A vegetarian day that follows the Swiss dietary recommendations supplies roughly 0.7 litres of water from food alone. That figure comes from adding up three vegetable portions, two fruit portions and one potato portion using the Swiss Food Composition Database. It is real, it is measurable, and it replaces nothing: the Federal Food Safety and Veterinary Office recommends 1 to 2 litres of unsweetened beverages per day on top of what you eat. For training, the Swiss Sports Nutrition Society gives a working range of 0.4 to 0.8 litres per hour, while stating in the same breath that sweat rates vary so much between individuals that no single recommendation fits everyone.

The rest of this page turns those three numbers into something usable, and clears away a few beliefs that circulate in plant-based sports circles. The most persistent one involves magnesium.

How much water a plant-based plate really provides

Lists of water-rich foods are everywhere, always in rounded percentages, never added up. Let us do the addition using the official Swiss portion sizes and the values in the Swiss Food Composition Database.

Food (100 g raw)	Water	Potassium	Sodium
Cucumber	96.3 g	140 mg	1.7 mg
Butterhead lettuce	95.5 g	230 mg	10 mg
Courgette	94.7 g	260 mg	9 mg
Tomato	94.1 g	240 mg	2.4 mg
Celery stalk	93.4 g	390 mg	79 mg
Watermelon	91 g	100 mg	trace
Strawberry	90.3 g	140 mg	1 mg
Banana	75.8 g	320 mg	trace
Baked potato, unpeeled	71 g	600 mg	2 mg

The Swiss recommendations set a fruit or vegetable portion at 120 g, with three vegetable portions and two fruit portions a day. Three vegetable portions along the lines of cucumber, courgette and tomato come to 360 g at roughly 95 per cent water, which is 342 ml. Two fruit portions such as strawberries and a banana come to 240 g, or 199 ml. A 250 g portion of baked potato adds 178 ml. Total: about 0.7 litres.

Two practical consequences follow. First, a diet built around plants genuinely delivers more dietary water than one low in fruit and vegetables, without anyone having to think about it. Second, 0.7 litres does not cover the need: the 1 to 2 litre beverage target is added to it, not subtracted from it. The reasoning that goes “I eat a lot of vegetables, so I can drink less” falls apart the moment you write the numbers down.

Potassium tells a different story. That same day supplies around 2800 mg of potassium from the plant foods alone, 1500 mg of which comes from the potato. There is no common situation in which a vegetarian athlete runs short of potassium, and yet potassium is the mineral that recovery drinks advertise hardest.

How much to drink during training

The Swiss Sports Nutrition Society publishes technical sheets written by Swiss researchers, revised and dated. The sheet on nutrition during training and competition, version 2.5 from December 2023, gives the following anchors.

For efforts lasting up to 45 minutes, drinking offers no performance benefit. That does not mean you should avoid it if you are thirsty; it means the bottle beside the treadmill during a 40-minute session is a matter of comfort rather than physiology.

Beyond that, the general recommendation is 0.4 to 0.8 litres per hour. The lower end applies to lighter people, easier efforts and cool conditions. The upper end applies to heavier people, hard efforts and heat. In practice this works out to 1 to 2 dl every 15 to 20 minutes, roughly two proper mouthfuls per quarter of an hour.

The same sheet stresses a point that hydration articles almost always skip: sweat volumes vary enormously between individuals under identical conditions, and it is entirely realistic for one person to sweat twice as much as another. A field study of 102 male and 64 female recreational runners measured a mean whole-body sweat rate of 1.3 litres per hour in men and 0.9 litres in women. In other words, the 0.4 to 0.8 L/h drinking guidance usually sits below actual losses, and that is deliberate: nobody is trying to match losses gram for gram during exercise.

Thirst, rehabilitated

The familiar version of this advice says thirst arrives too late and that you should drink before you feel it. The SSNS says the opposite, and explains why: in the 1990s in particular, thirst was regarded as an inadequate regulator for elite athletes, and a growing body of data now suggests that drinking to thirst may also be optimal for sports performance.

