Evidence check: Nährstoffcheck in the context of Sport

A nutrient check in the context of sports can provide insights into potential deficiencies or excesses, but interpretation requires caution. Evidence for routine blood testing in healthy athletes is limited: single measurements are affected by diurnal variation, diet, and training status. Water-soluble vitamins like B vitamins are generally excreted when in excess, but high doses of B6 (>100 mg/day) can cause nerve damage, and niacin can harm the liver. The products mentioned in the context (e.g., Hormon & VitalCheck) are marketed as lifestyle tests, not diagnostic tools. For athletes, specific nutrient needs (e.g., iron, magnesium, vitamin D) can be assessed via targeted lab work, but results need clinical context and repeat measurements. DNA-based nutrient tests (e.g., MTHFR) have weak predictive power. Conclusion: A nutrient check can be useful if there is a justified suspicion of deficiency, but it does not replace medical advice. Evidence level: practice (based on guidelines, but with limitations).