Clinicians see more individuals who are convinced that vitamins, minerals, and botanical extracts will enhance their health, even though these products offer limited added value to those who have already consumed a balanced diet.

Demand continues to rise, fuelled by aggressive marketing and high expectations; however, the evidence base and product quality remain uneven.

This series reviews the medical and pharmacologic data behind widely used dietary supplements and provides clinicians with practical guidance on recognising high-quality products, evaluating regulatory claims, determining when supplementation is clinically justified, and avoiding preparations that offer little benefit or risk to misleading patients.

Quality and Evidence

The sales of dietary supplements continue to grow, with global estimates indicating that the vitamin and mineral market may increase from approximately €27 billion in 2023 to nearly €41 billion by 2029.

In Germany, three quarters of the surveyed consumers reported taking supplements in the previous year, most often vitamins (61%), followed by minerals (36%) and proteins (28%).

Dietary supplements are available online in pharmacies, drugstores, and supermarkets, and their distribution is not limited to pharmacies.

Many lower-priced products sold in supermarkets and drugstores are produced by the same contract manufacturers that supply pharmacies.

The quality of a product does not depend on where it is sold but rather on its manufacturing, composition, dosage, and quality assurance. The frequently used term “pharmacy quality” is not legally protected, and there is no guarantee of the purity or effectiveness of the products.

Many products sold in supermarkets and drugstores are manufactured by the same contract manufacturers that supply pharmacies. The key differences between these products are related to their formulation, dose, and quality. Pharmacy products are usually labelled with greater precision, contain pharmaceutically tested raw materials, and undergo batch-wise testing. In the mass market, price often drives production decisions, which can lead to variable active ingredient content, incomplete labelling, or less rigorous testing.

Advice and product selection differed significantly. In pharmacies, recommendations are based on clinical indications, nutritional status, and potential interactions. Many pharmacies, in collaboration with external laboratories, now offer blood tests to confirm vitamin deficiency.

Supermarkets do not provide such assessments. Individuals receive no guidance on whether supplementation is necessary, whether a preparation contains an appropriate and safe dose, or whether a compound is likely to be absorbed to a clinically meaningful extent.

For magnesium supplements, the label should specify both the amount of elemental magnesium per capsule and its exact chemical composition. Organic compounds, such as magnesium citrate, have high bioavailability and are well absorbed. Poorly soluble salts, such as magnesium oxide, are absorbed only in limited amounts.

Who Requires Dietary Supplements?

According to the German Federal Institute for Risk Assessment (BfR), most individuals do not require supplements because a balanced diet generally provides adequate nutrients, and additional vitamins or minerals do not confer benefits in the absence of deficiencies. Targeted supplementation is advisable only during specific life stages or when there is a clear clinical need. Folic acid is a key example; women are advised to start supplementation before conception and continue it through early pregnancy to reduce the risk for neural tube defects in the foetus.

The EU’s Nutrition and Health Claims Regulation [EC] No. 1924/2006 governs nutrition- and health-related claims for these products.

Only claims that have been scientifically evaluated by the European Food Safety Authority (EFSA) and authorised by the European Commission (EC) may appear on labels, such as “vitamin D contributes to normal immune system function.”

Authorised claims for dietary supplements are health-related statements reviewed by the EFSA and approved by the EC. Only these statements may appear on product labels.

Claims that imply disease treatment are not permitted because supplements are not intended for this purpose. According to media reports and assessments by consumer organisations, these violations are most often observed in online marketing campaigns.

Identifying High-Quality Supplements

• Check labelling: Products should list all nutrients, the exact chemical forms (eg, magnesium citrate), and the amounts per daily dose.
• Review dosing: The doses should follow the BfR maximum intake recommendations, where available. Caution should be exercised when using high-dose or multi-ingredient preparations.
• Confirm manufacturer reliability: Look for batch numbers, clear manufacturer details, and quality documentation, including independent testing.
• Verify authorised claims: Claims must be listed in the EU register and meet all conditions of use. Avoid products that use vague or unauthorised terms, particularly in online advertisements.
• Use of indication-specific supplementation: Supplements should be recommended only when clinically appropriate, such as folic acid before and during early pregnancy, iodine during pregnancy, or vitamin D when the risk for deficiency is increased — assessing potential interactions always.
• Reinforce food first: Supplements should complement a balanced diet rather than replacing it.

This story was translated from Medscape’s Portuguese edition.