Micronutrients Explained: Vitamins, Minerals and What UK Adults Are Actually Missing

What Micronutrients Are — and Why They Are Non-Negotiable

Micronutrients are the vitamins and minerals your body requires in small but precise amounts to sustain every chemical reaction that keeps you alive, healthy and performing. They regulate enzyme function, hormone production, immune signalling, oxygen transport, bone mineralisation, and neurological health. Unlike macronutrients, they provide no energy — but without them, the machinery that burns energy grinds to a halt. A consistently poor micronutrient intake does not usually produce dramatic overnight symptoms; instead it creates a slow erosion of function: fatigue that never quite lifts, immunity that dips each winter, recovery that stalls, and concentration that slips. This is general information, not medical advice — if you suspect a deficiency, speak to your GP.

Key Vitamins and Their Food Sources

Vitamins split into two families with fundamentally different behaviours in the body.

Fat-soluble vitamins (A, D, E, K) are stored in fatty tissue and the liver. Because they accumulate, excessive supplementation carries a real toxicity risk — particularly for vitamin A. Food sources matter here, but so does caution with high-dose supplements.

• Vitamin A (as retinol): liver, oily fish, dairy, eggs. As beta-carotene (plant precursor): orange and dark-green vegetables — sweet potato, carrots, spinach, kale.
• Vitamin D: oily fish (salmon, mackerel, sardines), red meat, egg yolks, and UV-exposed mushrooms. Dietary sources are limited; sunlight is the primary route — which is why the NHS recommends supplementation across the UK population in autumn and winter.
• Vitamin E: nuts and seeds (especially sunflower seeds, almonds), plant oils, and avocado.
• Vitamin K (K1 for clotting, K2 for bone): dark leafy greens (K1), fermented foods and some dairy (K2).

Water-soluble vitamins (C and all eight B vitamins) are not stored in significant quantities, so daily dietary supply matters. Excess is excreted — but that also means depletion can occur relatively quickly on a restricted diet.

• Vitamin C: citrus fruits, kiwi, strawberries, peppers, broccoli — the UK Eatwell Guide's fruit-and-vegetable emphasis covers this comfortably for most people.
• B1 (thiamine): fortified cereals, wholegrains, legumes, pork.
• B2 (riboflavin): dairy, eggs, lean meat, fortified cereals.
• B3 (niacin): meat, fish, fortified cereals, peanuts.
• B6: poultry, fish, wholegrains, bananas, potatoes.
• B9 (folate/folic acid): dark leafy greens, legumes, fortified bread — critical at 400 µg/day before and during early pregnancy to prevent neural tube defects.
• B12: found almost exclusively in animal products — meat, fish, dairy, eggs. On a fully vegan diet, supplementation is essentially required; deficiency causes irreversible nerve damage if uncorrected.
• Biotin and pantothenic acid: widely distributed; true deficiency is rare on a varied diet.

Key Minerals and Their Food Sources

Minerals are inorganic elements — they cannot be synthesised and must come from food.

Iron is arguably the most clinically important mineral for UK women. The Reference Nutrient Intake (RNI) is 8.7 mg/day for men and post-menopausal women, but 14.8 mg/day for women aged 19–50 due to menstrual losses. Red meat, liver, oily fish, and fortified cereals supply haem iron (high bioavailability). Lentils, beans, tofu and dark leafy greens supply non-haem iron (lower bioavailability, but significantly enhanced when paired with vitamin C). Those following plant-based diets should be particularly attentive to iron intake — see the plant-based diet muscle and weight loss guide.

Calcium: essential for bone mineralisation, nerve transmission, and muscle contraction. The UK RNI is 700 mg/day for adults; post-menopausal women and older adults benefit from the upper end. Main sources: dairy (milk, yoghurt, cheese), fortified plant milks, tinned fish with bones (sardines, salmon), tofu set with calcium, sesame seeds, kale, and almonds.

