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Meet the Expert: Supplement FAQs

Members have questions, but do you and your staff have the answers? Here's what you should know about the dietary supplements sold in your juice bar and pro shop.

Good nutrition and a healthy lifestyle go together like peanut butter and jelly. Because of this, many fitness centers offer a variety of dietary supplements to their patrons. This opens the door for members to ask a lot of questions about dietary supplements when deciding which ones might be right for them. So, your staff should be educated about those supplements, and be able to answer some of the most frequently asked questions.

Meet the expert

Joe Cannon, M.S., CSCS, NSCA-CPT, is an exercise physiologist, personal trainer, health educator and dietary supplement investigator. He holds an M.S. degree in exercise science and a B.S. degree in chemistry and biology. He has lectured about exercise, personal training, dietary supplements and nutrition for more than 10 years at both the local and national levels for the American Aerobics Association International/International Sports Medicine Association (AAAI/ISMA). Cannon is director of wellness for a fitness center that is ranked among the top 100 of clubs in the U.S. He is the author of Nutritional Supplements: What Works and Why. A Review from A to Zinc - And Beyond.


By now most people have heard about creatine supplements and the multitude of research showing that it can enhance power output during high-intensity exercise lasting less than 30 seconds.26 Creatine essentially acts like a turbocharger, speeding the production of ATP (energy) faster than any other energy system.5 While many reviews of creatine are available, gym-goers still ask questions about this supplement.

Is creatine safe? For healthy adults, creatine is, indeed, safe. Studies have found that creatine supplements do not cause harm to the liver or kidneys, as is often claimed by laypersons.27 Likewise, research does not show that creatine supplements result in muscle cramping or tears to muscles or tendons, when used appropriately.23

What are possible side-effects? The most consistently observed side-effect from creatine supplementation is an increase in body weight, due mostly to enhanced water storage.5 Strength trainers often "load" creatine (e.g., 20 grams per day for a week) prior to going on a "maintenance phase" of 2 to 5 grams per day. While this strategy will work, research shows that using just 3 grams per day for a month results in similar muscle creatine content.15

Does caffeine neutralize the effect of creatine? Fears of the effect of caffeine on creatine stem from one study, the results of which have not been replicated.30 Athletes concerned about this issue may want to refrain from caffeine use several days prior to their event until more is known.

Creatine is not thought to be effective for cardiovascular exercise or for strength-training activities that incorporate high repetitions (e.g., greater than 12 repetitions maximum [RM]).


Most fitness centers offer a wide range of protein bars and drinks. In fitness circles, protein is as highly regarded as it is misunderstood.

How much protein is needed by people who exercise? While experts usually agree that the recommended dietary allowance of 0.8 grams per kilogram of body weight (i.e., about 0.4 grams per pound) is sufficient to stave off protein deficiency, the optimal amount needed for people who exercise is less concrete. That being said, the best available evidence suggests that most people who work out regularly should strive for an intake of about 1.2 to 1.8 grams per kilogram of body weight.25 This equals about 0.6 to 0.9 grams per pound.

When faced with the question about optimal protein intake for fitness enthusiasts, members (and some fitness trainers) will often recommend "1 gram per pound." This is actually just a little above the upper limit of 0.9 grams per pound, and is probably chosen to make the math easier. Thus, what is being said is technically not incorrect, but universally recommending 1 gram per pound is a cookie cutter approach that is not appropriate for everyone. More specifically, those engaging primarily in endurance activities may be best suited with lower levels of protein (1.2 to 1.4 grams per kilogram), while those who primary lift weights are usually better served at levels closer to the upper limit (1.7 grams per kilogram).25 Because an almost infinite variation between reps, sets, loads and cardio combinations exist, recommending an "optimal" amount of protein (e.g., 1 gram per pound) is not really possible.

Can protein supplementation be dangerous? Claims that protein damages the liver, kidneys or bones are usually not based on research. If protein really were detrimental to health, then bodybuilders, powerlifters and most professional athletes would be dying at alarming rates - but they are not. Those with health issues, liver or kidney problems, or osteoporosis should discuss protein supplementation with their physician.

What are the different types of protein? With respect to types of protein, fitness centers usually offer whey, casein or soy. Both whey and casein are derived from milk, are considered high-quality and can contribute to daily protein intake.

