Although rates of dietary supplement use vary by age, gender, race, and ethnicity, very little is known about the pattern of use among college age and young adults. Young adults are known to engage in high risk behaviors such as alcohol and tobacco use. Using certain dietary supplements, such as high dose ephedra product in a weight loss products or sport performance products is also a high risk behavior. Little is known about the correlation between high risk dietary supplements (stimulants or depressants) and other young adult's behavior.

Surveys of college athletes, college students, and young adults have demonstrated a strong link between high physical activity and use of sport supplements to enhance athletic performance [9-15]. Although this trend has been seen in special populations (i.e., athletes); it has not been replicated in a general population of young adults [9-15].

Higher rates of HDS use have also been reported among patients using prescription and non-prescription medications in pediatric and adult surveys [3]. This use is particularly concerning due to the potential for herb-medication interactions. This relationship has not been specifically evaluated in the young adult population.

Communication with health professionals about HDS use has been reported by fewer than half of adult and pediatric patients who use them [2,16,17]. This relationship has not been explored in the young adult population, but could have important implications for health care in this group.

For the NHIS, respondents were specifically asked, "Some people use natural herbs for a variety of health reasons. Some people drink an herbal tea to remedy a flu or cold. Others take a daily pill to help with a health condition or just stay healthy. Have you ever used natural herbs for your own health or treatment (for example ginger, echinacea or black cohosh including teas, tinctures, and pills) [18]?" Those respondents that said yes were asked "During the past 12 months, did you use natural herbs for your own health or treatment?" For the purpose of this analysis, we will refer to any herb use as having occurred in the prior 12 months. Of those that said yes to this question, respondents were asked a series of questions about individual HDS use and disclosure of that use to conventional health care providers.

Because we were interested in high risk HDS behaviors, we excluded use of vitamins and minerals (which may have been recommended by health professionals), and focused on non-vitamin/mineral supplements. Respondents chose from a list of 35 non-vitamin/mineral supplements dietary supplements (29 supplements were plant based and 6 supplements not plant based these included: s-adenosylmethionine (SAM-e) progesterone cream, melatonin, bee pollen, fish oil, glucosamine and chondroitin).

We defined a young adult age range between 18 years of age to 30 years of age based on education and earning potential. We considered socio-demographic factors including respondents' age (18–22, 23–30) gender, education (<high school, high school graduate, some college, college graduate), annual family income (<$15,000, $15,000–34,999, $35,000–64,999, ≥ $65,000), race/ethnicity (Hispanic, non-Hispanic white, non-Hispanic black non-Hispanic other (Asian, American Indian/Alaskan native, Asian Indian, Chinese, and Filipino) and region of U.S. residence (Northeast, Midwest, South, West).

We also included lifestyle/behavioral factors that we thought could interact with or cause adverse events with HDS. These included smoking (current, former, nonsmoker); alcohol use in the past 12 months (abstainer or former drinker, current infrequent or light drinker (< 3 drinks a week), current moderate to heavy (>3 drinks per week to >14 drinks a week), or unknown drinking status);

Although physical activity level, in itself, is not a high risk behavior, adolescent and adult athletes have been reported to use herbs and other performance enhancing supplements more frequently than others of their age groups. Therefore, we analyzed a physical activity level variable [high (vigorous activity 2 times/wk or moderate activity 4 times/wk), moderate (vigorous activity 1 time/wk or moderate activity 1–3 times/wk), or sedentary (no vigorous or moderate activity/week)] in the model to assess for an association high physical activity with HDS in a national population of youth [19].

Respondents were asked if they used prescription and over the counter (OTC) medications in the last 12 months. Respondents were asked if they disclosed natural herb use to conventional medical professionals including physicians, nurse practitioners, physician assistants, psychiatrists, and dentists.

Of the respondents, 17% (extrapolated for the U.S. adult population to 8.4 million) reported having used a non-vitamin, non-mineral HDS in the last 12 months. Demographic factors associated with higher HDS use included (Table ​(Table1):1): being older, having a higher income, having a college education and being Non-Hispanic others (Asian, American Indian/Alaskan native, Asian Indian, Chinese, and Filipino). The HDS most commonly used were echinacea (used by 45% of HDS users), ginseng (34%), ginkgo biloba (22%), garlic (15%), St. Johns wort (14%), peppermint (14%), ginger (10%), chamomile, (9%), kava kava (9 %), and ephedra (7 %). The most common conditions for which HDS were used were for were head or chest cold, (reported by 40% of HDS users), stomach or intestinal conditions (12%), musculoskeletal conditions (10%), severe headache or migraine (8%), anxiety of depression (7%), and insomnia (6%).

