Food supplements: how to choose wisely

The dietary supplement market is saturated. Hundreds of products, similar promises, highly variable prices. And behind each label, differences in formulation that completely change real efficacy.

Taking a supplement without understanding what you're buying is often a waste of money. Here's how to choose using the right criteria.

It's not the name of the active ingredient on the label that determines a supplement's effectiveness. It's its form, dose, and bioavailability.

The first pitfall: the form of the active ingredient

This is the most important criterion and the least highlighted on packaging. The same active ingredient can exist in several chemical forms with vastly different bioavailabilities.

Zinc is the most striking example. Zinc oxide is the least expensive and most common form in cheap dietary supplements. Its intestinal absorption is estimated between 10% and 20%. Zinc gluconate or zinc bisglycinate (chelated) have higher bioavailability, estimated between 40% and 60% depending on studies. Two supplements claiming "15 mg of zinc" can therefore deliver very different amounts of absorbable zinc depending on their form.

Magnesium follows the same logic: magnesium oxide is poorly absorbed and often has a laxative effect at high doses. Magnesium bisglycinate and marine magnesium are better tolerated and absorbed. "Marine" magnesium is not automatically superior—it all depends on the form in which it is extracted.

Ferrous iron (ferrous sulfate, ferrous fumarate) is better absorbed than ferric iron, but can irritate the digestive tract. Iron bisglycinate offers good bioavailability with superior digestive tolerance.

The second pitfall: insufficient dosage

A supplement that contains an active ingredient at a dose below the documented efficacy threshold will produce no measurable results, regardless of the quality of its formulation. This is the equivalent of fairy dusting in cosmetics—applied to dietary supplements.

Documented efficacy thresholds for the most common active ingredients in nutritional dermatology: zinc between 15 and 30 mg per day (gluconate or bisglycinate) for action on acne and hair loss. Omega-3 between 1 and 3 g of EPA+DHA per day for documented anti-inflammatory action—check that the label indicates the EPA and DHA content, not just "fish oil." Hydrolyzed collagen between 2.5 and 10 g per day depending on studies on hydration and elasticity. Vitamin D between 1,000 and 2,000 IU per day for winter prevention in adults.

A supplement containing 5 mg of zinc and 200 mg of untitrated fish oil does not meet any of these thresholds. It is legal. It is useless.

The third pitfall: counterproductive combinations

Some active ingredients inhibit each other when taken simultaneously. Calcium and iron compete for the same intestinal transporters—taking them together reduces the absorption of both. High-dose zinc inhibits copper absorption in the long term—prolonged supplementation with zinc alone can lead to copper deficiency. Iron is better absorbed with vitamin C and less well absorbed with tea or coffee.

These interactions do not make these active ingredients incompatible—they simply require them to be taken at different times or in carefully considered combinations.

What labels and certifications really say

In Europe, dietary supplements are subject to Directive 2002/46/EC but do not require prior market authorization—a simple notification to the DGCCRF is sufficient. This is not a guarantee of efficacy, only presumed safety.

Labels worth noting: GMP (Good Manufacturing Practice) certification guarantees rigorous manufacturing conditions. Independent third-party tests (Informed Sport, NSF, Eurofins) certify the conformity of the actual composition with the label. Brands that publish their Certificates of Analysis (CoA) demonstrate transparency regarding the actual active ingredient content.

Labels that guarantee nothing: "natural," "organic," "vegan" say nothing about bioavailability or efficacy. An organic supplement can be less well formulated than a conventional one.

Dosage forms: capsules, tablets, liquids, gummies

The dosage form influences absorption. Gastro-resistant capsules protect sensitive active ingredients (probiotics, certain forms of vitamin C) from gastric enzymes. Liposomal forms (liposomal vitamin C, liposomal glutathione) significantly improve the bioavailability of molecules that poorly cross cell membranes.

Gummies are generally underdosed and contain more sugar and additives to mask the taste of active ingredients. They are rarely the optimal format in terms of efficacy—even if they are more pleasant to consume.

The basic rule: identify your needs before choosing

Taking a supplement without having identified the need it covers is the first mistake. Tight-feeling skin is not automatically due to a zinc deficiency. Hair loss is not automatically a biotin deficiency—it is often a ferritin or zinc deficiency. A dull complexion is not automatically a lack of collagen—it is often dehydration combined with excessive oxidative stress.

Blind supplementation rarely produces results because it addresses hypothetical causes rather than identified needs. An assessment—even simple, even without a blood test—helps to target what truly matches your profile.

The Paradermia approach

Our pharmacist selects supplements based on their actual formulation: bioavailable form of each active ingredient, documented effective dosage, absence of counterproductive combinations, and appropriate dosage form. The supplements offered address needs identified in your profile—not a generic list of "good for skin" products.

Our nutrition quiz allows you to precisely identify your needs and receive targeted recommendations, whatever your goal—skin, hair, energy, immunity.

Frequently asked questions

How do I know if a supplement is truly well formulated?
Check the form of the active ingredient (bisglycinate rather than oxide for zinc and magnesium, EPA+DHA indicated separately for omega-3), the daily dose compared to documented efficacy thresholds, and the availability of an accessible certificate of analysis. Our pharmacist has done this work for every product listed on Paradermia.

Should I take several supplements at the same time?
Not necessarily. One or two well-targeted and well-formulated supplements are better than five underdosed and poorly matched ones. Our nutrition quiz identifies priorities based on your profile to avoid blind supplementation.