Whey protein. Relating to exercise, some research finds that whey protein supplementation (20 grams per day for three months) improves antioxidant status and muscular endurance in healthy individuals.18 This improvement in antioxidant status has also resulted in whey being studied for possible therapeutic effects in people with severe illness like cancer and HIV.19 Other research finds that whey supplementation may enhance fat loss and reduce muscle breakdown in obese individuals who consume a reduced-calorie diet.12 Whey is also a good source of branch chain amino acids (leucine, isoleucine, valine), which, some research suggests, may help immune function during long-duration aerobic exercise (e.g., triathlons).3 With respect to BCAAs (branched chain amino acids) offsetting fatigue during exercise, the evidence is controversial.20 While normally only discussed with respect to exercise, some intriguing research also suggests that BCAAs may help stimulate appetite in malnourished older individuals.14

Casein protein. Casein is the major protein found in milk. Some ask the question as to which is better at promoting muscle growth: whey or casein. While few head-to-head comparisons are available, one recent study did find that whey supplementation (1.5 grams per kilogram for 10 weeks) resulted in greater gains in 1 RM strength than did an equal amount of casein.6 That being said, casein is not without merit, and some research has found that it may help augment immunity.13 Because of a theoretical blood pressure lowering effect, those with blood pressure problems should speak with their physician prior to using casein-only protein supplements.29

Soy-based protein. Soy, like whey and casein, is a high-quality protein.10 Soy has been studied extensively for its effects on a number of health issues ranging from cholesterol levels, postmenopausal hot flashes, bone density and hypertension, to name a few. While it is beyond the scope of this article to completely review the therapeutic research on soy, people with certain types of cancer should avoid this supplement. There is some concern among medical professionals that people with a history of breast cancer or endometrial cancer may be unsuitable for soy supplementation because of soy's plant-based estrogens (isoflavones).24 While concrete evidence is lacking, in theory, chronic intake of plant-based estrogens may activate these types of cancer.5

Does soy-based protein lower testosterone levels? A big question that strength trainers often wonder about with respect to soy is whether it will lower testosterone levels.5 There is some evidence that a high soy-based diet may lower testosterone in young men.8 However, the effect of soy on resistance training has not been adequately studied. One investigation on this did find that both soy and whey protein resulted in similar gains in strength in healthy, experienced weightlifters.4 Unfortunately, testosterone levels were not measured in this study.

Amino acids

Related to protein, some fitness centers may offer individual amino acid powders that can be added to protein shakes. This is often done to not only improve the nutritional value of the shake, but also, it is hoped, to improve and quicken recovery from exercise. Amino acids come in two main types: essential amino acids, which the body cannot make and must obtain from either food or supplements, and non-essential amino acids, which the body can make. Some also add a third category to this list: conditionally essential amino acids. A conditionally essential amino acid is a non-essential amino acid that, under some conditions, the body cannot make enough of to meet its needs. When this happens, that amino acid becomes temporarily essential.

Does glutamine speed post-workout recovery? Currently, glutamine is king of the mountain in fitness circles when it comes to conditionally essential amino acids. People often use glutamine supplements in the hopes of speeding recovery after the stress of hard workouts. The rationale for this is actually based on clinical research; however, a fact hardly ever mentioned in magazines or on websites is that the vast majority of this research stems from intravenously injecting glutamine into people with serious diseases like cancer or HIV, or those with severe burns.16,28,32 There is a big difference between a person with cancer and a healthy person who exercises.

Does glutamine affect immunity? Some research shows that ultra-endurance athletic events like cycling or marathons may lead to lower glutamine levels, which, in turn, may compromise immune systems.21 As for strength training, what little peer-reviewed evidence that is available hints that glutamine supplements do not appear to enhance strength in resistance-trained men.2

Taken as a whole, the evidence for glutamine supplements appears to be strongest for helping immunity in high-end aerobic endurance athletes. The effects of glutamine on strength trainers, as well as the majority of gym-goers, remains to be conclusively demonstrated.5

Energy drinks

Energy drinks are also a big seller in fitness facilities. Energy drinks are usually composed of caffeine, caffeine-containing compounds (e.g., guarana) and the amino acid taurine.

