Dietary supplements refer to products made up of one or more of the essentialnutrients such as vitamins, minerals, and protein. The 1994 Dietary Supplement Health and Education Act (DSHEA) broadened the definition to include any product that was intended for ingestion as a supplement to the diet. This includes vitamins; minerals; herbs, botanicals, and other plant-derived substances; amino acids ( the building block of proteins), and concentrates, metabolites, constituents and extracts of these substances.
Dietary supplements come in many forms, including tablets, capsules, powders,soft gels, gelcaps, and liquids. A visit to your local health food store reveals aisles of vitamins, minerals, and herbs that make a variety of claims toimprove overall health. Besides health food stores, dietary supplements arealso sold in grocery, drug and national discount chain stores as well as through mail order catalogs, TV programs, the Internet and direct sales.
While some dietary supplements may hold medicinal value, Americans are spending over $700 million a year on various products that not only provide limitedhealth benefits, but also may pose significant health risks. Surveys show that more than half of the US adult population use these products. The AmericanDietetic Association, the National Academy of Sciences, the National Research Council, and other major medical societies agree that most people can get all the vitamins and minerals they need from eating a healthy, well-balanced diet.
Dietary supplements cannot replace the hundreds of additional nutrients, called phytochemicals, provided in whole foods. They are not to be treated as substitutes for conventional diets. Dietary supplements cannot be regarded as drugs either. A drug may sometimes be derived from a plant. However, it is intended to diagnose, cure, mitigate, treat, or even prevent disease. Therefore,before marketing, drugs undergo several clinical studies to determine their effectiveness, safety, possible interactions with other substances, and appropriate dosages. The Food and Drug Administration (FDA) must then review thesedata and authorize the use of the drugs before they are marketed. The FDA does not authorize or test dietary supplements.
In passing the DSHEA, the Congress acknowledged that many people believe dietary supplements offer health benefits and that consumers wanted a greater opportunity to determine whether such supplements may benefit them. The law essentially gave dietary supplement manufacturers freedom to market more productsas dietary supplements and provide information about the product's benefitsin the product labeling. What this means is that when choosing whether to usedietary supplements, the consumers and, manufacturers have the responsibility of checking the safety of the dietary supplements and determining the truthfulness of the label claims.
There are, however, situations in which taking supplements may be appropriate. Many people do not get all the nutrients they need from their diets becausethey do not eat properly. There are 13 vitamins needed by the body for normal growth, digestion, mental alertness, and resistance to infection. They alsoenable the body to use carbohydrates, fats, and proteins. They act as catalysts and initiate or speed up chemical reactions within the body. Besides thevitamins, the body also needs 15 minerals to regulate cell function and provide structure for cells. Major minerals are calcium, phosphorous, and magnesium. In addition, smaller amounts of chromium, fluorine, iodine, iron, manganese, selenium, zinc, chloride, potassium, and sodium are also needed. Togetherthese vitamins and minerals are called micronutrients. Lack of a micronutrient can sometimes cause a condition, which is usually reversed when the micronutrient is resupplied. The human body cannot make most vitamins and minerals.They must come from food and supplements.
Only one person in 10 regularly consumes the recommended five servings of fruits and vegetables a day. Skipping meals, dieting, and eating meals high in sugar and fat all contribute to poor nutrition. For these people taking supplemental vitamins would be reasonable. The Recommended Daily Allowance(RDA) hasbeen established for vitamins and several of the micronutrients. These RDAsare simply the amount of minerals and vitamins that needed to be consumed daily in order to prevent vitamin and mineral deficiency. It is considered safeto take doses 10 times higher than the RDA. Doses above that amount do not give extra protection, but can increase the risk of encountering toxic side effects. For example, large amounts of Vitamin D can indirectly cause kidney damage, and large amounts of Vitamin A can cause liver damage.
The elderly or those on a strict weight loss diet may benefit from a multivitamin. Postmenopausal women, especially those not taking estrogen, may need toincrease their intake of calcium and Vitamin D to protect against osteoporosis. In addition, people 65 years or older may need to increase their intake of vitamin B-6, vitamin B-12 and vitamin D because they may not be able to absorb these very well. People who have diseases of the digestive tract such asthe liver, gall bladder, intestine, and pancreas may also benefit from vitamin and mineral supplements. Disease or surgery may have interfered with theirnormal digestion and absorption of nutrients.