The qualification they add deserves quoting: drinking to thirst does not mean having no plan. Drinks have to be organised, available and scheduled so that you do not forget them. Thirst is a decent sensor; it does not fill bottles.

Two exceptions are spelled out. Beyond about ninety minutes of effort, you should not wait for thirst, especially if the drink also supplies carbohydrate, because at that point you are drinking for energy as much as for water. And in precision sports such as shooting or golf, where the load is low but the duration long, the guidance is to keep body mass loss to 1 to 2 per cent.

What a weight loss actually means

Weighing yourself before and after a session remains the simplest individual measurement available. The difference corresponds approximately to net fluid loss. The SSNS notes that being 1 to 2 kg lighter after a long effort or a match is normal, and cites a recent study in which fluid losses of up to 4 per cent of body mass during endurance competition did not reduce performance, with world-class marathon runners often losing more than that.

For a 70 kg runner, 4 per cent is 2.8 kg. This is not a target. It is an order of magnitude that puts the panic threshold where it belongs.

Sodium is the only electrolyte that really matters

This is where plant-based sports advice goes wrong most often. The usual argument runs: vegetarians eat fewer processed foods, therefore less salt, therefore they need to compensate more during exercise. It is intuitive, and it is wrong.

A retrospective analysis of 1944 sweat tests from 1304 people looked for what determines sweat sodium concentration. Dietary sodium intake had no significant effect in any of the models. Neither did age, relative humidity, exercise duration or fluid balance during exercise. The retained predictors were season of the year, exercise mode, sex, sweat rate and body mass, and the models together explained only 17 to 23 per cent of the variation. Eating a low-salt diet does not make your sweat saltier, nor less salty: sweat composition is largely an individual trait that your plate does not steer.

What does hold up is the quantity lost. In the runners measured above, sodium losses reached 54 mmol per hour in men and 39 mmol in women, which is 1.24 g and 0.90 g of sodium, or roughly 3.1 g and 2.2 g of table salt. Two hours at that rate means 4.4 to 6.2 g of salt, set against the WHO recommendation to stay below 2000 mg of sodium a day, that is under 5 g of salt, for the general population.

There is a genuine tension here that few articles acknowledge. The public health instruction to eat less salt addresses a population whose global mean intake was 4278 mg of sodium a day in 2021, equivalent to 11 g of salt. Someone training two hours a day in the heat is not part of that population on the days they train. Salting your food during a summer training camp and salting it in February are not the same act.

When to add sodium to the bottle

The SSNS is blunt: added sodium is only required when sweat losses are high, above 1 litre per hour, during efforts of two hours or more. Commercial sports drinks typically contain 0.2 to 0.4 g per litre, which corresponds to 0.5 to 1 g of table salt per litre.

For rapid recovery, the regeneration sheet raises the bar: in tournament situations, or when training more than once a day in hot weather, at least 1.5 g of table salt per litre is strongly recommended. The reason is mechanical. If you drink only water, which contains virtually no sodium, restoring balance takes longer, because water taken without sodium is partly passed back out as urine.

Comparing drinks by what they retain

A randomised trial in the American Journal of Clinical Nutrition had 72 euhydrated men drink one litre of one of thirteen common beverages over thirty minutes, then collected their urine for four hours. Only three beverages produced significantly less urine than still water: an oral rehydration solution, full-fat milk and skimmed milk, with total urine masses of 1038, 1052 and 1049 g against 1337 g for water.

Here is the part worth pausing on: cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water and a sports drink showed no difference from water. Tea and coffee do not dehydrate you. The Swiss recommendations say as much in plain language: caffeinated drinks such as coffee and black tea also count towards fluid intake, with a moderation note that concerns the caffeine rather than the water.

A more recent trial in 19 adults isolated the components. Electrolytes on their own, at sports-drink concentrations, did not consistently improve retention compared with water. It is the combination with carbohydrate or a dipeptide that increases fluid retention. That finding sits awkwardly with the marketing of sugar-free electrolyte tablets, whose central selling point is precisely that they deliver the minerals without the calories.

