Summary: This review examines few popular myths in the nutritional arena and debunks them based on existing scientific evidence.
Myth: High protein diets are harmful to your kidneys
This is perhaps the longest enduring myth in the sports nutrition field. The notion that eating more protein than the paltry recommended daily allowance will result in renal problems has no foundation in scientific fact or support. For instance, recent work investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. According to the authors, “the nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 grams of protein consumed daily per kilo of body weight but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate.” According to the authors, protein intake under 2.8 grams of protein daily per kilo of body weight does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study.” (1) Another study suggested that “while protein restriction may be appropriate for treatment of existing kidney disease, we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.” (2)
Myth: High protein diets are harmful to your bones
Oddly enough, not enough protein is deleterious to your bone health. According to Heaney, excess protein will not harm the skeleton if the calcium intake is adequate.(3) “Several recent epidemiological studies have shown that a reduced bone density and increased rates of bone loss in individuals habitually consuming low protein diets.”(4)
Myth: Caffeine or caffeine-containing beverages dehydrate you
The notion that coffee or caffeine-containing beverages promote dehydration is not supported by science. One investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean age, 22 y) consumed 3 mg caffeine per kilo body weight per day on days 1 to 6 (equilibration phase). This caffeine dose is equal to approximately 273 mg of caffeine for a 200 pound individual (or roughly 3 cups of coffee). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n= 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine per kilo of body weight per day in capsules, with no other dietary caffeine intake. Caffeine had no effect on body mass, urine osmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. According to the authors, “these findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic.”(2)
Myth: Drinking coffee is harmful to your health
Coffee is probably the second most frequently ingested beverage worldwide (second to water). However, “it is apparent that moderate daily filtered, coffee intake is not associated with any adverse effects on cardiovascular outcome. On the contrary, the data shows that coffee has a significant antioxidant activity, and may have an inverse association with the risk of type 2 diabetes mellitus.”(5)
Myth: Drinking coffee leaches your bones of calcium
Caffeine-containing beverage consumption has been reported to be associated with reduced bone mass and increased fracture risk in some, but not most, observational studies. However, this may be due to the fact that individuals who tend to drink a high volume of caffeinated beverages, tend not to drink calcium-containing beverages. That is, the epidemiologic studies showing a negative effect may be explained in part by an inverse relationship between consumption of milk and caffeine-containing beverages. Accordingly, the negative effect of caffeine on calcium absorption is small enough to be fully offset by as little as 1-2 tablespoons of milk. Thus, one paper concludes that, “there is no evidence that caffeine has any harmful effect on bone status or on the calcium economy in individuals who ingest the currently recommended daily allowances of calcium.”(6)
Myth: Creatine supplementation causes muscle cramps, renal problems and heat-related injuries
Though you may read in the mainstream press that creatine causes a whole host of problems, none of them are supported by scientific evidence. It is clear that for whatever reason, scientific data regarding creatine is routinely ignored by non-scientific journalists. Oral creatine supplements are often consumed by athletes in amounts of up to 20 g/day for a few days, followed by 1 to 10 g/day for weeks, months and years. One group investigated liver changes during medium term (4 weeks) creatine supplementation in young athletes. None showed any evidence of dysfunction on the basis of serum enzymes and urea production. Furthermore, short term (5 days), medium term (9 weeks) and long term (up to 5 years) oral creatine supplementation has been studied in small cohorts of athletes whose kidney function was monitored by clearance methods and urine protein excretion rate. No evidence of adverse effects were found regarding kidney function.(7, 8) In an open-label study during 1 season of National Collegiate Athletic Association Division IA football training and competition, it was discovered that creatine users had significantly less cramping; heat illness or dehydration; muscle tightness; muscle strains; and total injuries than nonusers. Thus, even for athletes who are well-trained, it is clear that regular creatine consumption does not cause harm and in fact, may have a protective effect against certain exercise-related maladies.(9)
Disclosure: Jose Antonio, Ph.D. is a principal in Javalution Coffee Company, Inc.
References
1. Poortmans JR, Dellalieux O. Do regular high protein diets have potential health risks on kidney function in athletes? Int J Sport Nutr Exerc Metab. 2000b;10(1):28-38.
2. Bennett T, Bathalon G, Armstrong D, 3rd, et al. Effect of creatine on performance of militarily relevant tasks and soldier health. Mil Med. 2001;166(11):996-1002.
3. Heaney RP. Effects of caffeine on bone and the calcium economy. Food Chem Toxicol. 2002;40(9):1263-70.
4. Kerstetter JE, O'Brien KO, Insogna KL. Low protein intake: the impact on calcium and bone homeostasis in humans. J Nutr. 2003;133(3):855S-861S.
5. Ranheim T, Halvorsen B. Coffee consumption and human health - beneficial or detrimental? - Mechanisms for effects of coffee consumption on different risk factors for cardiovascular disease and type 2 diabetes mellitus. Mol Nutr Food Res. 2005.
6. Armstrong LE. Caffeine, body fluid-electrolyte balance, and exercise performance. Int J Sport Nutr Exerc Metab. 2002;12(2):189-206.
7. Poortmans JR, Francaux M. Adverse effects of creatine supplementation: fact or fiction? Sports Med. 2000a;30(3):155-70.
8. Kreider RB, Melton C, Rasmussen CJ, et al. Long-term creatine supplementation does not significantly affect clinical markers of health in athletes. Mol Cell Biochem. 2003;244(1-2):95-104.
9. Greenwood M, Kreider RB, Greenwood L, Byars A. Cramping and Injury Incidence in Collegiate Football Players Are Reduced by Creatine Supplementation. J Athl Train. 2003;38(3):216-219.