It had been shown that smoking reduces vitamin C levels and causes productionof harmful free radicals. Doctors may therefore advise smokers to take 100 mg of vitamin C as opposed to the normal RDA of 60 mg for nonsmokers. Excessive amounts of alcohol may also affect the absorption, metabolism, and excretion of vitamins.
Pregnant and breast feeding women are generally advised to take certain nutrients, especially folic acid, iron and calcium, because their bodies have a greater need for those requirements during that phase. Another high-risk groupwho may benefit from additional vitamins are vegetarians who eliminate all animal products from their diets. They may need to supplement their diets withvitamin B-12. In addition, if they have limited milk intake and limited exposure to the sun, they may also need to take calcium and vitamin D as supplements.
Herbal supplements can have serious side effects. Those herbal supplements containing ephedrine have been linked with abnormal heart rhythms, stroke, hepatitis, and even death.
Consideration of even the most popular supplements should include weighing the benefits against the possible side effects. Beta-Carotene (Vitamin A) is anantioxidant (along with Vitamins C and E) that neutralizes harmful substances, called free radicals, resulting from cell metabolism. Some believe that antioxidants prevent the damage from free radicals that may contribute to cardiovascular disease or cancer. Some studies, however, found an increased risk of lung cancer in smokers who took beta-carotene supplements.
Folic acid, one of the B vitamins that helps prevent certain spinal cord birth defects, is also linked to cardiovascular benefits. Intake of folate can, however, mask a vitamin B12 deficiency if intake is over 1,000 micrograms per day.
Niacin is another B vitamin that reduces the fats (lipids) in the blood and potentially slows the progression of osclerosis when combined with diet and exercise. At doses higher than 2,000 micrograms, serious side effects may include liver damage, high blood pressure, and irregular heartbeats.
In addition to the antioxidant effects described above, Vitamin C is thoughtto strengthen resistance to viral infection and act as a mild antihistamine to help relieve cold symptoms. There is no evidence, however, to support the beliefs that high doses of Vitamin C can cure a cold; amounts above 500 milligrams are excreted in the urine.
Vitamin E also functions as a potent antioxidant, which may slow the progression of artherosclerosis. Regular intake of Vitamin E may also slow the effects of Parkinson's disease and Alzheimer's disease. High doses of Vitamin E cancause gastrointestinal side effects and bleeding, especially for individualson blood thinners (anticoagulants).
Caution should also be taken with use of the various minerals offered as dietary supplements. Chromium is thought to work with insulin for blood sugar utilization. There are no studies that support claims of increased muscle mass,weight loss, or prevention of osteoporosis. Selenium is another antioxidant claimed to prevent cancer and cardiovascular disease. Taking excessive amountsof selenium may cause hair and nail loss. Zinc has been shown in some studies to increase the immune response, reducing the severity of cold symptoms. Excess zinc, however, has been shown to interfere with the body's utilization of essential minerals, such as iron and copper.
While herbs are the basis for many of our medicines, there is no guarantee that the many herbal supplements on the market are worth the millions of dollars Americans spend on them annually. Ginkgo biloba is thought to dilate bloodvessels and improve blood flow to the brain and legs. Side effects of this herb include gastrointestinal problems, headaches, and allergic reactions. St.John's Wort may be effective for mild to moderate depression; however, studies are still in progress for possible side effects.
Any individual with a known health problem, or any one taking prescribed medications, should consult a doctor before using any nutritional supplements
Consumers cannot assume that these products are safe, pure, or that the quantities of active ingredients are listed on their labels--the nutritional supplement industry is largely unregulated. The Dietary Supplements Health and Education Act of 1994 altered the Food and Drug Administration's (FDA) ability to assess the safety of nutritional supplements before they go out on the market. As a result, the FDA can act only after an illness or injury has been reported through a "consumer complaint coordinator" at FDA district offices in cities across the country.