Nutrients for Runners & Endurance Athletes

Kilometre 15, your shirt is sticking, your legs are getting heavy – and you start to wonder whether your diet is really carrying you the way it should. Endurance sport places demands on your metabolism as well as your fluid and electrolyte balance. Here is the answer that matters.

For runners and endurance athletes, the most relevant nutrients are magnesium and potassium (muscle function, electrolytes), iron (oxygen transport), and B vitamins and vitamin C (energy metabolism, cell protection). The most important foundation remains: drink enough, get enough carbohydrates, and eat a balanced diet.

What happens in the body during endurance sport

On every longer run, several processes run at full throttle: your muscles burn carbohydrates and fats for energy, your blood carries oxygen to the working muscles, and through sweat you lose water and electrolytes. It is precisely at these three levers – energy supply, oxygen transport, electrolyte balance – that the relevant nutrients take effect. No miracle cure, but a solid foundation.

Electrolytes: magnesium and potassium

When you sweat, you lose not only water but also electrolytes. Magnesium contributes to normal muscle function, to a normal energy metabolism, to normal protein synthesis, to electrolyte balance, and to the reduction of tiredness and fatigue. Potassium contributes to normal muscle function and to the normal functioning of the nervous system. How much you lose depends on duration, intensity, temperature, and your individual sweat rate – a long run on a hot day is something different from an easy autumn loop.

Good sources of magnesium: nuts, whole grains, legumes, dark chocolate. Rich in potassium: bananas, potatoes, dried fruit, legumes. How to use both around training is explained in Electrolytes in sport: magnesium and potassium. On the choice of magnesium form, Which magnesium is the best? helps, and on timing Magnesium: morning or evening?.

Iron and oxygen transport

For endurance performance, oxygen transport is central – and here iron plays the leading role: it contributes to normal oxygen transport in the body, to the normal formation of red blood cells and haemoglobin, to a normal energy metabolism, and to the reduction of tiredness and fatigue. Especially with a high training volume and a plant-focused diet, it is worth keeping an eye on your iron supply – covered in detail in Recognising and preventing iron deficiency.

Everyday tip: plant-based iron from oats, legumes, and pumpkin seeds is absorbed better together with vitamin C from fruit or vegetables – a breakfast of oats with berries is a perfect example (more in Combining vitamin C and iron). Important: whether a deficiency exists should be clarified medically via the ferritin value, not treated “on suspicion” with high doses – too much iron is just as undesirable as too little. Endurance athletes with a high volume therefore have their values checked occasionally.

Energy and regeneration

Endurance sport means a high energy turnover. B vitamins such as B1 (thiamine), B2 (riboflavin), B6, B12, and niacin contribute to a normal energy metabolism and to the reduction of tiredness and fatigue – an overview in B vitamins at a glance, and holistic energy in More energy with magnesium, iron, and B vitamins. Vitamin C additionally contributes to the protection of cells from oxidative stress, to energy metabolism, and to the normal function of the immune system – including during intensive training phases.

Which supply for which run?

Not every session places the same demands. An overview of when which nutrients come particularly into focus:

Nutrition around training

For endurance athletes, energy supply matters most of all. Carbohydrates from whole grains, potatoes, rice, oats, and fruit fill the glycogen stores – the most important energy source on longer runs. Protein from legumes, dairy products, eggs, or fish supports regeneration, and healthy fats from nuts, seeds, and good oils round out the supply. Timing counts too: a meal that is too heavy right before a run sits heavily in the stomach, while a light, carbohydrate-focused snack is better tolerated. Whether a supplement fits your everyday life at all is put into context by Dietary supplements: worthwhile or a waste of money?.

What research is investigating

A great deal is being researched in endurance sport – for example on electrolyte and fluid losses during long exertion, on the iron status of endurance athletes, or on the role of carbohydrates for the glycogen stores. Well established in the textbooks is the role of iron for oxygen transport, of magnesium and potassium for muscle function, and of B vitamins for energy metabolism – and it is precisely to these that the authorised claims refer. How strongly individual needs rise depends on training volume, diet, and personal factors.