Magnesium: supports over 300 enzyme reactions including muscle relaxation, sleep quality, and blood pressure regulation. Found in wholegrains, nuts, seeds, legumes, and dark leafy greens. Intakes are below optimal in many adults eating heavily processed diets — another reason the whole-foods-vs-ultra-processed distinction matters.

Zinc: vital for immune function, wound healing, and protein synthesis. Sources: red meat, shellfish (especially oysters), pumpkin seeds, legumes, dairy. Absorption from plant sources is lower due to phytates — relevant for anyone following a fully plant-based diet.

Iodine: synthesised by the thyroid gland into hormones that regulate metabolism. Primary UK sources are dairy milk, white fish, and eggs. Plant milks are often not fortified with iodine, which can be a meaningful gap for vegans.

Potassium: critical for blood pressure regulation and muscle function. Widely available in fruit, vegetables, legumes, and wholegrains — most people eating adequate plant foods meet their needs.

Selenium: supports thyroid function and antioxidant defence. UK soils are relatively low in selenium, making Brazil nuts (1–2 per day provides the RNI), fish, and meat the most reliable sources.

Vitamin D: The UK Exception

Vitamin D deserves its own section because it sits at the intersection of biology and UK geography. The body synthesises vitamin D when UVB light hits skin — but from October to March in the UK, the sun's angle is too oblique for adequate UVB to reach ground level at our latitude. This means dietary and supplemental sources must carry the full load for roughly half the year.

The NHS recommends that all adults consider a 10 µg (400 IU) vitamin D3 supplement during autumn and winter. People who are housebound, have darker skin, wear covering clothing, or are over 65 are advised to supplement at 10 µg year-round. Severe deficiency causes rickets in children and osteomalacia (soft, painful bones) in adults. Moderate insufficiency is associated with impaired immune function and fatigue — and is remarkably common in the UK population. It is one of the very few supplements with a universal NHS recommendation, and it is one of the very few areas where food-first advice is genuinely insufficient without supplementation.

For those on a fat loss programme or general fitness programme, low vitamin D is worth addressing early — it affects muscle function, recovery and mood alongside its bone effects.

Common UK Shortfalls: Iron, B12, Folate and Magnesium

Beyond vitamin D, the National Diet and Nutrition Survey identifies a consistent cluster of micronutrients where significant portions of the UK population fall short:

Iron deficiency is the most prevalent nutritional deficiency worldwide and a common finding in UK women of reproductive age. Symptoms — fatigue, breathlessness, poor concentration — are easy to overlook or attribute to lifestyle. A GP can check ferritin (iron stores) and haemoglobin with a simple blood test.

Vitamin B12 deficiency is a serious risk for vegans and for older adults, in whom the intrinsic factor needed for B12 absorption declines with age. Deficiency progresses slowly but can cause irreversible peripheral neuropathy and anaemia if left untreated. Vegans and strict vegetarians should supplement reliably — 10–100 µg of cyanocobalamin daily, or a higher weekly dose, covers the need.

Folate (vitamin B9) is critical at 200 µg/day for all adults and 400 µg/day as a supplement from 12 weeks before conception through the first trimester of pregnancy. Dark green vegetables and fortified foods are the main dietary sources. Low folate during early pregnancy significantly increases the risk of neural tube defects — this is not a nice-to-have for women planning a family.

Magnesium intake is consistently below the Lower Reference Nutrient Intake in a significant fraction of UK adults — driven largely by low wholefood intake and high consumption of ultra-processed products that strip out the magnesium found naturally in grains and legumes.

Food First — When Supplements Are and Are Not the Answer

Whole foods deliver micronutrients in forms that come packaged with co-factors, phytochemicals and fibre that influence absorption and utilisation in ways isolated supplements simply cannot replicate. Spinach does not just deliver iron — it also delivers vitamin C (enhancing absorption), folate, magnesium and hundreds of phytochemicals with their own emerging roles. This matrix effect is why the evidence for whole-food dietary patterns — Mediterranean, high-vegetable, high-legume — is so consistently stronger than the evidence for individual supplements.

