In the United States, a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994 (DSHEA) as a product that is intended to supplement the diet and bears or contains one or more of the following dietary ingredients:

• a vitamin
• a mineral
• a herb or other botanical (excluding tobacco)
• an amino acid
• a dietary substance for use by man to supplement the diet by increasing the total dietary intake, or
• a concentrate, metabolite, constituent, extract, or combination of any of the above

Furthermore, it must be:

• intended for ingestion in pill, capsule, tablet, powder or liquid form
• not represented for use as a conventional food or as the sole item of a meal or diet
• labeled as a "dietary supplement"

Pursuant to the DSHEA, the Food and Drug Administration regulates dietary supplements as foods, and not as drugs. The FDA does not approve dietary supplements based on their safety and efficacy; the FDA can take action only after a dietary supplement has been proven harmful. However, certain foods (such as infant formula and medical foods) are deemed special nutritionals because they are consumed by highly vulnerable populations and are thus regulated more strictly than the majority of dietary supplements.  The claims that a dietary supplement makes are essential to its classification. If a dietary supplement claims to cure, mitigate, or treat a disease, it would be considered to be an unauthorized new drug and in violation of the applicable regulations and statutes.
Dietary supplements are permitted to make structure/function claims. These are broad claims that the product can support the structure or function of the body (e.g., "glucosamine helps support healthy joints"). The FDA must be notified of these claims within 30 days of their first use, and there is a requirement that these claims be substantiated.  Other claims that required approval from FDA include health claims and qualified health claims. Health claims are permitted to be made if they meet the requirements for the claims found in the applicable regulations. Qualified health claims can be made through a petition process, including scientific information, if FDA has not approved a prior petition.  Many of the claimed benefits of dietary supplements are supported by a large number of smaller scientific studies. These studies, however, do not fulfill the requirements for large, very expensive, double blind controlled studies that are used in testing pharmaceutical drugs.

Here is a quick reference to some of the popular supplements on the market today. 

Multivitamin:  It is a mixture of vitamins and minerals usually in pill form that are designed to supply the body with nutrients that may not be consumed in a person’s dietary intake.  Multivitamins work in combination with whole foods.  Everyone can benefit from consumption of a multivitamin.  Talk to your doctor about specific needs that your body requires to find which multivitamin will work best for you. 

Creatine:  This is the most popular and most researched supplement on the market.  There are countless studies that support the positive effects for both men and women.  Creatine works with your ATP and Phosphocreatine energy systems.  Every healthy human has Creatine in the body currently.  By taking a Creatine supplement you increase the amount of Creatine phosphate storage and make it readily available for use.  The recommended amounts for Creatine are currently under debate.  Don’t follow the instructions on the label, as the loading phase encouraged by the manufactures is a marketing scam increasing your usage and therefore increasing the sales of their product.  Most people need 5 grams or less a day.  The amounts are determined by your body weight.  The only known side effect of Creatine is dehydration, so make sure to consume plenty of fluids.  

NO2:  NO2 is a fairly new supplement that claims to increase blood flow to the muscles.  The manufactures claim increased strength and size are a result of use.  The main ingredient in NO2 is L-Arginine, which is an amino acid.  The recommended daily intake is based on body weight.  Since the product is new the known side effects are still under investigation.  Some of the common feedback reported by users was, increased pumps during and following a workout but a lose in that pump when they stopped taking the product.  Most manufacturers are combining NO2 with other ingredients that increase the effects.  Be aware of what ingredients you are consuming and pay close attention to your own bodies’ reactions.  Some studies have shown that NO2 supplementation increases the outbreak of cold sores.  Also, the complaint of the frequency and the amount of NO2 taken daily was excessive.  

Amino Acids (A.A.):  A.A.are the basic building blocks of proteins.  Proteins build and repair muscle and without it your muscles with atrophy.  A.A. should be consumed in whole foods but can be a great supplement to work in combination with the other amino acids consumed throughout your day.  A.A. supplements are available in mixtures such as Branched Chain Amino Acids (BCAA) or as individual amino acids.  Daily intake should be correlated with your body weight, current protein intake, and desired fitness goals. 

