Short answer
Only a few supplements are worth the space in your bag. Oral rehydration salts are the most useful, especially in hot countries. Melatonin helps with jet lag on flights across five or more time zones, where it is legal. Protein powder is worth packing if you struggle to eat enough protein while away, and creatine if it is easy to keep taking. Vitamin C, multivitamins, BCAAs and fat burners can stay at home.
It is tempting to pack your whole supplement shelf for a trip. Most of it is not worth the weight. A holiday changes what your body needs: more fluid and salt in the heat, help with sleep across time zones, and perhaps some extra protein if meals are unpredictable. It does not create a need for most of what a supplement shop sells.
Here is what is worth packing, what is optional, and what to leave behind, with the research behind each. For the rules on getting them through the airport, see our guide to flying with supplements.
The holiday supplement list
| Supplement | Verdict | Why |
|---|---|---|
| Oral rehydration salts | Pack | Heat, heavy sweating and upset stomachs. Light, cheap, and hard to replace at 2am |
| Protein powder | Pack if needed | Only if you struggle to eat enough protein on the road |
| Caffeine | Pack if you use it | Helps with jet lag and training, but local coffee usually does the job |
| Melatonin | Pack for 5+ time zones | Good evidence for jet lag; check whether it is legal where you are going |
| Creatine | Optional | Worth continuing if easy, but a week or two off costs you almost nothing |
| Probiotics | Optional | Mixed evidence for preventing travellers' diarrhoea |
| Vitamin C and "immune" blends | Leave | Does not prevent colds in most people |
| Multivitamins | Leave | Not needed for a short trip if you eat reasonably |
| BCAAs, fat burners, pre-workouts | Leave | Little evidence, and pre-workouts are mostly caffeine |
Worth packing
Oral rehydration salts
If you pack one thing, make it this. Oral rehydration salts (ORS) are small sachets of salt, sugar and potassium that you mix with water. The balance follows a formula set by the World Health Organization, and it helps your gut absorb fluid faster than water alone.
They are useful for two holiday problems. The first is an upset stomach: diarrhoea drains fluid and salt quickly, and ORS is the standard first treatment. The second is heat: training in a hot, humid gym in Bangkok or Bali can mean losing a litre or more of sweat an hour. A sachet after a session replaces the salt that water does not.
They weigh almost nothing, cost little, and are the kind of thing you will not want to go looking for when you are unwell. Most pharmacies around the world sell them, but packing a few saves the search.
Melatonin, for long-haul trips
Melatonin is the hormone that tells your body it is night. A Cochrane review by Herxheimer and Petrie found it reduced jet lag in nine of ten trials when taken close to bedtime at the destination, with the clearest benefit on flights crossing five or more time zones, especially flying east. Doses from 0.5 to 5 mg worked similarly well.
Take it at your new local bedtime for the first few nights. It is not a sleeping pill: it shifts your body clock rather than knocking you out. Our guide to training through jet lag covers when to train and how to use daylight to adjust faster.
Check the law first. Melatonin is sold over the counter in some countries, such as the US, but is prescription-only in others, including the UK. Rules on carrying it into a country vary too. Check the rules for where you live and where you are going before you buy or pack it.
Protein powder, if you need it
If you train, protein is the nutrient most worth protecting on a trip. Around 1.6 g per kilogram of body weight a day is the level most research points to for building or keeping muscle. Some destinations make that easy: grilled chicken, eggs and Greek yoghurt are everywhere in Greece or Spain. Others, especially if you rely on street food or long travel days, make it harder.
If you know you will struggle, a few single-serving sachets or a small bag of whey takes up little room. If you will not, leave it. See how to hit your protein on a travel day, and where to buy it abroad if you run out.
Caffeine
Caffeine is one of the best-supported performance aids there is. The International Society of Sports Nutrition's 2021 position stand found that 3 to 6 mg per kilogram of body weight, taken about an hour before exercise, reliably improves performance. On a trip it also helps you stay awake until a sensible local bedtime.
You rarely need to pack it, because coffee is sold almost everywhere. Caffeine tablets are worth bringing if you rely on a set dose before training, or if you are going somewhere coffee is hard to find. Avoid it in the eight hours or so before you want to sleep, or it will work against you on jet lag.
Optional
Creatine
Creatine works by keeping your muscle stores full, and those stores take about four to six weeks to return to normal after you stop. So a week or two off on holiday costs you very little. If it is easy to keep taking, do: a small bag or a few pre-measured doses travel well. If it is not, do not worry about it. Our creatine guide covers what it does and who it is for, and travelling with creatine covers taking it on a plane.