The supplement industry conflates correlation (people with higher blood levels of, say, vitamin E have better health outcomes) with causation (supplementing vitamin E will improve outcomes). In many cases it does not. Several large trials of antioxidant supplements have produced null or even harmful results, underlining that supplementing nutrients in isolation does not replicate eating foods that are rich in them.

The evidence-graded approach:

• Strong recommendation to supplement (evidence grade: strong): vitamin D in autumn/winter (all UK adults); B12 on a vegan diet (evidence grade: strong); folic acid before and during early pregnancy (evidence grade: strong).
• Worth addressing if blood test confirms deficiency (evidence grade: strong — do not self-supplement without testing): iron (iron overload is harmful); vitamin B12 in older adults (evidence grade: moderate); iodine on a dairy-free vegan diet (evidence grade: moderate).
• Rarely necessary with a varied diet (evidence grade: strong): vitamins A, C, E, K, and most B vitamins.
• Not recommended (evidence grade: strong): high-dose single-nutrient supplements without clinical supervision.

For specific supplement guidance, explore the supplements section of the site.

Micronutrients for Active People

If you are training regularly — whether for muscle growth, fat loss or athletic performance — your micronutrient demands are modestly elevated above the general population's.

Iron losses are higher with sweat, GI losses, and foot-strike haemolysis in runners. B vitamins (B1, B2, B3) are turnover-sensitive and rise in proportion to energy expenditure — the safest approach is ensuring calorie intake is adequate rather than supplementing blindly. Zinc and vitamin C support immune resilience during periods of high training load. Magnesium is lost through sweat and plays a direct role in muscle contraction, nerve function and sleep quality — and sleep is where adaptation actually happens.

The single most important micronutrient strategy for active people is not a supplement protocol — it is eating enough total food, with enough variety, to stay out of a chronic micronutrient deficit. Aggressive calorie restriction is where micronutrient status quietly deteriorates. Use the calorie target tool to make sure your deficit is sustainable rather than excessive, and check out how to build a meal plan for a practical framework.

A Micronutrient-Dense Day — What It Actually Looks Like

Building meals around a handful of principles naturally covers most micronutrient bases:

Breakfast: Fortified wholegrain cereal or oats (B vitamins, iron, iodine if using dairy milk) + a glass of orange juice or kiwi (vitamin C to enhance iron absorption). If plant milk, choose a fortified brand.

Lunch: Grilled salmon (vitamin D, B12, iodine, selenium, omega-3) + a large mixed salad with spinach, roasted peppers, chickpeas (folate, iron, magnesium, vitamin C) + olive oil dressing (vitamin E, K1).

Dinner: Lean beef or lentil-based dish (iron, zinc, B12 if beef; iron, folate, magnesium if lentils) + roasted sweet potato (vitamin A as beta-carotene) + broccoli and kale (vitamins C, K, calcium, folate).

Snack: A small handful of Brazil nuts (selenium) + full-fat Greek yoghurt (calcium, iodine, B12).

This single day — built around the NHS Eatwell Guide principle of variety across the main food groups — would hit or approach the RNI for the vast majority of micronutrients. No exotic supplements required.

The Verdict

Micronutrients are not optional extras — they are the molecular machinery that makes every cell in your body work. The evidence is clear: a varied, whole-food diet covers nearly all needs for nearly all people. The critical exceptions in the UK context are vitamin D (supplement in autumn/winter), B12 (supplement on a vegan diet), and folic acid (supplement before and during pregnancy). Beyond those three, if you are eating a variety of vegetables, legumes, wholegrains, quality protein sources and some dairy or fortified alternatives, you are almost certainly meeting your needs without a supplement pile.

If you are unsure whether your current diet is delivering the micronutrient foundation your health and body-composition goals require, the best diet is the one a coach builds around your life — book a free consultation and we will audit your nutrition from the ground up.