Vitamins

Part of Nutrition Science

An overview of essential vitamins — what they are, how they function, how they differ from minerals, and why their deficiency produces specific diseases rather than general malnutrition.

Why This Matters

Vitamins are organic compounds required in tiny amounts for normal metabolism — compounds the body either cannot synthesize at all, or cannot synthesize in sufficient quantities. Unlike proteins, fats, and carbohydrates, which provide energy and structural material in gram quantities, vitamins operate in microgram to milligram amounts as enzyme cofactors, signaling molecules, antioxidants, and regulators of gene expression.

Their discovery in the late nineteenth and early twentieth centuries reframed our understanding of disease. Diseases that had mystified physicians for centuries — scurvy, rickets, beriberi, pellagra, night blindness — were revealed to be caused not by infection, toxin, or bad air, but by the absence of a single microscopic organic molecule from the diet.

This insight remains practically important. A community that suffers from vitamin deficiency diseases is not sick in the conventional sense — there is no pathogen to treat, no wound to close. The intervention is dietary. Understanding what vitamins do and which deficiencies they prevent allows communities to diagnose these conditions, choose the right food-based treatments, and restructure diets to prevent recurrence.

Vitamins Versus Minerals

The distinction matters for practical reasons:

Vitamins are organic (carbon-containing) molecules. They can be degraded by heat, light, oxygen, and water. They are produced by living organisms (plants, animals, fungi, bacteria). Most must be consumed regularly because they cannot be stored for long periods. Being organic, they are destroyed by processing, cooking, and storage.

Minerals are inorganic elements — calcium, iron, zinc, magnesium, etc. They cannot be created or destroyed; heat does not change calcium into something else. They can, however, be leached from food by water or bound by other food components (phytates, oxalates) so they cannot be absorbed. Storage does not reduce mineral content.

This is why the advice “cook vegetables lightly and don’t throw away the cooking water” applies to vitamins but not minerals — minerals remain in the cooking water and can be recovered in soups, while vitamins partially degrade with heat regardless.

The Classification System

Fat-soluble vitamins (A, D, E, K):

• Absorbed with dietary fat; require fat in the same meal
• Stored in liver and body fat for weeks to months
• Toxicity from excess intake is possible (especially A and D)
• Less frequent dietary intake required — stores buffer short-term shortfalls

Water-soluble vitamins (B complex and C):

• Dissolve in water; absorbed directly in the gut
• Minimal storage; excess excreted in urine
• Must be consumed more regularly
• Overdose toxicity very rare (water-soluble excess is simply excreted)
• Vulnerable to leaching in cooking water and degradation by heat

Fat-Soluble Vitamins in Detail

Vitamin A

Functions: Vision (especially night vision), epithelial cell integrity (skin, respiratory tract, gut lining), immune function, embryonic development.

Deficiency disease: Night blindness (the first symptom), then xerophthalmia (eye dryness and corneal damage), and ultimately blindness. Also impairs immune function — vitamin A deficiency dramatically increases mortality from measles and other childhood infections.

Deficiency context: Most common in areas where animal foods are absent and diets are based on white rice or white cassava (low beta-carotene). Children 6 months to 5 years and pregnant women are highest risk.

Sources: Liver (preformed retinol, extremely concentrated), egg yolk, dairy, orange-yellow vegetables (beta-carotene as precursor).

Vitamin D

Functions: Regulates calcium and phosphorus absorption; essential for bone mineralization, muscle function, immune modulation, and many other cellular processes now being characterized.

Deficiency disease: Rickets (children), osteomalacia (adults), increased risk of infections, muscle weakness.

Primary source: Skin synthesis from UVB sunlight (not a dietary vitamin in evolutionary terms). Dietary sources: fatty fish, cod liver oil, sun-dried mushrooms, egg yolk.

Vitamin E

Functions: Antioxidant protecting cell membranes from lipid peroxidation; supports immune function; protects polyunsaturated fatty acids in cells and tissues from oxidative damage.

Deficiency disease: Peripheral neuropathy (nerve damage), muscle weakness, hemolytic anemia (especially in premature infants). Isolated deficiency in otherwise well-nourished adults is rare.

Sources: Nuts and seeds (especially sunflower seeds, almonds), plant oils, wheat germ, dark leafy greens.

Vitamin K

Functions: Blood clotting (K1 activates clotting factors); calcium deposition in bone and away from arteries (K2); activates matrix Gla protein, which inhibits arterial calcification.

Deficiency disease: Hemorrhagic disease of the newborn (infants born with very low K stores who bleed internally); prolonged clotting time in adults.

Sources: K1 from dark leafy greens (kale, spinach, parsley); K2 from natto, fermented cheeses, butter, egg yolk.

Water-Soluble Vitamins in Detail

Vitamin C (Ascorbic Acid)

Functions: Collagen synthesis, antioxidant, iron absorption enhancer, immune support, neurotransmitter synthesis.

Deficiency disease: Scurvy (bleeding gums, perifollicular hemorrhage, bone pain, death). See dedicated scurvy article.

Sources: Fresh fruits and vegetables — especially bell peppers, citrus, kiwi, broccoli; sauerkraut; rose hips; pine needle tea.

Thiamine (B1)

Functions: Cofactor in carbohydrate metabolism and neural function. Required for the conversion of glucose to energy.

