Essential vitamins are required for normal body functioning
They either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health, and so must be obtained from a dietary source. Many people are remarkably deficient in a lot of these leading to commonly found ‘medical’ conditions. This is like having a pot plant wilting in the dry soil and you just need the application of the correct missing link – in the plant’s case, water – in the ‘patient’, the right minerals or vitamins. Instantly, as with the pot plant, life is back to normal. See more here
Essential vitamins are also defined by the collective physiological evidence for their importance in the diet. Different species have very different essential nutrients.
For example, most mammals synthesize their own ascorbic acid, and it is therefore not considered an essential nutrient for such species. It is, however, an essential nutrient for human beings, who require external sources of ascorbic acid (known as Vitamin C in the context of nutrition).
Many essential vitamins can be toxic in large doses (see hypervitaminosis). Some can be taken in amounts larger than required in a typical diet, with no apparent ill effects.
Linus Pauling said of vitamin B3, (either niacin or niacinamide),
“What astonished me was the very low toxicity of a substance that has such very great physiological power. A little pinch, 5 mg, every day, is enough to keep a person from dying of pellagra, but it is so lacking in toxicity that ten thousand times as much can [sometimes] be taken without harm.”
More information on vitamins can be found here: