Vitamins are fundamental to life. They support virtually every biochemical process in the body — from energy production and immune defence to bone maintenance, skin integrity and cellular repair. The word itself comes from the Latin vita (life), a name that reflects just how foundational these compounds are.
But what exactly is a vitamin? Chemically, it's an organic compound found naturally in small amounts in food that is essential for normal physiological function — and one the body cannot synthesise in sufficient quantities on its own. Vitamin D, for example, can be produced through sun exposure, but for much of the population — particularly in regions with limited sunlight — dietary intake or supplementation becomes necessary. The same logic applies across the group.
There are 13 recognised vitamins in total. They fall into two broad categories based on solubility:
Fat-soluble vitamins (A, D, E and K) dissolve in fats and oils and can accumulate in the body's tissues. Water-soluble vitamins (vitamin C and the eight B vitamins) dissolve in water and are not stored — meaning they need to be replenished consistently through diet or supplementation.
The 13 Vitamins: Functions, Sources and Recommended Daily Intakes
Vitamin A
Vitamin A can be obtained from beta-carotenes — found in carrots and dark leafy greens — or directly from animal-based foods. Its active forms (retinol, retinal and retinoic acid) are found exclusively in animal products.
Key functions include:
- Maintaining eye health — it's a structural component of light-detecting pigments in the retina
- Regulating gene expression, including genes involved in cellular growth and differentiation
- Supporting immune function and bone health
- Contributing to foetal development
Recommended daily intake for adults: 800 μg/day (higher during pregnancy and breastfeeding).
B Vitamins
The B vitamin group comprises eight distinct compounds, each with specific roles in metabolism and cellular function.
Vitamin B1 (Thiamine) — carbohydrate metabolism and nervous system function. Found in yeast, liver and wholegrains. Recommended: 1.15 mg/day.
Vitamin B2 (Riboflavin) — energy production; supports skin, nail, hair and mucous membrane health. Found in dairy, meat, eggs and dark leafy greens. Recommended: 1.2 mg/day.
Vitamin B3 (Niacin) — energy metabolism and hair strength. Found in brewer's yeast and meat. Recommended: 15 mg/day.
Vitamin B5 (Pantothenic Acid) — skin regeneration, fatty acid synthesis and hormone production. Found in meat, wholegrains and royal jelly. Recommended: 5 mg/day.
Vitamin B6 — amino acid and protein metabolism. Found in meat, cereals, vegetables and nuts. Recommended: 1.3 mg/day (higher in adults over 51).
Vitamin B7 (Biotin) — carboxylation reactions, cellular signalling and maintenance of skin, hair and nails. Found in milk, liver, eggs and wholegrains. Recommended: 30 μg/day.
Note for Lumara customers: Lumara's Collagen Peptides formula includes biotin as a synergistic co-factor — chosen because collagen synthesis and structural integrity of skin, hair and nails operate through overlapping biological pathways.
Vitamin B9 (Folate) — DNA synthesis and cell division. Found in liver, legumes and vegetables. Recommended: 400 μg/day.
Vitamin B12 — essential for neurological health and red blood cell formation. Found in fermented foods and animal products. The only reliable dietary source for those following a plant-based diet is supplementation. Recommended: 2.4 μg/day.
Vitamin C
Also known as ascorbic acid, vitamin C is found primarily in fresh fruits and vegetables. It is heat-sensitive — a significant proportion is lost during cooking — making raw consumption preferable where possible.
Key functions:
- Collagen synthesis and stabilisation — vitamin C is required at multiple steps in the collagen production pathway, making it foundational for skin structure, joint integrity and connective tissue health
- Hormonal synthesis — including adrenaline and noradrenaline
- Iron absorption — increases the bioavailability of non-haem iron
- Immune defence — strengthens the function of immune cells
- Antioxidant activity — neutralises free radicals, often working synergistically with vitamin E
Recommended daily intake for adults: 85 mg/day (higher during breastfeeding).
