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[Physiology](https://durgical.com/en/physiology/) · [Temperature, exercise and metabolism](https://durgical.com/en/physiology/#s-integrative)

# Vitamins and minerals: a physiological overview

- Table to know
- Exam priority: medium

Vitamins and minerals are needed in small amounts, but without them blood, bones, nerves and the thyroid fail.

Updated 2026-11-01

Also called: Micronutrients

## Key points

- Fat-soluble A, D, E, K: deficiency accompanies fat malabsorption (cystic fibrosis, cholestasis, celiac disease).
- B12: liver stores last years; it needs intrinsic factor and the terminal ileum; deficiency causes megaloblastic anemia and nerve damage.
- Folate: stores last months; deficiency causes megaloblastic anemia without nerve damage, and neural tube defects.
- Thiamine (B1): cofactor of pyruvate dehydrogenase; beriberi and Wernicke in alcohol use disorder and malnutrition.
- Iron: duodenal absorption is set by hepcidin; there is no active excretion route.
- Iodine: needed for T₃/T₄; deficiency causes goitre and hypothyroidism (iodized salt reduced it in Colombia).

## What it is

Vitamins are organic cofactors the body cannot make in sufficient amounts; minerals are inorganic elements. Fat-soluble vitamins (A, D, E, K) are absorbed with fat and stored, so they can build up and become toxic. Water-soluble ones (B complex, C) are stored little, except B12. This page sums up function and classic deficiency; the chemistry lives in Biochemistry.

## Function and classic deficiency

| Nutrient | Key function | Deficiency |
| --- | --- | --- |
| Vitamin A | Rhodopsin (vision), epithelia | Night blindness, xerophthalmia |
| [Vitamin D](https://durgical.com/en/conditions/rickets-and-osteomalacia/) | Intestinal calcium and phosphate absorption | Rickets (child), osteomalacia (adult) |
| Vitamin K | Carboxylation of factors II, VII, IX, X | Bleeding (newborn) |
| [Thiamine (B1)](https://durgical.com/en/conditions/beriberi/) | Decarboxylation of pyruvate and α-ketoglutarate | Beriberi, Wernicke encephalopathy |
| [Niacin (B3)](https://durgical.com/en/conditions/pellagra/) | NAD⁺/NADP⁺ | Pellagra: dermatitis, diarrhea, dementia |
| [Vitamin C](https://durgical.com/en/conditions/scurvy/) | Collagen hydroxylation; iron absorption | Scurvy: bleeding gums, petechiae |
| [Cobalamin (B12)](https://durgical.com/en/conditions/pernicious-anaemia/) | DNA synthesis, myelin metabolism | Megaloblastic anemia, neuropathy |
| [Iron](https://durgical.com/en/conditions/iron-deficiency-anaemia/) | Hemoglobin, myoglobin, cytochromes | Microcytic anemia |
| [Iodine](https://durgical.com/en/conditions/goitre/) | Thyroid hormones | Goitre, hypothyroidism |

## Clinical notes

- Giving folate to someone with B12 deficiency corrects the anemia but not the nerve damage.
- Hypervitaminosis A (fish liver, supplements) causes raised intracranial pressure and liver injury.
- Newborns have little vitamin K (sparse gut flora): hence their bleeding risk.

## Memory aid

«A, D, E and K travel with fat and stay; B and C pass through quickly, except B12, which stays for years».

## Test yourself

Think of the answer, then tap the question to see it.

## Why can a patient with chronic cholestasis bleed and fracture bones?

Without bile, fat and fat-soluble vitamins are not absorbed: vitamin K (clotting factors) and vitamin D (bone calcium) run short.

## Why does B12 deficiency take years to appear after gastrectomy?

The liver stores several years of B12; deficiency appears only when that store runs out, once intrinsic factor is gone.

## Why does vitamin C improve absorption of plant iron?

It reduces ferric iron (Fe³⁺) to ferrous iron (Fe²⁺), the form the duodenal DMT1 transporter takes up.

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## Related topics

- [Prolonged fasting and starvation](https://durgical.com/en/physiology/prolonged-fasting-and-starvation/)
- [Energy metabolism and basal metabolic rate](https://durgical.com/en/physiology/energy-metabolism-and-basal-metabolic-rate/)

## Related conditions

- [Scurvy (vitamin C deficiency)](https://durgical.com/en/conditions/scurvy/)
- [Beriberi (thiamine deficiency)](https://durgical.com/en/conditions/beriberi/)
- [Rickets and osteomalacia](https://durgical.com/en/conditions/rickets-and-osteomalacia/)
- [Pellagra (niacin deficiency)](https://durgical.com/en/conditions/pellagra/)
- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)
- [Goitre](https://durgical.com/en/conditions/goitre/)
- [Pernicious anaemia](https://durgical.com/en/conditions/pernicious-anaemia/)
- [Wernicke encephalopathy (thiamine deficiency)](https://durgical.com/en/conditions/wernicke-encephalopathy/)

## In Biochemistry

- [Vitamin A (retinol)](https://durgical.com/en/biochemistry/molecules/vitamin-a/)
- [Vitamin D (calcitriol)](https://durgical.com/en/biochemistry/molecules/vitamin-d/)
- [Thiamine (vitamin B1)](https://durgical.com/en/biochemistry/molecules/thiamine/)
- [Cobalamin (vitamin B12)](https://durgical.com/en/biochemistry/topics/cobalamin/)
- [Iron](https://durgical.com/en/biochemistry/topics/iron/)
- [Iodine](https://durgical.com/en/biochemistry/topics/iodine/)
- [Vitamin C (ascorbic acid)](https://durgical.com/en/biochemistry/molecules/vitamin-c/)
- [Vitamin K (phylloquinone)](https://durgical.com/en/biochemistry/molecules/vitamin-k/)
- [Folate (vitamin B9)](https://durgical.com/en/biochemistry/molecules/folate/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [24.7 Nutrition and Diet](https://openstax.org/books/anatomy-and-physiology-2e/pages/24-7-nutrition-and-diet) (OpenStax (Rice University), 2022); [Vitamins: MedlinePlus](https://medlineplus.gov/vitamins.html) (MedlinePlus, US National Library of Medicine, 2026); [Minerals: MedlinePlus](https://medlineplus.gov/minerals.html) (MedlinePlus, US National Library of Medicine, 2026); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 72). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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