How to choose the right food supplement for your needs?

How to pinpoint your needs precisely?

Why establish an assessment before any supplementation?

The online survey carried out for the FSVO showed that vitamins, vitamin-mineral combinations and mineral salts dominate the basket of Swiss consumers^[9], often without a prior assessment. Establishing an assessment before intake steers you towards the right nutrient and avoids unnecessary supplementation. A narrative review published in Medical Sciences in 2026^[1] on the deficiencies associated with obesity confirmed that iron, zinc, magnesium, vitamin D and vitamin B12 deficiencies are often masked by a calorie-rich diet that is nevertheless poor in micronutrients. Without an assessment, the risk is twofold: missing a true deficiency or supplementing what is not lacking, whereas a food supplement requires a clear objective to support health. For nutrients whose status is easily evaluated through a blood test — ferritin, 25-OH vitamin D, B12 — a measurement is useful before a long course, and steers the choice of the form suited to the health goal. For magnesium, whose blood level poorly reflects tissue status, the clinical context and dietary intake guide the decision. Some kidney or cardiac situations call for particular caution, and the conditions in which renal insufficiency contraindicates certain supplements deserve to be discussed with a healthcare professional before any high-dose intake of potassium, magnesium or vitamin D.

How to recognise the signs of a true deficiency?

A true deficiency manifests as a coherent cluster of signs, not as an isolated symptom. For iron, chronic exhaustion, breathlessness on exertion, pallor, brittle nails or restless legs syndrome steer you towards a check by ferritin measurement. A review published in JAMA in 2026^[2] documented that restless legs syndrome affects about 3% of American adults at a clinically significant level, and that iron supplementation is recommended as soon as ferritin falls to 100 ng/mL or below, or transferrin saturation drops under 20%. For vitamin D, diffuse fatigue, bone pain or weakened immunity in winter suggest a measurement. For vitamin B12, tingling, memory disturbances and asthenia in people on a strict plant-based diet call for a check; the choice of a supplement suited to vegan profiles then depends on the form and the dosage selected. The pitfall: attributing temporary fatigue to a deficiency without first exploring sleep, stress, physical activity and the quality of a balanced diet.

When to consult rather than self-prescribe?

Any supplementation in a person under medical treatment goes through advice from a healthcare professional. Supplements interact with many medicines: St John’s wort modifies the metabolism of contraceptives and antidepressants, calcium and iron reduce the absorption of some antibiotics, vitamin K interferes with anticoagulants. A thorough analysis of the known drug interactions with food supplements is essential before any combination. Pregnant women, children, people with chronic renal, hepatic or cardiac conditions should also seek a doctor’s advice before the first intake. The community pharmacist remains a direct contact to verify the compatibility of a supplement with an ongoing treatment and to place the intake within a global lifestyle approach.

How to assess the quality of a product?

Which elements to read first on the label?

Checking the contents of a supplement’s label calls for attention to four unambiguous pieces of information: the quantity of active ingredient per daily dose, the exact chemical form of the nutrient, the full list of excipients and the mandatory warnings. In Switzerland, the Swiss food supplements ordinance^[3] requires the wording “food supplement”, the recommended intake, a warning not to exceed the daily dose and the statement that these products do not replace a varied diet. Reading “magnesium 300 mg” is not enough: you need to know whether it is oxide, citrate, bisglycinate or another form, because the blood response varies. The excipient list lets you spot allergens or unnecessary additives; a methodical reading of the label remains the first barrier against poorly formulated products. A supplement can trigger allergic reactions linked to gluten, lactose, soya, animal gelatine or colourings: the ingredient list is the first safety filter.

Why favour bioavailable forms?

Bioavailability describes the share of a nutrient actually absorbed and usable. A randomised clinical study published in Nutrients in 2024^[4] compared, in 40 volunteers, oxide, citrate, bisglycinate and a microencapsulated magnesium: only the microencapsulated form maintained a plasma rise over six hours, with oxide and citrate rising briefly, and bisglycinate not producing a significant plasma rise in this protocol. This does not disqualify bisglycinate, widely recognised for its digestive comfort and its passage into tissues, but it underlines that real effectiveness depends on the galenic form: the “declared dose” and the “effective dose” differ according to the form. For iron, oral supplementation is codified by the 2025 clinical review by Li and Finberg^[5], which stresses that the choice between oral and intravenous forms depends on the severity of the deficit; chelated forms such as bisglycinate are often favoured for their digestive tolerance in sensitive people. For omega-3, a human study on formulated ethyl esters observed a more marked improvement in the blood omega-6/omega-3 ratio with the enhanced-bioavailability formulation than with unformulated esters^[6].

Which labels and standards to look for in Switzerland?

