Unlike vitamins, which are organic compounds, minerals are inorganic elements — pulled from soil and water by plants, and passed up the food chain. Your body cannot synthesise a single one of them. They build bones, carry oxygen, power enzymes, regulate heartbeat, and protect DNA. Run short on any one and the consequences are specific, measurable, and often slow to announce themselves.
A mineral is a chemical element — the same kind of element that appears on the periodic table. Iron. Zinc. Magnesium. Calcium. Selenium. Iodine. They exist in the earth's crust, dissolve into soil and groundwater, and are absorbed by plant roots. When you eat plants — or animals that ate plants — you consume those elements. Your body uses them as structural components (calcium in bone), as parts of enzymes (zinc in over 300 of them), as electrolytes that regulate fluid balance and nerve transmission (sodium, potassium, magnesium), and as components of hormones (iodine in thyroid hormones) and oxygen-carrying proteins (iron in haemoglobin).
There are two categories: macrominerals, needed in relatively large amounts (calcium, magnesium, phosphorus, sodium, potassium, chloride, sulphur), and trace minerals, needed in much smaller amounts but no less critical (iron, zinc, selenium, iodine, copper, manganese, chromium, fluoride). "Trace" refers to the quantity needed, not the importance.
Most minerals are available in adequate amounts from a varied whole food diet. But several are chronically under-consumed in the UK population — not because the foods that contain them are exotic or expensive, but because the diet has drifted away from the whole plant foods where minerals are most concentrated.
Iron is the most common nutritional deficiency in the UK, and the situation is more nuanced than simply eating more iron-rich foods. There are two forms of dietary iron: haem iron, found in blood and muscle tissue, and non-haem iron, found in plants. Haem iron is absorbed at roughly 15–35%. Non-haem iron — the form in legumes, seeds, greens, and wholegrains — is absorbed at 2–20%, and the absorption rate varies dramatically depending on what else is in the meal.
Vitamin C dramatically increases non-haem iron absorption — it converts iron from its ferric form (poorly absorbed) to its ferrous form (readily absorbed) in the gut. Adding vitamin C to an iron-rich plant meal — a squeeze of lemon on lentil soup, a red pepper in a chickpea curry, a glass of orange juice with fortified oats — can increase iron absorption by two to four times. This is not a minor enhancement; it is a transformative one.
Conversely, tannins (in tea and coffee), calcium (in dairy or fortified milk), and phytates (in wholegrains and legumes, reduced by soaking and cooking) all inhibit non-haem iron absorption when consumed at the same meal. The practical rule: drink tea and coffee between meals rather than with them, do not take calcium supplements at the same time as iron-rich foods, and soak legumes and grains where possible.
Magnesium is involved in more biochemical reactions than almost any other mineral, yet surveys consistently show that a significant proportion of the UK population consumes less than the recommended amount. The reason it goes undetected is that the standard blood test — serum magnesium — measures the magnesium circulating in blood plasma, which the body maintains within a narrow normal range at the expense of bone and muscle stores. By the time serum magnesium falls below the reference range, intracellular depletion may have been developing for years.
The symptoms of sub-clinical magnesium insufficiency are non-specific — muscle cramps, disturbed sleep, anxiety, fatigue, migraines, constipation, raised blood pressure — and easily attributed to stress, poor sleep, or other causes. They are also the symptoms that many people have quietly accepted as normal. They do not have to be.
Magnesium is found in abundance in dark leafy greens (the central atom of the chlorophyll molecule is magnesium — colour is a reliable guide), pumpkin seeds, dark chocolate, almonds, cashews, black beans, avocado, and wholegrains. A diet rich in these foods provides adequate magnesium. A diet dominated by refined grain products, processed foods, and little plant variety almost certainly does not — refining removes the majority of the magnesium from grain, and processing removes it from nearly everything.
Iodine is the most significant mineral gap in plant-based diets — more so than iron, zinc, or calcium, because the options for meeting it from whole plant foods alone are genuinely limited. Iodine enters the food chain through soil and seawater. In the UK, the primary dietary sources are dairy products (cows graze on iodine-treated pasture and iodine is used in dairy equipment) and iodised salt. Plants grown in UK soil generally contain very little iodine because UK soils are naturally iodine-poor.
