What are the risks of overdosing on food supplements?

Which mechanisms make a food-supplement overdose dangerous?

Why do fat-soluble vitamins accumulate in the body?

Vitamins A, D, E and K are stored in the liver and adipose tissue because they are not water-soluble, unlike the B-group vitamins and vitamin C. Their urinary elimination is negligible, which creates a risk of toxic accumulation during prolonged intakes over a long period, beyond the tolerable upper intake level (UL). The liver centralises the storage of retinol in the form of retinyl esters in the hepatic stellate cells. Beyond this capacity, the accumulation triggers oxidative stress and activation of the stellate cells which leads, in the long term, to steatosis and then to liver fibrosis^[4]. As an example, vitamin B6, although water-soluble, is an exception with documented peripheral neurotoxicity of the nervous system at high prolonged doses, illustrating the impact on health of poorly supervised vitamin supplementation.

How does self-supplementation lead to cumulative dosing?

Overdose rarely comes from a single product: it results from the cumulation between several supplements, fortified foods and a normal diet. Most consumers do not know that the same nutrient can be present in three products they take simultaneously, for lack of being correctly informed about the ingredients of each item. The 2023 FSVO survey, carried out on 1,282 Swiss adults, recorded 699 food supplements consumed over seven days; three participants exceeded the UL for folic acid, another for vitamin A through voluntary exceedance of the recommended dose, and three for zinc through cumulation of several sources^[1]. Tox Info Suisse received around 1,200 enquiries linked to food supplements, slimming products and foods for athletes between 2014 and 2019, with a clear year-on-year increase in frequency over the period^[2]. This excessive consumption, which has become widespread use, reflects a market issue that is little visible to the general public.

Which vitamins and minerals present the best-documented overdose risks?

What toxic effects does excess vitamin A cause?

Chronic excess of preformed vitamin A (retinol) causes hepatotoxicity, bone pain and a teratogenic risk in pregnant women, a direct consequence of poorly dosed vitamin supplementation. The review by Pestalardo and colleagues published in 2025 describes the histological progression of vitamin A hypervitaminosis: hepatocyte ballooning, activation of stellate cells, perisinusoidal fibrosis and then cirrhosis^[4]. Early clinical signs include nausea, anorexia, bone pain and hepatomegaly. EFSA re-evaluated the UL in 2024 and kept it at 3,000 µg retinol equivalent per day for adults, including pregnant women^[3]. Women of childbearing age are advised to avoid the regular consumption of cod-liver oil and animal liver, a concentrated source particularly rich in retinol, to limit the risk of toxicity.

Why is vitamin D one of the major causes of intoxication?

Vitamin D is among the leading causes of food-supplement intoxication reported in Europe, through misuse in infants and self-supplementation at high doses in adolescents and adults, a topical issue regularly covered by news media. A 2025 American case report describes a 17-year-old adolescent presenting severe hypercalcaemia (corrected calcium at 13.2 mg/dL) after a high daily intake of 14,045 IU of vitamin D3 for one year; the 25-hydroxyvitamin D level reached 594 ng/mL, compared with a norm of 30-100 ng/mL^[5]. In France, the Anses nutrivigilance system has documented several paediatric cases of severe hypercalcaemia, nephrocalcinosis and kidney damage in infants supplemented with potentially dangerous, highly dosed products bought online (5,000 to 10,000 IU per drop)^[8]. The 2024 recommendations of the Endocrine Society now limit supplementation to documented at-risk populations^[6], to avoid overdose and its harmful health consequences.

Which populations are the most exposed to overdose in Switzerland?

Why are children particularly at risk?

