intestinal health but also strengthens overall immunity.

For healthcare professionals, advising patients on proper nutrition during antibiotic therapy should be an integral component of antimicrobial stewardship.

The following sources were consulted in the preparation of this material:

• World Health Organization – Probiotics
• Harvard Health Publishing – Should you take probiotics when you take antibiotics?
• Suez J. et al. (2018). „Post-Antibiotic Gut Mucosal Microbiome Reconstitution is Impaired by Probiotics”. Cell, 174(6), 1406–1423.e16.
• Mayo Clinic – Antibiotics and Side Effects
• Cleveland Clinic – Diet and the Microbiome

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