Vitamins and Minerals: What You Need and Why

What vitamins and minerals are, and how they differ

Vitamins are organic compounds. The body uses them to drive chemical reactions, release energy from food, build tissues, support immunity, and keep the nervous system working. There are thirteen essential vitamins: the body either cannot make them at all, or cannot make them in the amounts it needs, so they have to come from food (or, for vitamin D, partly from sunlight on the skin).

Minerals are inorganic. They are elements from the periodic table that the body uses for structure (calcium and phosphorus in bones and teeth), for electrical and water balance (sodium, potassium, chloride), and as cofactors that switch enzymes on (iron, zinc, copper, selenium, iodine, and others).

Fat-soluble versus water-soluble vitamins

Vitamins split into two groups based on how the body handles them.

• Fat-soluble vitamins (A, D, E, K) are absorbed with the fat in food and the body stores them, mostly in the liver and in fatty tissue. The store means a day or two of low intake is not a problem; it also means high-dose supplements can build up, so several fat-soluble vitamins have strict supplement upper limits (Vitamin A in particular).
• Water-soluble vitamins (vitamin C and the eight B vitamins) are not stored in large amounts. Surplus is excreted in urine. They need topping up regularly from food, which is straightforward on a varied diet, but means deficiencies show up sooner if intake drops (the picture seen with vitamin B12 on a strict plant-based diet, or thiamin in heavy alcohol use).

Macrominerals versus trace minerals

Minerals split by how much of them the body needs.

• Macrominerals are needed in larger amounts, hundreds of milligrams to grams a day. They are calcium, phosphorus, magnesium, potassium, sodium, and chloride.
• Trace minerals are needed in tiny amounts, milligrams or micrograms a day. They include iron, zinc, copper, iodine, selenium, manganese, molybdenum, chromium, and fluoride. "Trace" does not mean unimportant: iodine deficiency in pregnancy and iron deficiency in women of childbearing age are real UK public-health issues.

One vitamin-like nutrient

Choline sits alongside the B vitamins as a vitamin-like nutrient. The UK has not set a formal reference value for it; the entry explains where it shows up in food and what the European figure is for context.

More is not always better

From a food perspective, it is essentially impossible to overdose on most nutrients: the body excretes the excess of the water-soluble ones, regulates absorption of most of the minerals, and stores the fat-soluble ones in reasonable amounts. From a supplement perspective, that protection weakens. Several nutrients have strict NHS supplement uppers because the supplement form bypasses the body's natural brakes: vitamin B6 (10mg a day), selenium (350 micrograms a day), vitamin A (avoid liver and high-dose A supplements in pregnancy), and iron (only supplement when a blood test shows deficiency). The individual entries set out each upper limit.

Every nutrient on its own page

Each entry covers what the nutrient does, the UK reference intake by age and sex, deficiency signs, food sources, and supplement notes. Use the directory below to jump to one.

Do you need a supplement or a multivitamin?

For most healthy UK adults eating a varied, balanced diet, a routine multivitamin is not necessary. That is the NHS position, and it is the one this site takes. The body absorbs nutrients better from food than from tablets, the dose is usually safer, and a varied diet covers far more (fibre, plant compounds, the broader balance of nutrients) than any tablet can.

There are, however, specific situations where the NHS does recommend a particular supplement, and these are not optional. They are the cases where diet plus daylight plus normal physiology will not, on the evidence, fill the gap.

