Mercadona's €2 magnesium: real relief or placebo?

€2 magnesium promises a mood lift

An orange tube costing two euros reportedly restored good humor to someone who had been feeling sad and stressed by work for a while. The person who raised the issue said they took multivitamins that did nothing, bought effervescent magnesium to try it out, and noticed a change after three days. The uncomfortable detail is that the product's chemistry—magnesium carbonate and B vitamins—does not explain this result on its own. This sparks a discussion that has remained unresolved for months.

What Mercadona's magnesium actually contains

The bottle is cheap, which has consequences. According to those who reviewed its composition, the compound is magnesium carbonate, a salt poorly absorbed with notable laxative effects. This comparison is not from a sales pitch: along with magnesium oxide, it is one of the worst forms for the body to utilize. What it does contain is a cocktail of B vitamins, providing a clue for critics: if mood improves, the culprit might be the vitamin, not the mineral.

The exact composition also does not appear on the manufacturer's website, according to those who tried to check. Two euros do not buy high-quality magnesium; they buy a small dose of a cheap compound. This does not entirely invalidate it. A small dose of something weak may still suffice for what the user seeks.

From pharmacy to supermarket: €25 vs €2

The contrast with the pharmacy counter is another key point. One reported case: after cystitis, a pharmacy recommended magnesium for 25 euros, but a single capsule caused an urgent bathroom visit. The supermarket bottle, containing the same mineral, costs more than ten times less. Several conclude that quality is not always paid for; sometimes you pay for packaging and staff advice. According to one participant, this is where para-pharmacy becomes a lucrative business.

Why does it work for some and upset others?

There is more consensus here than it appears. Almost all types of magnesium have laxative effects; the difference is degree. Citrate is cited among the forms that most loosen the bowels, though not everyone agrees, while the cheap bottle's low quantity makes it barely noticeable. Some take this same brand and confirm improvements, but also experience loose digestion, and plan to switch to another chain's product. The repeated explanation: it is about dosage; even vitamin C causes more diarrhea than magnesium.

The mood lab: placebo or B12 deficiency?

The suspicion of the Doctor Placebo runs through half the conversation. The opposing hypothesis is equally reasonable: those with a real vitamin or magnesium deficiency notice the supplement because they lack it; those without it notice nothing. Several point to B group vitamins—B1, B6, B12—as possible culprits for the mood boost, noting that magnesium participates in hundreds of bodily reactions. Prudent warnings state that excess vitamins also have negative effects. An overdose can stop being antioxidant and become oxidizing.

Other brands and prices mentioned

The Mercadona bottle is not the only cheap option. Powdered magnesium from another supermarket chain is mentioned at 5 euros per tin, and another brand's magnesium calmed stress for one user. The range is wide: from 2 to 25 euros for what, on paper, is the same mineral. The difference lies in the compound and dosage, not the box.

Eating magnesium is cheaper than buying it

The calculation circulating in the thread is simple: half a kilo of shelled peanuts would provide around 1,250 mg of magnesium for a price similar to those two euros, according to a user's math. The list of magnesium-rich foods shared in the conversation adds pumpkin seeds, with about 540 mg per 100 grams; chia seeds, 335; almonds, 270; cashews, 260; dark chocolate, 228; cooked spinach, 87. Even mineral water from certain springs contributes.

Underlying criticism: better to eat than to supplement

Much of the skepticism is not against magnesium itself, but against the habit of solving with a bottle what can be fixed on the plate. Foods containing it are listed—nuts, whole grains, dairy, banana, avocado, chickpeas, lentils, whole wheat bread, spinach, chard—and it is noted they are cheaper and offer more benefits. In defense, the supplement argument is simple: some people do not eat like this, and for them, the bottle fills the gap.

The orange tube will likely continue selling by the thousands as long as the debate remains open. But one should not confuse relief with a cure: if the problem is mood-related or health-related, two euros of magnesium do not replace professional help. What it does demonstrate is something uncomfortable for the industry: that a two-euro product does, for many people, the same job as a twenty-five-euro one.