Dietary supplement

Dietary supplements are supplements used to restore or maintain health when the diet does not meet the needs of an individual. In some cases, there is strong evidence for their use, although conventional foods, such as milk, may routinely be supplemented with, for example, vitamin D. Persons at risk for osteoporosis must be sure they have adequate calcium and vitamin D intake, with supplements as necessary.

Regulation

In many countries, there is considerable freedom to advertise substances as dietary supplements, as opposed to drugs. Substances marketed as dietary supplements, however, may not have undergone safety and efficacy testing.

In the United States, supplements are regulated under Dietary Supplement Health and Education Act (DSHEA) which was enacted in 1994 after deaths from L-tryptophan in 1989.

Entities that independently test contents of supplements and provide seals certifying contents:

• The United States Pharmacopeial Convention
• ConsumerLab.com.

Entities that monitor advertising and labeling:

• Center for Food Safety & Applied Nutrition, U.S. Food and Drug Administration
• Council for Responsible Nutrition (CRN). The CRN is a "trade association representing ingredient suppliers and manufacturers in the dietary supplement industry."

Health policy considerations

While it is sufficiently widespread that it is not considered a dietary supplement, addition of fluoride ion to drinking water is common throughout the industrialized world. It was quite controversial when first proposed, but there is clear evidence of efficacy in preventing tooth decay. Adequate fluoride intake causes a higher concentration of more decay-resistant calcium fluoride in tooth enamel.

Some specific supplementation has been required by governments, although not always in a completely rational manner. For example, folic acid deficiency is strongly correlated with neural tube birth defects. There is general acceptance that all women, who might become pregnant, must ensure they have adequate folic acid intake. The U.S. requires that it be added to commercial baked goods, but, since woman does not live by bread alone, folic acid in uneaten bread benefits no one.

Although it is not standard practice, some researchers suggest widespread vitamin use may drastically cut public health spendings.

Another study suggests that while there may not be hard evidence of efficacy, supplements may decrease aging-related degeneration.

Vitamin supplements

There are recommended daily requirement (MDR) of many vitamins, but these are agreed to be minimum requirements. Mild supplementation, as, for example, a daily moderate-strength multivitamin, is widely accepted as potentially beneficial. A dose of a vitamin that greatly exceeds the MDR may be called a megadose, or a pharmacologic dose.

Moderate supplementation

As mentioned, there are some widely accepted reasons to supplement specific vitamins:

• Folic acid in women that may become pregnant
• Vitamin D in growing children, or for those at risk for osteoporosis

High-dose vitamins

Pharmacologic doses of vitamins are used in conventional medicine, but should be used with the care used for more mainstream drugs. Vitamins divide into two broad classes, water-soluble and fat-soluble; toxicity is much more likely with high doses of fat-soluble vitamins.

Water-soluble vitamins

Vitamin B complex

B vitamins may prevent macular degeneration.

Niacin

For example, niacin in pharmacologic doses can be an effective treatment for some dyslipedimias, or disorders of fat and cholesterol metabolism. It is available without a prescription. Such doses of niacin, however, have other physiologic effects. It is extremely common to experience skin flushing, which some patients regard as intolerable burning, shortly after taking a large oral dose of niacin. There are ways to reduce the flushing. Pharmacologic doses of niacin, however, also requires blood chemistry monitoring, as it can increase blood sugar levels, and rarely can damage cause hepatotoxicity (i.e., liver damages), muscle tissue breakdown (i.e., myolysis) or cause serious skin disease.

Vitamin B₁ (Thiamine)

Vitamin B₂ (Riboflavin)

Vitamin B₆ (Pyridoxine)

Vitamin B₉ (Folic acid)

Vitamin B₁₂ (Cobalamin)

Fat-soluble vitamins

Vitamin A

Toxicity is most commonly found with high doses of Vitamin A. Indeed, certain cold-weather animals, such as the polar bear, concentrate such high levels in their liver that the meat is actually toxic to humans.

Hypervitaminosis A is not uncommon with overzealous parents giving babies large doses of prescribed A and D supplements.

Vitamin A deficiency (hypovitaminosis A) is a serious problem in the developing world.

Mineral supplementation

Calcium supplementation is indicated for the prevention of osteoporosis, and is often recommended for pregnant and lactating women, as well as growing children. The latter groups may be able to obtain sufficient calcium with a generous dairy product intake. Note that vitamin D is a cofactor for calcium in bone formation; milk in the U.S. and some other countries is supplemented with this vitamin.

Iodine is necessary for proper thyroid function, and may not be present in certain diets. Again, it is added to commercial table salt in the U.S. and some other countries, although not all nutritional salt has this addition. Iodine will cause undesirable effects if used in salt used for pickling; commercial pickling salt has no added iodine. Since excessive dietary salt presents health risks, iodinized salt may not be the best way of supplementing iodine, especially for people on low-salt diets.

A number of drugs, especially diuretics, can cause potassium loss. It is quite common to have either potassium-rich foods, or potassium supplements and possibly potassium-sparing diuretics, for patients taking thiazide diuretics.

A major fraction of the American population fail to consume he recommended dietary intake of potassium ion, 4700 mg/day (=120 mmol/day), largely due to inadequate consumption of vegetable and fruit. Individuals, however, cannot self-prescribe a supplement of a potassium salt (e.g., potassium citrate, potassium chloride, potassium bicarbonate) to meet the recommended intake level, as only a physician can prescribe potassium supplements in such amounts, according to existing law. Obtaining a prescription for a potassium supplement thus entails the added cost of physician intervention and pharmaceutical overhead. Moreover, physicians do not usually prescribe potassium supplements solely to ensure patients meet recommended daily requirements, in patients who do not otherwise have a condition that leads to excessive external body loss of potassium, for fear the patients will experience the toxic effects of an abnormally high blood potassium concentration. Yet, they typically do not test such patients for their ability to consume potassium at the recommended daily level. For more information, and source-citations, see the article, Potassium in nutrition and human health.

Other supplements

• Chondroitin [r]: A mucopolysaccharide constituent of chondrin. ^[e]
• Glucosamine [r]: Amino sugar component of chitin, heparan sulphate, chondroitin sulphate and many complex polysaccharides, used in treatment of osteoarthritis. ^[e]