The sale and use of dietary supplements in the United States initially grew dramatically after the passage of the DSHEA. Figures of individual and mixtures of botanical supplements drove the market. The growth and demand led to a consolidation of manufacturing and retail corporations as well as new growth in botanical supplements produced by the major pharmaceutical corporations in the US.
It is estimated that from 30—53 per cent of Americans or 100 million people use dietary supplements on a regular basis (several times each week) (Aarts, 1998). In 1996 sales of dietary supplements totalled $9.8 billion and represented 51 per cent of the total sales in the nutrition industry in the United States. Sales of dietary supplements in natural food stores comprised 44 per cent of the total, and mass-market retail accounted for 26 per cent of the total with the remainder in direct marketing through the mail or Internet. Overall sales for dietary supplements grew 9 per cent in 1996 (Aarts, 1998). Sales continued to grow in 1997 and 1998 to a new record level for total sales of dietary supplements of $13.9 billion in 1998, which was a 10 per cent increase over sales in 1997. Of this market, for specialty supplements, glucosamine grew 23 per cent, botanical supplements sales increased 13 per cent, and sports-oriented supplements, as exemplified by energy bars, grew 12 per cent. In contrast, according to the Nutrition Business Journal (NBJ), vitamin and mineral sales grew less dramatically at the rates of 6 per cent and 8 per cent respectively (NBJ, 1999a). Online Internet sales for dietary supplements represented the 'fastest growing distribution channel' which totalled $40 million in 1998 and was a significant increase over the $12 million online sales total for 1997 (NBJ, 1999b).
In 1997 botanical supplements sales from all distribution channels totalled $3.6 billion with multi-herbal products comprising 27 per cent of the total. The top five single botanical products sold in 1997 were Echinacea (9 per cent, $324 million), ginseng (8 per cent, $288 million), Ginkgo (7 per cent, $252 million), garlic (6 per cent, $216 million), and St John's Wort (6 per cent, $216 million) (NBJ, 1998).
In 2000 the sales slowed significantly for this industry, but recent projections indicate continued growth in the future. At present, the nutrition industry, overall, represents $48 billion in annual sales with an expected growth rate of 6.2 per cent from
2001 to 2003. The nutrition industry is divided as follows: functional foods accounting for 36 per cent, dietary supplements accounting for 35 per cent, natural and organic foods accounting for 21 per cent and the remaining 8 per cent representing personal care products. In 2000, dietary supplement sales totalled $16.8 billion with vitamins and minerals accounting for 42 per cent, herbs and botanicals accounting for 25 per cent, and other supplements including meal supplements accounting for 31 per cent. From 2001 to 2003 mineral supplement sales are expected to grow 7.8 per cent, vitamins, 2.0 per cent, herbs and botanicals 2.4 per cent, while other supplements range from 4.7 per cent (meal supplements) to 10 per cent (specialty supplements/other). (Source: the Nutrition Business Journal as cited on the National Nutritional Foods Association website on 14 February 2002.)
Use of dietary supplements based on representative population samples in the United States
The first well-stratified statistical samples of the use of botanical supplements by the United States population are currently being conducted as part of the National Health and Nutrition Examination Survey (NHANES), which began in 1999, and includes questions on dietary supplement use. The other information on supplement use in the United States other than what is emerging from the NHANES, is garnered from market information and studies that have focused on specific populations.
The National Health and Nutrition Examination Survey (NHANES) and the Continuing Survey of Food Intakes by Individuals (CSFII) have traditionally been important sources for information on the relationship between health outcomes and dietary practices in the United States. These series of diet, nutrition and health surveys, which are managed by the federal government, utilize statistically driven samples of the diverse population of the United States. The data collected by these surveys prior to 1999 included questions on dietary supplements, but the focus was on vitamin and mineral supplements.
The NHANES is run from mobile health units that travel to specific locations throughout the country to reach the identified samples of the population. The data collected in each of the surveys prior to 1999 combined questionnaires with a series of measurements and samples on each individual that varied with the survey questions and government groups supporting the particular survey. In spring, 1999 the NHANES became a continuous survey that has the goal of visiting 15 locations and collecting data on 5,000 Americans each year (http://www.cdc.gov/nchs/nhanes.htm). As of January 2002, the NHANES merged with the CSFII and became the National Food and Nutrition Survey (NFNS). The goal of this new tool is to 'provide comprehensive information on health and nutrition characteristics of the US'. (http://www.cdc.gov/nchs/about/major/nhanes/current.htm). Since 1999 the NHANES has included questions about the use of supplements of plant origin and will provide a rich source of data to address health questions and their relationship to supplement intake.
Data from earlier national surveys provides information on Americans' use of vitamin and mineral supplements. For example, Slesinski and colleagues reviewed the data from the National Health Interview Surveys conducted in 1987 and 1992 to look at nutrient supplement use over the previous 12-month period. These authors found that the prevalence of supplement use remained unchanged between the two surveys.
Forty-six per cent of adults stated that they used vitamin and mineral supplements in the last year and 24 per cent reported regular use (Slesinski et al., 1995). Those who used nutrient supplements, as recorded by the 1992 survey, had overall diets that were lower in fat, higher in fibre and higher in specific vitamins and minerals than nonusers of supplements (Slesinski et al., 1996).
Data from the early NHANES (prior to 1999) similarly indicated that nutrient supplement users had a higher mean intake of nutrients from their diets, higher incomes and higher education levels than non-users (Koplan et al., 1986; Looker et al., 1998). In a survey that assessed the health habits of a representative sample of older residents in the state of Georgia, which included persons in their sixties and eighties, and 76 individuals over the age of 100, those who used nutrient supplements were more physically active and more consistently followed the United States Dietary Guidelines for Americans (Houston et al., 1997).
