Which supplement side effects in children and adolescents?

What are the real risks of food supplements in children?

Which vitamins present the highest risk of overdose?

Fat-soluble vitamins A, D, E and K are the most at-risk in children. Stored in the liver and adipose tissue, they can accumulate in the body and cause chronic toxicity: hepatomegaly, hypercalcaemia, intracranial hypertension^[8]. Water-soluble vitamins (B and C) are eliminated through urine and present a lower, but not nil, risk; in sufficient amounts, they contribute to the production of energy, to normal energy metabolism and to the normal functioning of the immune system, which helps to reduce passing fatigue.

The vitamin A hypervitaminosis documented in children occurs from 10,000 IU per day for one to six months^[8], according to the protocols of the French Society of Emergency Medicine. The therapeutic doses used against severe measles (100,000 to 400,000 IU) remain strictly supervised by a doctor. For vitamin D, Anses and ANSM raised the alert in 2021 about several cases of severe hypercalcaemia with stones or nephrocalcinosis^[1] in infants exposed to food supplements over several weeks.

Why do vitamin gummies pose a specific problem?

Gummies look like sweets, often flavoured and coloured like a candy recipe, which multiplies accidental ingestion and favours overdose. The Konsumentenschutz and BFH Bern study (2025) identified 15 out of 20 products exceeding the nutritional reference values for at least one vitamin^[7], sometimes several times the recommended dose for the age group. The “kid” or “junior” format sold in attractive jars in online pharmacies or on any general website provides no particular protection against this drift.

The format poses a double problem: it hides the pharmacological nature of the product and it makes voluntary excessive ingestion easier, particularly in children who perceive its taste as a treat. “Family brand” or “natural organic” marketing also maintains confusion between food and food supplement, whereas these products fall into a distinct regulatory category. In the United States, this risk was quantified for melatonin: the Centers for Disease Control and Prevention recorded around 11,000 emergency room visits for unsupervised ingestion in children aged 0 to 5 between 2019 and 2022, 47.3% of which involved gummy formats^[2].

Which supplements are really justified in children in Switzerland?

From what age is vitamin D recommended?

The FSVO recommends daily vitamin D supplementation during the first three years of life^[3], then an intake of around 600 IU per day in winter for children and adolescents when sun exposure is insufficient (recommendation of the Federal Nutrition Commission). It is the only vitamin for which systematic supplementation is scientifically validated in Swiss paediatrics. From the youngest age, the intake can be carried out via breast milk enriched by the mother or via a dedicated paediatric preparation according to the advice of the healthcare professional in charge of the child.

The reason is known: according to Swiss paediatric reviews, between 35 and 50% of Swiss children present hypovitaminosis D^[3]. Insufficient sun exposure in winter, skin colour, clothing coverage and a low dietary intake of fatty fish explain this deficit; vitamin D contributes to good child development, bone health (in synergy with calcium) and the normal functioning of the immune system. Swiss paediatricians prescribe first and foremost an oily preparation of cholecalciferol, in one intake per day, in liquid form or as chewable tablets according to age. Anses recommends favouring medicines over food supplements for this molecule^[1], because of the risk of overdose with over-the-counter products.

Do iron, iodine and vitamin K have a place in Swiss children?

Iron is prescribed in case of proven iron-deficiency anaemia, iodine if a deficiency is documented and vitamin K is administered at birth to prevent haemorrhagic disease of the newborn. Apart from these specific indications, these micronutrients must come from the diet: Switzerland uses iodised and fluoridated salt that ensures a sufficient intake for the majority of needs, supplemented by a healthy diet including vegetables, fruit, pulses, eggs and dairy products. Zinc and magnesium, also essential for normal energy metabolism and the normal functioning of the immune system, are generally covered by a varied and balanced diet without resorting to a food supplement.

The systematic review by Inchingolo et al., published in Frontiers in Pediatrics in January 2026, analysed 13 paediatric studies using the PRISMA method^[4]. The authors conclude that oral supplements show measurable bioactivity, but cannot be recommended for systematic use in the absence of a documented chronic condition. The MSD Manual furthermore states that unjustified iron supplementation exposes to digestive disorders, and that a chronic excess can lead to tissue overload (secondary haemochromatosis)^[8]. Supplementing a child without a documented deficiency therefore remains useless and potentially harmful.

Which supplements to avoid depending on the child’s or adolescent’s age?

Is melatonin safe in children?

No, not over the counter. In the United States, paediatric ingestions of melatonin were multiplied by 5.3 between 2012 and 2021^[5], with 4,097 hospitalisations recorded by the CDC over the period^[5]. In Switzerland, its use must remain supervised by a paediatrician, mainly for sleep disorders associated with neurodevelopmental disorders (autism, ADHD). Good sleep hygiene, a healthy lifestyle and a calm environment at home remain the first line of intervention before any recourse to medication.

The documented adverse effects include daytime sleepiness, agitation, headaches, abnormal dreams and, in some predisposed children, an increased risk of seizures, according to the safety summary published by Health Canada. A non-medicinal approach remains the first choice in primary sleep disorders in children, according to the Belgian Centre for Pharmacotherapeutic Information. Long-term follow-up is lacking, particularly on pubertal growth, the nervous system and hormonal maturation, which justifies systematic medical advice before any prolonged use.

Sports supplements (creatine, protein powders) in adolescents: what is the framework?

Creatine is not endorsed before age 18 by most North American sports medicine societies. The International Society of Sports Nutrition (ISSN) admits its use in young athletes only under four cumulative conditions: supervised competitive training, balanced diet rich in amino acids from dairy products, pulses and eggs, knowledge of the product and respect of the recommended doses. Protein powders are rarely useful: an active adolescent covers their needs (1.0 to 1.4 g/kg/day) through three balanced meals and a substantial breakfast. Before any supplementation, consulting a professional remains the basis of a sensible approach, especially in the middle of growth and physical development.

The American Academy of Pediatrics and the NCAA defend a “food first” approach, that is to say, the priority to food. Low-quality products expose to documented contaminants: mercury, arsenic, dicyandiamide, dihydrotriazine. A Norwegian study by Svantorp-Tveiten et al. (Frontiers in Sports and Active Living, 2021) involved 1,689 high-school students^[6] and highlights a correlation between use of protein supplements or creatine and risk factors for eating-behaviour disorders in adolescents^[6], in particular when physical activity is accompanied by a restrictive diet or chronic oxidative stress poorly compensated by a varied and balanced diet.

Frequently asked questions on food supplements in paediatrics