What coconut water and homemade drinks are worth

Coconut water is sold everywhere as a natural sports drink. According to the Swiss database, 100 ml supplies 19 kcal, 3.2 g of sugars, 26 mg of sodium and 170 mg of potassium. Per litre: 32 g of carbohydrate and 260 mg of sodium.

Measured against the SSNS specification for a sports drink, 60 to 80 g of carbohydrate and 0.2 to 0.4 g of sodium per litre, coconut water sits inside the sodium range and at under half the carbohydrate. In Switzerland, a beverage marketed as a sports drink must supply at least 90 per cent of its energy as carbohydrate and at least 250 kcal per litre; coconut water provides 190. It is a pleasant, reasonably composed drink. It is not a substitute for an exercise drink on a long session.

The classic homemade mix, half water and half fruit juice with a pinch of salt, deserves the same treatment. With orange juice at 9.6 g of sugars per 100 ml, a one-to-one blend gives 4.8 g of carbohydrate per 100 ml, below the 6 to 8 per cent range recommended for exercise. A pinch of salt weighs roughly 0.4 g, giving 0.16 g of sodium per litre, also below the range.

Two recalculated versions, to be tried in training before you take them to a race:

• For exercise: 700 ml orange juice, 300 ml water, 0.8 g salt. Result: 67 g of carbohydrate per litre, or 6.7 per cent, and 0.35 g of sodium per litre.
• For rapid recovery: 500 ml orange juice, 500 ml water, 1.5 g salt. Result: 48 g of carbohydrate and 0.61 g of sodium per litre, meeting the minimum of 1.5 g of salt per litre.

The word “isotonic” also has a legal meaning in Switzerland. Since 1 February 2024, the food information ordinance permits the term for an osmolarity between 260 and 300 mosmol per litre, and “hypotonic” below 260. The claim is not allowed on caffeinated or alcoholic drinks. A homemade drink obviously has no measured osmolarity, which matters not at all for its effectiveness: the SSNS points out that maltodextrin lowers osmolality at identical carbohydrate content, and that the potassium, magnesium, vitamins and amino acids added to commercial drinks are neither necessary nor supported by evidence.

One last detail that does work: temperature. A drink at 5 to 15 degrees is voluntarily consumed in larger amounts than one at 20 to 25 degrees. An insulated bottle does more for your hydration than half the ingredients people put in it.

Magnesium does not prevent cramp

The Swiss Sports Nutrition Society sheet on magnesium and cramp, revised in October 2025, is probably the sharpest document in the Swiss sports nutrition corpus. Its conclusion: there is no good-quality study examining the effect of magnesium on exercise-associated cramp. None.

The literature almost always points back to a single case report more than thirty years old. A 24-year-old tennis player employed at a club played five to ten hours a day, had suffered from a hyperventilation syndrome for five years, and had cramp in her hands and feet, not her legs. Her serum magnesium was slightly low; supplementation resolved the hand and foot cramps. Ever since that one case, magnesium has been recommended for leg cramps, which this patient did not have.

The SSNS adds two concrete points. The tolerable upper intake for magnesium from supplements and fortified foods is 250 mg per day; above that, the risk of diarrhoea rises and iron and zinc absorption can be inhibited. That last point deserves the attention of a vegetarian athlete, whose non-haem iron is already less well absorbed.

As for the dominant hypothesis, that dehydration and mineral losses cause cramp, it is not supported by the available evidence. The cause more likely lies in an imbalance in nerve-to-muscle signalling, which appears when you approach or exceed your physical limit.

One crossover trial in ten men qualifies this without overturning it. After downhill running at 35 to 36 degrees to a body mass loss of 1.5 to 2 per cent, calf cramp susceptibility, measured as the threshold frequency of an electrical stimulus, fell by 3.8 to 4.5 Hz when participants drank spring water and rose by 6.5 to 13.6 Hz when they drank an oral rehydration solution. Ten participants, one type of effort, a laboratory protocol: that is a pointer in favour of sodium, not proof, and certainly not an argument for magnesium.

