Vitamins are organic compounds that are needed in small quantities to sustain life. They are essential nutrients that play a crucial role in our body. Because our body cannot produce enough of them on its own, it has to get it from food. Insufficient amounts can cause deficiency diseases that usually disappear when we replenish the shortage.

Chemical structure of vitamins

Vitamins are classified by their biological and chemical activity, not their structure. They are grouped under an alphabetized generic descriptor (A, B, C, and so on) because their chemical structure was unknown at the time they were first classified.

The term vitamin is derived from ‘vitamine’, a combination word made up by Polish scientist Casimir Funk from ‘vital’ (from Latin vitae = life) and ‘amine’ (protein-like substances). He thought they were substances already known as ‘amines’, characterized by the chemical trait amino-group. When vitamins turned out not to be ‘amines’ after all, the name was already so widespread that it is still being used today.

Nowadays researchers, nutritionists and doctors prefer to use the scientific chemical name of vitamins and even the man in the street is starting to use them. Vitamin C is ascorbic acid, derived from anti-scorbutic acid (scorbutic = someone who suffers scurvy).

As the chemical structure of most vitamins is known today, they can easily be reproduced synthetically. Synthetic vitamins are usually just as effective as their natural counterpart.

Classification of vitamins

There are 13 vitamins classified, each with their own specific function. They are divided into fat-soluble and water-soluble vitamins. Vitamins do not resemble each other at all. They each have their own very specific chemical structure.

Fat-soluble vitamins are A, D, E and K.

Water-soluble vitamins are all B vitamins and vitamin C.



As mentioned before, vitamins are essential nutrients and thus crucial for the functioning of our body. Most vitamins cannot be produced by the body, which means we have to get them from our food. The body can make some vitamins itself from so-called pro-vitamins. A typical example of a pro-vitamin is the orange coloring agent beta-carotene in carrots. The body can convert beta-carotene into vitamin A, which maintains the health of the epithelium and acts on the retina's dark adaptation mechanism. When our mothers told us to eat carrots to improve eyesight, there was at least a grain of truth in it …

There are still a lot of things we don’t know about how vitamins operate. What we do know though, is that several of the vitamins function as hormones and enzymes. Enzymes are often dependent on co-enzymes. Vitamins act as co-enzymes. If the vitamin is lacking as co-enzyme, the enzyme reactions stagnate and illness can occur. Vitamins are also necessary to build certain hormones. The body converts them into substances with a hormonal function.

Vitamins: what you should know about them

As you can see in the table below, taking too many vitamins can be bad for you. This is especially true for vitamin B3, B6, C, D and E. No negative health effects are known for the other vitamins, yet a margin of safety is recommended (maximum 5 times the Recommended Daily Intake). When you are not getting enough vitamins from food (for instance during illness), you can take extra vitamin pills to replenish the deficits. Never take more vitamins than the RDI. A healthy balanced diet is still preferable!

Vitamins and food preparation

Most vitamins are heat-labile, which means there is substantial vitamin loss during cooking (30% loss on average). Canned vegetables are in some cases even healthier than fresh vegetables because production methods are so advanced that the vegetables only need very short heating times. If you are cooking fresh vegetables until they are very soft, much of their nutritional value, including the vitamins associated with them, may be lost. Beware of that when you are cooking fresh food! Microwave cooking also preserves more vitamins and minerals in foods than other cooking methods simply because it cooks faster.

Overview important vitamins

Vitamin Chemical name Function DRA mcg/day *) Can be found in …
A Retinol Building block of the color pigment in our eyes; antioxidant; conducive to the process of procreation, fertility and the development of sex hormones. 600 – 900 mcg R.E. Tripe, milk and dairy products, cheese, fatty fish. Additive in margarines.
B1 Thiamin Plays an important role in the carbohydrate metabolism; helps burn alcohol; helps nerve regeneration (mental health). 900 – 1200 Brown rice, whole grain wheat products, soybeans, nuts and seeds, pork, milk, eggs, potatoes and pulse crops.
B2 Riboflavin As coenzyme important to energy metabolism (processing proteins and carbohydrates). Improves growth and nail, hair and skin health. 900 – 1300 Tripe, milk and dairy products, almonds, mushrooms, whole grain products, soybeans and green leaf vegetables.
B6 Pyridoxine As coenzyme important to building proteins from amino acids. Prevents nausea during pregnancy. Takes part in converting tryptophan into vitamin B3. Plays an important role in the production of red blood cells. Is readily excreted in urine. 1000 – 1500 Meat, liver, fish, eggs, pulse crops, nuts and seeds, potatoes and whole grain products.
B11 Folate Helps tissues grow, cells work and build genetic material (DNA en RNA). 300 – 400 Green leaf vegetables, cabbage, asparagus, potatoes, oranges, nuts and seeds, salmon.
B12 Cyanocobalamin Interconnected with folic acid (B11) for DNA and RNA synthesis; key to red blood cell production (prevents anemia) and nervous system function. 1.8 – 2.4 Mainly in animal products: tripe, meat, fish, crustaceans, eggs, milk and cheese.
C Ascorbic acid The main function of vitamin C is the production of collagen (naturally occurring protein in flesh and connective tissues). Antioxidant activity. Enhances the absorption of iron. Increases the production of infection-fighting white blood cells. 45,000 – 90,000 Fresh fruit and vegetables such as leafy vegetables, cabbages, potatoes, berries, oranges, tangerines, grapefruit and lemon.
D Cholecalciferol Improves calcium and phosphorus absorption; prevents tooth decay; strengthens bones. 15 – 15 Fatty animal products, herring, salmon, mackerel, fish liver, egg yolk, milk and dairy products. Additive in margarines.
E Alpha-tocopherol Broad-spectrum antioxidant; protects against free radicals, heavy metals such as lead and mercury, environmentally damaging products such as benzene and solvents. Improves the absorption of vitamin A; boosts the immune system; regulates blood pressure. 11 – 15 Many foods, mainly vegetable oils, seeds, nuts, cacao beans, whole grain wheat, avocadoes and tomatoes.
K Phylochinon Vitamin K is required for blood coagulation. A deficiency of vitamin K is rare because bacteria in the intestines that produce this vitamin meet most of our needs. 65 – 120 Present in all vegetables and leafy vegetables, such as broccoli, peas, green cabbage, lettuce, spinach, ...

*) DRA = Dietary Reference Allowance. Amounts in microgram per day, based on average healthy adults of respectively 165 lbs (male) and 140 lbs (female). Recommendation from The American Food and Nutrition Board, Institute of Medicine

R.E. = Retinol Equivalent
mcg = microgram = 1/1000 milligram