Protein:  Protein contains amino acids and the consumption of protein is vital to muscle growth and repair.  There are many different sources of protein that can be taken in different forms.  Most commonly ingested protein supplements are powder form.  Be cautious when taken a protein supplement, more is not always better.  Your body can only digest a specific amount of protein and when taken large amounts at once you waste much of the supplement.  Protein powder can be taken with water or milk.  Protein supplementation should be taken within 45 minutes following a workout and can also be used as a quick meal.  Be creative with the shakes you make.  Choose fruits and other items that can make the taste better.  You can even try to add a scope of ice cream to reward yourself for a good workout.  When taken with milk you supply your body with more of a complete source of vitamins and minerals making the “shake” more of a complete meal.   

Meal Replacement Bar: Just like the name implies an MRB is developed to replace a meal.  It is a convenient way to supply your body with a complete source of fuel while on the go.  Two common mistakes that are associated with meal replacements is the idea that you can only eat these bars instead of your regular food.  Keep in mind that these MRB are processed foods and should be used in combination with other whole foods.  The second problem is people have the tendency to eat a MRB on top of a meal.  Even though MRB’s are not usually as filling as a regular meal they still supply the body with calories and can lead to weight gain when eating both together.  Since a major factor to proper nutrition is consistently feeding the metabolism than eating a MRB is a great way to satisfy that need while in a rush.

Thermogenics (Fat Burners):  There are many different kinds of fat burners on the market today.  Some are herbal based and others are caffeine based, while others are a combination of both.  A few characteristics that thermogenics have in common, 1) They increase core body temperature, by doing this it “jump starts” the metabolism, 2) Suppresses appetite, 3) Increases the body's adipose tissue metabolism.  Since most fat burners are naturally a stimulant be cautious on the amount taken and allow your body to adjust to the effects of the ingredients.  Be sure not to abuse the recommended dosage and taken these types of supplements is usually suggested with food.

Glutamine:  Glutamine is one of the 20 amino acids encoded by the standard genetic code.  Use of glutamine has shown to speed muscle recovery and aid in soreness usually associated with resistance training.  Glutamine is a supplement that is used in weightlifting, bodybuilding, endurance and other sports, as well as by those who suffer from muscular cramps or pain—particularly elderly people. The main use of glutamine within the diet of either group is as a means of replenishing the body's supply of amino acids that have been used during exercise or everyday activities.  Studies which are looking into problems with excessive consumption of glutamine thus far have proved inconclusive. However, normal supplementation is healthy mainly because glutamine is supposed to be supplemented after prolonged periods of exercise (for example, a workout or exercise in which amino acids are required for use) and replenishes amino acid supply; this being the main reason glutamine is recommended during fasting or for people who suffer from physical trauma, immune deficiencies, or cancer.

Glucosamine:  Oral glucosamine is commonly used for the treatment of osteoarthritis. Since glucosamine is a precursor for glycosaminoglycans, and glycosaminoglycans are a major component of joint cartilage, supplemental glucosamine may help to rebuild cartilage and treat arthritis. Its use as a therapy for osteoarthritis appears safe, but there is conflicting evidence as to its effectiveness (Laverty et al., 2005; Biggee et al., 2005).  A typical dosage of glucosamine salt is 1,500 mg per day. Glucosamine contains an amino group that is positively charged at physiological pH. The anion included in the salt may vary. Commonly sold forms of glucosamine are glucosamine sulfate and glucosamine hydrochloride. The amount of glucosamine present in 1500 mg of glucosamine salt will depend on which anion is present and whether additional salts are included in the manufacturer's calculation. Glucosamine is often sold in combination with other supplements such as chondroitin sulfate and methylsulfonylmethane.  In the United States, glucosamine is not approved by the Food and Drug Administration for medical use in humans. Since glucosamine is classified as a dietary supplement, evidence of safety and efficacy is not required as long as it is not advertised as a treatment for a medical condition. Nevertheless, glucosamine is a popular alternative medicine used by consumers for the treatment of osteoarthritis