Immune system in intensive phases

In phases with a very high training volume – for example during competition preparation – a good nutrient supply is a sensible building block. Vitamin C, vitamin D, zinc, and selenium contribute to a normal function of the immune system; good sources are fruit, vegetables, bell peppers, pumpkin seeds, cheese, and Brazil nuts (more in Immune system: vitamin C, D, and zinc). At least as important are recovery between sessions and enough sleep – overtraining cannot be offset by any supplement (Nutrients for regeneration after sport). In the case of persistent infections or exhaustion, please seek medical advice.

Bones, muscles, and vitamin D

Running is a repeated loading stimulus for bones, tendons, and muscles. Calcium and vitamin D contribute to the maintenance of normal bones, and vitamin D additionally to the maintenance of normal muscle function. Since the body produces vitamin D primarily through sunlight, your status can drop with a lot of early, late, or wintery training – how to assess it is explained in Vitamin D: dosage, blood value, winter. Magnesium too contributes to the maintenance of normal bones and to muscle function – relevant several times over.

In practice: hydration and electrolytes around long runs

If you run for more than 60 to 90 minutes at a stretch or train in the heat, you should manage fluids and electrolytes deliberately:

• Before the session: start well hydrated, but do not over-hydrate – a glass of water 30 to 60 minutes beforehand is usually enough.
• During long runs: for efforts of over about an hour, drink regularly in small amounts; if you sweat heavily, an electrolyte drink can be sensible.
• Afterwards: replace fluid losses and refill the glycogen stores with carbohydrates and a little protein.
• Signs of an electrolyte need: salty sweat marks on your clothing indicate high sodium losses – here a targeted replacement is worthwhile on long sessions.

Especially in summer and in the heat, special rules apply, which Electrolytes in summer and heat covers in detail.

An honest perspective: timing and sensible combination

Whether a nutrient is better taken before or after eating depends on the supplement (Nutrients before or after eating?). Around long sessions, sufficient fluid is decisive, and for very long exertion a targeted electrolyte replacement can be sensible. Which supplement fits your goal is clarified by Which dietary supplement fits your goal?, and how to combine several wisely is shown in Combining dietary supplements correctly. As a general rule: a well-thought-out diet with enough carbohydrates, protein, and fluids is more important than any single supplement. In the case of persistent complaints, please seek medical advice.

Suitable products from Scheunengut

For endurance athletes, the category Sport & Fitness is suitable, as well as magnesium, potassium, and iron supplements specifically under Minerals. Anyone keeping an eye on electrolytes will find something suitable in Potassium. All products are lab-tested and made in Germany.

Frequently asked questions (FAQ)

Which nutrients do runners and endurance athletes need?

Particularly relevant are magnesium and potassium for muscle function and electrolyte balance, iron for oxygen transport, and B vitamins and vitamin C for energy metabolism and cell protection. The most important foundation, however, remains sufficient fluid and enough carbohydrates.

Do I lose a lot of electrolytes through sweat when running?

Yes – through sweat you lose water and electrolytes such as magnesium and potassium. How much depends on duration, intensity, temperature, and your sweat rate. On long or intensive sessions, a targeted replacement of electrolytes can be sensible.

Should endurance athletes take iron?

With a high training volume and a plant-focused diet, iron needs can be increased, but iron should only be supplemented when a need has been medically established. Have your ferritin value determined instead of supplementing high doses on suspicion – too much iron is unfavourable.

What should I eat before a long run?

A light, carbohydrate-focused snack is usually well tolerated and provides energy, whereas a meal that is too heavy sits heavily in the stomach. Overall, filled glycogen stores from whole grains, potatoes, rice, and oats are the most important energy source on long runs.