Food supplements can be taken on a permanent basis as long as the guideline values for the daily intake (nutrient reference values) according to the Food Information Regulation are observed. A permanent overdose is not advisable and can have a negative effect on health. Overdoses are more of an issue with fat-soluble vitamins (e.g. vitamins A and D) than with water-soluble vitamins (e.g. vitamin C, B vitamins), which are excreted unused. Since the absorption of food supplements by the body depends on many influencing factors (timing, age, absorption-inhibiting foods such as coffee or black tea, intestinal environment), 100% absorption of the pure active ingredient in a food supplement can never be guaranteed. Therefore, a food supplement should be taken over several weeks to achieve a lasting effect.