Marie Curie understood the power of invisible substances – she shaped radiology because she knew: What we cannot see can still have enormous effects. Vitamins work similarly quietly, but decisively: small molecules, large levers for energy, regeneration, and longevity. Time for a sober fact check: Where do vitamins truly propel high performers forward – and where does the myth begin?

Vitamins are organic micronutrients that the body needs for essential processes – from mitochondrial functionenergy production in the cellular power plants to immune competencethe ability of the immune system to respond effectively. There is a distinction between water-soluble vitamins (B complex, C), which are hardly stored, and fat-soluble vitamins (A, D, E, K), which accumulate in tissues and can therefore lead to overdose. Bioavailabilitythe proportion of a nutrient that actually enters the blood and is utilized from food or supplements determines whether a preparation is effective or wasted. Context matters: fat enhances the absorption of fat-soluble vitamins; certain forms like calcifediol25-hydroxy vitamin D, more readily available than D3 or methylfolatebioactive form of folate have better bioavailability. Medications, age, and gut health modulate absorption – those planning for performance must also plan the context ^[1].

For bones and muscles, vitamin D remains central – but “the more, the better” does not hold true. Current evidence shows: in well-supplied individuals, high supplemental doses offer no broad additional benefit for fall or fracture prevention; high bolus doses may even increase the risk of falls. It makes sense to target and monitor the individual goal range instead of dosing blindly ^[2]. Vitamin C is less convincing as a “shield” against everyday colds, but can reduce infections under high stress – such as during training – and consistently taken can lower the duration and severity of colds. Therapeutically, higher doses can lead to shorter cold durations when started early; the effect is individual, but the safety profile is good ^[3]. On the flip side, there are risks: fat-soluble vitamins can become toxic. Massive doses of vitamin A have led to severe liver damage in case reports – a clear warning signal against uncontrolled long-term intake ^[4]. Vitamin D, in cases of overdose, can cause hypercalcemia, delirium, muscle weakness, and – in children – nephrological damage ^{[5] [6]}. And last but not least: vitamins interact with medications. In studies, potential vitamin-drug interactions were common, especially in people with chronic diseases – a reason for medical coordination instead of self-experimentation without a safety net ^{[7] [8]}.

Two current strands of research are particularly relevant for practice. First: bioavailability. In a double-blind crossover study, a liposomal coating of a multivitamin-mineral preparation altered the blood level kinetics of several nutrients compared to the non-liposomal form – indicating more efficient absorption and clearance of individual vitamins and minerals. This underscores that formulation is not merely cosmetic but can measurably shift efficacy ^[9]. A longer observation of a complex multivitamin preparation also showed increasing blood levels of many micronutrients over months – however, not linearly, as nutrients interact with each other and distribute differently in tissues. Practically relevant: patience, suitable forms, and composition matter; not every deficiency fills up at the same pace ^[10]. Second: precision vitamin D. A recent overview cautions against the one-size-fits-all approach: for bone health, 20–30 ng/ml of 25-OH-D may be sufficient, while certain metabolic effects are discussed for higher ranges. High-dose bolus doses carry safety risks; monitoring and individual target ranges are preferable to blanket high dosing – especially for performance-oriented individuals who need stability instead of fluctuations ^[2]. Supporting studies have shown that supplementation can efficiently correct deficiencies, but success varies depending on comorbidities and accompanying medications – adherence remains the strongest predictor for achieving the target range ^[8].

- Check your vitamin D status: Have 25-OH-D measured in late autumn and late winter and aim for the recommended range instead of blindly high dosing. Avoid high-dose bolus administration without medical indication ^[2].
- Choose smart multivitamins: Prefer certified products with verified bioavailability; technologies like liposomal formulations can improve absorption. Pay attention to sensible nutrient combinations and forms (e.g., active forms of folate) ^{[9] [10]}.
- Respect upper limits: Learn the symptoms of overdosing (e.g., nausea, muscle weakness, confusion with vitamin D; skin and liver signs with vitamin A) and avoid uncontrolled high doses – especially with fat-soluble vitamins A, D, E, K. In children, strictly supervise medically ^{[5] [6] [4]}.
- Use vitamin C strategically: In everyday life, it primarily reduces the duration and severity of colds; during periods of intense stress, it can lower the frequency of infections. Therapeutically, temporarily higher doses (watch for tolerance) can shorten the duration of colds ^[3].
- Check interactions: Coordinate supplements with your medication (e.g., proton pump inhibitors, statins, corticosteroid therapies). Personalized dosing and consistent intake increase the chance of reaching target values ^{[8] [7]}.

Vitamins are neither magic nor myth – they are precise tools. Measure, optimize form and dose, and respect boundaries. Start today with a vitamin D check, a high-quality multivitamin with proven bioavailability, and a smart vitamin C plan for your peak stress periods.