In contrast to nutrient supplement users, those who use botanical supplements present a different profile. In a random sample of 1,035 Americans, those who used botanical supplements were more highly educated but in generally poorer health; specifically they reported a higher prevalence of back pain, chronic pain and anxiety than those who did not use supplements (Astin, 1998).
Overall, representatives of health professional groups tend to use nutrient supplements in similar patterns to the general population. Of 1,732 nurses surveyed in the Nurses Health Study, 38 per cent reported regularly taking multivitamins. Use of single-nutrient supplements was less prevalent: vitamin C (23 per cent), vitamin E (15 per cent) and vitamin A (4 per cent) (Willett et al., 1981). Forty-seven per cent of 692 pharmacy students queried in a study by Ranelli et al. (1993) reported using nutrient supplements within the previous two weeks. Among 181 cardiologists, 44 per cent reported routinely taking antioxidants, 42 per cent were routinely taking aspirin and 28 per cent reported regular use of both products (Mehta, 1997). Dietitians appear to use supplements to a greater degree than other health professionals do. Of 665 dietitians polled in Washington State, 60 per cent reported using some form of dietary supplement (Worthington-Roberts and Breskin, 1984).
Two nationally representative random household telephone surveys in the 1990s that measured the use of alternative medicinal practices by Americans included questions on dietary supplements. Between 1990 and 1997 there was a dramatic increase by adults in the use of high-dose vitamins (130 per cent increase) and botanical supplements (380 per cent increase) (Eisenberg et al., 1998).
Not unexpectedly, a large percentage of cancer patients incorporate alternative medical therapies as adjuvants to conventional treatments. In a cohort of 480 patients who were newly diagnosed with early-stage breast cancer, 10.6 per cent of the women had used alternative medicine prior to their diagnosis and 28.1 per cent initiated the use of alternative medicine after surgery. In this study by Burstein and colleagues, alternative medicine included botanical supplements. There was no difference between alternative medicine users and non-users on quality-of-life measures at the time of surgery; however, at three months post-surgery, use of alternative practices was associated with depression, fear measures, lowered mental health ratings, and lowered sexual satisfaction (Burstein et al., 1999).
Rock and colleagues incorporated information on botanical supplement use as part of a secondary breast cancer prevention trial of 435 women. These women had completed their medical treatment and replied to four 24-hour dietary recalls over a two-
week period to identify their dietary patterns. In this study, 80.9 per cent of the women reported dietary supplement use on a regular basis, which is approximately double that of the general population. Women who used supplements, whether nutrient, botanical or biological, consumed diets with more dietary fibre and less dietary fat than non-users (Rock et al., 1997). In a localized breast cancer follow-up trial in postmenopausal women, 71 per cent of the first 724 patients randomized on the study were regularly taking dietary supplements. In a subset of 116 consecutive women on the same study, 82 per cent were taking at least one dietary supplement but the variety of the supplements taken each day varied from 1 to 10 and the number of pills consumed per day ranged from 1 to 26. Of those women who reported regular intake of dietary supplements, 22 per cent were taking botanical supplements and biologicals (Winters et al., 1997). Using data from comprehensive cancer centres, Richardson et al. (2000) reported that 38 per cent of survivors used botanical supplements and 60.3 per cent reported using vitamins. Ongoing work by these and similar groups are the main source of growing understanding of the parameters of use of dietary supplements by cancer patients. A good review of specific botanical supplements in use by cancer patients can be found in Spaulding-Albright (1997).
Much of the other data on botanical supplement use in the United States are from industry-sponsored, consumer-based surveys. In a 500-household survey conducted by the Celestial Seasons Company in partnership with the Harris Organization, 33 per cent of households regularly used botanical supplements (cited by Brevoort, 1998). A larger survey of 43,000 households reported the use of the botanical supplements: garlic (19 per cent), ginseng (10 per cent), Ginkgo (9 per cent) and Echinacea (7 per cent) (as cited in Brevoort, 1998). In a Gallup interview of 704 individuals the three most frequently cited reasons for using botanical supplements were to combat fatigue, stress and menopause/PMS (Gallup, 1997, as cited in Brevoort, 1998). A survey of their readership by Prevention Magazine indicated that 32 per cent of those who responded used botanical supplements and spent an average of $54 per year on botanical supplement purchases. Sixty-five per cent of the respondents indicated that they used botanical supplements because they believed these products were safer than drugs (Prevention Magazine, 1997, as cited in Brevoort, 1998).
Belief structure rather than scientific evidence appears to continue to drive dietary supplement use. In a recent survey, dietary supplement users were more likely than non-users to believe that supplements were beneficial for persons with cancer, and most surveyed reported positive attitudes towards the health benefits of supplements (Blendon et al., 2001). Yet data from well-controlled studies points to variability of product quality (cf. Shibata and Asetai, 1996; Hahm et al., 1999; Harkey et al., 2001), lack of beneficial results and the need for caution with regard to prolonged supplement use (King et al., 1999).
In general, comprehensive information on the use of dietary supplements, as defined in the DSHEA, is limited to select population-based studies. The current NHANES includes questions on the type and amount of supplement used and will therefore provide a stratified sample of these factors within the sampling model of the overall project. However, the necessary breadth of the NHANES and the complex nature of its design (as described previously) result in a limited set of questions related to dietary supplements. Targeted research is needed to develop more detailed information on determinants of supplement selection, rationale for supplement use, relation of price to choice patterns, specifics of use, etc.
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