Vitamins and Minerals Reference

The 13 essential vitamins divide into two groups based on how the body stores and uses them.

Property	Fat-soluble (A, D, E, K)	Water-soluble (B1–B12, C)
Storage	Liver and adipose tissue; stored for weeks–months	Minimal storage; excreted in urine daily
Toxicity risk	Higher — excess accumulates	Lower — excess excreted (exception: B6 at mega-doses)
Dietary frequency needed	Regular but not necessarily daily	Daily intake recommended
Absorption requirement	Requires dietary fat for absorption	Absorbed directly from gut
Common deficiency risk	Vitamin D (widespread), A (developing world)	B12 (vegans, elderly), folate (pregnancy), B1 (alcohol use)

Eating fat-soluble vitamins with a source of fat — even a small amount like a drizzle of olive oil — significantly improves absorption. Vitamin D absorption from supplements improves when taken with the largest meal of the day.

Tip: Cooking vegetables in oil (roasting, sautéing) boosts absorption of fat-soluble nutrients like beta-carotene (pro-vitamin A) and vitamin K compared to eating them raw.

These four vitamins account for the majority of deficiencies seen in developed countries, making them priority targets for dietary attention.

Vitamin	RDA / AI	Key functions	Best food sources	Deficiency signs
Vitamin D	600–800 IU (15–20 mcg)	Calcium absorption, immune function, bone mineralisation	Fatty fish (600–1,000 IU/100g), egg yolks, fortified milk	Bone pain, fatigue, increased infection rate
Vitamin B12	2.4 mcg/day	Red blood cell formation, nerve myelin, DNA synthesis	Beef liver (71 mcg/100g), salmon, dairy, eggs	Megaloblastic anaemia, peripheral neuropathy, memory decline
Vitamin C	75–90 mg/day	Collagen synthesis, antioxidant, iron absorption enhancer	Red bell pepper (190 mg/100g), kiwi, broccoli, citrus	Scurvy (rare): bleeding gums, poor wound healing
Folate (B9)	400 mcg DFE/day (600 in pregnancy)	DNA synthesis, cell division, neural tube development	Lentils (180 mcg/100g cooked), spinach, asparagus, fortified grains	Neural tube defects (fetal), megaloblastic anaemia

Warning: Vitamin B12 from plant foods is largely inactive. Anyone following a vegan or strict vegetarian diet should supplement with at least 250 mcg of cyanocobalamin daily or 1,000 mcg every other day.

Minerals are inorganic elements required for structural (bone, teeth) and functional (enzymes, electrical signals) roles. These four are the most clinically significant for the general population.

Mineral	RDA	Key role	Best sources	Absorption note
Iron	8 mg (men); 18 mg (women 19–50); 27 mg (pregnancy)	Haemoglobin synthesis, oxygen transport	Beef (2.7 mg/100g), lentils (3.3 mg/100g cooked), fortified cereals	Heme iron (meat) 15–35% absorbed; non-heme (plant) 2–20%. Vitamin C doubles non-heme absorption
Calcium	1,000–1,200 mg/day	Bone and teeth structure, muscle contraction, nerve signals	Milk 300 mg/cup, canned sardines 325 mg/100g, kale 150 mg/100g	Absorption drops above 500 mg in one dose — split across meals
Magnesium	310–420 mg/day	300+ enzyme reactions, muscle relaxation, blood glucose control	Pumpkin seeds 168 mg/28g, dark chocolate 64 mg/28g, almonds 80 mg/28g	Absorption decreases with high calcium or zinc intake
Zinc	8–11 mg/day	Immune function, wound healing, protein synthesis, taste/smell	Oysters 74 mg/100g, beef 4.8 mg/100g, hemp seeds 10 mg/100g	Phytates in grains/legumes reduce absorption; soaking and sprouting helps

Subclinical micronutrient deficiencies are widespread and often produce vague symptoms — fatigue, brain fog, and poor immunity — before reaching clinical thresholds on blood tests. Recognising patterns can prompt earlier dietary changes.

Symptom or sign	Potential micronutrient deficiency
Fatigue, pallor, shortness of breath	Iron, B12, folate
Bone pain, muscle weakness	Vitamin D, calcium
Numbness or tingling in hands/feet	Vitamin B12, B6
Cracked lips, sores at mouth corners	Riboflavin (B2), B6, iron
Hair loss, brittle nails	Iron, zinc, biotin
Frequent infections, slow healing	Vitamin C, zinc, vitamin D
Night blindness, dry eyes	Vitamin A
Muscle cramps, poor sleep	Magnesium, potassium

These signs are suggestive, not diagnostic. A serum blood panel is required to confirm deficiency. Work with your doctor before high-dose supplementing, as excess iron and fat-soluble vitamins can cause toxicity.

Supplements are useful to address specific gaps — not as an insurance policy against a poor diet. Research consistently shows that isolated supplements rarely replicate the health benefits of whole foods, which deliver nutrients alongside fibre, polyphenols, and other co-factors.

• Vitamin D: Consider 1,000–2,000 IU daily if you live above 37° latitude, work indoors, or have darker skin. Blood level target: 50–100 nmol/L (20–40 ng/mL).
• B12: Recommended for all vegans and vegetarians; also for adults over 50 (stomach acid declines, reducing absorption from food).
• Iron: Only supplement if blood work confirms deficiency — excess iron is harmful and masks other causes of anaemia.
• Folate/Folic acid: 400 mcg/day recommended for all people of childbearing age who could become pregnant, ideally started one month before conception.
• Omega-3 (EPA/DHA): Algae-based supplements provide the same EPA/DHA as fish oil — the best option for vegans.

Supplement	Who needs it	Typical dose
Vitamin D3	Most people in northern climates	1,000–2,000 IU/day
Vitamin B12	Vegans, over-50s, metformin users	250–1,000 mcg/day
Folate	Pre-conception and pregnancy	400–600 mcg/day
Iodine	People avoiding dairy and iodised salt	150 mcg/day

Tip: A general multivitamin fills small gaps but delivers nutrients in forms and amounts that aren't always ideal. Targeted single-nutrient supplements address confirmed deficiencies more precisely.