Dietary supplements: why you shouldn't take them lightly

While 37% of French people wrongly believe that food supplements "compensate for a poor diet" according to the 2025 critical thinking barometer, the French national health safety agency is hosting a round table discussion on Tuesday at the Cité des Sciences in Paris to "deconstruct preconceived ideas about these products."

Prominent in pharmacies, advertisements, and online, dietary supplements straddle the line between food and medicine. Whether it's vitamins B, C, D, or trace elements, the French are crazy about them. Since 2019, sales of dietary supplements in pharmacies have jumped 56%, according to a survey conducted by the non-prescription health products lobby, NèreS.

However, in general and in the absence of pathology, "nutritional needs can be met through a varied and balanced diet as part of a physically active daily life," ANSES reminds us. "The consumption of food supplements is then not necessary."

There are, however, some exceptions for populations at risk of deficiencies: pregnant women, the elderly, or vegans, "who, by excluding all foods of animal origin, do not have a vitamin B12 intake," explains Aymeric Dopter, head of the nutrition risk assessment unit at ANSES.

Unlike medications, dietary supplements are not subject to marketing authorization. No efficacy or safety studies are required before they are marketed. They therefore cannot claim therapeutic effects.

While they promise results against overwork, nervousness, sleep problems, or excess weight, the nutritional and health claims they can display on their packaging are regulated by the European Union. For example, zinc can claim to "contribute to the normal function of the immune system."

However, many dietary supplements—sold primarily online—go further, promising miracles for various conditions. Some claim to treat cancer, combat fertility problems, or cure endometriosis. "On the internet, we discover the dark side of dietary supplements: they sell absolutely anything and everything," observes Aymeric Dopter.

According to the General Directorate for Competition, Consumer Affairs and Fraud Control (DGCCRF), of the 95 websites selling food supplements inspected in 2017 (latest figures available), 76% were non-compliant.

What are the real risks?

"The problem is that the consumption of dietary supplements is wrongly trivialized," warns Irène Margaritis, deputy director of risk assessment.

Since 2009, ANSES has implemented a nutrivigilance system to monitor adverse effects related in particular to the consumption of food supplements. In 2024 alone, the agency—which has no health police powers—received more than 500 reports. After analysis, it issues an average of seventeen alerts each year regarding dangerous products to public authorities.

Far from being harmless, the consumption of food supplements can present nutritional risks, misuse or drug interactions, of which consumers are often unaware.

Zinc, for example, can cause copper deficiencies, aloe vera is contraindicated in cases of intestinal obstruction, and echinacea is contraindicated in cases of immune system disease. As for vitamin D, ANSES issued a warning in 2023 about overdoses in infants linked to the use of food supplements.

Recently, the Health Agency also sounded the alarm about "appetite suppressants" based on the plant Garcinia cambogia, following several cases of liver damage, including one fatality.

For these reasons, Anses recommends that any intake of food supplements be discussed beforehand with a health professional.

"Whether it's fatigue or a lack of energy, you shouldn't try to solve the problem alone by resorting to dietary supplements," argues Aymeric Dopter. "There could always be something more serious behind the problem, which could lead to a delay in treatment."