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The honest mineral guide

Minerals: test before you take, and food before pills

Minerals have a nastier catch than vitamins: several of them are actively harmful when you take too much, and "too much" is not always a lot. The pattern that keeps you safe is simple. Suspect a deficiency? Get a blood test. Otherwise, get your minerals from food, where overdosing is nearly impossible. Here is the honest rundown, mineral by mineral.

The ones that actually matter

IronThe most common genuine deficiency in the UK, especially in women with heavy periods, pregnant women and people on plant-based diets. But iron is also harmful in excess, so the rule is firm: blood test first, supplement only if your GP confirms a deficiency. Feeling tired has a hundred causes and iron is just one of them.
CalciumMost adults get enough from dairy or fortified alternatives, tinned fish with bones, and green vegetables. Worth auditing your intake if you are dairy-free (see our vegan diet review) or over 50, but food-first wins: calcium pills show weaker bone benefits and, at high doses, possible downsides.
IodineEasy to miss if you avoid dairy and fish, and vital for thyroid function, especially in pregnancy. But do not fix it with seaweed supplements: their iodine content swings wildly and can poison the same thyroid you were trying to help. Fortified milk alternatives or a measured supplement are the sensible routes.

The overhyped ones

MagnesiumThe wellness industry's favourite mineral. Most people eating wholegrains, nuts, pulses and greens get enough, and the evidence for magnesium fixing sleep, anxiety or cramps is thin. The elaborate form wars (glycinate versus citrate versus oxide) matter far less than the adverts suggest. Likely harmless at normal doses, just not the miracle it is sold as.
ZincOne genuinely interesting finding: zinc lozenges started within 24 hours of symptoms may shorten a cold by about a day, per Cochrane. Beyond that, routine high-dose zinc is a bad idea. It depletes copper and can cause nerve problems over time.
SeleniumYou need tiny amounts, and the gap between enough and too much is narrow. The "one Brazil nut a day" hack delivers unpredictable doses. A normal varied diet covers it.
PotassiumDo not supplement this one casually: excess potassium can stop your heart, which is why over-the-counter doses are tiny by law. Get it from potatoes, beans, bananas and vegetables instead. (People with kidney disease have the opposite problem and their own rules. See our renal diet review.)
Illustration for the Slimr honest guide to minerals

The test-first rule, and why it protects you

Fatigue, brain fog, hair shedding and low mood get blamed on mineral deficiencies constantly, and sometimes that is right. But the same symptoms come from thyroid problems, depression, sleep apnoea, coeliac disease and a dozen other things a supplement will never fix. A basic blood panel through your GP separates the real deficiencies from the expensive guesses. If a genuine deficiency shows up, treating it feels remarkable. If not, you have saved your money and learned something useful about your health. Either way, you win. And if you are on GLP-1 medication and eating much less than before, asking for that panel at your next review is a genuinely smart move.

The research behind this page

We link the actual research, not press releases. These are the papers and reviews the numbers on this page come from.

Sources worth reading yourself

Where to go next

Vitamins, honestly

The short UK list worth taking and the megadoses to skip.

Vitamin guide

Supplements: the truth

What works (creatine), what is marketing (most of it), MHRA warnings included.

Supplement guide

Audit your diet

Every Slimr diet review lists the nutrients it puts at risk.

Open the directory

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