What are the effects of energy drinks? Caffeine is one of the most frequently used products among those who exercise, with most research finding that its benefits are greatest among those participating in aerobic-type events.9 Taurine is a non-essential amino acid formed from the amino acids methionine and cysteine, and found naturally in fish, poultry, eggs and meat. Some research suggests that taurine and caffeine appear to enhance verbal skills, concentration, memory recall and attention span.1,31 Interestingly, there is a paucity of information comparing the taurine/caffeine combo to caffeine or taurine alone, which makes it difficult to determine which ingredient may be responsible for the effects observed.

Do vitamins in these drinks provide energy? The addition of B vitamins to energy drinks may be due to the public's mistaken belief that B vitamins give people extra energy.30 Energy drinks contain high levels of B vitamins, particularly B6 and B12. Vitamin B6 is needed for the production of taurine, but deficiencies in B6 and B12 are rare in healthy, non-elderly adults, especially in the case of B12, since healthy non-elderly meat eaters have enough B12 to last many years.

What are possible side-effects? Side-effects from energy drinks appear to be rare, but case reports of problems do occasionally appear in the medical literature. However, it is unknown whether the problems arose from taurine itself or other supplements the person was taking.22


Of all the supplements sold at fitness centers, water could be considered the most important of all. In general, people can live for months without food, but most die within a week without water.

How much water do exercisers need? Many gym-goers appear to be confused about how much water they really need. The big urban legend with water is that people should get 64 ounces per day. However, there is no good proof that people only need 64 ounces of water per day to stay healthy. In fact, according to the Institute of Medicine, women should aim for about 91 ounces per day, while men should strive for about 125 ounces per day.11 For those who don't want to spend their days counting ounces of water, Marjorie Geiser, R.D., NSCA-CPT, a dietitian, personal trainer and business coach in Running Springs, Calif., has a simpler solution: "Just drink enough water so that your urine is clear." Older adults may be a group particularly in need of adequate hydration, given that people sometimes lose their sense of thirst as they age.17

Does water in other beverages count toward a person's hydration goal? New guidelines highlight that water does not need to be the only fluid consumed to obtain proper hydration.11 While fluids found in food, teas, sodas and even coffee also count toward hydration goals, Geiser points out that if consuming caffeinated beverages, it may be wise to increase fluid intake by about 10 percent to compensate for the slight diuretic effect of caffeine, especially in those who are not accustomed to it.


While certainly not considered a supplement, many fitness centers have a variety of frozen fruits that can be added to protein shakes to enhance their nutritional value.

Do exercisers need more fruit? A serving of fruit is half a cup, and it's recommended that people aim for at least 2 cups (four servings) of fruit per day for those eating a 2,000 calorie diet.7 This amount is increased for those who exercise. Fruit is an excellent source of a broad spectrum of natural antioxidants the body needs to repair damage and help ward off disease. Because surveys show that most Americans do not get the often-recommended nine servings of fruits and vegetables per day, fitness centers might try advertising the nutritional value of their smoothies to their members to ramp up sales from this profit center.

Do juice bar staff need special training? Just as an educated fitness professional is an asset to a health club's bottom line, so, too, is an educated juice bar staff. While members allow for a steady stream of patrons to juice bars, how much more revenue could be had if the staff could do more than just blend together a protein shake? Members have many questions when it comes to nutrition. An educated and credentialed staff at the juice bar may be just what the doctor ordered when it comes to keeping members happy and informed.