Probiotics
Travellers' diarrhoea is the most common illness on trips abroad, so a supplement that prevents it would be valuable. Some meta-analyses, including one by McFarland in 2007, found certain probiotic strains such as Saccharomyces boulardii modestly reduced the risk. Results vary a lot between studies and products, though, and travel health bodies do not routinely recommend them. They are unlikely to harm you, but food and water hygiene matter far more.
Leave at home
Vitamin C and immune blends
A Cochrane review by Hemilä and Chalker in 2013 found that taking vitamin C regularly did not reduce how often people in the general population caught colds, though it shortened them slightly. Starting it once you feel ill made no consistent difference. The one exception was people under heavy physical stress, such as marathon runners, whose risk of catching a cold roughly halved. For most holidays, it is not worth packing.
Multivitamins
If you eat reasonably, a week or two away will not leave you short of vitamins. Your body stores most of them for weeks or longer. And if you are heading somewhere sunny, you will make plenty of vitamin D from the sun.
BCAAs, fat burners and pre-workouts
BCAAs add nothing if you are eating enough protein, because protein already contains them. Fat burners have little evidence and are among the products most likely to contain undeclared ingredients. Pre-workouts are mostly caffeine with extras, so a coffee does most of the same job.
The short packing list: a few sachets of oral rehydration salts, melatonin for long-haul flights where it is legal, protein powder if your trip will make protein hard to hit, and creatine if it is easy. Everything else is optional at best.
Buying supplements abroad
If you would rather not pack anything, most of these are easy to buy when you land. Pharmacies everywhere stock rehydration salts. Big cities and tourist areas usually have supplement shops, and gyms often sell protein and creatine at the front desk.
Quality control varies between countries, and contaminated or mislabelled products are a known problem. Stick to well-known brands from proper shops or pharmacies, check the seal, and look for third-party testing such as Informed Sport, especially if you compete in a drug-tested sport.
Sources
- Herxheimer A, Petrie KJ (2002). Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews.
- Guest NS et al. (2021). International Society of Sports Nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition.
- Hemilä H, Chalker E (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews.
- McFarland LV (2007). Meta-analysis of probiotics for the prevention of traveler's diarrhea. Travel Medicine and Infectious Disease.
- Morton RW et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine.
- Kreider RB et al. (2017). International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition.
- World Health Organization. Oral rehydration salts: production of the new ORS.
Frequently asked questions
What supplements should I take on holiday?
For most people, a few sachets of oral rehydration salts are the most useful thing to pack, especially for hot countries. Add melatonin if you are crossing five or more time zones, protein powder if you struggle to eat enough protein while away, and creatine if it is easy to keep taking. Most other supplements can stay at home.
Should I keep taking creatine on holiday?
If it is easy, yes, but missing it is not a big deal. Your muscle creatine stores take about four to six weeks to return to normal after you stop, so a one or two-week holiday without it makes almost no difference. If you do stop, you may lose a kilo or so of water weight, which comes back when you restart.
Does melatonin help with jet lag?
Yes. A Cochrane review of ten trials found melatonin reduced jet lag in nine of them when taken close to bedtime at the destination, particularly for flights crossing five or more time zones and when flying east. Doses of 0.5 to 5 mg worked similarly. It is prescription-only in some countries, including the UK, so check before you buy or carry it.
Are rehydration salts better than sports drinks?
For diarrhoea and serious dehydration, yes. Oral rehydration salts have a precise balance of salt and sugar that helps your gut absorb water, as set out by the World Health Organization. Most sports drinks have more sugar and less salt. For a sweaty gym session in the heat, either works.
Do probiotics prevent travellers' diarrhoea?
The evidence is mixed. Some meta-analyses have found a modest reduction in risk with certain strains, such as Saccharomyces boulardii, but results vary between studies and products. They are unlikely to do harm, but food and water hygiene matter far more.
Does vitamin C stop you getting ill when travelling?
For most people, no. A Cochrane review found that taking vitamin C regularly did not reduce how often people caught colds, though it slightly shortened them. The exception was people under heavy physical stress, such as marathon runners, whose risk roughly halved.
Is it safe to buy supplements abroad?
Usually, but quality control varies by country, and some products contain ingredients that are not on the label. Stick to well-known brands from proper shops or pharmacies, and look for third-party testing such as Informed Sport, especially if you compete in a drug-tested sport.
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