The youngest are particularly vulnerable to excess: their reduced body weight lowers the toxic threshold of each nutrient, and the playful or sweetened pill-like appearance of many products (gummies, flavoured syrups) favours an accidental or repeated ingestion, wrongly mistaken for a treat. A study by the Bern University of Applied Sciences and the Swiss Federation of Consumers published in 2025 showed that most food supplements for children sold in supermarkets and pharmacies contained doses higher than the recommended nutritional intake for their age range^[10], with a large number of items concerned. Tox Info Suisse reports that nearly two thirds of its 1,200 enquiries linked to supplements between 2014 and 2019 concerned accidental ingestions in young children^[2]. The FSVO recommends that paediatric supplementation should systematically be subject to a professional consultation and prior medical advice, in a perspective of cautious management.

Which adult groups deserve increased monitoring?

Pregnant women, older people on multiple medicines as part of chronic treatment and athletes consuming protein or stimulant supplements form the three adult groups most exposed to an increased risk of toxicity. A Chinese single-centre retrospective study on 17,946 cases of drug-induced hepatotoxicity showed that plant-based supplements represented 26.29% of the causes in adults over 65, the leading aetiological class in this age range^[7], with a direct impact on the digestive system and the liver. During pregnancy, Anses explicitly recommends avoiding the cumulation of vitamin D and iodine intakes without biological follow-up^[11]. On the athletes’ side, Tox Info Suisse recorded 22 moderate-to-serious cases linked to caffeine, 17 of which involved sport or fitness items containing doses higher than the 200 mg per intake recommended by EFSA^[2], possibly leading to palpitations, sleep disorders and high blood pressure.

• ①Infants and young children: narrow toxic window, visual attractiveness of sweet gummies.
• ②Pregnant women: teratogenic risk (vitamin A) and neonatal hypercalcaemia (vitamin D).
• ③Older people on multiple medicines: multiple interactions and hepatotoxicity increased by plants.

• ⚠Athletes: caffeine, creatine and stimulants at cumulative doses beyond the EFSA thresholds.
• ⚠Adolescents: self-supplementation at “performance” doses without biological follow-up.
• ⚠Online buyers: non-compliant dosages or banned substances in products outside the Swiss channel.

How to prevent an overdose and what to do in case of symptoms?

Which usage rules limit the risk of overdose?

Limiting the duration of courses, not cumulating items containing the same nutrients and checking the label and ingredients of each item consumed remain the three most effective prevention levers against the risk of overdose. Systematic supplementation of a healthy person is not useful and not justified according to the FSVO: food supplements, considered as a foodstuff, do not replace a healthy and balanced diet, and their intake must be based on a documented need (confirmed vitamin deficiency, specific physiological state, restricted diet). A chemical analysis of marketed products carried out by the American DILIN network showed that out of 54 re-evaluated hepatotoxicity cases, 37% saw their causality score increase after verification of the real composition, 70% of which moving from “probable” to “highly probable”^[9]. This gap between label and actual content is frequent for plant-based supplements, which makes the advice of a specialist useful before any purchase.

• ①Mentally add up the nutrients present in all the items consumed (multivitamin + targeted + fortified foods).
• ②Limit each course to the duration indicated by the manufacturer or by a healthcare professional.
• ③Prefer a medicine to a food supplement for vitamin D in infants.
• ④Keep supplements out of reach of young children, like any health product.
• ⑤Report any adverse effect to a doctor or a pharmacist.

Which signs should raise the alert and lead to consultation?

Unexplained fatigue, persistent nausea, joint or muscle pain, weight or hair loss, yellow discolouration of the skin, or unusual thirst call for close attention, the immediate stopping of any supplement intake and lead to consulting a professional without delay. The early signs of intoxication with fat-soluble compounds are not very specific: nausea, loss of appetite, headaches, mood swings, bone or joint pain^[4]. The hypercalcaemia linked to a vitamin D excess shows up as polyuria, polydipsia, digestive disorders and, at an advanced stage, cardiac disorders^[5]. In Switzerland, Tox Info Suisse, the national food and health information service, can be reached on the number 145 twenty-four hours a day live, at any time, for any suspicion of acute intoxication linked to a food supplement.

Frequently asked questions