Vitamins explained: types, food sources and deficiency effects

What vitamins are and the 13 the body needs

Vitamins are substances the body needs in small amounts to grow and develop normally. There are 13: vitamins A, C, D, E and K, plus the B vitamins, which are thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid, biotin, vitamin B6, vitamin B12 and folate. Each vitamin has specific jobs, and the best way to get enough of them is usually a balanced diet with a variety of foods.

The body can also make some vitamins itself: vitamin D is made in the skin through the action of sunlight, and vitamin K is also produced in the body. People eating a vegetarian diet may need to take a vitamin B12 supplement, since B12 comes mainly from animal foods. High doses of some vitamins can make you sick, so more is not automatically better.

Fat-soluble vs water-soluble vitamins

Vitamins A, D, E and K are fat-soluble: they dissolve in fat, are stored in the liver and body fat, and can therefore build up if taken in excess. The B vitamins and vitamin C are water-soluble: excess amounts are usually removed in the urine, though very large amounts can still cause harm.

This difference explains a classic exam point. A fat-soluble vitamin deficiency usually develops slowly because stores last a while, while water-soluble vitamins need a steadier supply from food. It also explains why sunlight matters for vitamin D and why a varied diet matters more than any single food.

Sources and deficiency effects to remember

Vitamin A, found in organ meats, dairy, egg yolk, yellow fruits and green vegetables, maintains healthy eyes, skin, bones and teeth; low levels are linked to night blindness and eye problems. Vitamin D, from fortified milk, eggs and sunlight on skin, builds and maintains bones and teeth; too little can cause rickets, poor bone and tooth development in children.

Vitamin C, from citrus fruits, melons, green vegetables and potatoes, helps wound healing and iron absorption; its deficiency disease is scurvy, with slow-healing wounds and bleeding gums. Among the B vitamins, B12 supports metabolism and healthy red blood cells, and its deficiency is linked to anaemia and nerve problems, while B6 deficiency is linked to anaemia and inflamed skin. Vitamin E, from vegetable oils, nuts and green vegetables, protects red blood cells. This article gives general educational information only, not personal medical advice.

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