Supplements for frequent travelers

The traveler stack — rationale by ingredient

Low-dose melatonin 0.3–0.5 mg for circadian realignment

For eastbound travel (advancing your clock), melatonin at the destination bedtime is the better-evidenced option. For westbound travel (delaying), it's usually optional. The Cochrane review supports 0.5–5 mg; the low-dose end (0.3–0.5 mg) is more physiologic and reduces next-day grogginess. The high-dose OTC versions (5–10 mg) sedate without realigning the clock better. Take 30–60 minutes before target sleep onset at the new time zone for 3–5 nights post-arrival.

Saccharomyces boulardii CNCM I-745 (500 mg twice daily)

The probiotic yeast with the strongest evidence in traveler's diarrhea prophylaxis (Cochrane review supports it in adults). Start 5 days before travel and continue throughout. Particularly useful for travel to higher-risk regions or for users with prior episodes. Not a substitute for food and water safety practices.

Zinc lozenges 75–80 mg/day (zinc acetate, 30 mg per lozenge) at first cold symptom

Cochrane review supports zinc lozenges shortening cold duration by about a day if started within 24 hours of symptom onset. Acetate is the best-evidenced form. Don't use chronically — short course at first symptom. Pack lozenges with your medications.

Vitamin D3 1,000–2,000 IU/day for baseline immune readiness

Mid-flight cabin pressure, sleep disruption, and dietary chaos all contribute to immune dip. Vitamin D adequacy is a foundational baseline; the post-trip cold rate is lower in adequately repleted users in observational data.

Magnesium glycinate 300–400 mg for sleep across time zones

Travel-related sleep disruption responds to the same magnesium-glycine combination as everyday insomnia. Glycinate is well-tolerated; avoid magnesium oxide for sleep (laxative effect inappropriate when traveling).

L-Theanine + caffeine 200 mg + 100 mg as the cognitive-focus stack

The 2:1 L-theanine:caffeine combination supports the alertness you need without the jitter that compounds with sleep deprivation. Time-bound your last caffeine to 6+ hours before target sleep onset at the destination.

Oral rehydration salts (WHO ORS or equivalent) for acute diarrhea or heat illness

Pack a few sachets. ORS is the WHO-recommended composition for acute diarrhea fluid replacement — far more effective than plain water and proportionally less expensive than sports drinks. Doubles as heat-illness response in hot destinations.

Elderberry standardised extract for cold symptom management

Modest evidence for symptom-duration reduction in upper-respiratory infections. Less effective than zinc lozenges acutely; useful for users who prefer a syrup or who can't tolerate zinc's metallic taste.