Seaweed does contain iodine, but the amount varies enormously between species and even between harvests of the same species. Nori (the thin sheets used in sushi) is lower and more consistent — a realistic daily source for some. Kelp and bladderwrack are extremely high and variable — high enough to potentially cause iodine toxicity if eaten regularly, which is as harmful to the thyroid as deficiency.
For anyone not consuming dairy, the most reliable solution is a supplement containing potassium iodide or potassium iodate at 150 micrograms per day — the UK reference nutrient intake for adults. Most multivitamins formulated for vegans include iodine at this level. It is worth checking the label specifically, as not all do.
If you do not eat dairy and do not use iodised salt, you almost certainly need a supplement. Iodine deficiency impairs thyroid function — producing fatigue, weight changes, cold intolerance, and depression that can be mistaken for many other conditions. During pregnancy, inadequate iodine causes irreversible cognitive impairment in the developing infant.
Do not rely on kelp or bladderwrack seaweed as your iodine source — the iodine content is too variable and too potentially high. A supplement standardised to 150mcg is far more reliable.
The selenium content of plant foods is almost entirely determined by the selenium content of the soil in which they were grown. UK soils are among the most selenium-depleted in Europe — a consequence of glaciation that stripped the topsoil and of acid rain that has leached selenium from agricultural land over decades. Average selenium intake in the UK has fallen significantly since the 1970s, when the UK imported more grain from North America, where soils are higher in selenium.
The practical consequence is that eating a varied wholefood diet in the UK does not reliably cover selenium in the way it might in the United States or Brazil. The exception is Brazil nuts — a single Brazil nut contains roughly 70–90 micrograms of selenium, and the UK reference nutrient intake for adults is 75 micrograms per day for women and 75 micrograms for men. Two Brazil nuts per day covers the requirement reliably. This is one of the more elegant nutritional solutions available: one specific food, eaten in tiny quantity, resolves a specific gap that a varied plant diet would otherwise leave open.
Do not eat handfuls of Brazil nuts daily — selenium toxicity (selenosis) is possible at consistently high intakes above 400 micrograms per day, and some Brazil nuts are extremely high. Two per day is both adequate and safe. More than that is unnecessary and potentially counterproductive.
Phytic acid — or phytate in its ionised form — is a compound found in the outer layers of grains, legumes, nuts, and seeds. It binds to minerals including iron, zinc, calcium, and magnesium in the gut and reduces their absorption. This is why the zinc and iron in plant foods has a lower absorption rate than in animal foods — not because the minerals are absent, but because phytate partially blocks their uptake.
The good news is that phytate is significantly reduced by preparation methods that most traditional food cultures have used for centuries without knowing the biochemistry: soaking, sprouting, and fermentation.
Soaking legumes and grains overnight, then rinsing and cooking in fresh water, reduces phytate content by 30–60%. Sprouting — allowing seeds, legumes, or grains to germinate — activates the plant's own phytase enzyme, which breaks down phytate directly. Fermentation, as in sourdough bread or tempeh, reduces phytate most effectively of all — well-fermented sourdough may have 90% less phytate than the equivalent unfermented flour. These are not complex techniques. They are what people did before they had a choice.
Vitamin C in the same meal also partially counteracts phytate's effect on iron — another reason to habitually combine iron-rich plant foods with vitamin C at the same meal.
Minerals are where the food quality conversation gets specific. It is not enough to eat broadly well — it matters which foods, how they are prepared, what they are combined with, and in some cases where they were grown. Iron without vitamin C. Zinc blocked by phytate. Selenium depleted by UK soils. Iodine absent from plant foods. Magnesium stripped out of refined grain. These are not obscure edge cases. They are the daily realities of eating in an industrialised food system on soil that has been depleted for decades.
The solutions are not complex. Soak your legumes. Squeeze lemon on your greens. Eat two Brazil nuts. Check your iodine. Choose wholegrains. Pair iron with vitamin C at every meal. These are small habits with measurable consequences — and they are the difference between a diet that looks adequate on paper and one that actually delivers what the body needs.