1. Alford, C., et al. The effects of Red Bull energy drink on human performance and mood. Amino Acids 21, 2: 139-150, 2001.
2. Antonio, J., et al. The effects of high-dose glutamine ingestion on weightlifting performance. Journal of Strength Conditioning Research 16: 157-160, 2002.
3. Bassit, R.A., et al. The effect of BCAA supplementation on immune function in triathletes. Medicine and Science in Sports and Exercise 32, 7: 1214-1219, 2000.
4. Brown, E.C., et al. Soy verses whey protein bars: Effects on exercise training, impact on lean body mass and antioxidant status. Nutrition Journal, 2004. Accessed April 28, 2008.
5. Cannon, J. Nutritional Supplements: What Works and Why. A Review From A to Zinc and Beyond. Buy Books on the Web.Com: West Conshohocken, Pa., 2006.
6. Cribb, P.J., et al. The effect of whey isolate and resistance training on strength, body composition and plasma glutamine. International Journal of Sports Nutrition and Exercise Metabolism 16: 494-509, 2006.
7. Dietary Guidelines for Americans. dietaryguidelines/dga2005/recommendations.htm, 2005. Accessed April 21, 2008.
8. Dillingham, B.L., et al. Soy protein isolates of varying isoflavone content exert minor effects on serum reproductive hormones in healthy young men. Journal of Nutrition 135: 584-591, 2005.
9. Doherty, M., et al. Effects of caffeine ingestion on exercise testing: A meta analysis. International Journal of Sports Nutrition and Exercise Metabolism 14: 626-646, 2004.
10. Erdman, J.W. AHA Science Advisory: Soy protein and cardiovascular disease. A statement for healthcare professionals from the Nutrition Committee of the AHA. Circulation 102: 2555-2559, 2000.
11. Food and Nutrition Board. Dietary Reference Intakes: Water, Potassium, Sodium, Chloride and Sulfate. The National Academies Press: Washington, D.C., 2004.
12. Frestedt, J.L., et al. A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: A randomized human clinical study. Nutrition and Metabolism 5: 8, 2008. Accessed April 28, 2008.
13. Gill, H.S., et al. Immunoregulatory peptides in bovine milk. British Journal of Nutrition 84: S111-S117, 2000.
14. Hiroshige, K., et al. Oral supplementation of branched-chain amino acid improves nutritional status in elderly patients on chronic haemodialysis. Nephrology, Dialysis, Transplantation 16, 1856-1862, 2001.
15. Hultman, E., et al. Creatine loading and man. Journal of Applied Physiology 81, 1: 232-237, 1996.
16. Kelly, D., et al. Role of L-glutamine and critical illness: New insights. Current Opinion in Clinical Nutrition and Metabolic Care 6: 217-222, 2003.
17. Kenney, W.L., et al. Influence of age on thirst and fluid intake. Medicine and Science in Sports and Exercise 33, 9: 1524-1532, 2001.
18. Lands, L.C., et al. Effect of supplementation with a cysteine donor on muscular performance. Journal of Applied Physiology 87, 4: 1381-1385, 1999.
19. Marshall, K. Therapeutic applications of whey protein. Alternative Medicine Review 9, 2: 136-156, 2004.
20. Meeusen, R., et al. Amino acids and the brain: Do they play a role in central fatigue? International Journal of Sports Nutrition and Exercise Metabolism 17: S327-S46, 2007.
21. Monograph: L-glutamine. Alternative Medicine Review 6, 4: 406-410, 2001.
22. Obermann, M., et al. Taurine induced toxic encephalopathy? Clinical Neurology and Neurosurgery 108: 812-813, 2006.
23. Persky, A.M., et al. Clinical pharmacology of the dietary supplement creatine monohydrate. Pharmacological Reviews 53, 2: 161-176, 2001.
24. Petrakis, N.L., et al. Stimulatory influence of soy protein isolate on breast secretion in pre- and post-menopausal women. Cancer Epidemiology, Biomarkers & Prevention 5: 785-794, 1996.
25. Phillips, S.M. A critical examination of dietary protein requirements, benefits and excess in athletes. International Journal of Sports Nutrition and Exercise Metabolism 17: S58-S76, 2007.
26. Rossouw, F., et al. The effect of creatine monohydrate loading on maximal intermittent exercise and sport-specific strength in well-trained powerlifters. Nutrition Research 20: 505-514, 2000.
27. Schilling, B.K., et al. Creatine supplementation and health variables: A retrospective study. Medicine and Science in Sports and Exercise 33: 183-188, 2001.
28. Shabert, J.K. Glutamine-antioxidant supplementation increases body cell mass in AIDS patients with weight loss: A randomized, double-blind controlled trial. Nutrition 15: 860-864, 1999.
29. Townsend, R.R., et al. A randomized, double-blind, placebo-controlled trial of casein protein hydrolysate (C12 peptide) in human essential hypertension. American Journal of Hypertension 17, 11 Pt 1: 1056-1058, 2004.
30. Vandenberghe, K., et al. Caffeine counteracts the ergogenic effect of creatine loading. Journal of Applied Physiology 80: 452-457, 1996.
31. Warburton, D.M., et al. An evaluation of a caffeinated taurine drink on mood, memory and information processing in healthy volunteers without caffeine abstinence. Psychopharmacology (Berl) 158: 322-328, 2001.
32. Wernerman, J. Glutamine and acute illness. Critical Care 9: 279-285, 2003.
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