Note for Lumara customers: Vitamin C is included in Lumara's Collagen Peptides formula because without adequate vitamin C, the body cannot complete the hydroxylation steps required to form stable collagen fibres. It's not an optional addition — it's biochemically necessary.
Vitamin D
Vitamin D is often called the "sunshine vitamin" — and for good reason. The amounts obtainable through diet alone are minimal. The primary source is cutaneous synthesis through sun exposure, with dietary sources including fish liver oils, eggs, butter and liver providing supplementary amounts.
Key functions:
- Calcium homeostasis — regulates blood calcium levels through hormonal mechanisms, directly affecting bone density
- Immune regulation — modulates both innate and adaptive immune responses
- Muscle function — particularly relevant as muscle mass and strength decline with age
The two main forms are D2 (ergocalciferol) and D3 (cholecalciferol), with D3 being the more bioavailable and commonly recommended form.
Recommended daily intake for adults: 15 μg/day (higher for adults over 70).
In Australia, vitamin D deficiency is more prevalent than commonly assumed — particularly in women over 40 who spend limited time outdoors, or who live in southern states with lower UV index in winter.
Vitamin E
Found primarily in wheat germ, vegetable oils, seeds and grain cereals, vitamin E exists in two main forms: tocopherols and tocotrienols.
Key functions:
- Antioxidant protection — scavenges free radicals, often in tandem with vitamin C
- Photoprotection and skin hydration
- Immune system support
Recommended daily intake for adults: 15 mg/day (higher during breastfeeding).
Vitamin K
Richest sources are dark leafy greens and liver. The gut microbiome can also synthesise vitamin K endogenously. It's frequently paired with vitamin D3 in supplementation given their complementary roles in calcium metabolism.
Key functions:
- Blood clotting — several coagulation factors are vitamin K-dependent
- Bone mineralisation — works alongside calcium and vitamin D to maintain bone density
Recommended daily intake for adults: 100 μg/day.
Summary Table
| Vitamin | Primary Functions | Key Food Sources | Recommended Daily Intake (Adults) |
|---|---|---|---|
| A | Eye health, cellular growth, immune function, bone health | Beta-carotenes; animal foods | 800 μg |
| B1 (Thiamine) | Carbohydrate metabolism, nervous system | Yeast, liver, wholegrains | 1.15 mg |
| B2 (Riboflavin) | Energy production, skin/nail/hair health | Dairy, meat, eggs, leafy greens | 1.2 mg |
| B3 (Niacin) | Energy metabolism, hair strength | Brewer's yeast, meat | 15 mg |
| B5 (Pantothenic Acid) | Skin regeneration, fatty acid & hormone synthesis | Meat, wholegrains, royal jelly | 5 mg |
| B6 | Amino acid & protein metabolism | Meat, cereals, vegetables, nuts | 1.3 mg |
| B7 (Biotin) | Cellular signalling, skin/hair/nail integrity | Milk, liver, eggs, wholegrains | 30 μg |
| B9 (Folate) | DNA synthesis | Liver, legumes, vegetables | 400 μg |
| B12 | Neurological health, red blood cell formation | Fermented foods, animal products | 2.4 μg |
| C | Collagen synthesis, immune defence, antioxidant | Fresh fruits and vegetables | 85 mg |
| D | Calcium metabolism, immune regulation, muscle function | Fish oils, eggs, butter, liver | 15 μg |
| E | Antioxidant, skin photoprotection, immune support | Wheat germ, vegetable oils, seeds | 15 mg |
| K | Blood clotting, bone mineralisation | Leafy greens, liver | 100 μg |
Vitamins are not optional extras — they're structural requirements for how the body functions at a cellular level. A well-designed diet covers many of these needs, but there are consistent gaps in the modern diet, particularly for women over 40 navigating changing hormonal and physiological demands. Identifying where those gaps exist — and addressing them precisely — is the foundation of intelligent supplementation.
References: NIH Office of Dietary Supplements: Vitamin A, B1, B2, B3, B5, B6, B7, B9, B12, C, D, E, K — Consumer Fact Sheets (ods.od.nih.gov)