Vitamins are organic compounds required by humans as nutrients in small amounts known as micronutrients. The term vitamin is derived from the Latin words ‘vital’ and ‘amine’, because vitamins are required for life and were originally thought to be amines. As most of the vitamins cannot be produced by humans, they must be obtained from the diet. An organic compound is considered a vitamin if a lack of that compound in the diet results in overt symptoms of deficiency. Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C). While fat-soluble vitamins are stored in the body’s fatty tissue, water-soluble vitamins must be used by the body right away. Any left over water-soluble vitamins leave the body through the urine. Vitamin B12 is the only water-soluble vitamin that can be stored in the liver for many years. Vitamins are essential to life and healthy living. Failing to get the necessary amounts of specific vitamins can cause deficiency states that are unhealthy and even dangerous. Thus, a sufficient intake of vitamins is crucial to prevent the development of deficiency-related diseases. In addition, some vitamins have a considerable potential in health promotion and disease treatment.
Vitamins are essential for virtually all chemical processes within the body that create and use energy, such as digestion of food and nutrients, elimination of waste through urine and faeces, growth and development, and regulation of cell function. Vitamins work together with proteins that regulate biochemical processes or enzymes, substances that assist those proteins known as cofactors, and other substances necessary for good health. Each vitamin has specific functions.
To date, research has generated a mass of data showing that insufficient vitamin intake can promote, in part, the development of chronic diseases such as cardiovascular disease, cancer and osteoporosis. In addition, clinical trials have shown that vitamins in diet, fortified foods or dietary supplements are effective in preventing deficiency-related diseases. On the other hand, studies have indicated that vitamin intake may not translate into risk reduction of disorders depending on a multitude of lifestyle factors, of which diet is only one. Other research has associated disease risk reduction with vitamins in food but not with supplement intake. The contradictory results show the complexity of the relationship between health and nutrition (see also Principles – The contradictory science of micronutrients). Fact is that an adequate intake of vitamins and other micronutrients is essential for virtually all chemical processes within the body and is necessary for a healthy life. But vitamins and other micronutrients in diet, fortified foods or dietary supplements cannot compensate for unhealthy lifestyle choices such as eating junk food, smoking or drinking to excess.
Throughout the years, the emphasis of vitamin research has shifted from mainly fighting deficiencies towards health promotion and disease treatment. However, the relationship between diet and multifactorial diseases is very complex, and experiments trying to measure micronutrient effects by applying standard methods used for drug testing seem to be only partially suitable (see also Principles – The contradictory science of micronutrients). High-dose vitamins are not ‘magic bullets’ capable of replacing standard medical therapies. However, in some cases the treatment of diseases with high-dose vitamins, some of them also registered as drugs, has shown promising results. As a rule, randomized controlled trials are needed in order to provide substantiated, well-observed effects. Please note: Any dietary or drug treatment with high-dose micronutrients needs medical supervision.
While overt vitamin deficiency diseases such as scurvy or pellagra are uncommon in people who consume a typical diet in developed countries, less obvious deficiencies also occur in wealthy societies. Often, large population groups ignore the true quality of nutrition or the consequences of their lifestyle choices. Such hidden deficiencies, mainly caused by diets lacking sufficient micronutrients, can lead to serious health problems over time. Some population groups are at higher risk of vitamin deficiency than others. Typical groups at risk for inadequate vitamin supply are: women of childbearing age pregnant or breast-feeding women children/teenagers with irregular eating habits older people vegetarians/vegans dieters people avoiding certain food groups people with eating disorders or medical conditions people who regularly eat processed and fast food.
The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods. Although this approach may involve education, change in nutrition behavior, and discipline, food is the number one source of natural vitamins as they contain many substances such as antioxidants that may contribute to disease risk reduction and health-promoting effects. Quite a few people in developed countries choose fortified foods, beverages or dietary supplements to help close nutritional gaps and to meet their individual needs. Older people may struggle with eating enough or cooking balanced meals and busy people living today’s fast-paced culture may lack the time to prepare meals or maintain healthy eating habits. Most fortified foods and dietary supplements contain vitamins and other micronutrients, alone or in combination, that have been added in isolated form respectively were made through chemical processes. There is some discussion as to whether isolated vitamins and those found naturally in whole food are comparable in terms of their effect. As the relationship between nutrition and health is extremely complex and adequate proof-generating methods are lacking, there are presently only theories and no definitive answers (see also Principles).