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biologically based practices: an overview

the cam domain of biologically based practices includes, but is not limited to, botanicals, animal-derived extracts, vitamins, minerals, fatty acids, amino acids, proteins, prebiotics and probiotics, whole diets, and functional foods. dietary supplements are a subset of this cam domain. in the dietary supplement health and education act (dshea) of 1994, congress defined a dietary supplement as a product taken by mouth that contains a "dietary ingredient" intended to supplement the diet. the "dietary ingredients" in these products may include vitamins, minerals, herbs or other botanicals, amino acids, and substances such as enzymes, organ tissues, glandulars, and metabolites. dietary supplements can also be extracts or concentrates, and they can occur in many forms, such as tablets, capsules, softgels, gelcaps, liquids, or powders. the food and drug administration (fda) regulates dietary supplements differently than drug products (either prescription or over-the-counter). first, drugs are required to follow defined good manufacturing practices (gmps). the fda is developing gmps for dietary supplements. however, until they are issued, companies must follow existing manufacturing requirements for foods. second, drug products must be approved by the fda as safe and efficacious prior to marketing. in contrast, manufacturers of dietary supplements are responsible for ensuring that their products are safe. while the fda monitors adverse effects after dietary supplement products are on the market, newly marketed dietary supplements are not subject to premarket approval or a specific postmarket surveillance period. third, while dshea requires companies to substantiate claims of benefit, citation of existing literature is considered sufficient to validate such claims. manufacturers are not required, as they are for drugs, to submit such substantiation data to the fda; instead, it is the federal trade commission that has primary responsibility for monitoring dietary supplements for truth in advertising. a 2004 institute of medicine (iom) report on the safety of dietary supplements recommends a framework for cost-effective and science-based evaluation by the fda. history and demographic use of biologically based practices dietary supplements reflect some of humankind's first attempts to improve the human condition. the personal effects of the mummified prehistoric "ice man" found in the italian alps in 1991 included medicinal herbs. by the middle ages, thousands of botanical products had been inventoried for their medicinal effects. many of these, including digitalis and quinine, form the basis of modern drugs. interest in and use of dietary supplements have grown considerably in the past two decades. consumers state that their primary reason for using herbal supplements is to promote overall health and wellness, but they also report using supplements to improve performance and energy, to treat and prevent illnesses (e.g., colds and flu), and to alleviate depression. according to a 2002 national survey on americans' use of cam, use of supplements may be more frequent among americans who have one or more health problems, who have specific diseases such as breast cancer, who consume high amounts of alcohol, or who are obese. supplement use differs by ethnicity and across income strata. on average, users tend to be women, older, better educated, live in one- or two-person households, have slightly higher incomes, and live in metropolitan areas. use of vitamin and mineral supplements, a subset of dietary supplements, by the u.s. population has been a growing trend since the 1970s. national surveys--such as the third national health and nutrition examination survey (nhanes iii, 1988-1994); nhanes, 1999-2000; and the 1987 and 1992 national health interview surveys--indicate that 40 to 46 percent of americans reported taking at least one vitamin or mineral supplement at some time within the month surveyed. data from national surveys collected before the enactment of dshea in 1994, however, may not reflect current supplement consumption patterns. in 2002, sales of dietary supplements increased to an estimated $18.7 billion per year, with herbs/botanical supplements accounting for an estimated $4.3 billion in sales.9 consumers consider the proposed benefits of herbal supplements less believable than those of vitamins and minerals. from 2001 to 2003, sales of herbs experienced negative growth. this was attributed to consumers' withering confidence and confusion. within the herbal category, however, formulas led single herbs in sales; products became increasingly condition-specific; and sales of women's products actually increased by approximately 25 percent. in contrast to dietary supplements, functional foods are components of the usual diet that may have biologically active components (e.g., polyphenols, phytoestrogens, fish oils, carotenoids) that may provide health benefits beyond basic nutrition. examples of functional foods include soy, nuts, chocolate, and cranberries. these foods' bioactive constituents are appearing with increasing frequency as ingredients in dietary supplements. functional foods are marketed directly to consumers. sales increased from $11.3 billion in 1995 to about $16.2 billion in 1999. unlike dietary supplements, functional foods may claim specific health benefits. the nutrition labeling and education act (nlea) of 1990 delineates the permissible labeling of these foods for health claims. whole diet therapy has become an accepted practice for some health conditions. however, the popularity of unproven diets, especially for the treatment of obesity, has risen to a new level as the prevalence of obesity and metabolic syndrome among americans has increased and traditional exercise and diet "prescriptions" have failed. popular diets today include the atkins, zone, and ornish diets, sugar busters, and others. the range of macronutrient distributions of these popular diets is very wide. the proliferation of diet books is phenomenal. recently, food producers and restaurants have been targeting their marketing messages to reflect commercially successful low-carbohydrate diets. public need for information about dietary supplements, functional foods, and selected strict dietary regimens has driven research on the effectiveness and safety of these interventions and the dissemination of research findings. summary of the major threads of evidence over the past few decades, thousands of studies of various dietary supplements have been performed. to date, however, no single supplement