A plate can cover its calories and still leave the body short on thirty micronutrients at once. That is the peculiarity of modern deficiencies: they do not carve out hunger, they degrade function. Fatigue that sleep does not fix, ridged nails, hair shedding beyond reason, night cramps, infections that follow one another: these ordinary signs are often the first writing of a deficit.
Vitamins and minerals do not produce energy. They make it possible: they are the cofactors without which the enzymes that turn food into ATP, the hormones that run metabolism and the antibodies that defend the body simply do not work. This guide reviews them family by family: roles, food sources, and the signs worth acting on.
The fat-soluble vitamins: A, D, E, K
Fat-soluble vitamins share two properties: they need fat to be absorbed, and the body stores them in the liver and adipose tissue. Two practical consequences follow: fat-free diets compromise their absorption, and supplement overdoses can accumulate to toxicity.
Vitamin A: vision and the epithelial barrier
Vitamin A comes in two forms: retinol, ready to use, in animal foods (liver, butter, eggs, oily fish), and beta-carotene, the plant precursor in carrots, sweet potatoes, spinach and apricots. Conversion of beta-carotene to retinol varies: it drops in hypothyroid people and in those with low zinc intake.
Vitamin A maintains night vision, the integrity of mucous membranes (the first anti-infectious barrier) and cell differentiation. Deficiency shows as night blindness, dry scaly skin and repeated respiratory infections. Excess, on the other hand, is teratogenic: retinol supplements are formally contraindicated in pregnancy.
Vitamin D: the hormone the sun makes
Vitamin D is not really a vitamin: it is a prohormone synthesised by the skin under UVB, then activated by the liver and kidneys. Between October and April at European latitudes, skin synthesis becomes inadequate: most adults spend the winter in insufficiency, and British and European surveys consistently find that the majority of the population falls short of recommended levels.
Its roles go well beyond bone: receptors are found in the immune system, muscles and brain. Deficiency dampens immunity, weakens bone (osteomalacia in adults, rickets in children) and is associated with chronic fatigue and low winter mood. Food sources are scarce: oily fish, egg yolks, UV-exposed mushrooms. It is the one micronutrient for which winter supplementation is near-consensus in adults, ideally guided by a blood test (25-OH-D).
Vitamin E: the membrane antioxidant
Vitamin E protects cell membranes from oxidation. It is abundant in cold-pressed vegetable oils, nuts (almonds, hazelnuts) and cereal germs. Frank deficiency is rare; moderate insufficiency appears in malabsorption and very low-fat diets.
Vitamin K: clotting and bone
Vitamin K1 (green leafy vegetables) activates clotting factors; K2 (fermented foods, natto, matured cheeses) directs calcium towards bone rather than arteries. One essential safety point: it interacts directly with warfarin-type anticoagulants. People on these drugs should not abruptly change their intake of green vegetables without medical advice.
The water-soluble vitamins: the B complex and C
Water-soluble vitamins are barely stored (the exception is B12, of which the liver keeps several years of reserve). They are excreted in urine: intake must be daily, and overdose is rare.
The B complex: eight cofactors of energy
The eight B vitamins work as a team in cellular energy production and neurotransmitter synthesis. Three deserve particular attention:
B9 (folate) is indispensable for DNA synthesis and for closure of the embryonic neural tube: it is the systematic supplement of the first month of pregnancy and the preconception period. Sources: green leafy vegetables, pulses, eggs.
B12 is the most frequent clinical case: found only in animal foods (meat, fish, eggs, dairy), it falls short in unsupplemented vegans, in people on long-term metformin or proton pump inhibitors, and in older adults whose gastric acidity declines. Deficiency produces anaemia, deep fatigue and neurological damage that can become irreversible if prolonged.
B6 takes part in serotonin and GABA synthesis: deficiency shows as irritability, sleep disturbance and mild neuropathies. Sources: poultry, fish, potatoes, bananas.
Vitamin C: the water-soluble antioxidant
Vitamin C supports immunity, collagen synthesis and the absorption of plant iron: a vitamin-C-rich food in the same meal multiplies iron absorption from pulses three- or fourfold. It is fragile, destroyed by prolonged heat and exposure to air. Sources: citrus fruit, kiwi, raw peppers, broccoli, parsley. Severe deficiency (scurvy) has disappeared from developed countries, but moderate insufficiency persists in smokers: each cigarette consumes roughly 25 mg of vitamin C.
The major minerals: calcium, magnesium, potassium
Calcium: more than a bone mineral
Calcium builds bone but also commands muscle contraction and nerve transmission. The best-absorbed sources remain dairy products, followed by calcium-rich mineral waters, green vegetables of the cabbage family, almonds and small fish eaten with their bones. Its absorption requires vitamin D and suffers from excess salt and caffeine. The article on osteoporosis and the Kidneys in TCM details the long-term strategy.
Magnesium: the stress cofactor
Magnesium takes part in more than 300 enzymatic reactions, including ATP production and regulation of the nervous system. European intake surveys converge: a large share of the population falls short of recommended intake, and chronic stress accelerates urinary losses. Deficiency shows as cramps, a twitching eyelid, irritability and light sleep. Sources: nuts and seeds, dark chocolate with high cocoa content, pulses, whole grains, magnesium-rich waters. The article on insomnia in TCM places this mineral within the picture of an agitated Shen.
