Dietary supplements are a very broad class of substances that are taken and consumed in the same fashion as food. Such supplements are generally intended to add nutritional value to the diet through their use. Supplements were well understood by native cultures throughout the world for thousands of years prior to the development of the scientific method. Examples include the addition of animal organs to the diets of the hunters of native tribes in early North America, the introduction of the herb ginseng by the Chinese into many foods to provide additional nutrition, and the harvest of guarana by Amazonians to fortify prepared foods.
Perhaps the most enduring symbol of a historic organized dietary supplement practice is the nickname given to British sailors in the seventeenth century; they were called limeys for their consumption of limes to counter the effect of scurvy, a potentially fatal vitamin C deficiency. Scurvy was a constant threat to seamen, who typically existed through long voyages on dried biscuits and salted meats. English sailors did not understand the biological mechanism of the limes that supplemented their diet, but they understood that the technique worked.
The science of diet supplements gained favor in the early part of the twentieth century, as the vitamin B complex began to be isolated in laboratories, starting with thiamine in 1903. Research conducted during World War II, both to assist in providing soldiers in the field with better rations as well as experiments directed to assist prisoners of war with speedier means of recovering lost weight, were a spur to further supplement development.
In the United States and most other countries of the Western world, the science of diet supplements grew into a very robust industry by the early 1990s. The seemingly limitless speed with which society moved fostered a huge fast-food industry, where the desire for convenience dictated the use of processed foods with questionable nutritional value. In many nations, dietary supplements have been promoted as a preventative measure to combat the effects of diseases as diverse as diabetes and macular degeneration, a loss of vision caused by malfunction of the macula, the central part of the retina, attributed to an amino acid deficiency.
In 1994, the United States, through an enactment known as the Dietary Supplement Health and Education Act (DSHEA), established a comprehensive scheme of regulation for the manufacture, distribution, sale, and marketing of all dietary supplements; many countries throughout the world have similar legislation in place.
The DSHEA created the term "dietary ingredient" to describe the component that would make certain kinds of foods dietary supplements, including vitamins (substances that assist in the healthy development and regulation of human metabolism and cell development); minerals (elements that are essential to musculoskeletal growth and function, as well as the operation of the central nervous system; herbs (botanical products that typically are used as sources of vitamins, minerals, or other substances); and amino acids (the central components of proteins used to build and maintain muscle and tissue).
An important and frequently misunderstood distinction is that between a dietary supplement and a drug. A drug is a substance that is either an entire medication, or forms a component of a medication. Although the distinction between drug and supplement may be a fine one in some circumstances, drugs are generally closely regulated regarding use or requiring a prescription from a medical doctor, with the object of curing, treating, or preventing the recurrence of a disease or illness. For this reason, a drug administered by a physician might contain substances that in other circumstances are dietary supplements.
"Dietary supplement" is an umbrella term, one that may include a number of other more general expressions, some of which have meanings that tend to overlap with others. For many years, the phrase "nutritional supplement" has been used interchangeably with dietary supplement, including any food or food-like product that will add nutritional value to a diet. Vitamin supplements are an equally generic description of various kinds of vitamins, either as a single vitamin (such as vitamin C), a vitamin B complex (with the eight members of the complex taken together), or as a multivitamin (with numerous vitamins in varying amounts). Protein supplements are often a reference to amino acid supplements, or inaccurately, to chemically derived substances such as creatine. Like vitamins, mineral supplements refer to single minerals such as calcium, or to multiple minerals.
No matter what kind of descriptors are used to define dietary supplements, these products traditionally had been consumed by both the general population as well as the athletic community. Supplements might be taken to improve general, day-to-day health. A body that has an optimal level of vitamins and minerals, in conjunction with a reasonable balance between carbohydrates, proteins, and fats, will tend to function better and more efficiently. Supplements are taken for a specific physical condition such as to address an iron deficiency (for cases of anemia), or to address a mineral deficiency such as calcium.
Supplements are also ingested as a preventative, such as fiber supplements to act as a defense to bowel or colon cancer, or to fine-tune and bolster athletic performance. For example, an athlete might take electrolytic drinks (containing among other substances sodium and potassium, minerals that are necessary to the function of the neurological and fluid systems) to maintain balance, or take creatine or amino acid supplements to build muscle mass.
