What Are Vitamins? A Simple Guide to Their Roles and Sources
✦ Key takeaways
- Vitamins are micronutrients the body needs in small amounts for vital functions.
- They split into fat-soluble (A, D, E, K) and water-soluble (C and the B group).
- A varied diet is the safest way to get them all.
- Supplements help with a confirmed deficiency, but excess of some can harm.
Vitamins are organic compounds the body needs in very small amounts — milligrams or less a day — yet they are essential to indispensable processes: producing energy, building bones, clotting blood and supporting immunity. The word itself roughly means “vital for life.” The body can’t make most of them in sufficient quantity, so they must come from food.
Two main types
Vitamins are classed by what they dissolve in. Fat-soluble ones (A, D, E, K) are stored in the liver and fatty tissue, so you don’t need them exactly every day, but excessive build-up from supplements can be harmful. Water-soluble ones (vitamin C and the B group) are barely stored, and the body flushes the surplus in urine, so regular intake is preferable.
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What does each vitamin do?
Each vitamin has a role: A for vision and immunity, D for calcium absorption and bone health, C for collagen building and immunity, and the B group for turning food into energy. Chronic deficiency in any of them causes known problems, such as weak bones with low D or fatigue with low B12.
Table: essential vitamins and their sources
| Vitamin | Type | Key role | Food sources |
|---|---|---|---|
| A | Fat-soluble | Vision and immunity | Carrots, sweet potato, liver, eggs |
| D | Fat-soluble | Bone health | Sunlight, oily fish, fortified dairy |
| E | Fat-soluble | Antioxidant | Nuts, vegetable oils |
| K | Fat-soluble | Blood clotting | Leafy greens |
| C | Water-soluble | Collagen and immunity | Citrus, peppers, strawberries |
| B12 | Water-soluble | Nerves and blood cells | Meat, eggs, dairy |
Do I need supplements?
For most people, a varied diet rich in vegetables, fruit and protein provides enough vitamins. Supplements help in specific cases: a confirmed deficiency on a test, pregnancy, diets that exclude whole groups (such as low B12 in vegans), or little sun exposure with vitamin D. Overdoing fat-soluble vitamins in particular can cause toxicity.
Health note: this is general educational information and does not replace advice from a doctor or dietitian, especially before starting any supplement or making a major change to your diet.