The NHS-recommended supplements

• Vitamin D, autumn and winter, for everyone. Between October and early March in the UK, the sun is too low for the skin to make vitamin D. The NHS advises everyone aged 5 and over to consider taking 10 micrograms a day of vitamin D during these months. Babies, young children, pregnant and breastfeeding women, people with darker skin, and people who cover up or stay indoors should take it all year. Full detail and dosing on the Vitamin D entry.
• Folic acid, pre-conception and early pregnancy. Women trying for a baby and women in the first 12 weeks of pregnancy should take a 400 microgram folic acid tablet every day. This reduces the risk of neural tube defects. Higher doses (5mg) apply where the woman has diabetes, takes anti-epilepsy medicine, has a body mass index of 30 or more, or has a personal or family history of neural tube defects. Full guidance on the Folate entry.
• Vitamin B12, for anyone avoiding animal foods. Vitamin B12 is not made by plants in a form the body can use. Vegans, and people on a mostly plant-based diet who do not regularly eat dairy or eggs, need a reliable B12 source: fortified plant milks and cereals, fortified nutritional yeast, or a B12 supplement. This is not negotiable. The Vitamin B12 entry sets out doses and forms.
• Iron, only if a blood test shows deficiency. Iron supplements should not be taken speculatively. They have side effects (constipation, dark stools, nausea) and a real overdose risk, and excess iron over time is implicated in other problems. Confirmed iron-deficiency anaemia is treated by a GP. Heavy periods, pregnancy, vegetarian and vegan diets, and frequent blood donation are situations to flag with the GP for a ferritin test. See the Iron entry for the full picture.
• Healthy Start vitamin drops, for eligible groups. The NHS Healthy Start scheme provides free vitamin drops (containing vitamins A, C, and D) for children under 4 in lower-income families, and free Healthy Start vitamins for pregnant women. Eligibility and how to apply are on the NHS Healthy Start website.

What about a general multivitamin?

A standard once-a-day multivitamin at sensible doses is unlikely to cause harm in an adult. The NHS position is simply that it is not a substitute for a varied diet, and it is not a routine recommendation. If you take one as a backstop while you are eating poorly through a busy period or after illness, that is reasonable; if you are otherwise eating well, the evidence that a multivitamin adds anything is weak.

Two practical cautions if you do take one:

• Read the label. Some products contain far more than the daily requirement of certain nutrients. The fat-soluble vitamins (A, D, E, K) and several minerals (iron, selenium, zinc) accumulate in the body, and high-dose products can push intake past the safe upper limit.
• Add up stacked products. A multivitamin plus a separate B-complex plus an energy drink plus a "stress" formula can push daily vitamin B6 above 10mg, which is enough to risk peripheral neuropathy over time. The 10mg cap is one of the strictest in UK supplement guidance.

Where more is clearly not better

For most water-soluble vitamins, the body excretes excess. For several other nutrients, excess from supplements causes real harm:

• Vitamin B6: NHS supplement cap is 10mg a day. Higher long-term doses can cause peripheral neuropathy (nerve damage in hands and feet).
• Selenium: NHS supplement cap is 350 micrograms a day. Brazil nuts are an extraordinarily concentrated source; do not have more than a few a day on a long-term basis.
• Vitamin A: in pregnancy, avoid liver and liver products (very high in retinol) and avoid supplements containing vitamin A unless your GP or midwife advises otherwise.
• Iron: do not supplement without a blood test. Iron supplements at the wrong dose can cause significant side effects and accidental overdose in children is a recognised paediatric emergency.
• Vitamin K: if you take an anticoagulant such as warfarin, do not start a vitamin K supplement; keep your dietary intake steady and follow the advice of your anticoagulant clinic.

In short: food first; the NHS-recommended supplements where they apply; check the label; and do not take more on the assumption that more must be better. The individual entries set out the specific dose, the upper limit, and the situations where supplementation is the right call.

Who is most likely to fall short

UK dietary survey data (the National Diet and Nutrition Survey) gives a fair picture of which groups are most at risk for which nutrients. The detail and the figures live on the individual entries; the short list here is the funnel.

• Pregnancy and pre-conception. Folic acid (mandatory), vitamin D, iodine, iron, and choline are the nutrients with the strongest pregnancy-specific case. See Folate, Vitamin D, Iodine, Iron, and the Vitamin A entry for what to avoid.
• Vegans and mostly plant-based diets. Vitamin B12 is non-negotiable; iodine, calcium, vitamin D, omega-3, iron, and zinc are the other ones to keep an eye on. See Vitamin B12, Iodine, Calcium, Iron, Zinc, and the plant-based eating article.
• Older adults. Vitamin D and calcium for bone health; vitamin B12 (absorption falls with age); appetite-related shortfalls across the board. See Vitamin D, Calcium, Vitamin B12.
• People with little sun exposure. Anyone who is housebound, regularly covered up, or with darker skin tones in northern UK latitudes is at higher risk of vitamin D shortfall. The NHS recommends a year-round supplement. See Vitamin D.
• Women of childbearing age. Iron is the standout risk because of menstrual losses; folate matters even if not currently planning a pregnancy. See Iron and Folate.
• People on restricted or weight-loss diets. Very low-calorie diets, restrictive eating patterns, after some types of bariatric surgery, and certain malabsorption conditions all reduce micronutrient intake. The relevant entries flag this.
• Children and teenagers. Vitamin D, iron in adolescent girls, calcium and iodine for growth. The children's nutrition article covers the full picture.