Exercise-associated hyponatraemia, or the risk of drinking too much

Drinking too much is a real, documented risk, and it concerns exactly the kind of person who reads articles about hydration.

At the 100 km race in Biel, Switzerland, 145 male runners were monitored. Seven of them, 4.8 per cent, developed exercise-associated hyponatraemia. All cases were asymptomatic and would not have been detected without measuring plasma sodium. The runners drank an average of 0.65 litres per hour.

At the Leadville Trail 100, a 161 km race between 2800 and 3840 metres, 20 per cent of participants sampled after the finish had hyponatraemia, again all asymptomatic, with only one sodium value below 130 mmol/l. The split between women and men was marked: 40 per cent against 16 per cent.

These figures come from ultra-endurance, not a Sunday bike ride. What they show is the direction the risk takes as duration grows: beyond three or four hours, the dangerous error is no longer drinking too little but drinking a great deal of plain water. It is also the situation in which sodium in the bottle stops being a detail.

The warning sign is easy to remember: gaining weight during a long event, or finishing heavier than you started, is never normal. If headache, nausea or confusion appear alongside weight gain, stopping fluid intake and seeking medical advice is the correct response, which is the exact opposite of the usual reflex.

After exercise

The thirty-minute rule exists, but it does not apply to everyone. The urgency of refuelling concerns back-to-back situations: two sessions in a day, a tournament, a stage race. When the next session is tomorrow, stores refill quietly across your normal meals.

On volume, the SSNS gives a range of 120 to 150 per cent of losses and is honest about where it comes from: the 150 per cent figure rests on a handful of studies, most examining only four hours of recovery, which makes it a poor guide for rehydration over 24 hours. For a measured loss of 1.5 kg, that means 1.8 to 2.25 litres spread across the following hours rather than downed at once.

For protein, the anchor is about 0.3 g per kilogram of body mass as soon as possible after training, so 21 g for a 70 kg person. The SSNS sheet on vegan sports nutrition notes that plant proteins are generally less well digested and that more is often needed for the same effect, with a telling example: it takes 300 to 400 g of cooked lentils to reach 30 to 40 g of protein. Firm tofu at 14.7 g per 100 g, or a fortified soya drink, solves the problem far more easily after a session. Our complete guide to plant proteins sets out the equivalents food by food.

The vegetarian specifics that actually exist

They are real. They are simply not the ones people repeat.

Fibre and FODMAPs. The SSNS vegan nutrition sheet is direct: the generally high content of dietary fibre and FODMAPs can promote bloating, abdominal pain, diarrhoea or constipation. This is not hydration in the strict sense, but it governs what you can tolerate before and during exercise. The same sheet recommends including refined grains, rice, pasta and buckwheat in plant-based sports nutrition for their lower volume and better digestive tolerance. If gut trouble during exercise is a recurring theme for you, our page on the low-FODMAP protocol and vegetarian diets explains where that approach is appropriate.

Calcium. The recommended 1000 mg a day applies to athletes too. With dairy as the main source in omnivorous diets, a plant-based diet has to lean on pulses, low-oxalate green vegetables, fortified plant drinks and calcium-rich mineral waters. Oxalate inhibits absorption, and beetroot, spinach and chard are particularly high in it. The coagulant used for tofu changes the picture: 220 mg of calcium per 100 g with calcium sulphate, against 72 mg with nigari. Our article on calcium and magnesium without dairy develops the topic.

Iodine. Mineral water does not supply it; iodised table salt does. The SSNS advice to vegan athletes is to use iodised and fluoridated salt. If you salt more heavily during hot spells, that salt may as well be iodised. Our page on balancing iodine in a plant-based diet covers both the sources and the excesses to avoid.