No label is compulsory beyond the Swiss food supplements ordinance, but several voluntary certifications strengthen trust. Compliance with the ordinance requires the maximum doses set out in its annex^[3] and excludes some substances such as melatonin as a food supplement or red rice yeast, classified by the FSVO because of their borderline status with the medicine category^[10]. A Swiss manufacturer or laboratory monitored by the cantonal chemist applies documented self-checking, a guarantee of health safety. Useful complementary certifications include independent purity (for example, IFOS for fish oils, which measures oxidation and heavy contaminants), the ISO 22000 standard on industrial food safety, the European organic label for the plant raw material and pharmaceutical GMP manufacturing for products aimed at informed consumers. A product without any of these signals is not unlawful, but the absence of a third-party certificate leaves the consumer alone with the brand’s promise; the quality criteria of a supplement then rest entirely on the manufacturer’s transparency.

How to adjust dosages to your profile?

How to avoid overdose when combining several supplements?

Overdose most often occurs through the invisible cumulation of several products that contain the same nutrients. The 2023 Swiss Nutrition Bulletin^[7] documented that several participants exceeded the maximum tolerable intake for nutrients such as vitamin D, magnesium, zinc or vitamin B6, most often through cumulation of several products. The practical advice is to carefully add up the doses of nutrients present in each supplement taken over 24 hours, then to compare them with the upper limits published by EFSA and adopted by the FSVO. A multivitamin plus a stand-alone vitamin D plus an immune complex frequently leads to an excess of zinc or vitamin A; choosing between a single-nutrient supplement or a combined formula reduces this risk of cumulation. The risks linked to overdose in food supplements include liver damage for vitamin A, hypercalcaemia for vitamin D, and digestive or neurological disorders for zinc and vitamin B6.

Which supplements for pregnant or breastfeeding women?

Pregnancy calls for a strict medical framework, with a few validated nutrients and much caution for the rest. Folic acid before conception and during the first trimester, iodine throughout pregnancy and vitamin D depending on the sunlight context form the consensus in European recommendations. Iron is added in cases of documented anaemia, not systematically. Adaptogenic plants, essential oils, some high-dose vitamins (in particular preformed vitamin A) and phytoestrogens are to be avoided; it is advisable to consult a healthcare professional before any use. The specific precautions for food supplements in pregnant women in Switzerland rest on the Swiss Society of Nutrition recommendations and on the advice of a gynaecologist or midwife before any new intake.

Which supplements for children and adolescents?

In children and adolescents, supplementation is justified case by case, never as a routine. Vitamin D is the exception: systematically recommended in infants in Switzerland and in several Nordic countries, it has been associated with better gum health in children aged 6 and 10 in a Polish study on 2,019 children^[8] published at the end of 2025. Apart from vitamin D, supplements aimed at children should answer a documented need alongside a healthy diet: a plant-based diet for vitamin B12, anaemia for iron, severe allergic profile for omega-3 fatty acids. “Sweet-flavoured” multivitamins claiming to strengthen the immune system expose users to overdose in case of repeated intake and their preventive value is not demonstrated in non-deficient children; the benchmarks for supporting winter immunity rest first of all on vitamin D, diet and sleep. The details on the safety of food supplements in children and adolescents overlap with the federal paediatric recommendations.

How to monitor tolerance day to day?

Which adverse effects to watch for from the very first days?

The most frequent early adverse effects are digestive, allergic or linked to a change in mood or sleep. Nausea, diarrhoea, bloating or constipation appearing within 48 to 72 hours of introducing a supplement often points to the form of the mineral or to a poorly tolerated excipient ingredient, which calls for prompt attention to the product consumed. The digestive disorders caused by food supplements mainly concern magnesium oxide, iron sulphate and high doses of vitamin C. A skin rash, itching or oedema call for immediate cessation and a consultation. Supplements based on adaptogenic plants can disturb sleep or mood during the first intakes; keeping a brief tolerance diary during the first week helps identify the responsible product.

When to stop or adjust your supplementation?

A supplementation should be reassessed at every checkpoint based on individual needs, not indefinitely. For a corrected deficiency, a follow-up measurement between three and six months after the start lets you decide whether to stop or to continue at a maintenance dose. For a magnesium course or a B-complex course linked to temporary stress, one to three months is enough in most cases, to be adjusted to the context — for example in athletes with specific needs in recovery. For vitamin D, supplementation extended through winter to spring is usual in regions with low sunlight, but a suitable dose avoids exceeding the tolerable upper intake level. Indefinite continuation without reassessment exposes you to the risk of cumulative overdose and financial waste. The rule: a supplement has an objective, a duration, a stop criterion — otherwise it becomes a habit without measurable benefit, disconnected from any coherent lifestyle.

Frequently asked questions