B vitamins and energy metabolism

October 25, 2025Michal Jetelina

What are B vitamins and why do they matter?

B vitamins are water-soluble micronutrients that play a crucial role in energy metabolism.
They do not provide energy on their own, but function as coenzymes , i.e. components of enzymes that enable the conversion of carbohydrates, fats and proteins into ATP – the main source of energy for muscle work.

During sports, their need increases because the metabolic activity of cells and the use of energy substrates increase.
In athletes, the need may be increased by 10–20% compared to the general population.

Main functions of individual B vitamins

Vitamin Main functions Deficit risk Risk of excess Typical sources
B1 (thiamine) Conversion of carbohydrates into energy, nervous activity Fatigue, irritability, decreased endurance Low risk, excess is excreted in urine Whole grains, pork, legumes
B2 (riboflavin) Component of FAD, fat oxidation, tissue regeneration Cracks in the corners, impaired healing No known toxicity risk Dairy products, eggs, vegetables
B3 (niacin) Component of NAD/NADP, glucose and lipid metabolism Weakness, decreased exercise tolerance Redness, itching, liver damage at > 500 mg/day Meat, fish, nuts
B5 (pantothenic acid) Formation of coenzyme A → oxidation of fatty acids Rare deficiency, fatigue No confirmed toxicity < 1 g/day Eggs, whole grain products
B6 (pyridoxine) Metabolism of amino acids, glycogen and neurotransmitters Nervous irritability, convulsions Neuropathy > 200 mg/day Bananas, potatoes, poultry
B7 (biotin) Synthesis of fatty acids, hair and skin Rare deficit No known toxicity risk Eggs, nuts, cereals
B9 (folic acid) DNA synthesis, erythrocyte formation Anemia, fatigue Masking B12 deficiency > 1 mg/day Leafy vegetables, legumes
B12 (cobalamin) Nerve regeneration, blood formation Megaloblastic anemia, tingling of the extremities Not toxic even in high doses Meat, eggs, dairy products


How B vitamins affect athletic performance

Energy metabolism

Without sufficient amounts of B vitamins, nutrients cannot be converted into energy efficiently.

  • B1, B2, B3 and B5 support the function of mitochondrial enzymes in the production of ATP.

  • B6, B9 and B12 are key for the synthesis of amino acids and the formation of hemoglobin, which carries oxygen.

Lack

A slight deficit can lead to decreased endurance, poorer muscle oxygenation, and poorer regeneration.
Athletes with high training loads or low energy intake (e.g. in the reduction phase) may experience a subclinical deficiency , which may not be evident in the laboratory, but will affect performance.

When does supplementation make sense?

Situation Recommendation Note
Low energy intake Increase your intake of B vitamins through diet or a multivitamin Typical for athletes in deficit or during weight reduction
Vegetarians/vegans Vitamin B12 supplementation necessary Plant foods do not contain B12.
High training load Slightly higher need, supplementation with appropriate diet Increased metabolism → higher turnover of coenzymes
Normal condition / adequate diet Supplementation has no performance effect Excess is excreted in urine, does not increase performance

Excessive doses of B vitamins provide no proven benefit to performance unless a deficiency is present.
The body will eliminate the excess, but extreme doses (especially B6 > 200 mg/day) can lead to neuropathy.

"Food first" – the best source of B vitamins

Most B vitamins are found in natural foods – whole grains, meat, fish, legumes, vegetables and eggs.
In addition, these sources also provide other micronutrients and bioactive substances that support absorption and overall regeneration.

Natural intake is therefore always preferred over supplementation.
Supplements only make sense in cases of proven deficiency or for athletes with a restricted diet.

Summary

  • B vitamins are essential for energy production, muscle regeneration and oxygenation.

  • Athletes have a higher need (approx. +10–20%) due to increased metabolism.

  • A deficiency can reduce performance and slow down regeneration, an excess does not increase the effect.

  • Supplementation only makes sense in cases of deficiency, veganism, or low energy intake.

  • The foundation remains a varied and balanced diet – the food first principle .

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