Iron. Counterintuitively, the most recent narrative review on iron in vegetarian athletes concludes that available studies do not consistently show a higher prevalence of deficiency, since total iron intake often equals or exceeds that of omnivores despite lower bioavailability, alongside adaptive absorption mechanisms. That is not a reason to ignore iron status; it is a reason not to supplement blindly. See our tips for improving plant-based iron absorption.

Energy availability. A 2026 review of vegetarian diets in female athletes concludes that performance and health outcomes are generally comparable to omnivorous diets, and that the variability observed depends more on energy availability, the risk of low energy availability and nutritional adequacy than on the exclusion of animal foods. The low energy density and high satiety of plant foods make adequate intake harder during intensive training blocks, and that mechanism, rather than vegetarianism itself, is what causes problems when problems occur.

Five common mistakes

Following a rigid drinking plan without ever weighing yourself. Weighing before and after a typical session, repeated across several conditions, gives you your own number within a month. Every published anchor is an average waiting to be replaced by that measurement.

Treating tea and coffee as enemies. No measurable effect on urine output in the reference trial, and the Swiss authorities count them towards fluid intake. Moderation concerns the caffeine, its effect on sleep and individual tolerance.

Taking magnesium for cramp. No good-quality study supports the use, the tolerable upper intake from supplements is 250 mg a day, and excess can interfere with iron and zinc absorption.

Loading on plain water during long events. Past three hours the direction of the risk flips. Sodium in the bottle, and keep an eye on body mass.

Testing a new drink on race day. The SSNS repeats it: during competition, consume only what has been tested in training. Drinks offered at an event should already have been tried under load.

Adapting to your situation

Efforts under 45 minutes. Drinking adds nothing to performance. A mouthful if your mouth is dry, nothing more.

Sessions of 1 to 2 hours in temperate conditions. 0.4 to 0.6 L/h of water is enough. Carbohydrate becomes useful beyond an hour at sustained intensity, at 30 to 60 g per hour.

Long sessions of 3 hours or more, or heat. 0.6 to 0.8 L/h with carbohydrate and sodium. A drink at 6 to 8 per cent carbohydrate, 0.2 to 0.4 g of sodium per litre, and 60 to 90 g of carbohydrate per hour combining glucose and fructose.

Two sessions in one day, or a tournament. This is where rapid recovery counts: 120 to 150 per cent of measured losses, at least 1.5 g of salt per litre, and about 0.3 g of protein per kilogram as soon as possible. A 15-minute break allows roughly 0.5 litres, which is worth testing.

Precision sports and winter sports. Losses are underestimated in cool weather and in dry indoor air. Keeping body mass loss to 1 to 2 per cent is the anchor. See our vegetarian dishes for Swiss winter sports.

Heatwaves. Hourly anchors rise, food matters more, and the question becomes one about the whole day. Our no-cook meals for surviving heatwaves approach it from the plate.

Limits of this page

The sweat rate and sodium loss figures come from studies of recreational runners in a tropical climate and from North American sweat-testing databases. They describe group means, and the analysis of 1944 tests shows precisely that models explain only 17 to 23 per cent of individual variation.

The beverage hydration trial was conducted in euhydrated men at rest, not in dehydrated athletes after exercise; its results describe retention of a drink, not rehydration capacity after a hard session.

The hyponatraemia data come from ultra-endurance events and do not transfer directly to two-hour efforts.

Water and mineral contents are calculated from the Swiss Food Composition Database rather than measured in the foods you buy; variation between cultivars, seasons and cooking methods is real.

Finally, none of the above is medical advice. Symptomatic hyponatraemia, recurrent cramp despite sound preparation, kidney or heart disease, pregnancy or diuretic treatment change the picture entirely and belong with a health professional.

Frequently asked questions

Do I really need two litres a day? The Swiss recommendation is 1 to 2 litres of unsweetened beverages per day, plus the water in food. The NHS offers a different but converging anchor, 6 to 8 cups or glasses a day, and the simplest check remains urine colour, which should be a clear pale yellow.

