With all the negative publicity surrounding medicinal herbs and dietary supplements, it's a wonder they're referred to as "performance enhancers."
The negative portrayal of supplements such as ephedra (which was recently banned from over-the-counter sale in the United States) has created a giant question mark over even moderate use of such products. This publicity has caused many consumers to believe the potential harm outweighs the benefits of these supplements.
Products such as ginseng, echinacea and ephedra can be used to help prevent cancer, stimulate the immune system and facilitate weight loss, respectively. What's more, in the U. S., herbal preparations and dietary supplements, including those regarded as performance enhancing, are easily attainable over the counter and available without a prescription.
It is important that both health care providers and patients understand the evidence behind beneficial claims made by manufacturers, as well as the potential adverse effects that come from using such supplements. Here are some of the better-known, widely used supplements, along with information every provider should know.
Perhaps the best-known, most publicized supplement is ephedra, found in such products as Xenadrine, Hydroxycut and Stacker 2. The product is most commonly used to aid in weight loss among both athletes and the general public.
Ephedra began garnering negative press in 2001 after the supplement was cited by attorneys as a cause for the death of Minnesota Vikings star Korey Stringer. An autopsy, however, found that Stringer died from multiple organ failure brought on by heatstroke while practicing in near-100 degree heat.
The Stringer tragedy did directly lead to the National Football League's ban of all ephedra-based substances, a ban that later caused numerous suspensions among the league's players.
But recent evidence calls into question what benefits ephedra can have for an athlete. A review of the literature presented by Lisa Dehner, PhD, PT, and Kelly Rouster-Stevens, PharmD, MD, at the 2003 annual conference of the American Physical Therapy Association (APTA) found instances of short-term (no follow-up longer than 6 months) weight loss - particularly in women - as a result of using ephedra. Many of the experiments, however, included caffeine and thus muddled any potential answer to whether ephedra alone causes weight loss.
There is currently insufficient data to support ephedra as an athletic performance enhancer. Adverse effects of ephedra include a higher risk of palpitations and other autonomic side effects, particularly when combined with other stimulants or when used in excess of the recommended dose.
Overall, the rate of serious side effects, including heart attack and stroke, was found to be less than one in 1,000 cases. While athletes and some health care providers have debated both the positive and negative effects of ephedra, this evidence suggests the product is neither as beneficial nor may it be as harmful as some would have you believe.
With college scholarships and potentially lucrative professional contracts on the line, the pressure on young athletes to get ahead is greater than ever before. Training for a season that may last 3 months has become a year-round process, complete with endurance and strength training.
In order to gain that desired edge, many athletes turn to presumed performance-enhancing products such as dehydroepiandrosterone (DHEA) or creatine monohydrate. Both products are naturally produced by the human body, but when added to a workout or athletic regimen, they are believed to enhance strength, endurance and overall performance.
Are the perceptions true? In the body, DHEA is a precursor to testosterone, and it is therefore thought that supplementation could increase the body's testosterone levels, resulting in increased muscle mass, strength and athletic performance. However, evidence indicates DHEA supplementation does not increase serum testosterone levels in men but may in women.
Consequently, clinical studies measuring athletic performance and strength show little to no benefit from DHEA supplementation. The body produces DHEA in declining levels as a person ages, and therefore it is thought that DHEA supplementation in the elderly may prevent or offset the effects of aging. While in one study, older men with the highest DHEA levels were most fit, the preponderance of evidence indicates that supplementation does not improve mood, cognition, strength or body composition.
Levels of DHEA are also significantly reduced in those with Alzheimer's disease. However, DHEA supplementation in individuals with Alzheimer's did not improve cognition nor change the severity of the disease. There is some support for the use of DHEA supplementation in women with symptoms of depression and for treatment of mood disorders.
Thus, there currently is not enough research to support DHEA supplementation in most cases. Additionally, patients should be aware that DHEA has the potential adverse effect of increasing the risk of various hormone-related cancers, such as prostate cancer and breast cancer, but the literature is limited and controversial on this point.
Creatine monohydrate is an endogenous substance important in muscle physiology. Supplementation is thought to increase muscle mass and reduce recovery time and thereby increase performance. The majority of studies of creatine supplementation demonstrate a clinically significant improvement in short-term high-intensity exercise performance in both young men and women when used in the recommended amounts (typically 20 grams per day for 5 days).
Additionally, evidence indicates that elderly individuals who combine creatine supplementation with resistive exercise demonstrate increased strength and longer time to fatigue. However, similar studies investigating only supplementation without resistive training found no significant result. Therefore, the extent to which the creatine supplementation is responsible for performance gains is uncertain.
Additional studies in animals suggest a neuroprotective role for creatine against Huntington's and Parkinson's diseases, but they need to be confirmed in humans. There is also preliminary evidence that creatine can increase the strength of individuals with neuromuscular disease.
Adverse effects of creatine supplementation reported in the literature are few and include minor short-term compartment pressure and renal dysfunction in isolated studies. One case study cited kidney problems in a subject who, upon further investigation, had a predisposal to kidney ailments. This, of course, stresses how important it is for a patient to consult a health care provider before using any of these products. A study involving NCAA athletes who supplemented with creatine for .25 to 5.6 years found no adverse effects; however, the study was not controlled.