For people with no specific risk factor on this list, the Eatwell Guide (UK government dietary framework) covers most micronutrient requirements without needing to think about them individually.

What is NOT a vitamin

A few substances are promoted online as "vitamins" but are not recognised as such by SACN, EFSA, or the NHS. Some are not even nutrients. They are listed here so the gap is explicit, not so they are endorsed.

• Vitamin B4 (adenine): adenine is a building block of DNA and RNA, which the body makes for itself; it is not a dietary requirement, and the term "vitamin B4" has been obsolete in nutrition science for decades.
• Vitamin B8 (inositol): inositol is a sugar alcohol the body synthesises itself in adequate amounts. It has roles in cell signalling and is sold as a supplement for various claims (notably polycystic ovary syndrome), but it is not a vitamin under any current definition and is not on the NHS, SACN, or EFSA list of essential nutrients.
• Vitamin B15 ("pangamic acid"): a marketing label for a mixture of substances with no agreed chemical identity and no recognised function in the body. Banned from sale as a food supplement in the US since the 1970s; not recognised as a vitamin in the UK.
• Vitamin B17 ("laetrile" or amygdalin): not a vitamin and not benign. Laetrile is amygdalin, a compound found in apricot kernels and some other seeds, which the body metabolises into hydrogen cyanide. It has been promoted online as a cancer treatment for decades. Multiple clinical trials have shown no anti-cancer benefit and clear cyanide toxicity. The NHS and major UK cancer charities warn against it.
• Other items occasionally labelled as vitamins:
  • "Vitamin P" (flavonoids and related plant compounds): a useful family of plant compounds, but not vitamins. They are not essential nutrients in the technical sense.
  • "Vitamin F" (essential fatty acids): the omega-3 and omega-6 fatty acids are essential, but they are fats, not vitamins. They have their own daily intake guidance.
  • "Vitamin Q" (coenzyme Q10 or ubiquinone): the body makes its own; not a vitamin and not required from food.
  • "Vitamin U" (S-methylmethionine): a plant compound, mostly from cabbage; not an essential nutrient.

If a product is sold as a "vitamin" you have not heard of, the safe assumption is that there is a reason mainstream UK nutrition guidance does not list it.

Sources and references

• NHS. Vitamins and minerals. nhs.uk/conditions/vitamins-and-minerals. Hub article and each per-nutrient page.
• NHS. Vitamin supplements in pregnancy. nhs.uk/pregnancy/keeping-well/vitamins-supplements-and-nutrition.
• NHS. Vitamin D supplement guidance (autumn and winter). nhs.uk/conditions/vitamins-and-minerals/vitamin-d.
• NHS Healthy Start. healthystart.nhs.uk. Free vitamin drops scheme.
• Scientific Advisory Committee on Nutrition (SACN). Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Department of Health Report 41 (1991), and the SACN 2016 vitamin D position statement.
• European Food Safety Authority. Dietary Reference Values for the EU. Cited where the UK has not set a value (notably choline).
• Office for Health Improvement and Disparities. National Diet and Nutrition Survey (NDNS) rolling programme. The UK's official record of what people actually eat and the nutrient intakes that result.
• Public Health England. McCance and Widdowson's The Composition of Foods, 7th summary edition (2015).

This article is reference information for UK shoppers and is not medical advice. Always check with a GP, midwife, pharmacist, or registered dietitian for personal advice, particularly during pregnancy, while taking prescribed medication, or for any specific health condition.