You open a bottle of capsules hoping for more energy, clearer skin or hair that holds up. The intention is good, and there is nothing naive about wanting to look after yourself. Except that the promise rarely survives a close look at the evidence, and the real question is not 'does it work?' but 'what does it work for, and for whom?'.

Young woman sitting at a kitchen table, an open bottle of supplements and a glass of water in front of her
Opening the bottle is already believing the promise

Two categories we mix up

On the shelf, everything carries the same label. Yet two very different uses sit side by side. On one hand, supplements that correct a documented deficiency: iron, vitamin D, B12, magnesium. On the other, formulas sold for concentration, tiredness or fragile hair, often with no identified deficiency behind them.

In the UK, a food supplement does not have to prove it works before it goes on sale, unlike a medicine. Only health claims authorised in the UK may appear on the pack. In practice, the label tells you more about the marketing than the evidence.

Trug of fresh vegetables and pulses in a kitchen, in natural light
Iron, B12, magnesium: food on your plate is still the first source

Deficiencies, really?

You often hear that our diet covers all our needs. That is largely true, but not for everyone.

Current UK data from the National Diet and Nutrition Survey (NDNS) show that many adults have low vitamin D status, especially at the end of winter. The survey has also documented iron intakes below recommendations in some women of reproductive age.

Some situations increase the risk: pregnancy, breastfeeding, strict veganism, older age, chronic illness, heavy periods, bariatric surgery. For these people, supplementation may be useful, with an appropriate dose and monitoring. For everyone else, no capsule makes up for broken sleep, an unbalanced plate or a winter spent indoors.

Woman in a wool jumper sitting by a large window in winter, a warm mug in her hands
A winter spent indoors, and vitamin D runs low

When is it effective?

What we know, and what we don't yet know: supplementation works when a deficiency is identified by a blood test, symptoms or a clinical context. It then corrects a real shortfall, and is checked with follow-up blood tests.

Straw hat, plain tube of sunscreen and sunglasses on a teak table
Sunscreen, hat, shade: protection doesn't come in a capsule

For broader promises — memory, immunity, complexion, energy — current data suggest little or no effect outside a deficiency. As for so-called sun capsules, meant to prepare the skin for sun, they are not enough to protect you: sunscreen, hat and shade remain the basics.

A supplement replaces neither a varied diet nor an ongoing treatment. Some combinations of herbs, vitamins or minerals with medicines deserve advice: anticoagulants, contraceptives, antidepressants or certain antibiotics, for example. If you are pregnant, taking medication or living with a chronic illness, speak to a healthcare professional before swallowing anything.

Too much can be harmful

It is tempting to imagine that excess vitamins are simply excreted without consequence. That is false for several of them. Too much vitamin A or vitamin D can become toxic, because these vitamins are stored in the body; vitamin B6 at high doses can lead to nerve problems; iron can accumulate dangerously in some people. These risks are known and monitored by health authorities.

Bathroom shelf crowded with bottles and sachets of supplements, an open pill organiser
Taking one course after another doesn't remove the risk of overdose

Interactions with medicines are the other sensitive area. UK health authorities record reported side effects from supplements: skin reactions, digestive problems, liver injury. If a symptom appears after taking one, you can report it to your doctor or pharmacist.

In practice, remember this

Take stock before you buy. A blood test prescribed by your doctor settles the question better than any test sold online. Ask your doctor or pharmacist for advice on form, dose and duration, and don't run three courses at once for fear of missing out.

Hand pouring capsules from a kraft pouch into an amber glass jar on a counter
Refilling rather than buying new: a simple habit, less packaging

When choosing, a few guides: a short ingredients list, the dose actually present per capsule, and the percentage of reference intakes. A glass jar or refill pack limits packaging; an organic certification such as Soil Association guarantees a proportion of organic ingredients and no GM ingredients, not effectiveness or accurate dosing. Don't confuse a claim with proof.

Budget

Expect to pay around £5 to £15 for a simple vitamin or mineral from a pharmacy, and more like £15 to £30 for a branded or combined formula. A three-month 'beauty' or 'energy' course from a health and beauty retailer often sits between £30 and £60. In supermarkets and online, prices frequently drop below £10, with less advice available.

What changes the bill: the dosage form (drops, capsules, powder), the number of capsules per day, the number of active ingredients, where you buy it and the label. The real cost is duration: a course repeated for several months weighs more heavily than a properly balanced plate. You'll find these products in pharmacies, health and beauty shops, health food shops, supermarkets or online — bearing in mind that the advice you get varies depending on where you ask.

Sources

  • NHS, vitamins and minerals: advice on food supplements
  • Office for Health Improvement and Disparities, National Diet and Nutrition Survey (NDNS)
  • Department of Health and Social Care, Great Britain nutrition and health claims register
  • Food Standards Agency, food supplements guidance
  • MHRA Yellow Card scheme, reporting suspected side effects

Food supplements do not replace a varied, balanced diet and a healthy lifestyle.