Potassium: the counterweight to sodium
Potassium counterbalances sodium in blood pressure regulation. Diets rich in processed foods reverse the ancestral ratio (plenty of sodium, little potassium): raising fruit, vegetables and pulses does more than simply cutting salt.
The trace elements: iron, zinc, iodine, selenium
Iron: the most widespread deficiency in the world
The WHO estimates that a quarter of the world’s population is anaemic, with iron the leading cause. Two forms exist: haem iron from animal foods (absorption of 15 to 35 %) and non-haem plant iron (2 to 10 %, boosted by vitamin C, inhibited by tea, coffee and calcium taken at the same meal). Women with heavy periods, pregnant women, vegetarians and endurance athletes form the at-risk groups. Signs: fatigue, pallor, breathlessness on exertion, thinning hair, craving for ice or starch (pica). Iron is never supplemented blindly: excess is toxic and fatigue has other possible causes.
Zinc: immunity, skin and the sense of taste
Zinc is involved in wound healing, immune function, protein synthesis and taste perception. Sources: oysters (by far the richest), meat, seafood, eggs, pumpkin seeds. Deficiency shows as repeated infections, slow healing, dulled taste and white-flecked nails.
Iodine: the fuel of the thyroid
Iodine is the building block of thyroid hormones T3 and T4. Reliable sources are few: sea fish, seafood, seaweed (in controlled amounts, since levels vary hugely and can become excessive), iodised salt, eggs and dairy. Deficiency causes hypothyroidism and goitre; in pregnancy it compromises the foetus’s neurological development. The connection with the slow thyroid as read in TCM is detailed in its own article.
Selenium: the thyroid’s antioxidant
Selenium cofactors the glutathione peroxidases and the conversion of T4 into T3. The selenium content of soil determines that of food: Europe is a poor zone. One or two Brazil nuts a day cover requirements; fish and eggs contribute. Deficiency weakens the thyroid and immunity; excess (badly dosed supplements) becomes toxic beyond 400 µg/day.
| Micronutrient | Warning signs | Priority sources |
|---|---|---|
Frequent deficiencies: the signs that should raise the alarm
Four profiles concentrate most of the deficits seen in practice:
The woman of childbearing age: iron (heavy periods), B9 (pregnancy plans), vitamin D. The trio is worth testing systematically before a pregnancy, alongside the preconception work that ideally begins three months ahead.
The older adult: B12 (declining gastric acidity), vitamin D (skin synthesis halved by age seventy), calcium, and sufficient protein to limit muscle loss.
The vegan: B12 (supplementation is mandatory), iron, zinc, iodine, calcium and omega-3. The diet is viable but requires deliberate construction, not merely removing animal foods.
The chronically stressed: magnesium (increased urinary losses), vitamin C (cortisol consumes it), B vitamins. This is the terrain where Chinese dietetics speaks of Liver Qi stagnation that ends by draining the Spleen.
Micronutrients and the Chinese reading: two maps of the same terrain
Biochemistry names molecules; Chinese dietetics names terrains. The two descriptions often converge strikingly: iron deficiency resembles Blood deficiency trait for trait (pallor, fatigue, dizziness, brittle nails); iodine and vitamin D deficits draw a picture TCM reads as Yang deficiency (feeling cold, slowing down, pallor, morning fatigue); magnesium deficiency recalls the insufficient Yin that lets the Shen grow restless.
The practical interest of the double reading: when a blood test confirms a deficiency, you correct the molecule AND the terrain that let it settle in. A woman with recurring iron deficiency despite supplements does not only need iron: she has a Spleen that no longer extracts and a mucosa that no longer absorbs. The article on phytotherapy and micronutrition applied to digestion develops this articulation.
Frequently asked questions about vitamins and minerals
Can food alone cover every requirement?
Yes for nearly all micronutrients, with a varied, minimally processed diet rich in colourful vegetables, pulses, nuts, fish and fermented foods. Two notable exceptions: vitamin D in winter at European latitudes, and B12 for vegans. Pregnancy adds systematic folate.
Are multivitamins useful?
They correct mild multiple deficiencies but replace neither testing nor targeted correction. Their value is limited in people without deficiency: large studies on cardiovascular and cognitive prevention with multivitamins have shown no clear benefit in well-nourished populations.
Why is plant iron absorbed less well?
Non-haem plant iron is absorbed at 2 to 10 %, against 15 to 35 % for animal haem iron. Vitamin C in the same meal multiplies absorption three- or fourfold; tea and coffee halve it. The practical trick: lemon juice on lentils, tea an hour after the meal.
Which signs justify testing without delay?
Persistent fatigue despite sleep, diffuse hair loss, ridged or brittle nails, repeated cramps, infections in succession, memory problems or tingling: these pictures justify a work-up (ferritin, 25-OH-D, B12, folate, TSH) rather than blind supplementation.
Molecules do not replace terrain
Micronutrients are the biochemical counterpart of what Chinese dietetics calls substance: what allows functions to run. The winning approach is always the same: identify the deficit through signs and testing, correct it with the best-absorbed food sources, and work on the terrain that allowed it (digestion, stress, increased losses). In the Yin Shi app, food cards list micronutrient content alongside nature and flavours: the two maps are read on the same page.
To go further
Yin Shi ecosystem resources directly related to this article.