has been proven effective in a compelling way. nevertheless, there are several supplements for which early studies yielded positive, or at least encouraging, data. good sources of information on some of them can be found at the natural medicines comprehensive database and a number of national institutes of health (nih) web sites. the nih office of dietary supplements (ods) annually publishes a bibliography of resources on significant advances in dietary supplement research. finally, the clinicaltrials.gov database lists all nih-supported clinical studies of dietary supplements that are actively accruing patients. for a few dietary supplements, data have been deemed sufficient to warrant large-scale trials. for example, multicenter trials have concluded or are in progress on ginkgo (ginkgo biloba) for prevention of dementia, glucosamine hydrochloride and chondroitin sulfate for osteoarthritis of the knee, saw palmetto (serenoa repens)/african plum (prunus africana) for benign prostatic hypertrophy, vitamin e/selenium for prevention of prostate cancer, shark cartilage for lung cancer, and st. john's wort (hypericum perforatum) for major and minor depression. the results of one of the depression studies showed that st. john's wort is no more effective for treating major depression of moderate severity than placebo. other studies of this herb, including its possible value in treatment of minor depression, are under way. reviews of the data regarding some dietary supplements have been conducted, including some by the members of the cochrane collaboration. the agency for healthcare research and quality has produced a number of evidence-based reviews of dietary supplements, including garlic, antioxidants, milk thistle, omega-3 fatty acids, ephedra, and s-adenosyl-l-methionine (same). the following are examples of findings from some of these reviews: analysis of the literature shows generally disappointing results for the efficacy of antioxidant supplementation (vitamins c and e, and coenzyme q10) to prevent or treat cancer. because this finding contrasts with the benefits reported from observational studies, additional research is needed to understand why these two sources of evidence disagree. similarly, the literature on the roles of the antioxidants vitamins c and e and coenzyme q10 for cardiovascular disease also shows discordance between observational and experimental data. therefore, the thrust of new research into antioxidants and cardiovascular disease should be randomized trials. the clinical efficacy of milk thistle to improve liver function is not clearly established. interpretation of the evidence is hampered by poor study methods or poor quality of reporting in publications. possible benefit has been shown most frequently, but not consistently, for improvement in aminotransferase levels. liver function tests are overwhelmingly the most common outcome measure studied. available evidence is not sufficient to suggest whether milk thistle is more effective for some liver diseases than others. available evidence does suggest that milk thistle is associated with few, and generally minor, adverse effects. despite substantial in vitro and animal research, the mechanism of action of milk thistle is not well defined and may be multifactorial. the review of same for the treatment of depression, osteoarthritis, and liver disease identified a number of promising areas for future research. for example, it would be helpful to conduct (1) additional review studies, studies elucidating the pharmacology of same, and clinical trials; (2) studies that would lead to a better understanding of the risk-benefit ratio of same compared to that of conventional therapy; (3) good dose-escalation studies using the oral formulation of same for depression, osteoarthritis, or liver disease; and (4) larger clinical trials once the efficacy of the most effective oral dose of same has been demonstrated. two high-quality randomized controlled trials provide good evidence that cranberry juice may decrease the number of symptomatic urinary tract infections in women over a 12-month period. it is not clear if it is effective in other groups. the fact that a large number of women dropped out of these studies indicates that cranberry juice may not be acceptable over long periods of time. finally, the optimal dosage or method of administration of cranberry products (e.g., juice or tablets) is not clear. there has been some study of other popular dietary supplements. for example, valerian is an herb often consumed as a tea for improved sleep, and melatonin is a pineal hormone touted for the same purpose. small studies suggest that these two supplements may relieve insomnia, and there may be little harm in a trial course of either one. echinacea has long been taken to treat or prevent colds; other supplements currently used for colds include zinc lozenges and high doses of vitamin c. as yet, only moderate-sized studies have been conducted with echinacea or zinc, and their outcomes have been conflicting. large trials of high doses of oral vitamin c showed little, if any, benefit in preventing or treating the common cold. because of widespread use, often for centuries, and because the products are "natural," many people assume dietary supplements to be inert or at least innocuous. yet, recent studies show clearly that interactions between these products and drugs do occur. for example, the active ingredients in ginkgo extract are reported to have antioxidant properties and to inhibit platelet aggregation. several cases have been reported of increased bleeding associated with ginkgo's use with drugs that have anticoagulant or antiplatelet effects. st. john's wort induces a broad range of enzymes that metabolize drugs and transport them out of the body. it has been shown to interact with a number of drugs that serve as substrates for the cytochrome p450 cyp3a enzymes responsible for metabolism of approximately 60 percent of current pharmaceutical agents. other dietary supplements shown to potentiate or interfere with prescription drugs include garlic, glucosamine, ginseng (panax), saw palmetto, soy, valerian, and yohimbe. in addition to interacting with other agents, some herbal supplements can be toxic. misidentification, contamination, and adulteration may contribute to some of the toxicities. but other toxicities may result from the products themselves. for example, in 2001, extracts of kava were associated with fulminant liver failure. more recently, the fda banned the sale of ephedra after it was shown to be associated with an increased risk of adverse events.

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