Do caffeinated drinks count towards fluid intake? Yes. The Swiss authorities count them explicitly, and the trial in 72 men found no difference in urine output between coffee, tea and still water over four hours.

Does coconut water replace a sports drink? For sodium, it sits in range at 260 mg per litre. For carbohydrate, it supplies 32 g per litre against the 60 to 80 g expected. On a long session it is not enough as an energy source.

Is diluted juice a good exercise drink? At a one-to-one dilution, orange juice gives 4.8 per cent carbohydrate, below the 6 to 8 per cent range. Shifting to seven parts juice to three parts water and adding 0.8 g of salt per litre yields 6.7 per cent carbohydrate and 0.35 g of sodium.

Should I salt my food more because I am vegetarian? Nothing suggests so. Dietary sodium intake did not influence sweat sodium concentration in the analysis of 1944 tests. The salt question depends on sweat volume, so on training and heat, not on diet.

Are sugar-free electrolyte tablets useful? The trial that isolated the components found that electrolytes alone, at sports-drink concentrations, did not consistently improve retention compared with water; carbohydrate is what moves the needle. During long efforts with heavy sweat losses, sodium retains its value, but not as a tablet taken instead of an energy source.

How long before exercise should I drink? The SSNS emphasises one thing above all: a fluid deficit cannot be made up during competition. Arriving hydrated matters more than any in-session strategy, and for team sports the sheet mentions an extra 3 to 5 dl shortly before kick-off, if tolerated.

Does a cold drink make any difference? Yes, through an unremarkable mechanism: people voluntarily drink more of a beverage at 5 to 15 degrees than one at 20 to 25 degrees. It is the simplest lever available for increasing intake.

Read next

• Natural hydration and electrolytes for vegetarian athletes
• Vegetarian diets and endurance sport
• Planning a vegetarian menu for endurance athletes
• Coffee and sports nutrition: synergy or hindrance?
• 24 hours of optimal hydration: infusions and flavoured waters

Sources

• Federal Food Safety and Veterinary Office, Swiss dietary recommendations
• Swiss Food Composition Database, FSVO
• Swiss Sports Nutrition Society, Nutrition during training and competition, version 2.5, December 2023
• Swiss Sports Nutrition Society, Supplement guide: sports drinks, version 3.1
• Swiss Sports Nutrition Society, Nutrition and recovery, version 1.4
• Swiss Sports Nutrition Society, Magnesium and cramp in sport, version 1.3, October 2025
• Swiss Sports Nutrition Society, Vegan nutrition in sport
• FDHA Ordinance on Food Information (OIDAl), SR 817.022.16, art. 42b
• WHO, sodium reduction fact sheet
• NHS, Water, drinks and hydration
• Maughan RJ et al., A randomized trial to assess the potential of different beverages to affect hydration status, Am J Clin Nutr 2016
• McCartney D et al., The Beverage Hydration Index: influence of electrolytes, carbohydrate and protein, Nutrients 2021
• Baker LB et al., Explaining variation in sweat sodium concentration, J Appl Physiol 2022
• Hydration status, fluid intake, sweat rate, and sweat sodium concentration in recreational tropical native runners, Nutrients 2021
• Effect of oral rehydration solution versus spring water intake during exercise in the heat on muscle cramp susceptibility, J Int Soc Sports Nutr 2021
• Knechtle B et al., Low prevalence of exercise-associated hyponatremia in male 100 km ultra-marathon runners in Switzerland, Eur J Appl Physiol 2011
• Incidence of exercise-associated hyponatremia during a high-altitude 161-km ultramarathon, Phys Act Nutr 2021
• Thomas DT, Erdman KA, Burke LM, Nutrition and Athletic Performance, joint position statement, Med Sci Sports Exerc 2016
• Iron deficiency in vegetarian athletes: a narrative review, Curr Nutr Rep 2026
• Vegetarian diets in female athletes: performance, health outcomes, and the implementation gap, Front Nutr 2026