“The dose makes the poison” – Paracelsus’ old wisdom fits perfectly with vitamin capsules. Many resort to the daily pill out of performance demands or caution. However, there is a fine line between a sensible filler and risky overconsumption. This article separates benefit from myth – and shows how to use supplements smartly without jeopardizing health and performance.

Vitamins are essential micronutrients: the body needs them in small amounts but often cannot produce them itself. Multivitamins are combination preparations that bundle several vitamins and minerals. It is important to distinguish between water-soluble vitamins (e.g., C, B-complex), which are usually excreted in excess, and fat-soluble vitamins Vitamin A, D, E, Kcan be stored in fatty tissue; increased risk of accumulation with overdose. Hypervitaminosispathological vitamin overload usually occurs with fat-soluble vitamins and can burden organs. Nutrient-medication interactionsinteractions between supplements and medications that alter absorption or effect are also relevant. The fundamental principle: food first, supplements targeted – and ideally monitored by a physician.

If used correctly, multivitamins can close small gaps and help in certain situations, such as increased demand or unbalanced diets. Evidence suggests that MVMs are well tolerated in the general population and could influence certain outcomes like specific cancer risks in men or cataracts as well as aspects of cognition ^[1]. The flip side: excessive vitamin intake – especially without medical supervision – can lead to hypervitaminosis, which can burden the kidneys, blood vessels, and metabolism. Cases of acute kidney damage and hypercalcemia due to high doses or contaminated vitamin D demonstrate how quickly “more” can turn into “too much” ^{[2] [3]}. Vitamin D can accumulate in fatty tissue, triggering hypercalcemia and soft tissue calcifications – effects that may persist even after discontinuation ^[4]. Furthermore, the effectiveness of supplements varies depending on accompanying medication; some drugs affect vitamin D metabolism, making under- or over-supply more likely ^[5]. A common misconception – “more is better” – can easily lead to unnecessary risks ^[6].

A comprehensive overview of multivitamin/mineral preparations emphasizes: a balanced diet remains the best foundation, but MVMs can close critical gaps and are generally well tolerated; there are indications of possible benefits in cancer prevention among men, cataract delay, and cognitive aspects ^[1]. Clinical case series and reports illustrate the risks of overdose: a young, athletic patient developed acute renal failure due to unrecognized high-dose supplementation with vitamin D hypervitaminosis – a typical pattern for readily available preparations without medical guidance ^[2]. Further reports show that vitamin D is stored in tissue due to its fat solubility; hypercalcemia and soft tissue calcifications can persist even after discontinuation, requiring close monitoring ^[4]. Particularly alarming is the documented contamination of a creatine product with extremely high amounts of vitamin D: two adolescents suffered severe hypercalcemia and kidney damage, even though the product officially contained no vitamin D – a sign of manufacturing errors as a real source of toxicity ^[3]. Additionally, prospective data from pharmacies show that vitamin D supplementation often corrects deficiencies and improves quality of life, but the effect size varies depending on comorbidities and concurrent medications; adherence was the strongest predictor for adequate levels, while corticosteroids made achieving targets more difficult ^[5].

- Strengthen dietary foundation: Use multivitamins as a backup, not as a replacement. First, optimize your diet with vegetables, fruits, whole grains, legumes, nuts, high-quality protein, and fatty fish – this covers most of the needs and provides synergies that capsules do not offer ^[1].
- Targeted rather than general: Assess your individual situation (nutritional profile, lifestyle, blood values). Use multivitamins to close small, specific gaps, such as increased demand, limited food variety, or certain life stages ^[1].
- Respect fat-soluble vitamins: Inform yourself about the overdose risks of A, D, E, and K. Vitamin D can be stored and cause hypercalcemia even after discontinuation; therefore, only use recommended dosages and monitor levels with long-term use ^{[7] [8]}.
- Ensure medical supervision: Avoid high-dose experiments without medical oversight. Investigate immediately if symptoms such as persistent thirst, nausea, muscle weakness, or confusion occur – these may be warning signs of hypervitaminosis ^{[2] [4]}.
- Check quality and purity: Prefer reliable manufacturers with quality certifications. Be cautious with “booster” products and combination preparations: rare but documented manufacturing errors have led to extreme vitamin D levels in non-vitamin products ^[3].
- Conduct a medication check: Have potential interactions with your medications evaluated (e.g., corticosteroids, NSAIDs, vitamin K antagonists). Personalized strategies and good adherence increase the chances of safely reaching target levels ^[5].
- Question the myth “more is better”: If your diet is solid and foods are partially fortified, additional high doses are often unnecessary and can be harmful. Instead, invest in fresh foods, daylight, exercise, and sleep – the return on investment is higher ^{[6] [1]}.

The next evolutionary stage of supplements is personalized: smart dosing, quality evidence, and monitoring instead of one-size-fits-all doses. With better data on interactions and long-term effects, algorithms will link your nutrition, blood values, and medications – so that vitamins act targetedly without risk. Until then, the rule remains: food first, supplements smart.