Dehner cautioned that interpretation of studies of adverse effects are only valid for those patients using the recommended dosage of creatine; exceeding that amount could potentially cause adverse effects unknown at this time. "Especially when managing the care of younger athletes, parents, physicians, trainers and physical therapists should be aware of any supplementation," she said.
Moving away from the athletic field, people with common everyday ailments such as osteoarthritis have also gone the supplement route, using such substances as chondroitin sulfate and glucosamine to both deal with the pain and attempt to offset the effects of osteoarthritis on their joints.
Again, both glucosamine and chondroitin are naturally present in the human body and contribute to the formation of proteoglycans, essential in normal cartilage. In OA, articular cartilage degenerates and thins, which reduces its ability to resist the forces of everyday activity. So the question becomes, will supplementation of proteoglycan precursors repair the damaged articular cartilage in a patient with OA?
Early in her review of the research, Dehner said she was skeptical that oral supplementation of proteoglycan precursors would lead to articular cartilage repair - whether an oral dose could actually improve or increase articular cartilage. Preliminary evidence does show that some of the supplement is present in joint tissues, but much of it is metabolized in the liver before it can get to the cartilage. Absolute bioavailability can range from 26% to 44% for glucosamine sulfate, to 12% to 21% for glucosamine hydrochloride, to 12% to 14% for chondroitin sulfate in studies of both human and animal subjects. However, there is controversy in the literature regarding whether that small amount of supplement that "makes it through" actually gets to the joint and increases the joints' production of proteoglycans - owing mainly to the difficulty in measuring such amounts accurately in vivo. Nonetheless, many clinical studies and meta-analyses have evaluated the clinical effects of supplementation.
Several studies show glucosamine sulfate supplementation (1.5g/day = 4 weeks) can result in significant reductions in pain and stiffness versus placebo and better than or equal effectiveness in the same versus ibuprofen (NSAID). Patients that responded to glucosamine had minimal to moderate OA and were younger and thinner than those who did not. Effect sizes and patient responses were categorized as minimal to moderate, meaning actual clinical or functional difference was low.
There is also preliminary evidence that glucosamine maintains an individual's joint space, versus a reduction in those taking placebo, but the outcome measures used and relationship of joint space to clinical change have been called into question.
Studies involving chondroitin sulfate supplementation (.8 to1.2g/day = 4 weeks) demonstrated a moderate-to-large effect in reducing subjects' pain and increasing their function. No study known to the researchers has compared chondroitin sulfate to an NSAID.
While current evidence suggests that the use of glucosamine sulfate, glucosamine hydrochloride and chondroitin sulfate demonstrates both short- and long-term (1 to 3 years) safety, researchers call for caution until further research can be performed.
When making a decision regarding the effectiveness of these supplements, Dehner stated, "It is important to note that the majority of studies investigating glucosamine and chondroitin have some manufacturer affiliation and are of poor methodological quality. Authors who take these factors into account believe the effects of glucosamine and chondroitin are much more conservative than proposed."
Good news for the future is that an independent, multicenter randomized controlled trial (GAIT) investigating the effects of both chondroitin sulfate and glucosamine sulfate, through funding from the National Institutes of Health, is in progress and will hopefully go a long way to confirm or refute current evidence.
Talking to Patients
According to Dehner, patients first need to be made aware of the lack of quality assurance of supplements, since currently there is no government regulation. Several studies have documented significant inconsistencies in the amount of supplement labeled and its actual contents. A patient's best bet is to buy supplements from reputable manufacturers.
"Just as it is important for physical therapists to understand the effects of medications prescribed to their patients, so too must we have an understanding about over-the-counter supplements and herbs and the potential interaction of the two. Many times, patients feel more comfortable asking their physical therapist about such supplements," Dehner advised. "Recommending the use or non-use of supplements or medications is not within our scope of practice, but it is appropriate for a physical therapist to inform the patient about the evidenced benefits and adverse effects, if known; to educate patients as to where they can get accurate medical information; and to advise them to speak to their doctor before taking any supplement."
As Dehner and Rouster-Stevens' research report at APTA 2003 stated, "Any supplement potent enough to have physiological effects can also be strong enough to cause harm."
As far as future research, Dehner indicated that people are finding new uses for supplements all the time - enough to keep researchers busy for years.
"Supplements and their marketing are constantly changing," she said. "It'll be a challenge to stay updated with all the new information, but I think it is important for us as therapists to do so, especially as we gain in autonomy, to ensure quality care."
Lisa Dehner is an assistant professor of physical therapy at the College of Mount St. Joseph in Cincinnati. She can be reached at firstname.lastname@example.org. For more information on Dehner's presentation at APTA 2003, see references and handout at www.apta.org/programming/pt/edProgMenuDay.cfm?which.Day=06/19/03.
Rob Senior is on staff at ADVANCE and can be reached at email@example.com.