Deficiency disease: Beriberi — wet beriberi (cardiovascular: heart failure, edema) and dry beriberi (neurological: peripheral neuropathy, muscle wasting). Wernicke-Korsakoff syndrome in alcoholics (alcohol blocks thiamine absorption and storage).

Deficiency context: Classic “white rice disease” — polished white rice removes the bran where thiamine resides. Populations depending on highly milled white rice without other thiamine sources develop beriberi. Whole grain rice or any varied diet prevents it.

Sources: Whole grains (especially unpolished rice, wheat bran), legumes, pork, sunflower seeds, nutritional yeast.

Riboflavin (B2)

Functions: Energy metabolism cofactor; antioxidant; supports iron metabolism.

Deficiency signs: Mouth sores (angular stomatitis — cracking at corners of mouth), glossitis (swollen, magenta tongue), seborrheic dermatitis. Not a dramatic disease but a sign of B vitamin depletion overall.

Sources: Dairy, eggs, liver, whole grains, dark leafy greens, nutritional yeast.

Niacin (B3)

Functions: Central to energy metabolism (NAD and NADP coenzymes); DNA repair; over 400 enzymatic reactions.

Deficiency disease: Pellagra (dermatitis, diarrhea, dementia, death). See dedicated rickets-pellagra article.

Sources: Meat, fish, poultry, peanuts, legumes, nixtamalized corn; body synthesizes some from tryptophan.

Pantothenic Acid (B5)

Functions: Component of coenzyme A; essential for fat, carbohydrate, and protein metabolism; adrenal hormone synthesis.

Deficiency: Extremely rare in varied diets — pantothenic acid is widely distributed in food. “Burning feet syndrome” and fatigue described in prisoners of war on very restricted diets.

Sources: Nearly all whole foods contain it — organ meats, legumes, eggs, whole grains, avocado, mushrooms.

Pyridoxine (B6)

Functions: Amino acid metabolism; neurotransmitter synthesis (serotonin, dopamine, GABA); immune function; hemoglobin synthesis.

Deficiency: Peripheral neuropathy, dermatitis, confusion, anemia, impaired immune function. Secondary deficiency common in alcoholics and those on very low protein diets.

Sources: Meat, fish, poultry, potatoes, bananas, chickpeas, legumes, whole grains.

Biotin (B7)

Functions: Cofactor for carboxylase enzymes involved in fatty acid synthesis and gluconeogenesis.

Deficiency: Hair loss, dermatitis, neurological symptoms. Raw egg whites contain avidin, which binds biotin and prevents absorption — consuming large quantities of raw eggs can induce biotin deficiency. Cooking destroys avidin.

Sources: Egg yolk (cooked), liver, legumes, nuts, whole grains.

Folate (B9)

Functions: DNA synthesis and methylation; amino acid metabolism; cell division. Critical in early pregnancy for neural tube formation.

Deficiency disease: Megaloblastic anemia (large, immature red blood cells that cannot function); neural tube defects (spina bifida, anencephaly) in embryos of deficient mothers.

Sources: Dark leafy greens (spinach, kale, asparagus), legumes, liver, eggs, avocado. Destroyed by heat and long cooking — eat some folate-rich foods raw.

Cobalamin (B12)

Functions: Nerve myelin maintenance, DNA synthesis, red blood cell formation, folate metabolism.

Deficiency disease: Pernicious anemia; irreversible neurological damage (subacute combined degeneration of the spinal cord) — tingling, weakness, balance problems, cognitive impairment.

Critical context: B12 is found only in animal foods and some fermented products. Strictly plant-based diets will develop B12 deficiency within 3-5 years, causing irreversible neurological damage. This is a critical consideration for communities with severely limited animal product access.

Sources: All animal products (meat, fish, eggs, dairy). Liver contains the highest concentration. Some fermented foods contain bacterial B12 but in less bioavailable forms.

Vitamin Summary Table

Vitamin	Critical Function	Deficiency Disease	Best Sources
A	Vision, immunity	Night blindness, xerophthalmia	Liver, egg yolk, orange vegetables
D	Calcium absorption, bone	Rickets, osteomalacia	Sunlight, fatty fish, cod liver oil
E	Antioxidant	Peripheral neuropathy (rare)	Nuts, seeds, plant oils
K	Clotting, bone	Bleeding, weak bones	Leafy greens, fermented foods
C	Collagen synthesis	Scurvy	Fresh vegetables, fruits
B1	Energy metabolism	Beriberi	Whole grains, legumes, pork
B2	Energy metabolism	Mouth sores, glossitis	Dairy, eggs, liver
B3	Energy metabolism	Pellagra	Meat, fish, legumes
B6	Amino acid metabolism	Neuropathy, anemia	Meat, potatoes, legumes
B9	DNA synthesis	Anemia, neural tube defects	Leafy greens, legumes, liver
B12	Nerve maintenance	Pernicious anemia, neuropathy	All animal foods

The Practical Message

Deficiency diseases are preventable with dietary diversity. Every deficiency disease on this list is eliminated by a diet that includes:

• Some animal products (meat, eggs, dairy, or fish)
• Fresh or fermented vegetables
• Whole grains and legumes
• Adequate sunlight exposure

A community that maintains this variety — even in modest quantities of each — will not see classic vitamin deficiency diseases. The diseases emerge when diets narrow to one or two staples, when animal products disappear entirely, or when seasonal food access is broken for months at a time without preserved alternatives.