Most health and nutritional experts agree that the best way for the body to obtain the benefits of vitamins, minerals, and other dietary substances is through foods obtained through a properly balanced diet, as opposed to taking pill, powder, or other forms of supplements. However, there is no chemical distinction between a compound such as vitamin A in pill form and that contained in foods such as eggs or milk; taken in proper amounts, the impact upon the body will be the same. The chief risk of taking a dietary supplement in the concentrated form of a pill or tablet is the risk that a person might accidentally ingest too much of the supplement, as some vitamins and minerals are toxic in large quantities, such as vitamin A and vitamin D (working in conjunction with calcium). Other supplements can be harmful to the processes of the body, such as using high levels of sodium.
The supplements that are taken for simple health promotion and protection do not specifically target a particular physical condition. These are dietary products intended to supplement existing good health and bodily function, an assurance and a safety net as opposed to a solution. For example, multivitamins are found in various combinations, advertised to supplement either the entire vitamin A through E range, or segments of it. Every vitamin and mineral has a proscribed recommended daily allowance (RDA), and as vitamin C and some of the vitamin B complex are water soluble, they are not stored in the body. Consequently, a supplement may address those shortages.
Herbal products, often sold in the form of teas or beverage ingredients, have a long history as dietary supplements. Preparations made from plants such as ginseng root and ephedra (ma huang) are said to assist with digestive, urinary, and sleep patterns. Also, fresh cultured bacterial yogurt is consumed as a supplement to strengthen the immune system. The mineral zinc is taken as a supplement to strengthen the immune system. In some limited circumstances, even alcohol, as a form of fermented sugar, is properly characterized as a dietary supplement. Alcohol, in limited amounts (less than the equivalent of ten 4-oz units [125 ml] of wine per week), where the person has no other relevant physical restrictions, has been established as a factor in reduced blood pressure and other symptoms of poor cardiovascular health.
Many dietary supplements are taken to help eliminate an existing physical condition. Bowel disorders and accompanying constipation are problems that are common with persons who eat inordinate amounts of highly processed foods. The gastrointestinal system has evolved to require roughage, or fiber, to assist in the waste disposal process through the bowels. Fiber powder supplements have been developed, using a variety of natural fibers and herbs, to compensate for dietary shortfalls.
Menstrual pain is a reality for millions of women. The dietary supplements that include combinations of vitamin B6, calcium, and magnesium are taken to help the body create its own relief from menstrual pain. Osteoporosis, the thinning and weakening of skeletal bone structures, is another condition that typically affects females, as its origins are related to calcium depletion tied to the nursing of children, combined by the effects of menopause. Calcium supplements are a common addition to the diets of persons with osteoporosis.
Many dietary supplements are taken for the express purpose of preventing the onset of a particular ailment, such as cancer and heart disease. Prevailing medical and nutritional theory indicates that a balanced diet, regular exercise, and the avoidance of unhealthy habits such as smoking, recreational drug use, and excessive alcohol consumption, are the most logical route to long-term health. The medical evidence is equally clear that in most cases there is not likelihood of harm from the ingestion of dietary supplements that appear to mimic the other components of a proper diet.
The dietary supplements used by athletes tend to have a specific performance focus, as opposed to being engaged as a preventative measure. Athletes, especially as they approach elite levels of training and performance, encounter progressively greater physical challenges that tax their bodies and tend to increase all dietary requirements. In events where the margin between victory and defeat may be measured in fractions of seconds or in inches or centimeters, the athlete, through a carefully monitored diet, must ensure that every conceivable body function is capable of being engaged to a maximum level.
Athletes will notice through performance whether they have optimum vitamin and mineral levels. Further, the recovery time that they experience after a difficult training session or a competition is a powerful indicator of nutritional health. The athletic dietary supplements are generally taken on a daily basis. In training and competitions, for marathon runners or triathletes, supplements are intended to replace carbohydrate stores consumed during the event as well as electrolytes such as sodium and potassium. These supplements may be consumed as fluids, energy bars, or gels. Supplements provide post-training or competition boosts to the bodily stores to assist in recovery. Protein or creatine supplements assist in the development of muscle mass.