High risk behaviors (current smoking and moderate/heavy drinking) were positively associated with HDS use. For example, rates of HDS use were 24% among former smokers, 21% among current smokers, and 15% in non-smokers. Rates of HDS use were 24% among moderate/heavy drinkers, compared with 9% in non-drinkers. Compared to non smokers, smokers used significantly more ginseng, gingko, and St. Johns wort (p < .001). Compared to non drinkers, moderate/heavy drinkers used significantly more ginseng, chamomile (p < .001 for each comparison), Echinacea (p = .04) and gingko biloba (p = .01) (Table ​(Table22).

The prevalence of HDS use was 23% for those with high physical activity, compared with for 9% low physical activity. Respondents with high physical activity used more stimulant herbs in particular (Table ​(Table22).

Use was also significantly higher among those who used prescription medications (22%) and OTC medications (18%), than among those use used neither (~13%, P < .01 for each comparison). Compared to non-prescription medication users, prescription medication users took more garlic (p = .03) and those who took OTCs used more echinacea (p = .001).

Previous studies have reported higher rates of HDS among college and university students with a prevalence ranging from of 26% to 79% [24-27]. These studies were restricted to single institutions with homogeneous populations; they also used different time periods of HDS use and used a different list of HDS [24-27]. Our rates may have been lower due to the omission of some HDS that are commonly used by athletes; for example, sport drinks, protein powders and body-building hormones were not included in the NHIS survey questions.

In our analysis, the types of individual herbs used by young adults were consistent with other studies [26,27]. Green tea, goldenseal, acidophilus, and aloe were reported as popular in previous studies but not asked about in NHIS [24].

In our multivariable analysis several lifestyle and behavioral factors were associated with HDS use. As in other studies of teenagers and adults, rates of HDS use in young adults are highest among those who are smokers and drinkers [1,5,22,23,27]. Further research is necessary to study the relationship between HDS lifestyle factors such as smoking and alcohol use and if other high risk behaviors are associated with specific herbs or supplements.

In our study, respondents with moderate and high physical activity level were more likely to use HDS. Numerous studies have found that adolescents and young adults involved in sports have a high prevalence of use dietary supplements [9,15,28-32]. The use of sport supplements is especially concerning due to their questionable safety and efficacy.

This picture becomes more complicated by reports that young adults who are athletes tend to have more alcohol and drug use [13,14]. Additionally, an association between anabolic steroid and other illicit drug use and high risk behaviors has been documented [23,33,34]. More research is necessary to understand why young athletes use HDS recreationally with alcohol or tobacco, for prevention, or for sport performance.

Among HDS users in our sample, 66% also used prescription medications and 74 % used an over the counter medication in the prior 12 months. Compared to non-prescription medication users, those who used prescription medications were more likely to use HDS. This trend has been reported in previous surveys of young adults [24,26]. Increasing numbers of reports describe clinically serious interactions between prescription drugs and herbals/supplements and concern has grown that the problem of adverse effects may be under reported [35-38].

Among young adult HDS users, the most common conditions associated with use were head or chest cold, stomach or intestinal conditions, musculoskeletal conditions, severe headache or migraine, anxiety of depression, and insomnia. In the general adult population, the most frequent conditions prompting HDS use were upper respiratory infections, depression, musculoskeletal pain, and memory improvement [4,35]. Other studies of young adults reported high use for musculoskeletal conditions, depression, weight loss, body building, allergies, gastrointestinal symptoms, and general health improvement [24-27].

In our analysis, the prevalence of talking with health professionals about HDS use (24%) is even lower than that reported in adult and young adults populations (approximately 35 to 44 %) [5,7,26,39-41]. More research is needed to understand how health care professionals and young adults discuss HDS, what benefits and adverse events young adults experience, and how best to advise them. It is critical that all health care professionals ask and counsel their patients about HDS use. For example, one study of college students, 14% reported an adverse reaction from an HDS yet 58% continued to take the supplement despite adverse reactions [26].